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Träfflista för sökning "LAR1:liu ;pers:(Syväjärvi Mikael);srt2:(1997-1999)"

Sökning: LAR1:liu > Syväjärvi Mikael > (1997-1999)

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1.
  • Kakanakova-Georgieva, Anelia, 1970-, et al. (författare)
  • Structural properties of 6H-SiC epilayers grown by two different techniques
  • 1997
  • Ingår i: Materials Science and Engineering B. - 0921-5107. ; 46:1-3, s. 345-348
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present work we investigated the structural properties of 6H-SiC homoepitaxial layers utilizing microhardness and X-ray characterization techniques. The growth was performed by chemical vapour deposition (CVD) and liquid phase epitaxy (LPE) under various growth conditions. The depth Knoop hardness profiles represent decreasing curves due to the indentation size effect. With load increasing the curves saturate reaching microhardness values comparable with the known Vickers ones. At about 0.4 μm beneath the layer surfaces the curves show small plateaus which may be attributed to structural inhomogeneity. This is suggested by X-ray diffraction spectra taken from the same samples, which contain additional peaks besides the typical ones for 6H-SiC.
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2.
  • Pecz, B, et al. (författare)
  • Structural investigation of SiC epitaxial layers grown under microgravity and on-ground conditions
  • 1999
  • Ingår i: Thin Solid Films. - 0040-6090. ; 357:2, s. 137-143
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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3.
  • Pecz, B, et al. (författare)
  • Structure of SiC layers grown by LPE in microgravity and on-ground conditions
  • 1999
  • Ingår i: Institute of Physics Conference Series. - 0951-3248. ; :164, s. 243-246
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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4.
  • Syväjärvi, Mikael, et al. (författare)
  • Anisotropy of dissolution and defect revealing on SiC surfaces
  • 1999
  • Ingår i: Journal of Physics : Condensed Matter. - 0953-8984. ; 11:49, s. 10041-10046
  • Tidskriftsartikel (refereegranskat)abstract
    • Micropipes and dislocations in silicon carbide single crystals are revealed by chemical etching. Micropipes are shown to be interconnected with other structural defects and the reason for this is discussed. The Si and C faces are attacked by molten KOH preferentially and isotropically, respectively. The mechanism is discussed in relation to the different surface free energies on the Si and C faces. The revealing of micropipes is more pronounced on the Si face. The hexagonal pattern of micropipes are revealed by rapid etching provided by a large undersaturation at the surface. It is shown that etching from a melt gives a disintegration of the SiC crystal at the micropipe via spiral dissolution which is due to etching near equilibrium conditions. The temperature dependence of the etch rate follows an Arrhenius dependence with an apparent activation energy of about 12-15 kcal mol(-1) derived from measuring etch rate and weight loss.
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5.
  • Syväjärvi, Mikael, et al. (författare)
  • Growth of 6H and 4H-SiC by sublimation epitaxy
  • 1999
  • Ingår i: Journal of Crystal Growth. - 0022-0248. ; 197:1-2, s. 155-162
  • Tidskriftsartikel (refereegranskat)abstract
    •   The epitaxial sublimation growth process of SiC has been investigated. Layers with specular surfaces and growth rates up to 2 mm/h have been obtained. No step bunching is observed by optical microscopy even on very thick layers which indicates a stable step growth mechanism. Under certain growth conditions the morphology degrades. The morphological stability is investigated and discussed in relation to the growth kinetics. Impurities in the epitaxial layers are investigated by secondary ion mass spectroscopy and low-temperature photoluminescence. The carrier concentration is measured by capacitance–voltage measurements. The structural quality of the grown material is improved compared to the substrate as shown by X-ray diffraction measurements. 
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6.
  • Syväjärvi, Mikael, et al. (författare)
  • Kinetics and morphological stability in sublimation growth of 6H and 4H-SiC epitaxial layers
  • 1999
  • Ingår i: Materials Science and Engineering: B. - 0921-5107. ; 61-62, s. 161-164
  • Tidskriftsartikel (refereegranskat)abstract
    • Very high growth rates (>2 mm h−1) in SiC epitaxy have been achieved. The rate determining mechanism changes from diffusion to kinetics when the growth pressure decreases below 5–10 mbar. At low pressures it is shown that sublimation of the SiC source is the rate determining step and that there is a free molecular transport from source to substrate. The growth rate is constant during several hours of growth and Si losses from the crucible are very small. These facts show that our growth system is stable. The obtained apparent activation energy (130 kcal mol−1) is attributed to the sublimation rate of the SiC source material. The morphology is smooth and the surfaces are specular if the growth conditions are selected within the given parameter window for morphological stability. The origin of the growth disturbances is discussed.
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7.
  • Syväjärvi, Mikael, et al. (författare)
  • Step-bunching in 6H-SiC growth by sublimation epitaxy
  • 1999
  • Ingår i: Journal of Physics : Condensed Matter. - 0953-8984. ; 11:49, s. 10019-10024
  • Tidskriftsartikel (refereegranskat)abstract
    • Thick 6H-SiC epitaxial layers grown by sublimation epitaxy have been investigated concerning step-bunching. The macrostep appearances on the surfaces were studied for both (0001) Si and (000 (1) over bar) C faces. The surface structure on the Si face is less regular compared with the C face. Data on the steps have been collected and the step height shows a linear relation with the step width.
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8.
  • Tuominen, M., et al. (författare)
  • Investigation of domain evolution in sublimation epitaxy of SiC
  • 1998
  • Ingår i: Journal of Crystal Growth. - 0022-0248. ; 193:1-2, s. 101-108
  • Tidskriftsartikel (refereegranskat)abstract
    • High resolution X-ray diffractometry has been applied to study domain misorientation in SiC epi-layers grown by the sublimation epitaxy method. A pronounced effect of the growth conditions on the mosaicity of the epi-layer has been observed. The results are discussed in terms of domain evolution and structural changes during the epi-growth under different growth conditions.
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