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Sun, Jianwu W.
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Publications (10 of 38) Show all publications
Patricia, C., Annett, T., Quanbao, M., Daniel Nielsen, W., Spyros, D., Augustinas, G., . . . Ole Martin, L. (2018). Boron-doping of cubic SiC for intermediate band solar cells: a scanning transmission electron microscopy study. SciPost Physics, 5(3), 1-17
Open this publication in new window or tab >>Boron-doping of cubic SiC for intermediate band solar cells: a scanning transmission electron microscopy study
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2018 (English)In: SciPost Physics, ISSN 2542-4653, Vol. 5, no 3, p. 1-17Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Amsterdam, Netherlands: SciPost Foundation, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-150976 (URN)10.21468/scipostphys.5.3.021 (DOI)
Available from: 2018-09-07 Created: 2018-09-07 Last updated: 2018-10-02Bibliographically approved
Shi, Y., Zakharov, A. A., Ivanov, I. G., Yazdi, G. R., Jokubavicius, V., Syväjärvi, M., . . . Sun, J. (2018). Elimination of step bunching in the growth of large-area monolayer and multilayer graphene on off-axis 3CSiC (111). Carbon, 140, 533-542
Open this publication in new window or tab >>Elimination of step bunching in the growth of large-area monolayer and multilayer graphene on off-axis 3CSiC (111)
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2018 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 140, p. 533-542Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-151054 (URN)10.1016/j.carbon.2018.08.042 (DOI)000450120200057 ()
Note

Funding agencies: Swedish Research Council (Vetenskapsradet) [621-2014-5461, 621-2014-5825]; Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) [2016-00559]; Swedish Foundation for International Cooperation in Research and Higher 

Available from: 2018-09-12 Created: 2018-09-12 Last updated: 2018-12-13
Ma, Q., Carvalho, P., Galeckas, A., Alexander, A., Hovden, S., Thøgersen, A., . . . Svensson, B. G. (2017). Characterization of B-Implanted 3C-SiC for Intermediate Band Solar Cells. Materials Science Forum, 897, 299-302
Open this publication in new window or tab >>Characterization of B-Implanted 3C-SiC for Intermediate Band Solar Cells
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2017 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 897, p. 299-302Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Trans Tech Publications, 2017
Keywords
silicon carbide, 3C-SiC, cubic, boron, implantation, characterization, intermediate band, photovoltaics, solar cells
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-137579 (URN)10.4028/www.scientific.net/MSF.897.299 (DOI)
Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2017-06-02Bibliographically approved
Ma, Q., Galeckas, A., Alexander, A., Thøgersen, A., Carvalho, P., Wright, D. N., . . . Svensson, B. G. (2016). Boron-implanted 3C-SiC for intermediate band solar cells. In: Silicon Carbide and Related Materials 2015: . Paper presented at International Conference on Silicon Carbide and Related Materials (pp. 291-294). , 858
Open this publication in new window or tab >>Boron-implanted 3C-SiC for intermediate band solar cells
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2016 (English)In: Silicon Carbide and Related Materials 2015, 2016, Vol. 858, p. 291-294Conference paper, Published paper (Refereed)
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.                    

Series
Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-128613 (URN)10.4028/www.scientific.net/MSF.858.291 (DOI)
Conference
International Conference on Silicon Carbide and Related Materials
Available from: 2016-05-25 Created: 2016-05-25 Last updated: 2019-01-31
Syväjärvi, M., Ma, Q., Jokubavicius, V., Galeckas, A., Sun, J., Liu, X., . . . Svensson, B. G. (2016). Cubic silicon carbide as a potential photovoltaic material. Solar Energy Materials and Solar Cells, 145, 104-108
Open this publication in new window or tab >>Cubic silicon carbide as a potential photovoltaic material
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2016 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 145, p. 104-108Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2016
Keywords
Intermediate band; Silicon carbide; Solar cell; Photovoltaic; Boron; Doping; 3C-SiC; Cubic
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-124457 (URN)10.1016/j.solmat.2015.08.029 (DOI)000367772200004 ()
Note

Funding Agencies|Angpanneforeningen Research Foundation (AForsk); NFR SunSic project; Swedish Energy Agency; Swedish Governmental Agency for Innovation Systems (Vinnova); STAEDTLER Foundation

Available from: 2016-02-02 Created: 2016-02-01 Last updated: 2017-11-30
Jokubavicius, V., Sun, J., Liu, X., Yazdi, G., Ivanov, I. G., Yakimova, R. & Syväjärvi, M. (2016). Growth optimization and applicability of thick on-axis SiC layers using sublimation epitaxy in vacuum. Journal of Crystal Growth, 448, 51-57
Open this publication in new window or tab >>Growth optimization and applicability of thick on-axis SiC layers using sublimation epitaxy in vacuum
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2016 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 448, p. 51-57Article in journal (Refereed) Published
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.

Keywords
Mass transfer;Substrates;Single crystal growth;Semiconducting materials
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-128610 (URN)10.1016/j.jcrysgro.2016.05.017 (DOI)
Available from: 2016-05-25 Created: 2016-05-25 Last updated: 2017-11-30
Sun, J., Jokubavicius, V., Gao, L., Booker, I. D., Jansson, M., Liu, X., . . . Syväjärvi, M. (2016). Solar driven energy conversion applications based on 3C-SiC. In: Materials Science Forum: . Paper presented at 16th International Conference on Silicon Carbide and Related Materials, ICSCRM 2015 (pp. 1028-1031). Trans Tech Publications Ltd, 858
Open this publication in new window or tab >>Solar driven energy conversion applications based on 3C-SiC
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2016 (English)In: Materials Science Forum, Trans Tech Publications Ltd , 2016, Vol. 858, p. 1028-1031Conference paper, Published paper (Refereed)
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.

Place, publisher, year, edition, pages
Trans Tech Publications Ltd, 2016
Series
Materials Science Forum, ISSN 0255-5476 ; 868
Keywords
Cubic silicon carbide (3C-SiC); Photoelectrochemical (PEC) water splitting; Solar cell
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-129242 (URN)10.4028/www.scientific.net/MSF.858.1028 (DOI)2-s2.0-84971577103 (Scopus ID)9783035710427 (ISBN)
Conference
16th International Conference on Silicon Carbide and Related Materials, ICSCRM 2015
Available from: 2016-06-14 Created: 2016-06-14 Last updated: 2016-11-15
Jokubavicius, V., Yazdi, G. R., Liljedahl, R., Ivanov, I. G., Sun, J., Liu, X., . . . Syväjärvi, M. (2015). Single Domain 3C-SiC Growth on Off-Oriented 4H-SiC Substrates. Crystal Growth & Design, 15(6), 2940-2947
Open this publication in new window or tab >>Single Domain 3C-SiC Growth on Off-Oriented 4H-SiC Substrates
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2015 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 15, no 6, p. 2940-2947Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2015
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-118525 (URN)10.1021/acs.cgd.5b00368 (DOI)000355890400051 ()
Note

Swedish Energy Agency; Swedish Research Council; Swedish Governmental Agency for Innovation Systems (Vinnova)

Available from: 2015-05-29 Created: 2015-05-29 Last updated: 2017-12-04
Collaert, N., Alian, A., Arimura, H., Boccardi, G., Eneman, G., Franco, J., . . . Thean, A.-Y. V. (2015). Ultimate nano-electronics: New materials and device concepts for scaling nano-electronics beyond the Si roadmap. Microelectronic Engineering, 132, 218-225
Open this publication in new window or tab >>Ultimate nano-electronics: New materials and device concepts for scaling nano-electronics beyond the Si roadmap
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2015 (English)In: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 132, p. 218-225Article in journal (Refereed) Published
Abstract [en]

Abstract In this work, we will give an overview of the innovations in materials and new device concepts that will be needed to continue Moore’s law to the sub-10 nm technology nodes. To meet the power and performance requirements high mobility materials in combination with new device concepts like tunnel FETs and gate-all-around devices will need to be introduced. As the density is further increased and it becomes increasingly difficult to put contacts, spacers and gate in the available gate pitch, disruptive integration schemes such as vertical transistors and monolithic 3D integration might lead the way to the ultimate scaling of CMOS.

Keywords
High mobility materials, FinFET, TFET, Nanowires
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-128845 (URN)10.1016/j.mee.2014.08.005 (DOI)
Available from: 2016-06-02 Created: 2016-06-02 Last updated: 2017-11-30
Ou, H., Ou, Y., Argyraki, A., Schimmel, S., Kaiser, M., Wellmann, P., . . . Syväjärvi, M. (2014). Advances in wide bandgap SiC for optoelectronics. European Physical Journal B: Condensed Matter Physics, 87, 58
Open this publication in new window or tab >>Advances in wide bandgap SiC for optoelectronics
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2014 (English)In: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 87, p. 58-Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2014
Keywords
Colloquium
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-105175 (URN)10.1140/epjb/e2014-41100-0 (DOI)000332697900001 ()
Available from: 2014-03-11 Created: 2014-03-11 Last updated: 2017-12-05Bibliographically approved
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