Metal–oxide–semiconductor structures with a Ge nanocrystal embedded in SiO2 films were fabricated by Ge+ ion implantation and subsequent high-temperature annealing. The Raman spectra indicate the evidence of self-assembled Ge nanocrystals in the SiO2 films. The Ge size and its density were estimated to 3–5 nm and 1×1012/cm2, respectively. Photoluminescence spectra showed a strong blue–violet band around 400 nm and a weak near-infrared band around 750 nm, respectively. The several implantation-induced deficient centers are believed to be responsible for the blue-light luminescence. Capacitance–voltage characteristics exhibit the flatband voltage shifts of 1.02 V after the electron injection into the SiO2/Ge/SiO2 potential well. An anomalous leakage current was clearly observed in the current–voltage characteristics. The precise simulation of quantum electron transport in the SiO2 film indicates that the anomalous conduction is originated from resonant tunneling in the SiO2/Ge/SiO2 double-well band structure.
Hetero-epitaxial CVD growth of 3C-SiC on a Si(110) substrate gives a (111) crystal with low defects density. However, double positioning growth often disturbs growth of a single crystal. The growth on an off-axis Si(110) substrate suppressed propagation of the double positioning defects in the grown layer effectively. Cross-sectional transmission electron microscopy revealed
the details of the suppression process on the off-axis substrate. The suppression mechanism and the origin of the defects formation at double positioning boundaries were interpreted by the growth model based on an anisotropic growth rate on (111) plane of 3C-SiC.
The preparation of porous 4H-SiC by electrochemical etching of SiC crystals was investigated. The porous layer was created at the porous SiC (PSC)/SiC interface but not from the SiC/electrolyte interface. The nanopores at the adjacent region of PSC/SiC interface were bigger than those at the top region. In the visible light region, the optical reflectance from PSC exhibits interference fringes. In the Reststrahlen region, the fourier transform infrared (FTIR) reflectance of porous 4H-SiC shows a splitting into more bands: a broad band with high reflectivity at low frequency and several sharp peaks near the LO frequency. The width and shape of FTIR spectra depended on the anodization current density. The anodization current density is a crucial parameter which determined the porosity, porosity depth profile, and the thickness of PSC layers. A pore transformation of porous structure was observed after chemical vapor deposition process.
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