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Publications (10 of 202) Show all publications
Suvanam, S. S., Larsen, J., Ross, N., Kosyak, V., Hallén, A. & Björkman, C. P. (2018). Extreme radiation hard thin film CZTSSe solar cell. Solar Energy Materials and Solar Cells, 185, 16-20
Open this publication in new window or tab >>Extreme radiation hard thin film CZTSSe solar cell
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2018 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 185, p. 16-20Article in journal (Refereed) Published
Abstract [en]

In this work, we have demonstrated the extreme radiation hardness of thin film CZTSSe solar cells. Thin film solar cells with CZTSSe, CZTS and CIGS absorber layers were irradiated with 3 MeV protons. No degradation in device parameters was observed until a displacement damage dose of 2 × 1010 MeV/g for CZTS and CZTSSe. CIGS solar cells degraded by 13% at the same dose. For the highest proton dose both the CZTSSe and CZTS degraded by 16% while CIGS suffered from 34% degradation in efficiency. The degradation in efficiency maybe attributed to the reduction in the minority carrier lifetime due to radiation induced lattice defects. Comparisons with previously available literature show that our CZTS technology has superior radiation hardness by about two orders of magnitude compared to existing state of the art Si and GaAs technology.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
CZTSSe, Proton radiation, Radiation hardness, Space solar cells
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:kth:diva-228694 (URN)10.1016/j.solmat.2018.05.012 (DOI)2-s2.0-85046621751 (Scopus ID)
Note

QC 20180530

Available from: 2018-05-30 Created: 2018-05-30 Last updated: 2018-05-30Bibliographically approved
Chulapakorn, T., Primetzhofer, D., Sychugov, I., Suvanam, S. S., Linnros, J. & Hallén, A. (2018). Impact of H-uptake by forming gas annealing and ion implantation on photoluminescence of Si-nanoparticles. Physica Status Solidi (a) applications and materials science, 215(3), Article ID 1700444.
Open this publication in new window or tab >>Impact of H-uptake by forming gas annealing and ion implantation on photoluminescence of Si-nanoparticles
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2018 (English)In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 215, no 3, article id 1700444Article in journal (Refereed) Published
Abstract [en]

Silicon nanoparticles (SiNPs) are formed by implanting 70 keV Si+ into a SiO2-film and subsequent thermal annealing. SiNP samples are further annealed in forming gas. Another group of samples containing SiNP is implanted by 7.5 keV H+ and subsequently annealed in N2-atmosphere at 450 °C to reduce implantation damage. Nuclear reaction analysis (NRA) is employed to establish depth profiles of the H-concentration. Enhanced hydrogen concentrations are found close to the SiO2surface, with particularly high concentrations for the as-implanted SiO2. However, no detectable uptake of hydrogen is observed by NRA for samples treated by forming gas annealing (FGA). H-concentrations detected after H-implantation follow calculated implantation profiles. Photoluminescence (PL) spectroscopy is performed at room temperature to observe the SiNP PL. Whereas FGA is found to increase PL under certain conditions, i.e., annealing at high temperatures, increasing implantation fluence of H reduces the SiNP PL. Hydrogen implantation also introduces additional defect PL. After low-temperature annealing, the SiNP PL is found to improve, but the process is not found equivalently efficient as conventional FGA.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
H-quantification, nuclear reaction analysis, photoluminescence, silicon nanoparticles
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-219544 (URN)10.1002/pssa.201700444 (DOI)000424387300006 ()2-s2.0-85031427795 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20171219

Available from: 2017-12-17 Created: 2017-12-17 Last updated: 2018-02-22Bibliographically approved
Suvanam, S. S., Usman, M., Martin, D., Yazdi, M. G., Linnarsson, M. K., Tempez, A., . . . Hallén, A. (2018). Improved interface and electrical properties of atomic layer deposited Al2O3/4H-SiC. Applied Surface Science, 433, 108-115
Open this publication in new window or tab >>Improved interface and electrical properties of atomic layer deposited Al2O3/4H-SiC
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2018 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 433, p. 108-115Article in journal (Refereed) Published
Abstract [en]

In this paper we demonstrate a process optimization of atomic layer deposited Al2O3 on 4H-SiC resulting in an improved interface and electrical properties. For this purpose the samples have been treated with two pre deposition surface cleaning processes, namely CP1 and CP2. The former is a typical surface cleaning procedure used in SiC processing while the latter have an additional weak RCA1 cleaning step. In addition to the cleaning and deposition, the effects of post dielectric annealing (PDA) at various temperatures in N2O ambient have been investigated. Analyses by scanning electron microscopy show the presence of structural defects on the Al2O3 surface after annealing at 500 and 800 °C. These defects disappear after annealing at 1100 °C, possibly due to densification of the Al2O3 film. Interface analyses have been performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight medium energy ion scattering (ToF MEIS). Both these measurements show the formation of an interfacial SiOx (0 < x < 2) layer for both the CP1 and CP2, displaying an increased thickness for higher temperatures. Furthermore, the quality of the sub-oxide interfacial layer was found to depend on the pre deposition cleaning. In conclusion, an improved interface with better electrical properties is shown for the CP2 sample annealed at 1100 °C, resulting in lower oxide charges, strongly reduced flatband voltage and leakage current, as well as higher breakdown voltage.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
4H-SiC, Al2O3, High-K dielectric, Interface trap densities, Annealing, Atomic layer deposition, Cleaning, Deposition, Optimization, Scanning electron microscopy, Silicon carbide, Surface cleaning, Surface defects, Atomic layer deposited, Interface analysis, Interface trap density, Medium energy ion scattering, Structural defect, Surface cleaning procedure, X ray photoelectron spectroscopy
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-223127 (URN)10.1016/j.apsusc.2017.10.006 (DOI)000418883800014 ()2-s2.0-85031746823 (Scopus ID)
Funder
Swedish Research Council, D0674701
Note

QC 20180327

Available from: 2018-03-27 Created: 2018-03-27 Last updated: 2018-04-11Bibliographically approved
Azarov, A., Rauwel, P., Hallén, A., Monakhov, E. & Svensson, B. G. (2017). Extended defects in ZnO: Efficient sinks for point defects. Applied Physics Letters, 110(2), Article ID 022103.
Open this publication in new window or tab >>Extended defects in ZnO: Efficient sinks for point defects
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2017 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, no 2, article id 022103Article in journal (Refereed) Published
Abstract [en]

Dopant-defect reactions dominate the defect formation in mono-crystalline ZnO samples implanted with Ag and B ions. This is in contrast to most other ion species studied and results in an enhanced concentration of extended defects, such as stacking faults and defect clusters. Using a combination of B and Ag implants and diffusion of residual Li atoms as a tracer, we demonstrate that extended defects in ZnO act as efficient traps for highly mobile Zn interstitials. The results imply that dynamic annealing involving interaction of point defects with extended ones can play a key role in the disorder saturation observed for ZnO and other radiation-hard semiconductors implanted with high doses.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-202434 (URN)10.1063/1.4973463 (DOI)000392835300033 ()2-s2.0-85009191857 (Scopus ID)
Note

QC 20170306

Available from: 2017-03-06 Created: 2017-03-06 Last updated: 2017-11-29Bibliographically approved
Chulapakorn, T., Sychugov, I., Suvanam, S. S., Linnros, J., Primetzhofer, D. & Hallén, A. (2017). Influence of swift heavy ion irradiation on the photoluminescence of Si-nanoparticles and defects in SiO2. Nanotechnology, 28, Article ID 375606.
Open this publication in new window or tab >>Influence of swift heavy ion irradiation on the photoluminescence of Si-nanoparticles and defects in SiO2
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2017 (English)In: Nanotechnology, Vol. 28, article id 375606Article in journal (Refereed) Published
Abstract [en]

The influence of swift heavy ion (SHI) irradiation on the photoluminescence (PL) of silicon nanoparticles (SiNPs) and defects in SiO2-film is investigated. SiNPs were formed by implantation of 70 keV Si+ and subsequent thermal annealing to produce optically active SiNPs and to remove implantation-induced defects. Seven different ion species with energy between 3-36 MeV and fluence from 10(11)-10(14) cm(-2) were employed for irradiation of the implanted samples prior to the thermal annealing. Induced changes in defect and SiNP PL were characterized and correlated with the specific energy loss of the employed SHIs. We find that SHI irradiation, performed before the thermal annealing process, affects both defect and SiNP PL. The change of defect and SiNP PL due to SHI irradiation is found to show a threshold-like behaviour with respect to the electronic stopping power, where a decrease in defect PL and an anticorrelated increase in SiNP PL after the subsequent thermal annealing are observed for electronic stopping exceeding 3-5 keV nm(-1). PL intensities are also compared as a function of total energy deposition and nuclear energy loss. The observed effects can be explained by ion track formation as well as a different type of annealing mechanisms active for SHI irradiation compared to the thermal annealing.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2017
Keywords
silicon nanoparticle; ion implantation; photoluminescence; swift heavy ion irradiation
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-219545 (URN)10.1088/1361-6528/aa824f (DOI)000408244000002 ()2-s2.0-85028462224 (Scopus ID)
Note

QC 20171219

Available from: 2017-12-17 Created: 2017-12-17 Last updated: 2017-12-19Bibliographically approved
Linnarsson, M. K., Hallén, A., Khartsev, S., Suvanam, S. S. & Usman, M. (2017). Interface between Al2O3 and 4H-SiC investigated by time-of-flight medium energy ion scattering. Journal of Physics D: Applied Physics, 50(49), Article ID 495111.
Open this publication in new window or tab >>Interface between Al2O3 and 4H-SiC investigated by time-of-flight medium energy ion scattering
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2017 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 50, no 49, article id 495111Article in journal (Refereed) Published
Abstract [en]

The formation of interfacial oxides during heat treatment of dielectric films on 4H-SiC has been studied. The 4H-SiC surface has been carefully prepared to create a clean and abrupt interface to Al2O3. An amorphous, 3 nm thick, Al2O3 film has been prepared on 4H-SiC by atomic layer deposition and rapid thermal annealing was then performed in N2O ambient at 700 degrees C and 1100 degrees C during 1 min. The samples were studied by time-of-flight medium energy ion scattering (ToF-MEIS), with sub-nanometer depth resolution and it is seen that, at both annealing temperatures, a thin SiOx (1 <= x <= 2) is formed at the interface. Our results further indicate that carbon remains in the silicon oxide in samples annealed at 700 degrees C. Additional electrical capacitance voltage measurements indicate that a large concentration of interface traps is formed at this temperature. After 1100 degrees C annealing, both MEIS and XRD measurements show that these features disappear, in accordance with electrical data.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2017
Keywords
ALD, ToF-MEIS, 4H-SiC, Al2O3, interface
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-219324 (URN)10.1088/1361-6463/aa9431 (DOI)000415834100006 ()2-s2.0-85039788159 (Scopus ID)
Funder
Swedish Research Council, E0510501; D0674701
Note

QC 20171205

Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2018-01-11Bibliographically approved
Rubel, M., Moon, S., Petersson, P., Garcia Carrasco, A., Hallén, A., Krawczynska, A., . . . Widdowson, A. (2017). Metallic mirrors for plasma diagnosis in current and future reactors: tests for ITER and DEMO. Paper presented at 16th International Conference on Plasma-Facing Materials and Components for Fusion Applications (PFMC), MAY, 2017, GERMANY. Physica Scripta, T170, Article ID 014061.
Open this publication in new window or tab >>Metallic mirrors for plasma diagnosis in current and future reactors: tests for ITER and DEMO
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2017 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T170, article id 014061Article in journal (Refereed) Published
Abstract [en]

Optical spectroscopy and imaging diagnostics in next-step fusion devices will rely on metallic mirrors. The performance of mirrors is studied in present-day tokamaks and in laboratory systems. This work deals with comprehensive tests of mirrors: (a) exposed in JET with the ITER-like wall (JET-ILW); (b) irradiated by hydrogen, helium and heavy ions to simulate transmutation effects and damage which may be induced by neutrons under reactor conditions. The emphasis has been on surface modification: deposited layers on JET mirrors from the divertor and on near-surface damage in ion-irradiated targets. Analyses performed with ion beams, microscopy and spectro-photometry techniques have revealed: (i) the formation of multiple co-deposited layers; (ii) flaking-off of the layers already in the tokamak, despite the small thickness (130-200 nm) of the granular deposits; (iii) deposition of dust particles (0.2-5 mu m, 300-400 mm(-2)) composed mainly of tungsten and nickel; (iv) that the stepwise irradiation of up to 30 dpa by heavy ions (Mo, Zr or Nb) caused only small changes in the optical performance, in some cases even improving reflectivity due to the removal of the surface oxide layer; (v) significant reflectivity degradation related to bubble formation caused by the irradiation with He and H ions.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-220611 (URN)10.1088/1402-4896/aa8e27 (DOI)000417694700006 ()
Conference
16th International Conference on Plasma-Facing Materials and Components for Fusion Applications (PFMC), MAY, 2017, GERMANY
Note

QC 20180112

Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2018-03-12Bibliographically approved
Ayedh, H. M., Nipoti, R., Hallén, A. & Svensson, B. G. (2017). Thermodynamic equilibration of the carbon vacancy in 4H-SiC: A lifetime limiting defect. Journal of Applied Physics, 122(2), Article ID 025701.
Open this publication in new window or tab >>Thermodynamic equilibration of the carbon vacancy in 4H-SiC: A lifetime limiting defect
2017 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 122, no 2, article id 025701Article in journal (Refereed) Published
Abstract [en]

The carbon vacancy (V-C) is a prominent defect in as-grown 4H-SiC epitaxial layers for high power bipolar devices. V-C is electrically active with several deep levels in the bandgap, and it is an efficient "killer" of the minority carrier lifetime in n-type layers, limiting device performance. In this study, we provide new insight into the equilibration kinetics of the thermodynamic processes governing the V-C concentration and how these processes can be tailored. A slow cooling rate after heat treatment at similar to 2000 degrees C, typically employed to activate dopants in 4H-SiC, is shown to yield a strong reduction of the V-C concentration relative to that for a fast rate. Further, post-growth heat treatment of epitaxial layers has been conducted over a wide temperature range (800-1600 degrees C) under C-rich surface conditions. It is found that the thermodynamic equilibration of V-C at 1500 degrees C requires a duration less than 1 h resulting in a V-C concentration of only similar to 10(11) cm(-3), which is, indeed, beneficial for high voltage devices. In order to elucidate the physical processes controlling the equilibration of V-C, a defect kinetics model is put forward. The model assumes Frenkel pair generation, injection of carbon interstitials (C-i's) from the C-rich surface (followed by recombination with V-C's), and diffusion of V-C's towards the surface as the major processes during the equilibration, and it exhibits good quantitative agreement with experiment.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-211608 (URN)10.1063/1.4991815 (DOI)000405663800057 ()2-s2.0-85024404894 (Scopus ID)
Note

QC 20170811

Available from: 2017-08-11 Created: 2017-08-11 Last updated: 2017-08-11Bibliographically approved
Suvanam, S. S., Lanni, L., Malm, B. G., Zetterling, C.-M. & Hallén, A. (2017). Total Dose Effects on 4H-SiC Bipolar Junction Transistors. In: : . Paper presented at European Conference on Silicon Carbide and Related Materials 2016 (ECSCRM-16). Material science Forum
Open this publication in new window or tab >>Total Dose Effects on 4H-SiC Bipolar Junction Transistors
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2017 (English)Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Material science Forum, 2017
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-199903 (URN)10.4028/www.scientific.net/MSF.897.579 (DOI)2-s2.0-85020007905 (Scopus ID)
Conference
European Conference on Silicon Carbide and Related Materials 2016 (ECSCRM-16)
Note

QC 20170201

Available from: 2017-01-17 Created: 2017-01-17 Last updated: 2017-10-23Bibliographically approved
Linnarsson, M. K., Suvanam, S. S., Vines, L. & Hallén, A. (2016). Alkali metal re-distribution after oxidation of 4H-SiC. In: 16th International Conference on Silicon Carbide and Related Materials, ICSCRM 2015: . Paper presented at 4 October 2015 through 9 October 2015 (pp. 677-680). Trans Tech Publications Ltd
Open this publication in new window or tab >>Alkali metal re-distribution after oxidation of 4H-SiC
2016 (English)In: 16th International Conference on Silicon Carbide and Related Materials, ICSCRM 2015, Trans Tech Publications Ltd , 2016, p. 677-680Conference paper, Published paper (Refereed)
Abstract [en]

Relocation of alkali metals sodium, potassium and cesium during oxidation of 4H-SiC has been studied by secondary ion mass spectrometry. The alkali metal source has been introduced by ion implantation before oxidation into n- and p-type 4H-SiC samples. Dry oxidation of SiC has been performed at 1150 ºC during 4, 8 and 16 h. In the formed oxide, the main part of the alkali metals diffuses out via the SiO2 surface. Close to the moving SiO2/SiC interface, a minor amount of alkali metals is retained. In the SiC material, the main amount of implanted alkali atoms is not redistributed during the oxidation, although a minor amount diffuses deeper into the samples. For ptype 4H-SiC, the diffusion deeper into the samples of the studied alkali metals decreases as the mass increases, Na+&lt;K+&lt;Cs+, but the sodium mobility is substantial already at 1150 °C.

Place, publisher, year, edition, pages
Trans Tech Publications Ltd, 2016
Keywords
Cesium, Diffusion, Oxidation, Potassium, SIMS, Sodium, Ion implantation, Mass spectrometry, Metals, Secondary ion mass spectrometry, Silicon oxides, Alkali atoms, Dry oxidation, Mass increase, P-type 4H-SiC, Re-distribution, SiC materials, Silicon carbide
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-195473 (URN)10.4028/www.scientific.net/MSF.858.677 (DOI)2-s2.0-84971570725 (Scopus ID)9783035710427 (ISBN)
Conference
4 October 2015 through 9 October 2015
Note

QC 20161125

Available from: 2016-11-25 Created: 2016-11-03 Last updated: 2016-11-25Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8760-1137

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