| 1. |
- Pecz, B., et al.
(författare)
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GaN heterostructures with diamond and graphene
- 2015
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Ingår i: Semiconductor Science and Technology. - : IOP PUBLISHING LTD. - 0268-1242 .- 1361-6641. ; 30:11, s. 114001-
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Kasama, T., et al.
(författare)
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Direct observation of doping incorporation pathways in self-catalytic GaMnAs nanowires
- 2015
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Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 118:5
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Tidskriftsartikel (refereegranskat)abstract
- Doping mechanisms of Mn in GaAs nanowires (NWs) that have been grown self-catalytically at 600 degrees C by molecular beam epitaxy (MBE) are investigated using advanced electron microscopy techniques and atom probe tomography, Mn is found to be incorporated primarily in the form of non-magnetic tetragonal Ga0.82Mn0.18 nanocrystals in Ga catalyst droplets at the ends of the NWs, while trace amounts of Mn (22 +/- 4 at. ppm) are also distributed randomly in the NW bodies without forming clusters or precipitates. The nanocrystals are likely to form after switching off the reaction in the MBE chamber, since they are partially embedded in neck regions of the NWs. The Ga0.82Mn0.18 nanocrystals and the low Mn concentration in the NW bodies are insufficient to induce a ferromagnetic phase transition, suggesting that it is difficult to have high Mn contents in GaAs even in 1-D NW growth via the vapor-liquid-solid process. (C) 2015 AIP Publishing LLC.
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| 3. |
- Sharma, V., et al.
(författare)
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Improved mechanical properties of a Ti-48Al alloy processed by mechanical alloying and spark plasma sintering
- 2023
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Ingår i: Materials Today Communications. - : Elsevier BV. - 2352-4928. ; 35
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Tidskriftsartikel (refereegranskat)abstract
- Bulk Ti-48Al alloy samples were prepared by the high energy ball milling (HBM) of elemental powders, followed by spark plasma sintering (SPS) of the HBM processed powders. The microstructure, phase evolution and mechanical properties of the bulk alloy were studied. The resulting TiAl + Ti3Al two phase alloy possessed an equiaxed fine grain structure, unlike the usual lamellar structure produced by arc melting. The process parameters of HBM and SPS, e.g., milling speed, milling time and sintering temperature were used to tune the phase fraction, microstructure, and grain size. A very high nanohardness of up to ∼12 GPa was obtained, ∼2.4 times higher than the corresponding value of the as-cast counterpart. The combined influence of powder size reduction during HBM, high Ti3Al phase fraction and microstructural development during SPS resulted in higher hardness, wear resistance and yield pressure. Thus, a HBM+SPS processing approach is a promising processing route for the manufacture of high hardness bulk TiAl alloys.
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