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  • 201.
    Nuala, Mai Caffrey
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Armiento, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Abrikosov, Igor
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. NUST MISIS, Russia; Tomsk State University, Russia.
    Charge neutrality in epitaxial graphene on 6H-SiC(0001) via nitrogen intercalation2015Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, nr 8, artikel-id 081409Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electronic properties of epitaxial graphene grown on SiC(0001) are known to be impaired relative to those of freestanding graphene. This is due to the formation of a carbon buffer layer between the graphene layers and the substrate, which causes the graphene layers to become strongly n-doped. Charge neutrality can be achieved by completely passivating the dangling bonds of the clean SiC surface using atomic intercalation. So far, only one element, hydrogen, has been identified as a promising candidate. We show, using first-principles density functional calculations, how it can also be accomplished via the growth of a thin layer of silicon nitride on the SiC surface. The subsequently grown graphene layers display the electronic properties associated with charge neutral graphene. We show that the surface energy of this structure is considerably lower than that of others with intercalated atomic nitrogen and determine how its stability depends on the N-2 chemical potential.

  • 202.
    Olbrich, P.
    et al.
    University of Regensburg, Germany .
    Drexler, C.
    University of Regensburg, Germany .
    Golub, L. E.
    Russian Academic Science, Russia .
    Danilov, S. N.
    University of Regensburg, Germany .
    Shalygin, V. A.
    St Petersburg State Polytech University, Russia .
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Lara-Avila, S.
    Chalmers, Sweden .
    Kubatkin, S.
    Chalmers, Sweden .
    Redlich, B.
    Radboud University of Nijmegen, Netherlands .
    Huber, R.
    University of Regensburg, Germany .
    Ganichev, S. D.
    University of Regensburg, Germany .
    Reststrahl band-assisted photocurrents in epitaxial graphene layers2013Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, nr 24, s. 245425-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the observation of the reststrahl band-assisted photocurrents in epitaxial graphene on SiC excited by infrared radiation. The peculiar spectral dependence for frequencies lying within the reststrahl band of the SiC substrate provides a direct and noninvasive way to probe the electric field magnitude at atomic distances from the materials surface. Furthermore our results reveal that nonlinear optical and optoelectronic phenomena in two-dimensional crystals and other atomic scale structures can be giantly enhanced by their deposition on a substrate with negative dielectric constant.

  • 203.
    Ou, Yiyu
    et al.
    Technical University of Denmark, Lyngby, Denmark.
    Aijaz, Imran
    Technical University of Denmark, Lyngby, Denmark.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. 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.
    Ou, Haiyan
    Technical University of Denmark, Lyngby, Denmark.
    Broadband antireflection silicon carbide surface by self-assembled nanopatterned reactive-ion etching2013Ingår i: OPTICAL MATERIALS EXPRESS, ISSN 2159-3930, Vol. 3, nr 1, s. 86-94Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An approach of fabricating pseudoperiodic antireflective subwavelength structures on silicon carbide by using self-assembled Au nanopatterns as etching mask is demonstrated. The nanopatterning process is more time-efficiency than the e-beam lithography or nanoimprint lithography process. The influences of the reactive-ion etching conditions and deposited Au film thickness to the subwavelength structure profile and its corresponding surface reflectance have been systematically investigated. Under the optimal experimental conditions, the average reflectance of the silicon carbide in the range of 390-784 nm is dramatically suppressed from 21.0 % to 1.9 % after introducing the pseudoperiodic nanostructures. A luminescence enhancement of 226 % was achieved at an emission angle of 20 degrees on the fluorescent silicon carbide. Meanwhile, the angle-resolved photoluminescence study presents a considerable omnidirectional luminescence enhancement.

  • 204.
    Ou, Yiyu
    et al.
    Technical University of Denmark, Lyngby.
    Jokubavicius, Valdas
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Hens, Philip
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Kaiser, Michl
    University of Erlangen-Nurnberg, Erlangen, Germany .
    Wellmann, Peter
    University of Erlangen-Nurnberg, Erlangen, Germany.
    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.
    Ou, Haiyan
    Technical University of Denmark, Lyngby.
    Broadband and omnidirectional light harvesting enhancement of fluorescent SiC2012Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, nr 7, s. 7575-7579Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, antireflective sub-wavelength structures have been fabricated on fluorescent 6H-SiC to enhance the white light extraction efficiency by using the reactive-ion etching method. Broadband and omnidirectional antireflection characteristics show that 6H-SiC with antireflective sub-wavelength structures suppress the average surface reflection significantly from 20.5 % to 1.01 % over a wide spectral range of 390-784 nm. The luminescence intensity of the fluorescent 6H-SiC could be enhanced in the whole emission angle range. It maintains an enhancement larger than 91 % up to the incident angle of 70 degrees, while the largest enhancement of 115.4 % could be obtained at 16 degrees. The antireflective sub-wavelength structures on fluorescent 6H-SiC could also preserve the luminescence spectral profile at a large emission angle by eliminating the Fabry-Perot microcavity interference effect.

  • 205.
    Ou, Yiyu
    et al.
    Technical University of Denmark, Lyngby.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Kaiser, Michl
    University of Erlangen-Nuremberg, Germany.
    Wellmann, Peter
    University of Erlangen-Nuremberg, Germany.
    Linnarsson, Margareta
    KTH Royal Institute of Technology, Kista, Sweden.
    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.
    Ou, Haiyan
    Technical University of Denmark, Lyngby.
    Fabrication of Broadband Antireflective Sub-Wavelength Structures on Fluorescent SiC2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Surface nanocones on 6H-SiC have been developed and demonstrated as an effective method of enhancing the light extraction efficiency from fluorescent SiC layers. The surface reflectance, measured from the opposite direction of light emission, over a broad bandwidth range is significantly suppressed from 20.5% to 1.0 % after introducing the sub-wavelength structures. An omnidirectional light harvesting enhancement (>91%), is also achieved which promotes fluorescent SiC as a good candidate of wavelength converter for white light-emitting diodes.

  • 206.
    Ou, Yiyu
    et al.
    Technical University of Denmark, Lyngby.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Kamiyama, Satoshi
    Meijo University, Nagoya.
    Liu, Chuan
    Technical University of Denmark, Lyngby.
    Berg, Rolf W.
    Technical University of Denmark, Lyngby.
    Linnarsson, Margareta
    School of Information and Communication Technology, Royal Institute of Technology, Kista.
    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.
    Ou, Haiyan
    Meijo University, Nagoya .
    Donor-acceptor-pair emission characterization in N-B doped fluorescent in SiC2011Ingår i: Optical Materials Express, ISSN 2159-3930, Vol. 1, nr 8, s. 1439-1446Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, we investigated donor-acceptor-pair emission in N-B doped fluorescent 6H-SiC, by means of photoluminescence, Raman spectroscopy, and angle-resolved photoluminescence. The photoluminescence results were interpreted by using a band diagram with Fermi-Dirac statistics. It is shown that with N and B concentrations in a range of 1018cm−3 the samples exhibit the most intense luminescence when the concentration difference (n-type) is about 4.6x1018cm−3. Raman spectroscopy studies further verified the doping type and concentrations for the samples. Furthermore, strong luminescence intensity in a large emission angle range was achieved from angle-resolved photoluminescence. The results indicate N-B doped fluorescent SiC as a good wavelength converter in white LEDs applications.

  • 207.
    Ou, Yiyu
    et al.
    Technical University of Denmark, Lyngby.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Linnarsson, Margareta
    Royal Institute of Technology, Kista, Sweden .
    Yakimova, Rositza
    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.
    Ou, Haiyan
    Technical University of Denmark, Lyngby.
    Characterization of donor–acceptor-pair emission in fluorescent 6H-SiC2012Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T148, s. 014003-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated donor–acceptor-pair emission in N–B-doped 6H-SiC samples by using photoluminescence (PL) and angle-resolved PL. It is shown that n-type doping with concentrations larger than 1018 cm−3 is favorable for observing luminescence, and increasing nitrogen results in stronger luminescence. A dopant concentration difference greater than 4×1018 cm−3 is proposed to help achieve intense PL. Angular-dependent PL was observed that was attributed to the Fabry–Pérot microcavity interference effect, and a strong luminescence intensity in a large emission angle range was also achieved. The results indicate that N–B-doped fluorescent SiC is a good wavelength converter in white LED applications.

  • 208.
    Ou, Yiyu
    et al.
    Technical University of Denmark, Lyngby.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Liu, Chuan
    Technical University of Denmark, Lyngby.
    Berg, Rolf W.
    Technical University of Denmark, Lyngby.
    Linnarsson, Margareta
    Kamiyama, Satoshi
    Meijo University, Nagoya, Japan.
    Lu, Zhaoyue
    Technical University of Denmark, Lyngby.
    Yakimova, Rositza
    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.
    Ou, Haiyan
    Technical University of Denmark, Lyngby.
    Photoluminescence and Raman spectroscopy characterization of boron and nitrogen-doped 6H silicon carbide2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Nitrogen-boron doped 6H-SiC epilayers grown on low off-axis 6H-SiC substrates have been characterized by photoluminescence and Raman spectroscopy. The photoluminescence results show that a doping larger than 1018 cm-3 is favorable to observe the luminescence and addition of nitrogen is resulting in an increased luminescence. A dopant concentration difference larger than 4x1018 cm-3 is proposed to achieve intense photoluminescence. Raman spectroscopy further confirmed the doping type and concentrations for the samples. The results indicate that N-B doped SiC is being a good wavelength converter in white LEDs applications.

  • 209.
    Ou, Yiyu
    et al.
    Department of Photonics Engineering, Technical University of Denmark, Lyngby.
    Jokubavicius, Valdas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositza
    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.
    Ou, Haiyan
    Department of Photonics Engineering, Technical University of Denmark, Lyngby.
    Omnidirectional luminescence enhancement of fluorescent SiC via pseudoperiodic antireflective subwavelength structures2012Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, nr 18, s. 3816-3818Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, an approach of fabricating pseudoperiodic antireflective subwavelength structures (ARS) on fluorescent SiC by using self-assembled etch mask is demonstrated. By applying the pseudoperiodic (ARS), the average surface reflectance at 6° incidence over the spectral range of 390–785 nm is dramatically suppressed from 20.5% to 1.62%, and the hydrophobic surface with a large contact angle of 98° is also achieved. The angle-resolved photoluminescence study presents a considerable omnidirectional luminescence enhancement with an integral intensity enhancement of 66.3% and a fairly preserved spatial emission pattern.

  • 210.
    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.

  • 211.
    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.

  • 212.
    Panchal, V
    et al.
    NPL.
    Cedergren, K
    Chalmers.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Tzalenchuk, A
    NPL.
    Kubatkin, S
    Chalmers.
    Kazakova, O
    NPL.
    Small epitaxial graphene devices for magnetosensing applications2012Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, nr 7, s. 07E509-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hall sensors with the width range from 0.5 to 20.0 mu m have been fabricated out of a monolayer graphene epitaxially grown on SiC. The sensors have been studied at room temperature using transport and noise spectrum measurements. The minimum detectable field of a typical 10-mu m graphene sensor is approximate to 2.5 mu T/root Hz, making them comparable with state of the art semiconductor devices of the same size and carrier concentration and superior to devices made of CVD graphene. Relatively high resistance significantly restricts performance of the smallest 500-nm devices. Carrier mobility is strongly size dependent, signifying importance of both intrinsic and extrinsic factors in the optimization of the device performance.

  • 213.
    Panchal, Vishal
    et al.
    National Physical Laboratory, Teddington, UK.
    Burnett, Tim L.
    National Physical Laboratory, Teddington, UK.
    Pearce, Ruth
    National Physical Laboratory, Teddington, UK.
    Cedergren, Karin
    Chalmers University of Technology, Göteborg Sweden.
    Yakimova, Rositza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Tzalenchuk, Alexander
    National Physical Laboratory, Teddington, UK.
    Kazakova, Olga
    National Physical Laboratory, Teddington, UK.
    Surface Potential Variations in Epitaxial Graphene Devices Investigated by Electrostatic Force Spectroscopy2012Ingår i: Nanotechnology (IEEE-NANO), 2012, IEEE , 2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electrostatic Force Spectroscopy and Scanning Kelvin Probe Microscopy techniques are used to study the performance of side-gated Hall devices made of epitaxial graphene on 4H-SiC(0001). Electrostatic Force Spectroscopy is a novel method which allows quantitative surface potential measurements with high spatial resolution. Using these techniques, we calibrate work function of the metal coated tip and define the work functions for single and double-layer graphene. We also show that the use of moderate strength electrical fields in the side-gate geometry does not notably change the performance of the device.

  • 214.
    Panchal, Vishal
    et al.
    National Phys Lab, England .
    Cox, David
    National Phys Lab, England .
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Kazakova, Olga
    National Phys Lab, England .
    Epitaxial Graphene Sensors for Detection of Small Magnetic Moments2013Ingår i: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 49, nr 1, s. 97-100Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Micron-sized Hall sensors made of epitaxial graphene grown on 4H-SiC(0001) have been fabricated and studied at room temperature using transport and noise spectrum measurements. We report detection of 1-mu m Dynal bead with the magnetic moment of similar to 4 x 10(8) mu(B), using a 2-mu m epitaxial graphene device. A phase-sensitive AC-DC Hall magnetometry method was used to reliably detect the bead with a relatively large response of V-x(AC) similar to 7 mu V. Bead positioning was performed using a nanomanipulator inside of the FIB system. Long-term effect of the small dose of e-beam irradiation (similar to 4 x 10(14) e/cm(2))on the performance of graphene Hall devices is reported.

  • 215.
    Panchal, Vishal
    et al.
    National Phys Lab, England.
    Iglesias-Freire, Oscar
    CSIC, Spain.
    Lartsev, Arseniy
    Chalmers, Sweden.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Asenjo, Agustina
    CSIC, Spain.
    Kazakova, Olga
    National Phys Lab, England.
    Magnetic Scanning Probe Calibration Using Graphene Hall Sensor2013Ingår i: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 49, nr 7, s. 3520-3523Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnetic force microscopy (MFM) offers a unique insight into the nanoscopic scale domain structures of magnetic materials. However, MFM is generally regarded as a qualitative technique and, therefore, requires meticulous calibration of the magnetic scanning probe stray field (Bprobe) for quantitative measurements. We present a straightforward calibration of Bprobe using scanning gate microscopy on epitaxial graphene Hall sensor in conjunction with Kelvin probe force microscopy feedback loop to eliminate sample-probe parasitic electric field interactions. Using this technique, we determined Bprobe ~ 70 mT and ~ 76 mT for probes with nominal magnetic moment ~ 1 × 10-13 and > 3 × 10-13 emu, respectively, at a probe-sample distance of 20 nm.

  • 216.
    Panchal, Vishal
    et al.
    National Physical Laboratory, England, University of London, England .
    Lartsev, Arseniy
    Chalmers, Sweden .
    Manzin, Alessandra
    Istituto Nazionale di Ricerca Metrologica, Italy .
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Tzalenchuk, Alexander
    National Physical Laboratory, England, University of London, England .
    Kazakova, Olga
    National Physical Laboratory, England .
    Visualisation of edge effects in side-gated graphene nanodevices2014Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, nr 5881Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using local scanning electrical techniques we study edge effects in side-gated Hall bar nanodevices made of epitaxial graphene. We demonstrate that lithographically defined edges of the graphene channel exhibit hole conduction within the narrow band of similar to 60-125 nm width, whereas the bulk of the material is electron doped. The effect is the most pronounced when the influence of atmospheric contamination is minimal. We also show that the electronic properties at the edges can be precisely tuned from hole to electron conduction by using moderate strength electrical fields created by side-gates. However, the central part of the channel remains relatively unaffected by the side-gates and retains the bulk properties of graphene.

  • 217.
    Panchal, Vishal
    et al.
    National Phys Lab, England.
    Pearce, Ruth
    National Phys Lab, England.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Tzalenchuk, Alexander
    National Phys Lab, England.
    Kazakova, Olga
    National Phys Lab, England.
    Standardization of surface potential measurements of graphene domains2013Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We compare the three most commonly used scanning probe techniques to obtain a reliable value of the work function in graphene domains of different thickness. The surface potential (SP) of graphene is directly measured in Hall bar geometry via a combination of electrical functional microscopy and spectroscopy techniques, which enables calibrated work function measurements of graphene domains in ambient conditions with values Φ1LG ~4.55 ± 0.02 eV and Φ2LG ~ 4.44 ± 0.02 eV for single- and bi-layer, respectively. We demonstrate that frequency-modulated Kelvin probe force microscopy (FM-KPFM) provides more accurate measurement of the SP than amplitude-modulated (AM)-KPFM. The discrepancy between experimental results obtained by different techniques is discussed. In addition, we use FM-KPFM for contactless measurements of the specific components of the device resistance. We show a strong non-Ohmic behavior of the electrode-graphene contact resistance and extract the graphene channel resistivity.

  • 218. Paskaleva, A
    et al.
    Ciechonski, Rafal
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Syväjärvi, Mikael
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Atanassova, E
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Characterization of 4H-SiC MOS structures with Al2O3 as gate dielectric2005Ingår i: Materials Science Forum, Vols. 483-485, 2005, Vol. 483, s. 709-712Konferensbidrag (Refereegranskat)
    Abstract [en]

    The electrical properties of Al2O3 as a gate dielectric in MOS structures based on n- and p-type 4H-SiC grown by sublimation method have been investigated and compared to the properties of similar structures utilizing SiO2. The electrically active defects in the structures are studied by CV method. The results show that the type as well as spatial and energy distribution of defects in Al2O3/SiC and SiO2/SiC samples are different. The structures with Al2O3 on p-type 4H-SiC demonstrate much better C-V characteristics than the p-type 4H-SiC/SiO2 structures.

  • 219. Paskaleva, A
    et al.
    Ciechonski, Rafal
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Syväjärvi, Mikael
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Atanassova, E
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Electrical behavior of 4H-SiC metal-oxide-semiconductor structures with Al2O3 as gate dielectric2005Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 97, nr 12, s. 124507-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electrical properties of Al2O3 as a gate dielectric in metal-oxide-semiconductorstructures based on n- and p-type 4H-SiC grown by sublimation method have been investigated and compared to the properties of similar structures utilizing SiO2. The electrically active defects in the structures are studied by capacitance–voltage (C–V) and current–voltage (I–V) methods. The results show that the type as well as spatial and energy distributions of defects in Al2O3/SiC and SiO2/SiC samples are different. The structures with Al2O3 on p-type 4H-SiC demonstrate much better electrical characteristics than the p-type 4H-SiC/SiO2 structures. It is demonstrated that the conduction process in the former is governed by Fowler–Nordheim electron tunneling from the Al gate whereas in the latter the hole tunneling from SiC is the more probable process. This difference combined with the higher defect density in p-type SiC/SiO2 structures defines the higher leakage currents compared to the structures utilizing Al2O3.

  • 220.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Goldys, E.M.
    Semiconduct. Sci. and Technol. Labs., Macquarie University, Sydney, NSW 2109, Australia.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Svedberg, E.B.
    Henry, Anne
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Influence of growth rate on the structure of thick GaN layers grown by HVPE2000Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 208, nr 1, s. 18-26Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thick GaN films grown by hydride vapour phase epitaxy have been investigated by cathodoluminecsence, X-ray diffraction, and photoluminescence. Cross-sectional studies of thick GaN layers grown on sapphire without buffers reveal three zones: a highly disordered interface region, a columnar defective region and a good quality main region of the layer. The influence of the highly doped columnar region on the surface morphology and crystal structure of the layers has been studied. We show that the columnar region influences the material quality more strongly in thinner films. Thicker layers exhibit improved morphology with lower surface pit density and better crystal quality shown in photoluminescence and X-ray diffraction spectra. The relationship between the near-interface columnar structures and surface pits is revealed. A strong effect of the growth rate on the structure of thick layers is found. The results suggest that GaN layers with optimum crystalline quality may be obtained by varying the growth rate during growth.

  • 221.
    Pearce, Ruth
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Becker, Elin
    Chalmers Göteborg.
    Haglin, A
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Söderlind, Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Käll, Per-Olov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Fysikalisk Kemi. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Skoglundh, Magnus
    Chalmers, Göteborg.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Understanding the gas sensor response of ZnO and Ga:ZnO2010Ingår i: IMCS13, 2010, s. 376-Konferensbidrag (Refereegranskat)
  • 222.
    Pearce, Ruth
    et al.
    National Physical Laboratory, Teddington, UK.
    Eriksson, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Iakimov, Tihomir
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    On the Differing Sensitivity to Chemical Gating of Single and Double Layer Epitaxial Graphene Explored Using Scanning Kelvin Probe Microscopy2013Ingår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, nr 5, s. 4647-4656Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using environmental scanning Kelvin probe microscopy we show that the position of the Fermi level of single layer graphene is more sensitive to chemical gating than that of double layer graphene. We calculate that the difference in sensitivity to chemical gating is not entirely due to the difference in band structure of 1 and 2 layer graphene. The findings are important for gas sensing where the sensitivity of the electronic properties to gas adsorption are monitored and suggest that single layer graphene could make a more sensitive gas sensor than double layer graphene. We propose that the difference in surface potential between adsorbate-free single and double layer graphene, measured using scanning kelvin probe microscopy, can be used as a non-invasive method of estimating substrate-induced doping in epitaxial graphene.

  • 223.
    Pearce, Ruth
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Iakimov, Tihomir
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Andersson, M
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Towards Optimisation of Epitaxially Grown Graphene Based Sensors for Highly Sensitive Gas Detection2010Ingår i: 2010 IEEE Sensors, Piscataway, NJ, United States: IEEE , 2010, s. 898-902Konferensbidrag (Refereegranskat)
    Abstract [en]

    Epitaxially grown single-layer and many-layer (10 atomic layers thick) resistive graphene devices were fabricated and compared for response towards NO2. Single-layer devices showed far greater sensitivity. The many-layer devices reduced in resistance on exposure to electron withdrawing NO2 demonstrating a majority hole carriers (p-type), whereas the single-layer device demonstrated an increase in resistance upon NO2 exposure demonstrating a majority of electron carriers (n-type). An n-p shift is observed for the single-layer device upon exposure to increasing concentrations of NO2. This shift is thought to be due to the reduction of electrons in the conduction band upon adsorption of electron-withdrawing NO2 making holes the majority carriers.

  • 224.
    Pearce, Ruth
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Iakimov, Tihomir
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Andersson, Mike
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Epitaxially grown graphene based gas sensors for ultra sensitive NO(2) detection2011Ingår i: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 155, nr 2, s. 451-455Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Epitaxially grown single layer and multi layer graphene on SiC devices were fabricated and compared for response towards NO(2). Due to electron donation from SiC:, single layer graphene is n-type with a very low carrier concentration. The choice of substrate is demonstrated to enable tailoring of the electronic properties of graphene, with a SiC substrate realising simple resistive devices tuned for extremely sensitive NO(2) detection. The gas exposed uppermost layer of the multi layer device is screened from the SiC by the intermediate layers leading to a p-type nature with a higher concentration of charge carriers and therefore, a lower gas response. The single layer graphene device is thought to undergo an n-p transition upon exposure to increasing concentrations of NO(2) indicated by a change in response direction. This transition is likely to be due to the transfer of electrons to NO(2) making holes the majority carriers. (C) 2011 Elsevier B.V. All rights reserved.

  • 225.
    Pearce, Ruth
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Söderlind, Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska högskolan.
    Hagelin, Alexander
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Käll, Per-Olov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Fysikalisk Kemi. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Becker, Elin
    Competence Centre for Catalysis Chalmers University of Technology, Göteborg, Sweden.
    Skoglundh, Magnus
    Competence Centre for Catalysis Chalmers University of Technology, Göteborg, Sweden.
    Effect of Water vapour on Gallium doped Zinc Oxide nanoparticle sensor gas response2009Ingår i: IEEE Sensors, 2009, Piscataway, NJ, United States: IEEE , 2009, s. 2039-2043Konferensbidrag (Refereegranskat)
    Abstract [en]

    Zinc oxide is a wide band gap (similar to 3.4ev) semiconductor material, making it a promising material for high temperature applications, such as exhaust and flue environments where NO and NO2 monitoring is increasingly required due to stricter emission controls[1]. In these environments water vapour and background levels of oxygen are present and, as such, the effect of humidity on the sensing characteristics of these materials requires further study. The reaction mechanisms in the presence of water vapour are poorly understood and there is a need for deeper understanding of the principles and mechanisms of gas response of these materials. An investigation of the influence of changing water vapour (H2O) and oxygen (O-2) backgrounds on the response of nanoparticulate Ga-doped ZnO resistive sensors is presented.

  • 226.
    Pearce, Ruth
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Eriksson, Johan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Yt- och Halvledarfysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mike
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Development of FETs and resistive devices based on epitaxially grown single layer graphene on SiC for highly sensitive gas detection2012Ingår i: Materials Science Forum Vols 717 - 720, Trans Tech Publications Inc., 2012, Vol. 717-720, s. 687-690Konferensbidrag (Refereegranskat)
    Abstract [en]

    Epitaxially grown single layer graphene on silicon carbide (SiC) resistive sensors were characterised for NO2 response at room and elevated temperatures, with an n-p type transition observed with increasing NO2 concentration for all sensors. The concentration of NO2 required to cause this transition varied for different graphene samples and is attributed to varying degrees of substrate induced Fermi-level (E-F) pinning above the Dirac point. The work function of a single layer device increased steadily with increasing NO2 concentration indicating no change in reaction mechanism for high and low concentrations despite a change in sensor response direction. Epitaxially grown graphene device preparation is challenging due to poor adhesion of the graphene layer to the substrate. A field effect transistor (FET) device is presented which does not require wire bonding to contacts on graphene.

  • 227.
    Pearce, Ruth
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mike
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Development of FETs based on epitaxially grown single layer graphene on SiC for highly sensitive gas detection2011Ingår i: Proceedings of the International Conference on Silicon Carbide and Related materials, 2011, s. 405-Konferensbidrag (Refereegranskat)
  • 228.
    Pecz, B.
    et al.
    Hungarian Academic Science, Hungary.
    Toth, L.
    Hungarian Academic Science, Hungary.
    Tsiakatouras, G.
    University of Crete, Greece; University of Crete, Greece.
    Adikimenakis, A.
    University of Crete, Greece.
    Kovacs, A.
    Forschungszentrum Julich, Germany.
    Duchamp, M.
    Forschungszentrum Julich, Germany.
    Dunin-Borkowski, R. E.
    Forschungszentrum Julich, Germany.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Neumann, P. L.
    Hungarian Academic Science, Hungary.
    Behmenburg, H.
    AIXTRON SE, Germany.
    Foltynski, B.
    AIXTRON SE, Germany.
    Giesen, C.
    AIXTRON SE, Germany.
    Heuken, M.
    AIXTRON SE, Germany.
    Georgakilas, A.
    University of Crete, Greece; University of Crete, Greece.
    GaN heterostructures with diamond and graphene2015Ingår i: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 30, nr 11, s. 114001-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The full performance of GaN devices for high power applications is not exploited due to their self-heating. Possible solutions are the integration of materials with high heat conductivity i.e., single crystalline diamond and graphene layers. We report the growth of single crystalline (0001)-oriented GaN thin films on (100), (110) and (111) diamond single crystals studied by transmission electron microscopy (TEM) in cross-sections. As for graphene, we show a high quality GaN layer that was deposited on patterned graphene layers and 6H-SiC. The atomic structures of the interfaces in the heterostructure are studied using aberration-corrected scanning TEM combined with energy dispersive x-ray and electron energy-loss spectroscopy.

  • 229.
    Pecz, B
    et al.
    Hungarian Acad Sci, Res Inst Tech Phys & Mat Sci, H-1525 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Outokumpu Semitron AB, S-17824 Ekero, Sweden Swedish Space Corp, S-17104 Solna, Sweden Royal Inst Technol, S-16440 Kista, Sweden.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Syväjärvi, Mikael
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Lockowandt, C
    Hungarian Acad Sci, Res Inst Tech Phys & Mat Sci, H-1525 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Outokumpu Semitron AB, S-17824 Ekero, Sweden Swedish Space Corp, S-17104 Solna, Sweden Royal Inst Technol, S-16440 Kista, Sweden.
    Radamson, H
    Hungarian Acad Sci, Res Inst Tech Phys & Mat Sci, H-1525 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Outokumpu Semitron AB, S-17824 Ekero, Sweden Swedish Space Corp, S-17104 Solna, Sweden Royal Inst Technol, S-16440 Kista, Sweden.
    Radnoczi, G
    Hungarian Acad Sci, Res Inst Tech Phys & Mat Sci, H-1525 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Outokumpu Semitron AB, S-17824 Ekero, Sweden Swedish Space Corp, S-17104 Solna, Sweden Royal Inst Technol, S-16440 Kista, Sweden.
    Janzén, Erik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Structural investigation of SiC epitaxial layers grown under microgravity and on-ground conditions1999Ingår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 357, nr 2, s. 137-143Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thick 4H-, and 6H-SiC epitaxial layers have been grown by LPE from Si-Sc-C solvent at microgravity conditions during a space experiment, as well as on-ground. The samples are characterised by cross-sectional TEM and HRXRD. Layers grown at microgravity are relatively defect free, although their surfaces are always stepped. Control samples grown on-ground have similar surface appearance, but contain scandium carbide precipitates, nanopipes, micropipes and/or cavities as verified by TEM. However, none of the aforementioned defects was traced in the layers grown at microgravity conditions. So, samples grown at space microgravity conditions are superior in their defect structure to those ones grown on the ground. The defects called nanopipes can be described as empty pipes of about 200 nm diameter traversing the layer in the [0001] (growth) direction. The steps in the microgravity and on-ground samples have facets of {104} type crystallographic planes both in 6H-, and 4H-SiC. We suggest, that those facets are formed and preferred during growth due to a possible mechanism of decreasing the high energy of the growing Si terminated (0001) surface. (C) 1999 Elsevier Science S.A. All rights reserved.

  • 230.
    Pecz, B
    et al.
    Res Inst Tech Phys & Mat Sci, H-1525 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Swedish Space Corp, S-17104 Solna, Sweden.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Syväjärvi, Mikael
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Lockowandt, C
    Res Inst Tech Phys & Mat Sci, H-1525 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Swedish Space Corp, S-17104 Solna, Sweden.
    Radnoczi, G
    Res Inst Tech Phys & Mat Sci, H-1525 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Swedish Space Corp, S-17104 Solna, Sweden.
    Janzén, Erik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Structure of SiC layers grown by LPE in microgravity and on-ground conditions1999Ingår i: Institute of Physics Conference Series, ISSN 0951-3248, E-ISSN 2154-6630, nr 164, s. 243-246Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High quality, hexagonal SiC layers have been grown in microgravity conditions and on-ground as well. The surface of the layers is always stepped. The dislocation density of the layers is increased closer to the surface. Scandium carbide precipitates, nanopipes and cavities were found in the SiC layers grown on-ground, but none of them were traced in the layers grown under microgravity conditions.

  • 231.
    Persson, Per
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Hultman, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Janson, M.S.
    Royal Institute of Technology, Solid State Electronics, P.O. Box E229, S-164 40 Kista-Stockholm, Sweden.
    Hallen, A.
    Hallén, A., Royal Institute of Technology, Solid State Electronics, P.O. Box E229, S-164 40 Kista-Stockholm, Sweden.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Dislocation loop evolution in ion implanted 4H-SiC2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 93, nr 11, s. 9395-9397Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The evolution of dislocation loop in the ion implanted 4H-SiC epilayers was investigated. The formation of dislocation loop after high temperature annealing was studied using transmission electron microscopy (TEM). The variation in the loop area with increase in implanted dose was found to be linear. For both, prolonged annealing and increasing temperature, the amount of interstitials bound to loops remained constant.

  • 232.
    Persson, Per
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Hultman, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Janson, M.S.
    Royal Institute of Technology, Solid State Electronics, P.O. Box E229, S-164 40 Kista-Stockholm, Sweden.
    Hallen, A.
    Hallén, A., Royal Institute of Technology, Solid State Electronics, P.O. Box E229, S-164 40 Kista-Stockholm, Sweden.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Panknin, D.
    FWIM Forschungszentrum Rossendorf, D-01474 Schoenfeld-Weissig, Germany.
    Skorupa, W.
    FWIM Forschungszentrum Rossendorf, D-01474 Schoenfeld-Weissig, Germany.
    On the nature of ion implantation induced dislocation loops in 4H-silicon carbide2002Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 92, nr 5, s. 2501-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    [No abstract available]

  • 233.
    Petoral, Rodrigo Jr
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Yazdi, Gholamreza
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Lloyd-Spets, Anita
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Uvdal, Kajsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Organosilane-functionalized wide band gap semiconductor surfaces2007Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, nr 22Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface functionalization of wide band gap semiconductors, SiC, ZnO, and GaN, with organosilane is reported. Formation of self-assembled monolayers of mercaptopropyltrimethoxysilane is confirmed by x-ray photoelectron spectroscopy and atomic force microscopy. The molecules are adsorbed on the surfaces through the silane groups with the free thiol groups molecularly oriented away from the surface. Moreover, chemisorption via the thiolate is observed for the ZnO surface. Immobilization of a model biomolecule to the functionalized surface is demonstrated. An amino acid derivative, i.e., phosphotyrosine derived thiol, is linked on the functionalized ZnO and GaN surfaces via formation of disulfide bridges. © 2007 American Institute of Physics.

  • 234.
    Petoral, Rodrigo Jr
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik.
    Yazdi, Gholamreza
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Vahlberg, Cecilia
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik.
    Syväjärvi, Mikael
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Lloyd Spetz, Anita
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik.
    Uvdal, Kajsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Surface Functionalization of SiC for Biosensor Applications2007Ingår i: ECSCRM 2006,2006, Material Science Forum, vol 556-557: Trans Tech Publications , 2007, s. 957-Konferensbidrag (Refereegranskat)
  • 235. Pirri, CF
    et al.
    Porro, S
    Ferrero, S
    Celasco, E
    Guastella, S
    Scaltrito, L
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Syväjärvi, Mikael
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Ciechonski, Rafal
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    De Angelis, S
    Crippa, D
    Growth, morphological and structural characterization of silicon carbide epilayers for power electronic devices applications2005Ingår i: Crystal research and technology (1981), ISSN 0232-1300, E-ISSN 1521-4079, Vol. 40, nr 10-Nov, s. 964-966Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Silicon carbide (SiC) is a wide band gap semiconductor, interesting for its physical properties such as high breakdown field, high saturated drift velocity and high thermal conductivity, which has been intensively studied in the last years. Although the high potentiality of this material, the SiC technology shows at the moment some limitations, indeed, the reliability of SiC-based devices is strictly correlated to the defects present in the crystalline structure. 4H-SiC epilayers were grown by Hot Wall Chemical Vapor Deposition (at 1600 degrees C) and by Sublimation techniques (at 2000 degrees C). A surface investigation of the epilayers has been performed finding particular physical finger-prints correlated with several kind of defects aimed at giving an important feedback to the epitaxial growth processes. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 236. Polychroniadis, E
    et al.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Stoemenos, J
    Microstructural characterization of very thick freestanding 3C-SiC wafers2004Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 263, nr 1-4, s. 68-75Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The microstructural characteristics of 300μm thick freestanding 3C-SiC wafers, provided by HOYA, were studied by transmission electron microscopy. The observed defects were mainly stacking faults (SFs), microtwins and inversion domain boundaries (IDBs). The defect density is reduced fast from the SiC/Si interface up to the first 20μm, and then it remains constant up to the surface, suggesting a defect growth and elimination mechanism. At the uppermost part of the film the distribution of the SFs is very inhomogeneous, large zones were completely free of SFs with the SFs mainly concentrating in areas where IDBs exist and their density was lower by more than one order of magnitude than the SFs. 3C-SiC 40μm thick layers were grown on the wafers by sublimation epitaxy. Optical micrographs of these layers exhibit macro-features different from the substrate, but still indicating large bands of SFs.

  • 237.
    Porro, Samuele
    et al.
    Department of Physics, Polytechnic of Torino, Torino, Italy.
    Ciechonski, Rafal
    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.
    Electrical Analysis and Interface States Evaluation of of Ni Schottky diodes on 4H-SiC thick epilayers2005Ingår i: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 202, nr 13, s. 2508-2514Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work has been focused on characterization of thick 4H-SiC layers produced by sublimation epitaxy. Nickel Schottky contacts have been fabricated in order to characterize the grown material and evaluate the interfacial layer between metal and semiconductor. The characterization study includes current-voltage and capacitance-voltage high temperature measurements, from which Schottky barrier, net donor concentration and on-state resistance values have been extracted. The diodes show a typical behavior of J-V and C-V curves with temperature, with Schottky barrier heights of 1.3 eV ÷ 1.4 eV and net donor concentration of 4 × 1015 cm-3 ÷ 1 × 1016 cm-3. From the Bardeen's model on reverse J-V, the density of states of the interfacial layer has been estimated to 7 × 1011 eV-1 cm-2 ÷ 8 × 1011 eV-1 cm-2, a value that is similar to the density of states of oxide layers in deliberated MOS structures realized on the same epilayers.

  • 238.
    Puglisi, Donatella
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Bur, Christian
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan. Saarland University, Lab for Measurement Technology, Germany.
    Bastuck, Manuel
    Saarland University, Lab for Measurement Technology, Germany.
    Schuetze, Andreas
    Saarland University, Germany.
    Andersson, Mike
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Eriksson, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Mastering VOC detection for better indoor air quality2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study, we use two different sensor technologies based on gas sensitive silicon carbide field effect transistors (SiC-FETs) and epitaxial graphene on SiC (EG/SiC) for highly sensitive and selective detection of trace amounts of three hazardous volatile organic compounds (VOCs), i.e. formaldehyde (CH2O), benzene (C6H6), and naphthalene (C10H8), present in indoor environments in concentrations of health concern.

    Iridium and platinum are used as sensing layers for the gate contacts. The FET sensors are operated at high temperature, under static and dynamic conditions. Excellent detection limits of 10 ppb for CH2O, about 1 ppb for C6H6, and below 0.5 ppb for C10H8 are measured at 60 % relative humidity (r.h.) [1]. The selectivity of the sensors is increased by temperature cycled operation and data evaluation based on multivariate statistics. Discrimination of CH2O, C6H6, and C10H8 independent of the level of background humidity is possible with a very high cross-validation rate up to 90 % [2]. These results are very encouraging for indoor air quality control, being below the threshold limits recommended by the WHO guidelines.

    Graphene-based chemical sensors offer the advantage of extreme sensitivity due to graphene’s unique electronic properties and the fact that every single atom is at the surface and available to interact with gas molecules. For this reason, uniform monolayer graphene is crucial [3], which is guaranteed by our optimized epitaxial growth process. Graphene-based chemical gas sensors normally show ultra-high sensitivity to certain gas molecules but suffer from poor selectivity. Functionalization or modification of the graphene surface can improve selectivity, but most such measures result in poor reproducibility. We demonstrate reproducible, non-destructive means of graphene surface decoration with nanostructured metals and metal oxides, and study their effect on the gas interactions at the graphene surface.

  • 239.
    Puglisi, Donatella
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Bur, Christian
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan. Saarland University, Saarbruecken, Germany.
    Kang, Yu Hsuan
    No University.
    Yakimova, Rositza
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Schütze, Andreas
    Saarland University, Saarbruecken, Germany.
    Andersson, Mike
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Eriksson, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    SiC-FET and graphene-based gas sensors for sensitive detection of toxic substances in indoor environments2014Ingår i: Proc of IMCS 2014, Buenos Aires, ARgentina, March 17-19, 2014Konferensbidrag (Refereegranskat)
  • 240.
    Raback, P
    et al.
    Ctr Sci Comp, FIN-02101 Espoo, Finland Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Okmet AB, SE-17824 Ekero, Sweden Helsinki Univ Technol, Phys Lab, FIN-02015 Helsinki, Finland.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Syväjärvi, Mikael
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Iakimov, Tihomir
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Nieminen, R
    Ctr Sci Comp, FIN-02101 Espoo, Finland Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Okmet AB, SE-17824 Ekero, Sweden Helsinki Univ Technol, Phys Lab, FIN-02015 Helsinki, Finland.
    Janzén, Erik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Considerations on the crystal morphology in the sublimation growth of SiC2000Ingår i: Materials Science Forum, Vols. 338-343, Trans Tech Publications Inc., 2000, Vol. 338-3, s. 95-98Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper the shape evolution of SiC source and seed is studied with simulations. Some basic geometries and temperature distributions are investigated. Also the condition for stable growth is discussed.

  • 241.
    Ranguelov, Bogdan
    et al.
    Bulgarian Academy of Sciences, Bulgaria .
    Goranova, Desislava
    Bulgarian Academy of Sciences, Bulgaria .
    Tonchev, Vesselin
    Bulgarian Academy of Sciences, Bulgaria .
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Diffusion Limited Aggregation with modified local rules2012Ingår i: Comptes Rendus de l'Academie Bulgare des Sciences / Proceedings of the Bulgarian Academy of Sciences, ISSN 1310-1331, E-ISSN 2367-5535, Vol. 65, nr 7, s. 913-918Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Results from a modified Diffusion Limited Aggregation (DLA) model are presented. The modifications of the classical DLA model are in the attachment to the cluster rules and in the scheme of particle generation/killing. In the classical DLA model, if a particle reaches the growing cluster, it sticks to it immediately and irreversibly and then the next particle is released. We will abandon this original prerequisite, and by changing the sticking probability to the cluster we will change the diffusion regime towards a more kinetic one. For a growing cluster consisting of only one type of particles this variation in the sticking probability is (more or less) a rude violation of the hypothesis for diffusion limitation in the DLA model. Since in a lot of experiments different types of particles are used with different sticking probabilities (e.g. different regimes of attachment), we develop a modified DLA model with two types of particles. The second modification we introduce at that point is a scheme for particle generation/killing we call "second chance" - when a particle is killed after reaching a given limiting distance from the cluster, it is killed and then returned to the point it was originally generated. Thus the model is capable of producing a great variety of growing patterns (fractals, spirals) by changing only a single parameter and we are able to construct a morphological diagram of our generalized DLA model with two different types of particles.

  • 242.
    Sadollah Khani, Azar
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan. Shahid Chamran University, Iran.
    Nour, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Kazeminezhad, Iraj
    Shahid Chamran University, Iran.
    Khranovskyy, Volodymyr
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Eriksson, Martin O.
    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 högskolan.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    A detailed optical investigation of ZnO@ZnS core-shell nanoparticles and their photocatalytic activity at different pH values2015Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 41, nr 5, s. 7174-7184Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study zinc oxide nanoparticles (NPs) were synthesized via a co-precipitation method and were covered by zinc sulfate using a chemical approach at a temperature of 60 degrees C forming ZnO@ZnS core-shell nanoparticles (CSNPs). In order to investigate the effect of the shell thickness on the optical and photocatalytic properties, many samples were grown with different concentration of the sulfur source. The results show that, covering ZnO with ZnS leads to form a type II band alignment system. In addition, the band gap of the ZnO@ZnS CSNPs was found less than both of the core and the shell materials. Also the emission peak intensity of the ZnO NPs changes as a result of manipulating oxygen vacancies via covering. The photocatalytic activity of the ZnO@ZnS CSNPs was invpstigated for degradation of the Congo red dye. As dye pollutants can be found in mediums with different pH, the experiments were performed at three pH values to determine the best photocatalyst for each pH. Congo red dye degradation experiments indicate that the ZnO@ZnS CSNPs act more efficiently as a photcatalyst at pH values of 4 and 7 compare to the pure ZnO NPs.

  • 243.
    Sankin, V I
    et al.
    AF Ioffe Physicotech Institute, Russia.
    Shkrebiy, P P
    AF Ioffe Physicotech Institute, Russia.
    Yakimova , Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik. Linköpings universitet, Tekniska högskolan.
    Strong field hole transport in 6H-SiC2009Ingår i: APPLIED PHYSICS LETTERS, ISSN 0003-6951 , Vol. 94, nr 8, s. 082101-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In materials with a small degree of ionicity ranging 10%-15%, such as in SiC, carrier scattering on polar optical potential is plausible. J-F characteristics of hot hole transport in 6H-SiC with N-a-N-d similar to 5x10(17) cm(-3) are studied at electrical fields of 1-150 kV/cm and temperatures from 300 to 600 K. In this work possible mechanisms contributing to the J-F characteristics are considered: scattering on ionized impurities, impurity breakdown due to Al acceptors, hole transport in the light valence subband formed due to splitting by crystal field, and dielectric breakdown related to polar optical scattering.

  • 244. Sankin, V.I.
    et al.
    Shkrebiy, P. P.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Wannier-Stark ladder conditions in 4H-SiC p-n junctions grown on off axis substrates2006Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, nr 23, s. 233508-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    4H-SiC p+ - n- - n+ junctions have been prepared on 8° off oriented plane aiming to investigate conditions of Wannier-Stark localization (WSL), and respectively the occurrence of a negative temperature coefficient of avalanche breakdown voltage (TCABV). A method is proposed that can enable obtaining important results without reaching the regime of destructive avalanche breakdown. By analyzing the photocurrent of light with different wavelengths and at strong electric fields, a negative differential photoconductance has been discovered testifying that the WSL is not suppressed at the field inclination in 8° off axis, and a negative TCABV is expected in commercial p-n junctions. © 2006 American Institute of Physics.

  • 245. Sankin, V.I.
    et al.
    Shkrebiy, P.P.
    Lepneva, A.A.
    Ostroumov, A.G.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Features of hot hole transport in 6H-SiC2009Ingår i: ECSCRM2008,2008, Materials Science Forum Vols. 615-617: Trans Tech Publications , 2009, s. 307-310Konferensbidrag (Refereegranskat)
    Abstract [en]

    In materials with a small degree of ionicity ranging 10-15%, such as in SiC, carrier scattering on polar optical potential is possible. Unlike scattering on deformation potential, the drift mobility in this case increases continuously. As this phenomenon may be realized in SiC hot hole transport, I-F characteristics in 6H-SiC with Na-Nd ~ 5x1017 cm-3 have been studied at electrical field 1-150 kV/cm for temperature from 300 to 600K. Furthermore, we studied the breakdown of Al impurity.

  • 246. Sankin, V.I.
    et al.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Wannier-Stark ladder and negative differential conductance in 4H-SiC2006Ingår i: Materials Science Forum, Vols. 527-529, 2006, Vol. 527-529, s. 707-710Konferensbidrag (Refereegranskat)
  • 247.
    Scajev, P.
    et al.
    Vilnius University, Lithuania.
    Onufnjevs, P.
    Vilnius University, Lithuania .
    Manolis, G.
    Vilnius University, Lithuania.
    Karaliunas, M.
    Vilnius University, Lithuania.
    Nargelas, S.
    Vilnius University, Lithuania.
    Jegenyes, N.
    University Claude Bernard Lyon 1, France.
    Lorenzzi, J.
    University Claude Bernard Lyon 1, France.
    Ferro, G.
    University Claude Bernard Lyon 1, France.
    Beshkova, Milena
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Vasiliauskas, Remigijus
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Syvajärvi, 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.
    Kato, M.
    Nagoya Institute of Technology, Japan.
    Jarasionas, K.
    Vilnius University, Lithuania.
    On applicability of time-resolved optical techniques for characterization of differently grown 3C-SiC crystals and heterostructures2012Ingår i: HETEROSIC and WASMPE 2011 / [ed] Daniel Alquier, Trans Tech Publications Inc., 2012, Vol. 711, s. 159-163Konferensbidrag (Refereegranskat)
    Abstract [en]

    We applied a number of time-resolved optical techniques for investigation of optical and photoelectrical properties of cubic SiC grown by different technologies on different substrates. The excess carriers were injected by a short laser pulse and their dynamics was monitored by free-carrier absorption, light-induced transient grating, and photoluminescence techniques in a wide excitation range. Combining an optical and electrical probe beam delay, we found that free carrier lifetimes in differently grown layers vary from few ns up to 20 mu s. Temperature dependences of carrier diffusivity and lifetime revealed a pronounced carrier trapping in thin sublimation grown layers. In free-standing layers and thick sublimation layers, the ambipolar mobility was found the highest (120 cm(2)/Vs at room temperature). A linear correlation between the room-temperature band edge emission and carrier lifetime in differently grown layers was attributed to defect density, strongly dependent on the used growth conditions.

  • 248.
    Schimmel, Saskia
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan. University of Erlangen, Germany.
    Kaiser, Michl
    University of Erlangen, Germany.
    Hens, Philip
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Jokubavicius, Valdas
    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.
    Sun, Jianwu
    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.
    Ou, Yi Yu
    Technical University of Denmark, Lyngby.
    Ou, Hai Yan
    Technical University of Denmark, Lyngby.
    Linnarsson, Margareta K.
    KTH Royal Institute of Technology, Sweden.
    Wellmann, Peter
    University of Erlangen, Germany.
    Syväjärvi, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Step-flow growth of fluorescent 4H-SiC layers on 4 degree off-axis substrates2013Ingår i: Silicon Carbide and Related Materials 2012 / [ed] Alexander A. Lebedev, Sergey Yu. Davydov, Pavel A. Ivanov and Mikhail E. Levinshtein, Trans Tech Publications , 2013, Vol. 740-742, s. 185-188Konferensbidrag (Refereegranskat)
    Abstract [en]

    Homoepitaxial layers of fluorescent 4H-SiC were grown on 4 degree off-axis substrates by sublimation epitaxy. Luminescence in the green spectral range was obtained by co-doping with nitrogen and boron utilizing donor-acceptor pair luminescence. This concept opens possibilities to explore green light emitting diodes using a new materials platform.

  • 249.
    Selegård, Linnéa
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Khranovskyy, Volodymyr
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Söderlind, Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Vahlberg, Cecilia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik. Linköpings universitet, Tekniska högskolan.
    Ahrén, Maria
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Käll, Per-Olov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Fysikalisk Kemi. Linköpings universitet, Tekniska högskolan.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Uvdal, Kajsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Biotinylation of ZnO Nanoparticles and Thin Films: A Two-Step Surface Functionalization Study2010Ingår i: ACS APPLIED MATERIALS and INTERFACES, ISSN 1944-8244, Vol. 2, nr 7, s. 2128-2135Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study reports ZnO nanoparticles and thin film surface modification using a two-step functionalization strategy. A small silane molecule was used to build up a stabilizing layer and for conjugation of biotin (vitamin B7), as a specific tag. Biotin was chosen because it is a well-studied bioactive molecule with high affinity for avidin. ZnO nanoparticles were synthesized by electrochemical deposition under oxidizing condition, and ZnO films were prepared by plasma-enhanced metal organic chemical vapor deposition. Both ZnO nanoparticles and ZnO thin films were surface modified by forming a (3-mercaptopropyl)trimethoxysilane (MPTS) layer followed by attachment of a biotin derivate. lodoacetyl-PEG2-biotin molecule was coupled to the thiol unit in MPTS through a substitution reaction. Powder X-ray diffraction, transmission electron microscopy, X-ray photoemission electron microscopy, atomic force microscopy. X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy were used to investigate the as-synthesized and functionalized ZnO materials. The measurements showed highly crystalline materials in both cases with a ZnO nanoparticle diameter of about 5 nm and a grain size of about 45 nm for the as-grown ZnO thin films. The surface modification process resulted in coupling of silanes and biotin to both the ZnO nanoparticles and ZnO thin films. The two-step functionalization strategy has a high potential for specific targeting in bioimaging probes and for recognition studies in biosensing applications.

  • 250.
    Shavanova, Kateryna
    et al.
    National University of Life and Environm Science Ukraine, Ukraine.
    Bakakina, Yulia
    National Academic Science Belarus, Byelarus.
    Burkova, Inna
    National University of Life and Environm Science Ukraine, Ukraine.
    Shtepliuk, Ivan
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Viter, Roman
    University of Latvia, Latvia.
    Ubelis, Arnolds
    University of Latvia, Latvia.
    Beni, Valerio
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Starodub, Nickolaj
    National University of Life and Environm Science Ukraine, Ukraine.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Khranovskyy, Volodymyr
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology2016Ingår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 16, nr 2Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct "beyond graphene" domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials.

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