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Liu, Xinyu
Publications (6 of 6) Show all publications
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
Zhao, Q., Liu, X. & Holtz, P.-O. (2014). Properties of shallow donors in ZnMgO epilayers grown by metal organic chemical vapor deposition. Journal of Applied Physics, 116(18), 183508
Open this publication in new window or tab >>Properties of shallow donors in ZnMgO epilayers grown by metal organic chemical vapor deposition
2014 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, no 18, p. 183508-Article in journal (Refereed) Published
Abstract [en]

High quality Zn1-xMgxO epilayers have been grown by means of metal organic chemical vapor deposition technique on top of ZnO templates. The grown samples were investigated by x-ray photoelectron spectroscopy and photoluminescence. The magnesium (Mg) concentration was varied between 0% and 3% in order to study the properties of shallow donors. The free and donor bound excitons could be observed simultaneously in our high quality Zn1-xMgxO epilayers in the photoluminescence spectra. The results indicate that both built-in strain and Mg-concentration influence the donor exciton binding energy. It clearly shows that the donor exciton binding energy decreases with increasing Mg-concentration and with increasing built-in strain. Furthermore, the results indicate that the donor bound exciton transition energy increases with decreasing strength of the built-in strain if the Mg-concentration is kept the same in the Zn1-xMgxO epilayers.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2014
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-113011 (URN)10.1063/1.4902007 (DOI)000345216300017 ()
Available from: 2015-01-12 Created: 2015-01-08 Last updated: 2017-12-05
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