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The effects of quantum corrections on electron conductivity in bilayer graphene have been studied under various temperatures and gate voltages to seek the origin of the restrictions in electron conductions. Although previous studies suggested the enhanced intervalley scattering effect to be the major reason behind the restriction on electron transport, tested samples in this work exhibited the weak localization effect due to much weaker intervalley scattering rates. The enhancement of inelastic scattering near Dirac point are further tested to show the reason behind the inconsistency. It is successfully shown that the amount of electron-hole puddles, and thus, screening effects could enhance intervalley scattering near Dirac point.

The most desirable approach to the hydrometallurgical process consists in using larger silicon particles by exposing the metallic impurities contained in the silicon to its surface via a thermallyactivated elution prior to chemical treatment. The present study reports experimental findings concerning the effect of a thermal pre-treatment using a mixture of 5-wt% nitric acid and 2.5-wt% hydrofluoric acid for the purification of metallurgical-grade silicon particles of different sizes on the hydrometallurgical process. The extraction rates of metallic impurities from inside the silicon were in inverse proportion to the size of the silicon particle. However, the effect of the thermal pre-treatment on the extraction rate became greater with increasing particle size.

With direct growth technologies for obtaining ribbon-type silicon (Si) wafers from molten Si, the horizontal growth process is much faster than the vertical one in terms of the growth rate of the wafer. However, such a fast growth rate is likely to create grains of a relatively small size in the Si wafer, resulting in limited efficiency caused by grain boundary recombination. In this regard, controlling the grain growth behavior of the Si wafer with processing parameters such as the temperature of the substrate and its moving speed is very important in the horizontal growth process. The present investigation produced the experimental findings concerning the processing parameters for controlling the grain size. The size of the grains on the surface of the Si wafer increased to around 180 μm at a lower substrate temperature and a slower the moving speed of the substrate due to the increasing thickness of the Si wafer. However, the growth rate of the grains was observed to have little relation to the variations in the wafer thickness resulting from the processing parameters unless the nucleation behavior had been controlled.

Single-crystalline InSb nanowires were synthesized on a SiO2wafer through the vapor-liquid-solid mechanism by using the chemical vapor deposition method. We also identified the effect of the source container system, closed- or open-boat, which contained SiO2 wafers, on the InSb powder, and the single-crystalline InSb nanowires were found to have different growth mechanisms. The structural characterization of the InSb nanowires was performed using a scanning electron microscope. The crystallinity and the composition of the InSb nanowires were investigated using X-ray diffraction and energy dispersive X-ray spectroscopy. We demonstrated that the InSb nanowires were thick and long, when an open-boat system was used, because the open-boat system can carry a greater amount of the vapor-phase InSb precursor than the closed-boat system. A high yield of the InSb nanowires can be obtained using the open-boat system. Additionally, the diameter of the InSb nanowires was quite thick because of the increased the growth time as a result of the dominant vapor-solid mechanism.

SiO1.39 nanoparticles synthesized by using an evaporation and condensation process were composited with phenol resin and conducting carbon (C), and their microstructures and electrochemical properties were investigated. A dense, micro-sized SiO1.39-C composite was synthesized to prevent capacity fading of the SiO x nanoparticles. To densify and coarsen this composite, we carried out pelletizing, annealing and crushing of the sample. The electrical conductivity was also improved by the composition without any structural change. Crushed particles were used as an anode material for a Li-ion battery, and its cyclic performance was evaluated. By composition, the coulombic efficiency was observed to increase from 93.6 to 97.5% at the 5 th cycle, and it continued increasing with each additional cycle. For the composite annealed at 1,000 °C in a 4-vol.% H2/Ar atmosphere, the specific capacity and the coulombic efficiency at the 20 th cycle were measured as 426 mAhg−1 and 99.7%, respectively.

Depolarization of luminescence from pyronine B dye molecules was studied using polarized photoluminescence spectroscopy. When the molecules were dissolved in a solvent, the viscosity and the electronic dipole moment of the solvent affected the depolarization ratio and the photoluminescence peak position, respectively. In addition, the concentration of the dye molecules also influenced the depolarization ratio and the photoluminescence. For pyronine B molecules embedded in zeolite-L crystals, the photoluminescence peak position was independent of the concentration, and the depolarization ratio showed a dependence on the concentration that was opposite to the case of dye molecules in a solvent. The energy transfer between the molecules or the re-absorption process is suggested to explain the experimental results.

We analyzed the photoluminescence (PL) peak shift and the anisotropy of dye molecules and dye molecule zeolite composites as function of the concentration of pyronine B (PyB) molecules. We used PyB dye molecules and zeolite L. The PL of PyB molecules was red-shifted with increasing concentration of PyB molecules. However the PL of PyB incorporated zeolite composite was independent of the concentration. The PL intensity anisotropy value also increased with increasing concentration in these composites. The anisotropy of zeolite dye composites was about 2.8 at high concentration; which is close to the theoretical anisotropy value of 3. Since the host zeolite protects dye molecules from aggregation, these results are di erent form the case of dye molecules in a solvent. In addition, we observed the con nement e ect of dye molecule zeolite composites from the blue shift of the PL spectrum.

SiOx nanoparticles were synthesized by using an evaporation and condensation process involving induction melting of silicon (Si) chunks followed by the injection of a H2/Ar mixed gas into the melt. In particular, this research studied the effects of hydrogen gas on the nanoparticles’ microstructural and electrochemical properties, etc. During the microstructural analysis, regardless of H2 content, all the nanoparticles were observed to have random shapes; their average particle sizes were 30 ∼ 35 nm. However, a crystalline Si phase, even though it was a small amount, was formed when H2/Ar gas was injected. From the X-ray photoelectron spectroscopy (XPS) analysis, the amount of the SiO2 phase in SiOx decreased when the H2/Ar gas ratio was higher than 1.0 vol.%. Injected hydrogen produced a Si-H network in SiOx, and the Si-H concentration was independent of the amount of injected gas. Consequently, due to hydrogen incorporation, not only was a crystalline Si phase formed, but also the amount of the SiO2 phase decreased. In addition, Si-H bonds were formed in the nanoparticles. The crystalline Si phase and the relatively small amount of the SiO2 phase resulted in an enhancement of the Li-ion capacity when those nanoparticles were applied as an anode material for a Li-ion battery. Furthermore, cycle performance was improved even when hydrogen was incorporated. For the sample synthesized with 5.0-vol.% H2/Ar gas, the discharge capacity and the columbic efficiency at the 21st cycle were 889.1 mAhg−1 and 95.0%, respectively.