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We generate amorphous Si1 − xGex alloys for various Ge compositions by the simulated quenching method using the first-principles molecular-dynamics approach. We find that dangling bonds at Ge sites dominate the local defect structures in a wide range of Ge compositions of x ≥ 0.15, although their backbonding states change with Ge composition. This is due to the minimization of strain energy by having dangling bonds at Ge sites in the network. By postulating that only dangling bonds contribute to the g-value, the calculated g-values are in excellent agreement with the observed ones.

A UV sensor was fabricated by screen printing indium–tin-oxide (ITO) nanocrystals on to quart glass. The initial printed ITO layer showed a resistivity too high for sensing applications, but considerable improvements were achieved through annealing under external pressure. The effects of this pressurized annealing were investigated using a commercial ITO film. The annealing aided the development of low-resistivity ITO through the repression of complex defects. The feasibility of the ITO sensor was confirmed through annealing coil-shaped ITO sensors under different conditions. Pressurized annealing greatly enhanced the output signal intensity under similar UV illumination conditions.

The band-edge potential and photocurrent density of N-face GaN were experimentally determined to be more negative and greater than those of Ga-face GaN, respectively, in this photoelectrochemical experiment. These results indicate that the N-face GaN could generate much more hydrogen than Ga-face GaN. Although the time dependence of the photocurrent density of N-face GaN was almost constant, that of Ga-face GaN stabilized only after 260 min of reaction time. From these results, we conclude that N-face GaN, which has a more negative band-edge potential and a more stable photocurrent density, could be suitable for higher-photocurrent generation than Ga-face GaN.

We report on the growth and characterization of GaN rods selectively grown on the apex of hexagonal GaN pyramids. SiO2 near the apex of the hexagonal GaN pyramids was removed by an optimized photolithography process and subsequently subjected to Au deposition and selective growth of GaN rods by metal organic vapor phase epitaxy (MOVPE). It was observed that there were preferred GaN rods orientations toward directions. The GaN rods had triangular cross section enclosed with (1122), (1122), and (0001) side facets. A particular feature was that each rod has sharp edge at its very end. We found that the GaN rods could be formed not by vapor–liquid–solid (VLS) process but Ga–Au intermediate state. This work opens up new growth methods for position and density controlled III–nitride nano- and micro-structures which have potential use in high functional devices, such as field emitters and gas sensors.

We propose a new equation considering strain effect for the temperature dependence of bandgap transition of GaN films grown on sapphire. By using the chemical lift-off method the GaN films were separated from the sapphire substrate and we evaluated the energy shift of the bandgap transition due to the strain caused by the sapphire substrate quantitatively. The transition energies of the free exciton A (FXA) in the GaN film at a finite temperature are described by the equation E(T) = E(0) ? (?T2/(? + T)) + ?E(0) + ?(TECfilm ? TECsub)T, where ? and ? are the temperature coefficients, ? is the strain coefficient, and TECfilm and TECsub are thermal expansion coefficients of the film and the substrate, respectively. This equation is divided into an ordinary temperature component and an additional strain component of the hetero-epitaxial film. The temperature dependence of exciton transition energy of the strained GaN film should be expressed by the above equation with E(0) = 3.4774?eV, ? = 0.93?meV?K?1, ? = 1280?K, ?E(0) = 10.87?meV and ? = 2.04 ? 10?3?eV.

The diameter of ZnO nanowires grown by chemical vapour deposition was controlled by employing CrN buffer structures on the c-Al2O3 substrate. The nanosized CrN islands with different morphologies were prepared by nitridation of thickness-controlled Cr film in NH3 atmosphere. The ZnO nanowires grew normal to the surface of the CrN/c-Al2O3 templates due to reduction in the lattice mismatch between ZnO and c-Al2O3 by the CrN buffer layer. Investigation of the interface between CrN and ZnO by high resolution transmission electron microscopy revealed the presence of reactive layers such as ZnCr2O4 and Cr2O3. The diameter of nanowires significantly affected their stimulated emission characteristics. At room temperature, the threshold intensity for stimulated emission increased from 35 to above 500?kW?cm?2 as the diameter of ZnO nanowires decreases from 223 to 77?nm. This dependence of threshold intensity for stimulated emission from nanowires is caused by an increase in the surface recombination and/or enhanced leakage of optical field in narrower nanowires.