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  • 1.
    Kaushik, Priya Darshni
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Jamia Millia Islamia, India.
    Rodner, Marius
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Lakshmi, G. B. V. S.
    Jawaharlal Nehru Univ, India.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Greczynski, Grzegorz
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Palisaitis, Justinas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Solanki, Pratima
    Jawaharlal Nehru Univ, India.
    Aziz, Anver
    Jamia Millia Islamia, India.
    Siddiqui, Azher M.
    Jamia Millia Islamia, India.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholamreza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Surface functionalization of epitaxial graphene using ion implantation for sensing and optical applications2020Ingår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 157, s. 169-184Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface functionalization has been shown to allow tailoring of graphene lattice thus making it suitable for different applications like sensing, supercapacitance devices, drug delivery system and memory devices. In this work, surface functionalization of epitaxial graphene on SiC (EG/SiC) was done by ion beam technology (30 keV Ag- ions at fluences ranging from 5 x 10(12) ions/cm(2) to 5 x 10(14) ions/cm(2)), which is one of the most precise techniques for introducing modifications in materials. Atomic force microscopy showed presence of nanostructures in ion implanted samples and Photoluminescence and X-ray photoelectron spectroscopy revealed that these are probably silicon oxy carbide. High-resolution transmission electron microscopy (HRTEM) showed decoupling of buffer layer from SiC substrate at many places in ion implanted samples. Further, HRTEM and Raman spectroscopy showed amorphization of both graphene and SiC at highest fluence. Fluence dependent increase in absorbance and resistance was observed. Gas sensors fabricated on pristine and ion implanted samples were able to respond to low concentration (50 ppb) of NO2 and NH3 gases. Detecting NH3 gas at low concentration further provides a simple platform for fabricating highly sensitive urea biosensor. We observed response inversion with increasing fluence along with presence of an optimal fluence, which maximized gas sensitivity of EG/SiC. (C) 2019 Elsevier Ltd. All rights reserved.

  • 2.
    Shi, Yuchen
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Höjer, Pontus
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholamreza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu W.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    A comparative study of high-quality C-face and Si-face 3C-SiC(1 1 1) grown on off-oriented 4H-SiC substrates2019Ingår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 52, nr 34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a comparative study of the C-face and Si-face of 3C-SiC(111) grown on off-oriented 4H-SiC substrates by the sublimation epitaxy. By the lateral enlargement method, we demonstrate that the high-quality bulk-like C-face 3C-SiC with thickness of ~1 mm can be grown over a large single domain without double positioning boundaries (DPBs), which are known to have a strongly negative impact on the electronic properties of the material. Moreover, the C-face sample exhibits a smoother surface with one unit cell height steps while the surface of the Si-face sample exhibits steps twice as high as on the C-face due to step-bunching. High-resolution XRD and low temperature photoluminescence measurements show that C-face 3C-SiC can reach the same high crystalline quality as the Si-face 3C-SiC. Furthermore, cross-section studies of the C- and Si-face 3C-SiC demonstrate that in both cases an initial homoepitaxial 4H-SiC layer followed by a polytype transition layer are formed prior to the formation and lateral expansion of 3C-SiC layer. However, the transition layer in the C-face sample is extending along the step-flow direction less than that on the Si-face sample, giving rise to a more fairly consistent crystalline quality 3C-SiC epilayer over the whole sample compared to the Si-face 3C-SiC where more defects appeared on the surface at the edge. This facilitates the lateral enlargement of 3C-SiC growth on hexagonal SiC substrates.

  • 3.
    Jian, Jingxin
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Shi, Yuchen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Ekeroth, Sebastian
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Keraudy, Julien
    Oerlikon Balzers, Liechtenstein.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    A nanostructured NiO/cubic SiC p-n heterojunction photoanode for enhanced solar water splitting2019Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, nr 9, s. 4721-4728Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Photoelectrochemical (PEC) water-splitting offers a promising method to convert the intermittent solar energy into renewable and storable chemical energy. However, the most studied semiconductors generally exhibit a poor PEC performance including low photocurrent, small photovoltage, and/or large onset potential. In this work, we demonstrate a significant enhancement of photovoltage and photocurrent together with a substantial decrease of onset potential by introducing electrocatalytic and p-type NiO nanoclusters on an n-type cubic silicon carbide (3C-SiC) photoanode. Under AM1.5G 100 mW cm(-2) illumination, the NiO-coated 3C-SiC photoanode exhibits a photocurrent density of 1.01 mA cm(-2) at 0.55 V versus reversible hydrogen electrode (V-RHE), a very low onset potential of 0.20 V-RHE and a high fill factor of 57% for PEC water splitting. Moreover, the 3C-SiC/NiO photoanode shows a high photovoltage of 1.0 V, which is the highest value among reported photovoltages. The faradaic efficiency measurements demonstrate that NiO also protects the 3C-SiC surface against photo-corrosion. The impedance measurements evidence that the 3C-SiC/NiO photoanode facilitates the charge transfer for water oxidation. The valence-band position measurements confirm the formation of the 3C-SiC/NiO p-n heterojunction, which promotes the separation of the photogenerated carriers and reduces carrier recombination, thus resulting in enhanced solar water-splitting.

  • 4.
    Lin, Li
    et al.
    Tech Univ Denmark, Denmark.
    Ou, Yiyu
    Tech Univ Denmark, Denmark.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Liang, Meng
    Chinese Acad Sci, Peoples R China.
    Liu, Zhiqiang
    Chinese Acad Sci, Peoples R China.
    Yi, Xiaoyan
    Chinese Acad Sci, Peoples R China.
    Schuh, Philipp
    Univ Erlangen Nurnberg, Germany.
    Wellmann, Peter
    Univ Erlangen Nurnberg, Germany.
    Herstrom, Berit
    Tech Univ Denmark, Denmark.
    Jensen, Flemming
    Tech Univ Denmark, Denmark.
    Ou, Haiyan
    Tech Univ Denmark, Denmark.
    An adhesive bonding approach by hydrogen silsesquioxane for silicon carbide-based LED applications2019Ingår i: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 91Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report an adhesive bonding approach using hydrogen silsesquioxane (HSQ) for silicon carbide (SiC) samples. A hybrid light-emitting diode (LED) was successfully fabricated through bonding a near-ultraviolet (NUV) LED grown on a commercial 4H-SiC substrate to a free-standing boron-nitrogen co-doped fluorescent-SiC epi-layer. The bonding quality and the electrical performance of the hybrid LED device were characterized. Neither voids nor defects were observed which indicates a good bonding quality of the proposed HSQ approach. A strong warm white emission was successfully obtained from the hybrid LED through an electric current injection of 30 mA.

  • 5.
    Rafique, Asia
    et al.
    COMSATS Univ Islamabad, Pakistan; Govt Punjab, Pakistan.
    Raza, Rizwan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. COMSATS Univ Islamabad, Pakistan.
    Ali, Amjad
    COMSATS Univ Islamabad, Pakistan; Univ Okara, Pakistan.
    Ahmad, Muhammad Ashfaq
    COMSATS Univ Islamabad, Pakistan.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    An efficient carbon resistant composite Ni0.6Zn0.4O2-delta-GDC anode for biogas fuelled solid oxide fuel cell2019Ingår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 438, artikel-id 227042Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes the fabrication of Ni0.6Zn0.4-Gd0.2Ce0.8O2-delta (NiZn-GDC) via a two-step wet chemical synthesis technique. This composite was found to be more thermally stable and carbon resistive under the intense reducing environment of biogas. This was confirmed by different characterization techniques. The maximum power density P-max, was achieved at 600 degrees C as 820 mW/cm(2) and 548 mW/cm(2) with hydrogen and biogas, respectively. Different characterization techniques have been performed, such as X-ray diffractometry (XRD), scanning electron microscopy (SEM/EDX), UV visible spectroscopy, and Raman spectroscopy. The XRD pattern by Rietveld refinement showed two-phase structures of the anode composite with an average crystallite size of 25 35 nm before and after reduction with methane. The optical band gap (E-g(opt)) of NiZn-GDC was calculated to be 2.24eV from the Tauc plot using absorbance data. The Nyquist plot was also drawn to study the AC electrochemical impedance spectra (EIS) of the nanocomposite anode from 450 degrees C to 600 degrees C in air. The maximum DC conductivity of 1.37 S/cm was observed at a temperature of 600 degrees C using the four-probe DC technique.

  • 6.
    Vagin, Mikhail
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Sekretareva, Alina
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten. Stanford Univ, CA 94305 USA; Uppsala Univ, Sweden.
    Håkansson, Anna
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Iakimov, Tihomir
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Graphens AB, Teknikringen 1F, SE-58330 Linkoping, Sweden.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Graphens AB, Teknikringen 1F, SE-58330 Linkoping, Sweden.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Graphens AB, Teknikringen 1F, SE-58330 Linkoping, Sweden.
    Lundström, Ingemar
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Mats
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Bioelectrocatalysis on Anodized Epitaxial Graphene and Conventional Graphitic Interfaces2019Ingår i: CHEMELECTROCHEM, ISSN 2196-0216, Vol. 6, nr 14, s. 3791-3796Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Graphitic materials exhibit significant anisotropy due to the difference in conductivity in a single layer and between adjacent layers. This anisotropy is manifested on epitaxial graphene (EG), which can be manipulated on the nanoscale in order to provide tailor-made properties. Insertion of defects into the EG lattice was utilized here for controllable surface modification with a model biocatalyst and the properties were quantified by both electrochemical and optical methods. A comparative evaluation of the electrode reaction kinetics on the enzyme-modified 2D material vs conventional carbon electrode materials revealed a significant enhancement of mediated bioelectrocatalysis at the nanoscale.

    Publikationen är tillgänglig i fulltext från 2020-07-01 15:20
  • 7.
    Jian, Jingxin
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Shi, Yuchen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Cubic SiC Photoanode Coupling with Ni:FeOOH Oxygen-Evolution Cocatalyst for Sustainable Photoelectrochemical Water Oxidation2019Ingår i: SOLAR RRL, ISSN 2367-198X, artikel-id 1900364Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As an efficient water oxidation cocatalyst, the Earth-abundant nickel-iron oxyhydroxide (Ni:FeOOH) is introduced to coat on the cubic silicon carbide (3C-SiC) photoanode surface for improving the photoelectrochemical (PEC) water oxidation performance. The FeOOH is prepared on the 3C-SiC photoanode surface by hydrothermal deposition, followed by a photoassisted electrodeposition of NiOOH. It is shown that the Ni:FeOOH layer is composed of the beta-FeOOH nanorods with a conformal coating of the amorphous NiOOH. Under AM1.5G 100 mW cm(-2) illumination, the 3C-SiC/Ni:FeOOH photoanode exhibits a very low onset potential of 0.2 V versus reversible hydrogen electrode (V-RHE) and a high photocurrent density of 1.15 mA cm(-2) at 1.23 V-RHE, distinctly outperforming the 3C-SiC and the 3C-SiC/FeOOH counterparts. Open-circuit potential and impedance spectroscopy results demonstrate that the nanostructured Ni:FeOOH layer on the 3C-SiC surface increases the photovoltage and promotes the charge transfer toward the electrolyte, thus significantly improving the PEC water-splitting performance. These results provide new insights for the development of photoanodes toward efficient solar-fuel generation.

  • 8.
    Tarekegne, Abebe T.
    et al.
    Tech Univ Denmark, Denmark.
    Norrman, K.
    Tech Univ Denmark, Denmark.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Schuh, P.
    FAU Erlangen Nuremberg, Germany.
    Wellmann, P.
    FAU Erlangen Nuremberg, Germany.
    Ou, H.
    Tech Univ Denmark, Denmark.
    Impacts of carrier capture processes in the thermal quenching of photoluminescence in Al-N co-doped SiC2019Ingår i: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 125, nr 9, artikel-id 172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High concentrations of aluminum (Al) and nitrogen (N) dopants of 6H SiC have been achieved by a fast sublimation growth process. The Al-N co-doped 6H-SiC layer exhibits a strong light-blue photoluminescence emission at low temperatures due to emissions from D-I centers and donor acceptor pairs (DAP). The photoluminescence quenching mechanisms of those emissions are different. The decrease of free carrier capture cross-section as temperature increases according to the cascade capture process causes quenching of the photoluminescence emission form D-I centers. Emission from Al-N DAP centers exhibits an exponential quenching with activation energy of (95 +/- 10) meV. This is attributed to a competing hole capture by non-radiative defect in a multiphonon emission process.

  • 9.
    Syväjärvi, Mikael
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Stekovic, Svjetlana
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    S. Gustafsson, Mariana
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Statsvetenskap. Linköpings universitet, Filosofiska fakulteten.
    Using Buurtzorg model as innovation clustering model for regional capacity building in an entrepreneurial context2019Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Smart Specialization (RIS3) is an innovative approach/strategy to bring together local authorities, academia, businesses and society to boost growth and jobs in Europe. It prioritizes domains, areas and economic activities where regions have a competitive advantage.

     

    We introduce an innovation model to facilitate translation of ideas and knowledge into regional implementation. Instead of focusing on technology, the innovator / entrepreneur himself is in focus. The proposed model is based on the Buurtzorg model which originally focusses on supporting patients in health care, and which has an onion frame: the patient is surrounded by informal network (family, etc), next is the Buurtzorg support team, and final level is the formal network (society). The individuals need are steering the health care support, rather than adapting it to the social and economic constraints of the health care system. The team consists of specialists who decide how they organize the work, share responsibilities and make decisions. The team is self-managing and with entrepreneurial spirit.

     

    We will argue in this paper that a support mechanism as innovation model may be applicable to regional capacity building, and the support acts as a clustering process. Clusters are often limited by geographical constraints, such as having a number of local actors in a certain field. Clustering may be based on other values than given by physical ones.

     

    Our model approach is based on that there are innovators who have visionary ideas which are outside their traditional business. They could potentially be of great important for regional growth since they will create value chains, jobs etc, but given the non traditional innovation character they will not be realized unless there is a support mechanism. Similar to the Buurtzorg model, there is a team of specialists that will support the innovator and the innovator informal network. The specialist team has competencies related to smart specialization, regional growth etc (formal network).

     

    When RIS3 is applied to broad areas like advanced materials or nanotechnology such a mediation becomes highly complex. Both these areas include an extremely broad range of areas, examples include anything from food (through modifying functional properties by physical and chemical changes), digital communication or connected systems (new materials’ approaches for faster processors or use of higher/faster band frequencies), to construction related materials (buildings, transport, etc). Very likely they do not have actors located geographically close to create a cluster.

     

    For synergistic effects, activities in the RIS3 within advanced materials can be linked to other fields, as well as to implementation synergies. If the smart specialization of advanced materials can interact with efforts in building competence, smart industry, sustainable production, automation, digitalization etc, the advanced materials could then find a value chain in specific avenues instead of building ones in its own area. This is a viable route to hold together the fragmented and broad character of advanced materials field, where transferring/translation activities (competence, technical, etc) are a binding agent. Therefore, the specialist team is crucial for such transfer, and a core element in an innovation model.

  • 10.
    Li, Hao
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Shang, Huan
    Cent China Normal Univ, Peoples R China.
    Shi, Yuchen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Zhang, Lizhi
    Cent China Normal Univ, Peoples R China.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Atomically manipulated proton transfer energizes water oxidation on silicon carbide photoanodes2018Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, nr 47, s. 24358-24366Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surmounting the sluggish water oxidation kinetics beyond the hole-dominated thermodynamic effect is a topic of great scientific interest to establish fully renewable hydrogen technology from solar-powered water splitting. Herein, we demonstrate that the bottleneck of photoelectrochemical water oxidation can be overcome via atomic manipulation of proton transfer on the polar surfaces of silicon carbide (SiC) photoanodes. On the typical carbon-face SiC, where proton-coupled electron transfer governed the interfacial hole transfer for water oxidation, substantial energy loss was inevitable due to the highly activated proton-transfer steps. Via preferentially exposing the silicon-face, we enabled surface-catalyzed barrierless O-H breaking with a facile proton exchange and migration character. This mechanistically shifted the rate limiting step of water oxidation from sluggish proton-coupled electron transfer to a more energy-favorable electron transfer. The proof-of-concept study introduced here may open up new possibilities to design sophisticated photoelectrodes for an unbiased solar water splitting cell via surface engineering.

  • 11.
    Patricia, Carvalho
    et al.
    SINTEF Materials Physics, Oslo, Norway; University of Lisbon, Instituto Superior Tecnico, Lisbon, Portugal.
    Annett, Thørgesen
    SINTEF Materials Physics, Oslo, Norway.
    Quanbao, Ma
    University of Oslo, Department of Physics, Oslo, Norway.
    Daniel Nielsen, Wright
    SINTEF Instrumentation, Oslo, Norway.
    Spyros, Diplas
    SINTEF Materials Physics, Oslo, Norway; University of Oslo, Department of Chemistry, Oslo, Norway.
    Augustinas, Galeckas
    University of Oslo, Department of Physics, Oslo, Norway.
    Alexander, Azarov
    University of Oslo, Department of Physics, Oslo, Norway.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu W.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Bengt Gunnar, Svensson
    University of Oslo, Department of Physics, Oslo, Norway.
    Ole Martin, Løvvik
    SINTEF Materials Physics, Oslo, Norway; University of Oslo, Department of Physics, Oslo, Norway.
    Boron-doping of cubic SiC for intermediate band solar cells: a scanning transmission electron microscopy study2018Ingår i: SciPost Physics, ISSN 2542-4653, Vol. 5, nr 3, s. 1-17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Boron (B) has the potential for generating an intermediate band in cubic silicon carbide (3C-SiC), turning this material into a highly efficient absorber for single-junction solar cells. The formation of a delocalized band demands high concentration of the foreign element, but the precipitation behavior of B in the 3C polymorph of SiC is not well known. Here, probe-corrected scanning transmission electron microscopy and secondary-ion mass spectrometry are used to investigate precipitation mechanisms in B-implanted 3C-SiC as a function of temperature. Point-defect clustering was detected after annealing at 1273 K, while stacking faults, B-rich precipitates and dislocation networks developed in the 1573 - 1773 K range. The precipitates adopted the rhombohedral B13C2 structure and trapped B up to 1773 K. Above this temperature, higher solubility reduced precipitation and free B diffused out of the implantation layer. Dopant concentrations E19 at.cm-3 were achieved at 1873 K.

  • 12.
    Shi, Yuchen
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Zakharov, Alexei A.
    MAXIV Laboratory, Lund, Sweden.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholamreza Reza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Elimination of step bunching in the growth of large-area monolayer and multilayer graphene on off-axis 3CSiC (111)2018Ingår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 140, s. 533-542Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multilayer graphene has exhibited distinct electronic properties such as the tunable bandgap for optoelectronic applications. Among all graphene growth techniques, thermal decomposition of SiC is regarded as a promising method for production of device-quality graphene. However, it is still very challenging to grow uniform graphene over a large-area, especially multilayer graphene. One of the main obstacles is the occurrence of step bunching on the SiC surface, which significantly influences the formation process and the uniformity of the multilayer graphene. In this work, we have systematically studied the growth of monolayer and multilayer graphene on off-axis 3CSiC(111). Taking advantage of the synergistic effect of periodic SiC step edges as graphene nucleation sites and the unique thermal decomposition energy of 3CSiC steps, we demonstrate that the step bunching can be fully eliminated during graphene growth and large-area monolayer, bilayer, and four-layer graphene can be controllably obtained on high-quality off-axis 3CSiC(111) surface. The low energy electron microscopy results demonstrate that a uniform four-layer graphene has been grown over areas of tens of square micrometers, which opens the possibility to tune the bandgap for optoelectronic devices. Furthermore, a model for graphene growth along with the step bunching elimination is proposed.

    Publikationen är tillgänglig i fulltext från 2020-08-24 11:11
  • 13.
    Wang, Weimin
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Shi, Yuchen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Zakharov, A.A.
    MAX IV Laboratory, Lund, Sweden.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Uhrberg, Roger
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Flat-Band Electronic Structure and Interlayer Spacing Influence in Rhombohedral Four-Layer Graphene2018Ingår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, nr 9, s. 5862-5866Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The stacking order of multilayer graphene significantly influences its electronic properties. The rhombohedral stacking sequence is predicted to introduce a flat band, which has high density of states and the enhanced Coulomb interaction between charge carriers, thus possibly resulting in superconductivity, fractional quantum Hall effect, and many other exotic phases of matter. In this work, we comprehensively study the effect of the stacking sequence and interlayer spacing on the electronic structure of four-layer graphene, which was grown on a high crystalline quality 3C-SiC(111) crystal. The number of graphene layers and coverage were determined by low energy electron microscopy. First-principles density functional theory calculations show distinctively different band structures for ABAB (Bernal), ABCA (rhombohedral), and ABCB (turbostratic) stacking sequences. By comparing with angle-resolved photoelectron spectroscopy data, we can verify the existence of a rhombohedral stacking sequence and a nearly dispersionless electronic band (flat band) near the Fermi level. Moreover, we find that the momentum width, bandgap, and curvature of the flat-band region can be tuned by the interlayer spacing, which plays an important role in superconductivity and many other exotic phases of matter. © 2018 American Chemical Society.

  • 14.
    Kaushik, Priya Darshni
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Jamia Millia Islamia, India.
    Aziz, Anver
    Jamia Millia Islamia, India.
    Siddiqui, Azher M.
    Jamia Millia Islamia, India.
    Greczynski, Grzegorz
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Jafari, Mohammad Javad
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska fakulteten.
    Lakshmi, G. B. V. S.
    Interuniv Accelerator Centre, India.
    Avasthi, D. K.
    Interuniv Accelerator Centre, India; Amity Institute Nanotechnol, India.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholamreza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Modifications in structural, optical and electrical properties of epitaxial graphene on SiC due to 100 MeV silver ion irradiation2018Ingår i: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 74, s. 122-128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Epitaxial graphene (EG) on silicon carbide (SiC) is a combination of two robust materials that are excellent candidates for post silicon electronics. In this work, we systematically investigate structural changes in SiC substrate as well as graphene on SiC and explore the potential for controlled applications due to 100 MeV silver swift heavy ion (SHI) irradiation. Raman spectroscopy showed fluence dependent decrease in intensity of first and second order modes of SiC, along with decrease in Relative Raman Intensity upon ion irradiation. Similarly, Fourier-transform infrared (FTIR) showed fluence dependent decrease in Si-C bond intensity with presence of C = O, Si-O-Si, Si-Si and C-H bond showing introduction of vacancy, substitutional and sp(3) defects in both graphene and SiC. C1s spectra in XPS shows decrease in C = C graphitic peak and increase in interfacial layer following ion irradiation. Reduction in monolayer coverage of graphene after ion irradiation was observed by Scanning electron microscopy (SEM). Further, UV-Visible spectroscopy showed increase in absorbance of EG on SiC at increasing fluence. I-V characterization showed fluence dependent increase in resistance from 62.9 O in pristine sample to 480.1 Omega in sample irradiated at 6.6 x 10(12) ions/cm(2) fluence. The current study demonstrates how SHI irradiation can be used to tailor optoelectronic applicability of EG on SiC.

  • 15.
    Galeckas, A.
    et al.
    University of Oslo, Department of Physics, Centre for Materials Science and Nanotechnology, PO Box 1048 Blindern, Oslo, Norway.
    Carvalho, P.A.
    SINTEF Materials and Chemistry, Forskningsveien 1, Oslo, Norway.
    Ma, Q.B.
    University of Oslo, Department of Physics, Centre for Materials Science and Nanotechnology, PO Box 1048 Blindern, Oslo, Norway.
    Azarov, A.
    University of Oslo, Department of Physics, Centre for Materials Science and Nanotechnology, PO Box 1048 Blindern, Oslo, Norway.
    Hovden, S.
    SINTEF Materials and Chemistry, Forskningsveien 1, Oslo, Norway.
    Thøgersen, A.
    SINTEF Materials and Chemistry, Forskningsveien 1, Oslo, Norway.
    Wright, D.N.
    SINTEF ICT, Forskningsveien 1, Oslo, Norway.
    Diplas, S.
    SINTEF Materials and Chemistry, Forskningsveien 1, Oslo, Norway.
    Løvvik, O.M.
    SINTEF Materials and Chemistry, Forskningsveien 1, Oslo, Norway.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Svensson, B.G.
    University of Oslo, Department of Physics, Centre for Materials Science and Nanotechnology, PO Box 1048 Blindern, Oslo, Norway.
    Optical and microstructural investigation of heavy B-doping effects in sublimation-grown 3C-SiC2018Ingår i: Materials Science Forum, Trans Tech Publications Ltd , 2018, Vol. 924 MSF, s. 221-224Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, a complementary microstructural and optical approach is used to define processing conditions favorable for the formation of deep boron-related acceptor centers that may provide a pathway for achieving an intermediate band behavior in highly B-doped 3C-SiC. The crystallinity, boron solubility and precipitation mechanisms in sublimation-grown 3C-SiC crystals implanted to 1-3 at.% B concentrations were investigated by STEM. The revealed defect formation and boron precipitation trends upon thermal treatment in the range 1100-2000oC have been crosscorrelated with the optical characterization results provided by imaging PL spectroscopy. We discuss optical activity of the implanted B ions in terms of both shallow acceptors and deep D-centers, a complex formed by a boron atom and a carbon vacancy, and associate the observed spectral developments upon annealing with the strong temperature dependence of the D-center formation efficiency, which is further enhanced by the presence of implantation-induced defects. © 2018 Trans Tech Publications, Switzerland.

  • 16.
    Jokubavicius, Valdas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Silicon Carbide Surface Cleaning and Etching2018Ingår i: Advancing Silicon Carbide Electronics Technology I / [ed] Konstantinos Zekentes and Konstantin Vasilevskiy, Materials Research Forum LLC , 2018, s. 1-26Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Silicon carbide (SiC) surface cleaning and etching (wet, electrochemical, thermal) are important technological processes in preparation of SiC wafers for crystal growth, defect analysis or device processing. While removal of organic, particulate and metallic contaminants by chemical cleaning is a routine process in research and industrial production, the etching which, in addition to structural defects analysis, can also be used to modify wafer surface structure, is very interesting for development of innovative device concepts. In this book chapter we review SiC chemical cleaning and etching procedures and present perspectives of SiC etching for new device development.

  • 17.
    Kaushik, Priya Darshni
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Jamia Millia Islamia, India.
    Aziz, Anver
    Jamia Millia Islamia, India.
    Siddiqui, Azher M.
    Jamia Millia Islamia, India.
    Lakshmi, G. B. V. S.
    Jawaharlal Nehru Univ, India.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholamreza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Structural and Optical Modification in 4H-SiC Following 30 keV Silver ion irradiation2018Ingår i: INTERNATIONAL CONFERENCE ON INVENTIVE RESEARCH IN MATERIAL SCIENCE AND TECHNOLOGY (ICIRMCT 2018), AMER INST PHYSICS , 2018, Vol. 1966, artikel-id UNSP 020035-1Konferensbidrag (Refereegranskat)
    Abstract [en]

    The market of high power, high frequency and high temperature based electronic devices is captured by SiC due to its superior properties like high thermal conductivity and high sublimation temperature and also due to the limitation of silicon based electronics in this area. There is a need to investigate effect of ion irradiation on SiC due to its application in outer space as outer space is surrounded both by low and high energy ion irradiations. In this work, effect of low energy ion irradiation on structural and optical property of 4H-SiC is investigated. ATR-FTIR is used to study structural modification and UV-Visible spectroscopy is used to study optical modifications in 4H-SiC following 30 keV Ag ion irradiation. FTIR showed decrease in bond density of SiC along the ion path (track) due to the creation of point defects. UV-Visible absorption spectra showed decrease in optical band gap from 3.26 eV to 2.9 eV. The study showed degradation of SiC crystallity and change in optical band gap following low energy ion irradiation and should be addressed while fabricationg devices based on SiC for outer space application. Additionally, this study provides a platform for introducing structural and optical modification in 4H-SiC using ion beam technology in a controlled manner.

  • 18.
    Ma, Quanbao
    et al.
    University of Oslo.
    Carvalho, Patricia
    SINTEF.
    Galeckas, Augustinas
    University of Oslo.
    Alexander, Azarov
    University of Oslo.
    Hovden, Sigurd
    SINTEF.
    Thøgersen, Annett
    SINTEF.
    Wright, Daniel N.
    SINTEF ICT.
    Diplas, Spyros
    SINTEF.
    Løvvik, Ole M.
    SINTEF.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Svensson, Bengt G.
    University of Oslo.
    Characterization of B-Implanted 3C-SiC for Intermediate Band Solar Cells2017Ingår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 897, s. 299-302Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sublimation-grown 3C-SiC crystals were implanted with B ions at elevated temperature (400 °C) using multiple energies (100 to 575 keV) with a total dose of 1.3×1017 atoms/cm2 in order to form intermediate band (IB) in 3C-SiC. The samples were then annealed at 1400 °C for 60 min. An anomalous area in the center was observed in the PL emission pattern. The SIMS analysis indicated that the B concentration was the same both within and outside the anomalous area. The buried boron box-like concentration profile can reach ~3×1021 cm-3 in the plateau region. In the anomalous area a broad emission band (possible IB) emerges at around ~1.7-1.8 eV, which may be associated with B-precipitates having a sufficiently high density.

  • 19.
    Yakimova, Rositsa
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Gueorguiev Ivanov, Ivan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Vines, Lasse
    University of Oslo, Norway.
    Linnarsson, Margareta K.
    KTH Royal Institute Technology, Sweden.
    Gällström, Andreas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Giannazzo, Filippo
    CNR, Italy.
    Roccaforte, Fabrizio
    CNR, Italy.
    Wellmann, Peter
    University of Erlangen Nurnberg, Germany.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Growth, Defects and Doping of 3C-SiC on Hexagonal Polytypes2017Ingår i: ECS Journal of Solid State Science and Technology, ISSN 2162-8769, E-ISSN 2162-8777, Vol. 6, nr 10, s. P741-P745Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Technologies for the growth of 3C-SiC with crystalline quality and crystal size similar to hexagonal counterparts (6H- or 4H-SiC) are still at the laboratory stage. There are several challenges in the control of polytype stability and formation of structural defects which have to be eliminated to reveal the full potential of this material. Nevertheless, 3C-SiC has been explored for various energy, environment and biomedical applications which significantly benefit from the intrinsic semiconductor properties of this material. The future of 3C-SiC and its applications depends on the advances which will be made in improving crystalline quality, enlarging crystal size and controlling doping levels which have not been entirely explored due to the lack of high quality 3C-SiC substrates. This paper reviews recent progress in growth and doping of thick 3C-SiC layers on hexagonal SiC substrates using sublimation epitaxy. It covers the growth process on off-axis substrates and defects occurrence, as well as the issue of obtaining high resistivity material. (c) 2017 The Electrochemical Society. All rights reserved.

  • 20.
    Yakimova, Rositsa
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Vines, L.
    Univ Oslo, Norway.
    Linnarsson, M. K.
    KTH Royal Inst Technol, Sweden.
    Gällström, Andreas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Giannazzo, F.
    CNR IMM, Italy.
    Roccaforte, F.
    CNR IMM, Italy.
    Wellmann, P.
    Univ Erlangen Nurnberg, Germany.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Growth, Defects and Doping of 3C-SiC on Hexagonal Polytypes2017Ingår i: GALLIUM NITRIDE AND SILICON CARBIDE POWER TECHNOLOGIES 7, ELECTROCHEMICAL SOC INC , 2017, Vol. 80, nr 7, s. 107-115Konferensbidrag (Refereegranskat)
    Abstract [en]

    Technologies for the growth of 3C-SiC with crystalline quality and crystal size similar to hexagonal counterparts (6H-or 4H-SiC) are still at the laboratory stage. There are several challenges in the control of polytype stability and formation of structural defects which have to be eliminated to reveal the full potential of this material. Nevertheless, 3C-SiC has been explored for various energy, environment and biomedical applications which significantly benefit from the intrinsic semiconductor properties of this material. The future of 3C-SiC and its applications depends on the advances which will be made in improving crystalline quality, enlarging crystal size and controlling doping levels which have not been entirely explored due to the lack of high quality 3C-SiC substrates. This paper reviews recent progress in growth and doping of thick 3C-SiC layers on hexagonal SiC substrates using sublimation epitaxy. It covers the growth process on off-axis substrates and defects occurrence, as well as the issue of obtaining high resistivity material.

  • 21.
    Christle, David J.
    et al.
    University of Chicago, IL 60637 USA.
    Klimov, Paul V.
    University of Chicago, IL 60637 USA.
    de las Casas, Charles F.
    University of Chicago, IL 60637 USA.
    Szasz, Krisztian
    Hungarian Academic Science, Hungary.
    Ivády, Viktor
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. Hungarian Academic Science, Hungary.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Ul-Hassan, Jawad
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Koehl, William F.
    University of Chicago, IL 60637 USA.
    Ohshima, Takeshi
    National Institute Quantum and Radiol Science and Technology, Japan.
    Nguyen, Son Tien
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Janzén, Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Gali, Adam
    Hungarian Academic Science, Hungary; Budapest University of Technology and Econ, Hungary.
    Awschalom, David D.
    University of Chicago, IL 60637 USA.
    Isolated Spin Qubits in SiC with a High-Fidelity Infrared Spin-to-Photon Interface2017Ingår i: Physical Review X, ISSN 2160-3308, E-ISSN 2160-3308, Vol. 7, nr 2, artikel-id 21046Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The divacancies in SiC are a family of paramagnetic defects that show promise for quantum communication technologies due to their long-lived electron spin coherence and their optical addressability at near-telecom wavelengths. Nonetheless, a high-fidelity spin-photon interface, which is a crucial prerequisite for such technologies, has not yet been demonstrated. Here, we demonstrate that such an interface exists in isolated divacancies in epitaxial films of 3C-SiC and 4H-SiC. Our data show that divacancies in 4H-SiC have minimal undesirable spin mixing, and that the optical linewidths in our current sample are already similar to those of recent remote entanglement demonstrations in other systems. Moreover, we find that 3C-SiC divacancies have a millisecond Hahn-echo spin coherence time, which is among the longest measured in a naturally isotopic solid. The presence of defects with these properties in a commercial semiconductor that can be heteroepitaxially grown as a thin film on Si shows promise for future quantum networks based on SiC defects.

  • 22.
    Vagin, Mikhail
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Sekretareva, Alina
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten. Department of Chemistry, Stanford University, Stanford, USA.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Håkansson, Anna
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Iakimov, Tihomir
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Graphensic AB, Teknikringen 1F, Linköping, Sweden.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Graphensic AB, Teknikringen 1F, Linköping, Sweden.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Graphensic AB, Teknikringen 1F, Linköping, Sweden.
    Lundström, Ingemar
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Mats
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemiska och optiska sensorsystem. Linköpings universitet, Tekniska fakulteten.
    Monitoring of epitaxial graphene anodization2017Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 238, s. 91-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Anodization of a graphene monolayer on silicon carbide was monitored with electrochemical impedance spectroscopy. Structural and functional changes of the material were observed by Raman spectroscopy and voltammetry. A 21 fold increase of the specific capacitance of graphene was observed during the anodization. An electrochemical kinetic study of the Fe(CN)(6)(3) (/4) redox couple showed a slow irreversible redox process at the pristine graphene, but after anodization the reaction rate increased by several orders of magnitude. On the other hand, the Ru(NH3) (3+/2+)(6) redox couple proved to be insensitive to the activation process. The results of the electron transfer kinetics correlate well with capacitance measurements. The Raman mapping results suggest that the increased specific capacitance of the anodized sample is likely due to a substantial increase of electron doping, induced by defect formation, in the monolayer upon anodization. The doping concentration increased from less than 1 x 10(13) of the pristine graphene to 4-8 x 10(13) of the anodized graphene. (C) 2017 Elsevier Ltd. All rights reserved.

  • 23.
    Schuh, P.
    et al.
    FAU Erlangen Nurnberg, Germany.
    Schoeler, M.
    FAU Erlangen Nurnberg, Germany.
    Wilhelm, M.
    FAU Erlangen Nurnberg, Germany.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Litrico, G.
    Lab Nazl Sud, Italy.
    La Via, F.
    CNR, Italy.
    Mauceri, M.
    Lpe SPA, Italy.
    Wellmann, P. J.
    FAU Erlangen Nurnberg, Germany.
    Sublimation growth of bulk 3C-SiC using 3C-SiC-on-Si (100) seeding layers2017Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 478, s. 159-162Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have developed a transfer process of 3C-SiC-on-Si (100) seeding layers grown by chemical vapor deposition onto a poly-or single-crystalline SiC carrier. Applying subsequent sublimation growth of SiC in [100] direction resulting in large area crystals (up to approximate to 11 cm(2)) with a thickness of up to approximately 850 lm. Raman spectroscopy, Laue X-ray diffraction and electron-backscattering-diffraction revealed a high material quality in terms of single-crystallinity without secondary polytype inclusions, antiphase boundaries or double positioning grain boundaries. Defects in the bulk grown 3C-SiC, like protrusions with surrounding stressed areas, stem from the epitaxial seeding layer. The presented concept using 3C-SiC-on-Si seeding layers reveals a path for the growth of bulk 3C-SiC crystals. (C) 2017 Elsevier B.V. All rights reserved.

  • 24.
    Kaushik, Priya Darshni
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Jamia Millia Islamia, India.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Lin, Pin-Cheng
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Kaur, Gurpreet
    University of Delhi, India.
    Eriksson, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska fakulteten.
    Lakshmi, G. B. V. S.
    Interuniv Accelerator Centre, India.
    Avasthi, D. K.
    Interuniv Accelerator Centre, India; Amity Institute Nanotechnol, India.
    Gupta, Vinay
    University of Delhi, India.
    Aziz, Anver
    Jamia Millia Islamia, India.
    Siddiqui, Azher M.
    Jamia Millia Islamia, India.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholamreza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Surface functionalization of epitaxial graphene on SiC by ion irradiation for gas sensing application2017Ingår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 403, s. 707-716Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, surface functionalization of epitaxial graphene grown on silicon carbide was performed by ion irradiation to investigate their gas sensing capabilities. Swift heavy ion irradiation using 100 MeV silver ions at four varying fluences was implemented on epitaxial graphene to investigate morphological and structural changes and their effects on the gas sensing capabilities of graphene. Sensing devices are expected as one of the first electronic applications using graphene and most of them use functionalized surfaces to tailor a certain function. In our case, we have studied irradiation as a tool to achieve functionalization. Morphological and structural changes on epitaxial graphene layers were investigated by atomic force microscopy, Raman spectroscopy, Raman mapping and reflectance mapping. The surface morphology of irradiated graphene layers showed graphene folding, hillocks, and formation of wrinkles at highest fluence (2 x 10(13) ions/cm(2)). Raman spectra analysis shows that the graphene defect density is increased with increasing fluence, while Raman mapping and reflectance mapping show that there is also a reduction of monolayer graphene coverage. The samples were investigated for ammonia and nitrogen dioxide gas sensing applications. Sensors fabricated on pristine and irradiated samples showed highest gas sensing response at an optimal fluence. Our work provides new pathways for introducing defects in controlled manner in epitaxial graphene, which can be used not only for gas sensing application but also for other applications, such as electrochemical, biosensing, magnetosensing and spintronic applications. (C) 2017 Elsevier B.V. All rights reserved.

  • 25.
    Lu, Weifang
    et al.
    Technical University of Denmark, Denmark.
    Ou, Yiyu
    Technical University of Denmark, Denmark.
    Maria Fiordaliso, Elisabetta
    Technical University of Denmark, Denmark.
    Iwasa, Yoshimi
    Meijo University, Japan.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Kamiyama, Satoshi
    Meijo University, Japan.
    Michael Petersen, Paul
    Technical University of Denmark, Denmark.
    Ou, Haiyan
    Technical University of Denmark, Denmark.
    White Light Emission from Fluorescent SiC with Porous Surface2017Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikel-id 9798Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report for the first time a NUV light to white light conversion in a N-B co-doped 6H-SiC (fluorescent SiC) layer containing a hybrid structure. The surface of fluorescent SiC sample contains porous structures fabricated by anodic oxidation method. After passivation by 20 nm thick Al2O3, the photoluminescence intensity from the porous layer was significant enhanced by a factor of more than 12. Using a porous layer of moderate thickness (similar to 10 mu m), high-quality white light emission was realized by combining the independent emissions of blue-green emission from the porous layer and yellow emission from the bulk fluorescent SiC layer. A high color rendering index of 81.1 has been achieved. Photoluminescence spectra in porous layers fabricated in both commercial n-type and lab grown N-B co-doped 6H-SiC show two emission peaks centered approximately at 460 nm and 530 nm. Such blue-green emission phenomenon can be attributed to neutral oxygen vacancies and interface C-related surface defects generated dring anodic oxidation process. Porous fluorescent SiC can offer a great flexibility in color rendering by changing the thickness of porous layer and bulk fluorescent layer. Such a novel approach opens a new perspective for the development of high performance and rare-earth element free white light emitting materials.

  • 26.
    Ma, Quanbao
    et al.
    University of Oslo, Norway.
    Galeckas, Augustinas
    University of Oslo, Norway.
    Alexander, Azarov
    University of Oslo, Norway.
    Thøgersen, Annett
    SINTEF Materials and Chemistry, Norway.
    Carvalho, Patricia
    SINTEF Materials and Chemistry, Norway.
    Wright, Daniel N.
    SINTEF ICT, Norway.
    Diplas, Spyros
    SINTEF Materials and Chemistry, Norway.
    Løvvik, Ole M.
    SINTEF Materials and Chemistry, Norway.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Liu, Xinyu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Svensson, Bengt G.
    University of Oslo, Norway.
    Boron-implanted 3C-SiC for intermediate band solar cells2016Ingår i: Silicon Carbide and Related Materials 2015, 2016, Vol. 858, s. 291-294Konferensbidrag (Refereegranskat)
    Abstract [en]

    Sublimation-grown 3C-SiC crystals were implanted with 2 atomic percent of boron ions at elevated temperature (400 °C) using multiple energies (100 to 575 keV) with a total dose of 8.5×1016 atoms/cm2. The samples were then annealed at 1400, 1500 and 1600 °C for 1h at each temperature. The buried boron box-like concentration profile can reach ~2×1021 cm-3 in the plateau region. The optical activity of the incorporated boron atoms was deduced from the evolution in absorption and emission spectra, indicating possible pathway for achieving an intermediate band behavior in boron doped 3C-SiC at sufficiently high dopant concentrations.                    

  • 27.
    Syväjärvi, Mikael
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Ma, Quanbao
    University of Oslo, Norway.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Galeckas, Augustinas
    University of Oslo, Norway.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Liu, Xinyu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Jansson, Mattias
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material. Linköpings universitet, Tekniska fakulteten.
    Wellmann, Peter
    University of Erlangen Nurnberg, Germany.
    Linnarsson, Margareta
    KTH Royal Institute Technology, Sweden.
    Runde, Paal
    St Gobain Ceram Mat AS, Norway.
    Andre Johansen, Bertil
    St Gobain Ceram Mat AS, Norway.
    Thogersen, Annett
    SINTEF Mat and Chemistry, Norway.
    Diplas, Spyros
    SINTEF Mat and Chemistry, Norway.
    Almeida Carvalho, Patricia
    SINTEF Mat and Chemistry, Norway.
    Martin Lovvik, Ole
    SINTEF Mat and Chemistry, Norway.
    Nilsen Wright, Daniel
    SINTEF ICT, Norway.
    Yu Azarov, Alexander
    University of Oslo, Norway.
    Svensson, Bengt G.
    University of Oslo, Norway.
    Cubic silicon carbide as a potential photovoltaic material2016Ingår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 145, s. 104-108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work we present a significant advancement in cubic silicon carbide (3C-SiC) growth in terms of crystal quality and domain size, and indicate its potential use in photovoltaics. To date, the use of 3C-SiC for photovoltaics has not been considered due to the band gap of 2.3 eV being too large for conventional solar cells. Doping of 3C-SiC with boron introduces an energy level of 0.7 eV above the valence band. Such energy level may form an intermediate band (IB) in the band gap. This IB concept has been presented in the literature to act as an energy ladder that allows absorption of sub-bandgap photons to generate extra electron-hole pairs and increase the efficiency of a solar cell. The main challenge with this concept is to find a materials system that could realize such efficient photovoltaic behavior. The 3C-SiC bandgap and boron energy level fits nicely into the concept, but has not been explored for an IB behavior. For a long time crystalline 3C-SiC has been challenging to grow due to its metastable nature. The material mainly consists of a large number of small domains if the 3C polytype is maintained. In our work a crystal growth process was realized by a new approach that is a combination of initial nucleation and step-flow growth. In the process, the domains that form initially extend laterally to make larger 3C-SiC domains, thus leading to a pronounced improvement in crystalline quality of 3C-SiC. In order to explore the feasibility of IB in 3C-SiC using boron, we have explored two routes of introducing boron impurities; ion implantation on un-doped samples and epitaxial growth on un-doped samples using pre-doped source material. The results show that 3C-SiC doped with boron is an optically active material, and thus is interesting to be further studied for IB behavior. For the ion implanted samples the crystal quality was maintained even after high implantation doses and subsequent annealing. The same was true for the samples grown with pre-doped source material, even with a high concentration of boron impurities. We present optical emission and absorption properties of as-grown and boron implanted 3C-SiC. The low-temperature photoluminescence spectra indicate the formation of optically active deep boron centers, which may be utilized for achieving an IB behavior at sufficiently high dopant concentrations. We also discuss the potential of boron doped 3C-SiC base material in a broader range of applications, such as in photovoltaics, biomarkers and hydrogen generation by splitting water. (C) 2015 Elsevier B.V. All rights reserved.

  • 28.
    Rawat, Niharika
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    Mishra, Prashant
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    Ashaduzzaman, Md
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    Yazdi, R
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Michael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Turner, Anthony
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    Tiwari, Ashutosh
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten. Tekidag AB UCS Mjärdevi Science Park, Sweden.
    Fabrication of an atom-thick graphene bioanode for biofuel cell applications2016Ingår i: Biosensors 2016 – The World Congress on Biosensors, Gothenburg, Sweden, 25-27 May 2016, Elsevier, 2016Konferensbidrag (Övrigt vetenskapligt)
  • 29.
    Jokubavicius, Valdas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Liu, Xinyu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholamreza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Growth optimization and applicability of thick on-axis SiC layers using sublimation epitaxy in vacuum2016Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 448, s. 51-57Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate growth of thick SiC layers (100–200 µm) on nominally on-axis hexagonal substrates using sublimation epitaxy in vacuum (10−5 mbar) at temperatures varying from 1700 to 1975 °C with growth rates up to 270 µm/h and 70 µm/h for 6H- and 4H–SiC, respectively. The stability of hexagonal polytypes are related to process growth parameters and temperature profile which can be engineered using different thermal insulation materials and adjustment of the induction coil position with respect to the graphite crucible. We show that there exists a range of growth rates for which single-hexagonal polytype free of foreign polytype inclusions can be maintained. Further on, foreign polytypes like 3C–SiC can be stabilized by moving out of the process window. The applicability of on-axis growth is demonstrated by growing a 200 µm thick homoepitaxial 6H–SiC layer co-doped with nitrogen and boron in a range of 1018 cm−3 at a growth rate of about 270 µm/h. Such layers are of interest as a near UV to visible light converters in a monolithic white light emitting diode concept, where subsequent nitride-stack growth benefits from the on-axis orientation of the SiC layer.

  • 30.
    Pallon, J.
    et al.
    Lund University, Sweden.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Graphens AB, Teknikringen 1F, SE-58330 Linkoping, Sweden.
    Wang, Q.
    ACREO Swedish ICT AB, Sweden.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Graphens AB, Teknikringen 1F, SE-58330 Linkoping, Sweden.
    Iakimov, Tihomir
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Graphens AB, Teknikringen 1F, SE-58330 Linkoping, Sweden.
    Elfman, M.
    Lund University, Sweden.
    Kristiansson, P.
    Lund University, Sweden.
    Nilsson, E. J. C.
    Lund University, Sweden.
    Ros, L.
    Lund University, Sweden.
    Ion beam evaluation of silicon carbide membrane structures intended for particle detectors2016Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 371, s. 132-136Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin ion transmission detectors can be used as a part of a telescope detector for mass and energy identification but also as a pre-cell detector in a microbeam system for studies of biological effects from single ion hits on individual living cells. We investigated a structure of graphene on silicon carbide (SiC) with the purpose to explore a thin transmission detector with a very low noise level and having mechanical strength to act as a vacuum window. In order to reach very deep cavities in the SiC wafers for the preparation of the membrane in the detector, we have studied the Inductive Coupled Plasma technique to etch deep circular cavities in 325 mu m prototype samples. By a special high temperature process the outermost layers of the etched SiC wafers were converted into a highly conductive graphitic layer. The produced cavities were characterized by electron microscopy, optical microscopy and proton energy loss measurements. The average membrane thickness was found to be less than 40 mu m, however, with a slightly curved profile. Small spots representing much thinner membrane were also observed and might have an origin in crystal defects or impurities. Proton energy loss measurement (also called Scanning Transmission Ion Microscopy, STIM) is a well suited technique for this thickness range. This work presents the first steps of fabricating a membrane structure of SiC and graphene which may be an attractive approach as a detector due to the combined properties of SiC and graphene in a monolithic materials structure. (C) 2015 Elsevier B.V. All rights reserved.

  • 31.
    Lu, Wei Fang
    et al.
    Technical University of Denmark.
    Ou, Yiyu
    Technical University of Denmark.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Fadi, lAhmed
    Technical University of Denmark.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Buschmann, Volker
    PicoQuant GmbH, Rudower Chaussee 29, 12489 Berlin, Germany.
    Rüttinger, Steffen
    PicoQuant GmbH, Rudower Chaussee 29, 12489 Berlin, Germany.
    Petersen, Paul Michael
    Technical University of Denmark.
    Ou, Haiyan
    Technical University of Denmark.
    Photoluminescence enhancement in nano-textured fluorescent SiC passivated by atomic layer deposited Al2O3 films2016Ingår i: Silicon Carbide and Related Materials 2015, 2016, Vol. 858, s. 493-496Konferensbidrag (Refereegranskat)
    Abstract [en]

    The influence of thickness of atomic layer deposited Al2O3 films on nanotextured fluorescent 6H-SiC passivation is investigated. The passivation effect on the light emission has been characterized by photoluminescence and time-resolved photoluminescence at room temperature. The results show that 20nm thickness of Al2O3 layer is favorable to observe a large photoluminescence enhancement (25.9%) and long carrier lifetime (0.86ms). This is a strong indication for an interface hydrogenation that takes place during post-thermal annealing. These result show that an Al2O3 layer could serve as passivation in fluorescent SiC based white LEDs applications.

  • 32.
    Yang, M.
    et al.
    University of Toulouse, France.
    Couturaud, O.
    University of Montpellier, France.
    Desrat, W.
    University of Montpellier, France.
    Consejo, C.
    University of Montpellier, France.
    Kazazis, D.
    University of Paris Saclay, France; Paul Scherrer Institute, Switzerland.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Goiran, M.
    University of Toulouse, France.
    Beard, J.
    University of Toulouse, France.
    Frings, P.
    University of Toulouse, France.
    Pierre, M.
    University of Toulouse, France.
    Cresti, A.
    University of Grenoble Alpes, France; CNRS, France.
    Escoffier, W.
    University of Toulouse, France.
    Jouault, B.
    University of Montpellier, France.
    Puddle-Induced Resistance Oscillations in the Breakdown of the Graphene Quantum Hall Effect2016Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 117, nr 23, artikel-id 237702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the stability of the quantum Hall plateau in wide Hall bars made from a chemically gated graphene film grown on SiC. The v = 2 quantized plateau appears from fields B similar or equal to 5 T and persists up to B similar or equal to 80 T. At high current density, in the breakdown regime, the longitudinal resistance oscillates with a 1/B periodicity and an anomalous phase, which we relate to the presence of additional electron reservoirs. The high field experimental data suggest that these reservoirs induce a continuous increase of the carrier density up to the highest available magnetic field, thus enlarging the quantum plateaus. These in-plane inhomogeneities, in the form of high carrier density graphene pockets, modulate the quantum Hall effect breakdown and decrease the breakdown current.

  • 33.
    Sun, Jianwu
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Gao, L.
    Department of Chemical Engineering and Chemistry, Eindhoven University of of Technology, P.O. Box 513, Eindhoven, Netherlands.
    Booker, Ian Don
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Jansson, Mattias
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material. Linköpings universitet, Tekniska fakulteten.
    Liu, Xinyu
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Hofmann, J.P.
    Department of Chemical Engineering and Chemistry, Eindhoven University of of Technology, P.O. Box 513, Eindhoven, Netherlands.
    Hensen, E.J.M.
    Department of Chemical Engineering and Chemistry, Eindhoven University of of Technology, P.O. Box 513, Eindhoven, Netherlands.
    Linnarsson, M.
    School of Information and Communication Technology, KTH Royal Institute of Technology, Kista, Sweden.
    Wellmann, P.
    Department of Materials Science 6, University of of Erlangen-Nuremberg, Martensstr. 7, Erlangen, Germany.
    Ramiro, I.
    Instituto de Energía Solar, Universidad Politécnica de Madrid, E.T.S.I. Telecomunicación, Av. De la Complutense 30, Madrid, Spain.
    Marti, A.
    Instituto de Energía Solar, Universidad Politécnica de Madrid, E.T.S.I. Telecomunicación, Av. De la Complutense 30, Madrid, Spain.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Solar driven energy conversion applications based on 3C-SiC2016Ingår i: Materials Science Forum, Trans Tech Publications Ltd , 2016, Vol. 858, s. 1028-1031Konferensbidrag (Refereegranskat)
    Abstract [en]

    There is a strong and growing worldwide research on exploring renewable energy resources. Solar energy is the most abundant, inexhaustible and clean energy source, but there are profound material challenges to capture, convert and store solar energy. In this work, we explore 3C-SiC as an attractive material towards solar-driven energy conversion applications: (i) Boron doped 3C-SiC as candidate for an intermediate band photovoltaic material, and (ii) 3C-SiC as a photoelectrode for solar-driven water splitting. Absorption spectrum of boron doped 3C-SiC shows a deep energy level at ~0.7 eV above the valence band edge. This indicates that boron doped 3C-SiC may be a good candidate as an intermediate band photovoltaic material, and that bulk like 3C-SiC can have sufficient quality to be a promising electrode for photoelectrochemical water splitting. © 2016 Trans Tech Publications, Switzerland.

  • 34.
    Jokubavicius, Valdas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholamreza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Ivanov, Ivan G.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Niu, Yuran
    Max Lab, Lund University.
    Zakharov, Alexei
    Max Lab, Lund University.
    Lakimov, Tihomir
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Surface engineering of SiC via sublimation etching2016Ingår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 390, s. 816-822Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a technique for etching of SiC which is based on sublimation and can be used to modify the morphology and reconstruction of silicon carbide surface for subsequent epitaxial growth of various materials, for example graphene. The sublimation etching of 6H-, 4H- and 3C-SiC was explored in vacuum (10−5 mbar) and Ar (700 mbar) ambient using two different etching arrangements which can be considered as Si-C and Si-C-Ta chemical systems exhibiting different vapor phase stoichiometry at a given temperature. The surfaces of different polytypes etched under similar conditions are compared and the etching mechanism is discussed with an emphasis on the role of tantalum as a carbon getter. To demonstrate applicability of such etching process graphene nanoribbons were grown on a 4H-SiC surface that was pre-patterned using the thermal etching technique presented in this study.

  • 35.
    Lu, Weifang
    et al.
    Technical University of Denmark, Denmark.
    Ou, Yiyu
    Technical University of Denmark, Denmark.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Fadil, Ahmed
    Technical University of Denmark, Denmark.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Michael Petersen, Paul
    Technical University of Denmark, Denmark.
    Ou, Haiyan
    Technical University of Denmark, Denmark.
    Surface passivation of nano-textured fluorescent SiC by atomic layer deposited TiO22016Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 91, nr 7, s. 074001-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nano-textured surfaces have played a key role in optoelectronic materials to enhance the light extraction efficiency. In this work, morphology and optical properties of nano-textured SiC covered with atomic layer deposited (ALD) TiO2 were investigated. In order to obtain a high quality surface for TiO2 deposition, a three-step cleaning procedure was introduced after RIE etching. The morphology of anatase TiO2 indicates that the nano-textured substrate has a much higher surface nucleated grain density than a flat substrate at the beginning of the deposition process. The corresponding reflectance increases with TiO2 thickness due to increased surface diffuse reflection. The passivation effect of ALD TiO2 thin film on the nano-textured fluorescent 6H-SiC sample was also investigated and a PL intensity improvement of 8.05% was obtained due to the surface passivation.

  • 36.
    Noor-Ul-Ain,
    et al.
    Islamia University of Bahawalpur, Pakistan.
    Eriksson, Martin O
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Schmidt, Susann
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Asghar, M.
    Islamia University of Bahawalpur, Pakistan.
    Lin, Pin-Cheng
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholamreza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Tuning the Emission Energy of Chemically Doped Graphene Quantum Dots2016Ingår i: NANOMATERIALS, ISSN 2079-4991, Vol. 6, nr 11, artikel-id 198Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tuning the emission energy of graphene quantum dots (GQDs) and understanding the reason of tunability is essential for the GOD function in optoelectronic devices. Besides material-based challenges, the way to realize chemical doping and band gap tuning also pose a serious challenge. In this study, we tuned the emission energy of GQDs by substitutional doping using chlorine, nitrogen, boron, sodium, and potassium dopants in solution form. Photoluminescence data obtained from (Cl- and N-doped) GQDs and (B-, Na-, and K-doped) GQDs, respectively exhibited red- and blue-shift with respect to the photoluminescence of the undoped GQDs. X-ray photoemission spectroscopy (XPS) revealed that oxygen functional groups were attached to GQDs. We qualitatively correlate red-shift of the photoluminescence with the oxygen functional groups using literature references which demonstrates that more oxygen containing groups leads to the formation of more defect states and is the reason of observed red-shift of luminescence in GQDs. Further on, time resolved photoluminescence measurements of Cl- and N-GQDs demonstrated that Cl substitution in GQDs has effective role in radiative transition whereas in N-GQDs leads to photoluminescence (PL) quenching with non-radiative transition to ground state. Presumably oxidation or reduction processes cause a change of effective size and the bandgap.

  • 37.
    Rankl, Dominik
    et al.
    Crystal Growth Lab, University of Erlangen.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Wellmann, Peter
    Crystal Growth Lab, University of Erlangen.
    Quantitative Study on the Role of Supersaturation during Sublimation Growth on the Yield of 50 mm diameter 3C-SiC2015Ingår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 821, s. 77-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have investigated the growth of 3C-SiC using sublimation growth in the temperature range from 1800°C to 1950°C. The supersaturation was determined using numerical modeling of the temperature field and gas phase composition by applying quasi-equilibrium thermodynamic conditions. Analysis of the 3C-SiC yield was carried out by optical microscopy, optical absorption, Raman spectroscopy and x-ray analysis. Quantitative data on supersaturation are compared with most stable 3C-SiC nucleation and growth condition. Finally the application to large area growth in a physical vapor transport growth reactor is briefly addressed.

  • 38.
    Jokubavicius, Valdas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholam Reza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Liljedahl, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Liu, Xinyu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Philipp, Schuh
    University of Erlangen, Erlangen, Germany.
    Wilhelm, Martin
    University of Erlangen, Erlangen, Germany.
    Wellmann, Peter
    University of Erlangen, Erlangen, Germany.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Single Domain 3C-SiC Growth on Off-Oriented 4H-SiC Substrates2015Ingår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 15, nr 6, s. 2940-2947Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated the formation of structural defects in thick (∼1 mm) cubic silicon carbide (3C-SiC) layers grown on off-oriented 4H-SiC substrates via a lateral enlargement mechanism using different growth conditions. A two-step growth process based on this technique was developed, which provides a trade-off between the growth rate and the number of defects in the 3C-SiC layers. Moreover, we demonstrated that the two-step growth process combined with a geometrically controlled lateral enlargement mechanism allows the formation of a single 3C-SiC domain which enlarges and completely covers the substrate surface. High crystalline quality of the grown 3C-SiC layers is confirmed using high resolution X-ray diffraction and low temperature photoluminescence measurements.

  • 39.
    Karlsson, Mikael
    et al.
    Department of Sensor System, Acreo Swedish ICT AB, Box 1070, SE-16440 Kista, Sweden; Department of Materials and Nano Physics, KTH-Royal Institute of Technology, Kista, Sweden .
    Wang, Qin
    Department of Sensor System, Acreo Swedish ICT AB, Box 1070, SE-16440 Kista, Sweden.
    Zhao, Yichen
    Department of Materials and Nano Physics, KTH-Royal Institute of Technology, Kista, Sweden.
    Zhao, Wei
    Department of Sensor System, Acreo Swedish ICT AB, Box 1070, SE-16440 Kista, Sweden; Department of Materials and Nano Physics, KTH-Royal Institute of Technology, Kista, Sweden.
    Toprak, Muhammet S.
    Department of Materials and Nano Physics, KTH-Royal Institute of Technology, Kista, Sweden.
    Iakimov, Tihomir
    Graphensic AB, Mjärdevi Science Park, Teknikringen 1F, SE-58330 Linköping, Sweden.
    Ali, Amer
    Graphensic AB, Mjärdevi Science Park, Teknikringen 1F, SE-58330 Linköping, Sweden.
    Yakimova, Rositsa
    Graphensic AB, Mjärdevi Science Park, Teknikringen 1F, SE-58330 Linköping, Sweden.
    Syväjärvi, Mikael
    Graphensic AB, Mjärdevi Science Park, Teknikringen 1F, SE-58330 Linköping, Sweden.
    Ivanov, Ivan G.
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Wafer-scale epitaxial graphene on SiC for sensing applications2015Ingår i: Micro+Nano Materials, Devices, and Systems / [ed] Benjamin J. Eggleton, Stefano Palomba, SPIE - International Society for Optical Engineering, 2015, Vol. 9668, s. 96685T-1-96685T-7Konferensbidrag (Refereegranskat)
    Abstract [en]

    The epitaxial graphene-on-silicon carbide (SiC-G) has advantages of high quality and large area coverage owing to a natural interface between graphene and SiC substrate with dimension up to 100 mm. It enables cost effective and reliable solutions for bridging the graphene-based sensors/devices from lab to industrial applications and commercialization. In this work, the structural, optical and electrical properties of wafer-scale graphene grown on 2’’ 4H semi-insulating (SI) SiC utilizing sublimation process were systemically investigated with focus on evaluation of the graphene’s uniformity across the wafer. As proof of concept, two types of glucose sensors based on SiC-G/Nafion/Glucose-oxidase (GOx) and SiC-G/Nafion/Chitosan/GOx were fabricated and their electrochemical properties were characterized by cyclic voltammetry (CV) measurements. In addition, a few similar glucose sensors based on graphene by chemical synthesis using modified Hummer’s method were also fabricated for comparison. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  • 40.
    Murugesan, Murali
    et al.
    Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Gothenburg, Sweden.
    Zanden, Carl
    Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Gothenburg, Sweden.
    Luo, Xin
    Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Gothenburg, Sweden; School of Mechatronics and Mechanical Engineering, Key Laboratory of New Displays and System Integration, Shanghai University, China .
    Ye, Lilei
    SHT Smart High-Tech AB, Gothenburg, Sweden.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Liu, Johan
    Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Gothenburg, Sweden; School of Mechatronics and Mechanical Engineering, Key Laboratory of New Displays and System Integration, Shanghai University, China .
    A carbon fiber solder matrix composite for thermalmanagement of microelectronic devices2014Ingår i: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 2, nr 35, s. 7184-7187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A carbon fiber based tin-silver-copper alloy matrix composite (CF-TIM) was developed via electrospinning of a mesophase pitch with polyimide and carbonization at 1000 °C, followed by sputter coating with titanium and gold, and alloy infiltration. The carbonized fibers, in film form, showed a thermal conductivity of ∼4 W m-1 K-1 and the CF-TIM showed an anisotropic thermal conductivity of 41 ± 2 W m-1 K-1 in-plane and 20 ± 3 W m-1 K-1 through-plane. The thermal contact resistance of the CF-TIM was estimated to be below 1 K mm2 W-1. The CF-TIM showed no reduction in effective through-plane thermal conductivity after 1000 temperature cycles, which indicates the potential use of CF-TIM in thermal management applications.

  • 41.
    Ou, Haiyan
    et al.
    Technical University of Denmark, Lyngby, Denmark .
    Ou, Yiyu
    Technical University of Denmark, Lyngby, Denmark .
    Argyraki, Aikaterini
    Technical University of Denmark, Lyngby, Denmark .
    Schimmel, Saskia
    University of Erlangen-Nuremberg, Erlangen, Germany .
    Kaiser, Michl
    University of Erlangen-Nuremberg, Erlangen, Germany .
    Wellmann, Peter
    University of Erlangen-Nuremberg, Erlangen, Germany .
    Linnarsson, Margareta
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Liljedahl, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Advances in wide bandgap SiC for optoelectronics2014Ingår i: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 87, s. 58-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Silicon carbide (SiC) has played a key role in power electronics thanks to its unique physical properties like wide bandgap, high breakdown field, etc. During the past decade, SiC is also becoming more and more active in optoelectronics thanks to the progress in materials growth and nanofabrication. This paper will review the advances in fluorescent SiC for white light-emitting diodes, covering the poly-crystalline doped SiC source material growth, single crystalline epitaxy growth of fluorescent SiC, and nanofabrication of SiC to enhance the extraction efficiency for fluorescent SiC based white LEDs.

  • 42.
    Ou, Yiyu
    et al.
    Technical University of Denmark.
    Zhu, Xiaolong
    Technical University of Denmark.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Mortensen, N. Asger
    Technical University of Denmark.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Xiao, Sanshui
    Technical University of Denmark.
    Ou, Haiyan
    Technical University of Denmark.
    Broadband Antireflection and Light Extraction Enhancement in Fluorescent SiC with Nanodome Structures2014Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, s. 4662-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate a time-efficient and low-cost approach to fabricate Si3N4 coated nanodome structures in fluorescent SiC. Nanosphere lithography is used as the nanopatterning method and SiC nanodome structures with Si3N4 coating are formed via dry etching and thin film deposition process. By using this method, a significant broadband surface antireflection and a considerable omnidirectional luminescence enhancement are obtained. The experimental observations are then supported by numerical simulations. It is believed that our fabrication method will be well suitable for large-scale production in the future.

  • 43.
    Grivickas, V.
    et al.
    Institute of Applied Research, Vilnius University, Lithuania .
    Gulbinas, K
    Institute of Applied Research, Vilnius University, Lithuania .
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Karaliunas, M.
    Institute of Applied Research, Vilnius University, Lithuania.
    Kamiyama, Satoshi
    Meijo University, Nagoya, Japan .
    Linnarsson, Margareta
    Kaiser, Michl
    University of Erlangen-Nuremberg, Germany.
    Wellmann, Peter
    University of Erlangen-Nuremberg, Germany.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Carrier Lifetimes and Influence of In-Grown Defects in N-B Co-Doped 6H-SiC2014Ingår i: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 56, nr 1, s. 012004-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The thick N-B co-doped epilayers were grown by the fast sublimation growth method and the depth-resolved carrier lifetimes have been investigated by means of the free-carrier absorption (FCA) decay under perpendicular probe-pump measurement geometry. In some samples, we optically reveal in-grown carbon inclusions and polycrystalline defects of substantial concentration and show that these defects slow down excess carrier lifetime and prevent donor-acceptor pair photo luminescence (DAP PL). A pronounced electron lifetime reduction when injection level approaches the doping level was observed. It is caused by diffusion driven non-radiative recombination. However, the influence of surface recombination is small and insignificant at 300 K.

  • 44.
    Gavryushin, V.
    et al.
    Institute of Applied Research, Vilnius University, Lithuania .
    Gulbinas, K
    Institute of Applied Research, Vilnius University, Lithuania .
    Grivickas, V.
    Institute of Applied Research, Vilnius University, Lithuania .
    Karaliunas, M.
    Institute of Applied Research, Vilnius University, Lithuania .
    Stasiūpnas, M.
    Institute of Applied Research, Vilnius University, Lithuania .
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Examination of Photoluminescence Temperature Dependencies in N-B Co-doped 6H-SiC2014Ingår i: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 56, nr 1, s. 012003-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two overlapping photoluminescent (PL) bands with a peaks (half-width) at 1.95 eV (0.45 eV) and 2.15 eV (0.25 eV), correspondingly at 300 K, are observed in heavily B-N co-doped 6H-SiC epilayers under high-level excitation condition. The low energy band dominates at low temperatures and decreases towards 300 K which is assigned to DAP emission from the nitrogen trap to the deep boron (dB) with phonon-assistance. The 2.15 eV band slightly increases with temperature and becomes comparable with the former one at 300 K. We present a modelling comprising electron de-trapping from the N-trap, i.e. calculating trapping and de-trapping probabilities. The T-dependence of the 2.15 eV band can be explained by free electron emission from the conduction band into the dB center provided by similar phonon-assistance

  • 45.
    Hens, Philip
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan. University of Marburg, Germany.
    Zakharov, Alexei A.
    Lund University, Sweden.
    Iakimov, Tihomir
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Large area buffer-free graphene on non-polar (001) cubic silicon carbide2014Ingår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 80, s. 823-829Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Graphene is, due to its extraordinary properties, a promising material for future electronic applications. A common process for the production of large area epitaxial graphene is a high temperature annealing process of atomically flat surfaces from hexagonal silicon carbide. This procedure is very promising but has the drawback of the formation of a buffer layer consisting of a graphene-like sheet, which is covalently bound to the substrate. This buffer layer degenerates the properties of the graphene above and needs to be avoided. We are presenting the combination of a high temperature process for the graphene production with a newly developed substrate of (0 0 1)-oriented cubic silicon carbide. This combination is a promising candidate to be able to supply large area homogenous epitaxial graphene on silicon carbide without a buffer layer. We are presenting the new substrate and first samples of epitaxial graphene on them. Results are shown using low energy electron microscopy and diffraction, photoelectron angular distribution and X-ray photoemission spectroscopy. All these measurements indicate the successful growth of a buffer free few layer graphene on a cubic silicon carbide surface. On our large area samples also the epitaxial relationship between the cubic substrate and the hexagonal graphene could be clarified.

  • 46.
    Jokubavicius, Valdas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Yazdi, G. Reza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Liljedahl, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Lateral Enlargement Growth Mechanism of 3C-SiC on Off-Oriented 4H-SiC Substrates2014Ingår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, nr 12, s. 6514-6520Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We introduce a 3C-SiC growth concept on off-oriented 4H-SiC substrates using a sublimation epitaxial method. A growth model of 3C-SiC layer development via a controlled cubic polytype nucleation on in situ formed on-axis area followed by a lateral enlargement of 3C-SiC domains along the step-flow direction is outlined. Growth process stability and reproducibility of high crystalline quality material are demonstrated in a series of 3C-SiC samples with a thickness of about 1 mm. The average values of full width at half-maximum of ω rocking curves on these samples vary from 34 to 48 arcsec indicating high crystalline quality compared to values found in the literature. The low temperature photoluminescence measurements also confirm a high crystalline quality of 3C-SiC and indicate that the residual nitrogen concentration is about 1–2 × 1016 cm–3. Such a 3C-SiC growth concept may be applied to produce substrates for homoepitaxial 3C-SiC growth or seeds which could be explored in bulk growth of 3C-SiC.

  • 47.
    Kaiser, Michl
    et al.
    University of Erlangen, Germany.
    Schimmel, Saskia
    University of Erlangen, Germany.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Linnarsson, Margareta
    Ou, Haiyan
    Technical University of Denmark, Lyngby.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Wellmann, Peter
    University of Erlangen, Germany.
    Nucleation and growth of polycrystalline SiC2014Ingår i: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 56, nr 1, s. 012001-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nucleation and bulk growth of polycrystalline SiC in a 2 inch PVT setup using isostatic and pyrolytic graphite as substrates was studied. Textured nucleation occurs under near-thermal equilibrium conditions at the initial growth stage with hexagonal platelet shaped crystallites of 4H, 6H and 15R polytypes. It is found that pyrolytic graphite results in enhanced texturing of the nucleating gas species. Reducing the pressure leads to growth of the crystallites until a closed polycrystalline SiC layer containing voids with a rough surface is developed. Bulk growth was conducted at 35 mbar Ar pressure at 2250°C in diffusion limited mass transport regime generating a convex shaped growth form of the solid-gas interface leading to lateral expansion of virtually [001] oriented crystallites. Growth at 2350°C led to the stabilization of 6H polytypic grains. The micropipe density in the bulk strongly depends on the substrate used.

  • 48.
    Kwasnicki, Pawel
    et al.
    CNRS, L2C UMR 5221, F-34095, Montpellier, France.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Sun, Jianwu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Peyre, H.
    Université Montpellier 2, L2C UMR 5221, F-34095, Montpellier, France .
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Camasse, J.
    CNRS, L2C UMR 5221, F-34095, Montpellier, France .
    Juillaguet, S.
    Université Montpellier 2, L2C UMR 5221, F-34095, Montpellier, France.
    Optical investigation of 3C-SiC hetero-epitaxial layers grown by sublimation epitaxy under gas atmosphere2014Ingår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 778-780, s. 243-246Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated three 3C-SiC samples grown on 6H SiC substrate by sublimation epitaxy under gas atmosphere. We focus on the low temperature photoluminescence and Raman measurements to show that compare to a growth process under vacuum atmosphere, the gas atmosphere favor the incorporation of impurities at already existing and/or newly created defect sites.

  • 49.
    Vasiliauskas, Remigijus
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Marinova, M.
    Department of Physics, Aristotle University of Thessaloniki, GR54124, Thessaloniki, Greece.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Polychroniadis, E. K.
    Department of Physics, Aristotle University of Thessaloniki, GR54124, Thessaloniki, Greece..
    Yakimova, Risitza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Polytype transformation and structural characteristics of 3C-SiC on 6H-SiC substrates2014Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 395, s. 109-115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The 3C-SiC (111) was grown on on-axis 6H-SiC substrates in a temperature interval ranging from 1675oC where 3C-SiC nucleated, to 1825oC where coverage of the substrate by 3C-SiC was  nearly  100%.  The  6H-  to  3C-SiC  transformation  was  not  abrupt  and  two  different transitions could be observed. The first one occurs before or during 3C-SiC nucleation and consists  of 6H-,  3C-, 15R-SiC  and other  unresolved  stacking  sequences.  The second  one appears due to 6H-SiC and 3C-SiC competition  during the growth and results in non flat needle-like interface. A proposed model elucidates connection between four-fold twins nucleating at the 6H-/3C-SiC interface and the formation of depressions at the surface of the 3C-SiC layer.

  • 50.
    Gulbinas, Karolis
    et al.
    Vilnius University, Lithuania .
    Ščajev, P,
    Vilnius University, Lithuania .
    Bikbajavas, V.
    Vilnius University, Lithuania .
    Grivickas, V.
    Vilnius University, Lithuania .
    Korolik, O.V.
    Belarusian State University, Minsk, Belarus .
    Mazanik, A.V
    Belarusian State University, Minsk, Belarus .
    Fedotov, A.K.
    Belarusian State University, Minsk, Belarus .
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Linnarsson, Margareta
    Royal Institute of Technology, Kista, Sweden .
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Kamiyama, Satoshi
    Meijo University, Nagoya, Japan .
    Raman Scattering and Carrier Diffusion Study in Heavily Co-doped 6H-SiC Layers2014Ingår i: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 56, nr 1, s. 012005-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thick 6H-SiC epilayers were grown using the fast sublimation method on low-off-axis substrates. They were co-doped with N and B impurities of ≈1019 cm−3 and (41016–51018) cm−3 concentration, respectively. The epilayers exhibited donor-acceptor pair (DAP) photoluminescence. The micro-Raman spectroscopic study exposed a compensated n-6H-SiC epilayer of common quality with some 3C-SiC inclusions. The compensation ratio of B through 200 μm thick epilayer varied in 20-30% range. The free carrier diffusivity was studied by transient grating technique at high injection level. The determined ambipolar diffusion coefficient at RT was found to decrease from 1.15 cm2/s to virtually 0 cm2/s with boron concentration increasing by two orders.

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