Boron (B) doped silicon nanowires (SiNWs) were synthesized by laser ablation. Local vibrational modes of B in SiNWs were observed by micro-Raman scattering measurements at room temperature. Broadening due to a coupling between the discrete optical phonon and a continuum of interband hole excitations was also observed in the Si optical phonon peak. This is called Fano broadening. These results prove that B atoms were doped in substitutional sites of crystalline Si core of SiNWs during laser ablation.

Zinc oxide (ZnO) films doped with aluminum (Al) were deposited with a pulsed laser deposition technique to characterize the charge compensation phenomena in ZnO. In particular, oxygen radical (O*) irradiation during film deposition was used to modify the oxygen stoichiometry. Irradiation with O* decreased electron concentration in Al-doped ZnO. The lattice parameter of the resultant films also varied with the growth conditions. However, no obvious correlation between electron concentration and lattice parameter was found. The self-diffusion coefficients indicated the presence of non-equilibrium defects. The properties of the films are discussed from the viewpoint of non-equilibrium compensated defects detected in the diffusion measurements.

A nanometer-scale ZnO light emission array device was fabricated using the multi-level metallization technique of the CMOS process. Square arrays of pits with an inverted pyramid shape made from {111}Si planes were formed on a (100)Si substrate using selective etching. ZnO was deposited on the substrate by chemical vapor deposition (CVD), and the surface of the deposited ZnO film was carefully polished by chemical mechanical planarization (CMP). As a result, ZnO-filled nanometer-scale arrays were obtained after removing the ZnO layer except for the ZnO in the pits by CMP. Cathodoluminescence (CL) from the ZnO arrays was observed.

Noble metal-coated polydiacetylene (PDA) nanocrystals are expected to enlarge effective third-order nonlinear optical susceptibility, owing to the enhancement of optical electric field induced by localized surface plasmon. The surface of PDA nanocrystals was decorated with silver nanoparticles, and the linear optical properties were investigated. The well-defined PDA nanocrystals were first prepared by the conventional reprecipitation method as an aqueous dispersion. The following two-steps of reduction methods, namely, seed deposition and seed growth, enabled higher silver coverage on the surface of PDA nanocrystals. Silver fine seeds were successfully deposited on the PDA surface by particularly employing an anionic surfactant as a binder. The extinction spectra of the PDA nanocrystals covered with silver exhibited the red-shift and broadening of surface plasmonic peak for silver nanoparticles, which would indicate the interaction among silver nanoparticles on the same PDA nanocrystal. In addition, the red-shift of excitonic peak for PDA nanocrystals was observed, resulting from the changes of dielectric properties around PDA nanocrystal. Both spectral changes would have an influence on nonlinear optical properties of PDA nanocrystal.

The effects of hydrogen on the deep level luminescence in Si, ZnO and diamond were studied by means of cathodoluminescence. It is well known that most of the deep levels in Si are passivated by hydrogen. Scratch lines on Si surface, which do not show any characteristic luminescence, obtain so-called D-line luminescence by hydrogen plasma treatment. It indicates that only nonradiative defects are passivated but D-line luminescence is not passivated by hydrogenation. Contrarily, typical ZnO crystal shows the green emission, which is attributed to the point defects or impurities. Hydrogen completely passivates this green emission, and in turn, enhances the band edge emission. The effect of hydrogen passivation disappeared by the annealing at temperatures higher than 600 °C. Hydrogen behaves more peculiarly in diamond. The hydrogenated diamond film shows the characteristic emission around 2.3 eV in photon energy. Since it disappears by oxidization treatment, this emission is attributed to hydrogen at the subsurface region. The detailed study indicated that hydrogen in diamond has bistable states.

Hydrogen doping effects on luminescence properties of bulk ZnO samples were examined by using a pulse-modulated plasma irradiation technique. Three kinds of ZnO samples, including both single- and poly-crystals, were employed as specimens. Secondary-ion-mass-spectroscopy analysis revealed that the surface layer to 100 nm was doped with hydrogen after the irradiation and its concentration was in the order of 1017 cm-3. The efficiency of band edge emission was increased by the hydrogenation. However, the degree of the improvements depended on impurity and defect concentration in the original samples.

Effects of hydrogen sulfide on the structure of carbon nanotubes (CNTs) were studied using high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). The CNTs were synthesized with an iron thin-film catalyst by microwave plasma-assisted CVD on the diamond substrate. The HRTEM images revealed that essentially all of the CNTs obtained in this study were multiwall (MWCNT). The addition of H2S resulted in nanotubes with split skins as cornhusks and/or frills. Electron energy loss spectra of the cornhusks indicated that they consist of sp2, sp3 and amorphous carbon phase. The spectra revealed that the sp3 to sp2 ratio at the points where cornhusks divide from the main stem was more than that at the edge of the cornhusks. No evidence of sulfur incorporation into the MWCNTs grown with the H2S addition was found. We speculate that the chemical nature of sulfur on the CNT growth yields such anomalous structure.

The band-A emission (around 2.8 eV) observed in high quality (device-grade) homoepitaxial diamond films grown by microwave-plasma chemical vapor deposition (CVD) was studied by means of scanning cathodoluminescence spectroscopy and high-resolution transmission electron microscopy. Recent progress in our study on homoepitaxial diamond films was obtained through the low CH4/H2 conditions by CVD. These showed atomically flat surfaces and the excitonic emission at room temperature, while the band-A emission (2.95 eV) decreased. Using these samples, we found that the band-A emission only appeared at unepitaxial crystallites (UC) sites, while other flat surface parts still showed the excitonic emission. High-resolution transmission electron microscopy revealed that there were grain boundaries which contained π-bonds in UC. This indicates that one of the origin of the band-A emission in diamond films is attributed to π bonds of grain boundaries.

We have developed a cathodoluminescence (CL) system with high spatial resolution using a thermal-field emission gun operating with low electron beam energies. Since the electron range is proportional to the 1.7th power of the electron beam energy, operation with a low energy electron beam strongly reduces the probe size of CL. Luminescence property of ZnO tetrapods was studied with this system. High spatial resolution better than 100 nm was achieved when it was operated with a beam energy less than 3 keV. The variation of CL spectra along one leg of tetrapod was recorded. The ratio of the ultraviolet emission to the visible luminescence at the center of tetrapod was different from those of the points along the arm, suggesting that the center of tetrapod is much defective compared with the arms. We also observed a decrease of CL intensity during observation. Possible degradation mechanisms were discussed.

Grain boundaries in polycrystalline silicon are most likely to generate localized states in band gap. The localized states play a dominant role in determining the performance of solar cells by acting as traps or recombination center of carriers. In the present investigation, the scanning electron microscope - electron channeling pattern(SEM/ECP) method and SEM - electron back scattered diffraction pattern(SEM/EBSD) technique were applied to characterize the grain boundaries in p-type polycrystalline silicon with 99.999%(5N) in purity. Thereafter, temperature dependence of electrical activity of individual grain boundaries was measured by an electron beam induced current(EBIC) technique.

It has been found that temperature dependence of EBIC contrast at grain boundaries can change, depending on the misorientation angle the orientation of the boundary plane. The results can be explained by the difference in the position of the localized state within the band gap on the basis of the Shockley-Read-Hall statistics. The {111} ∑3 symmetrical tilt boundary has shallow states, while high ∑ boundaries have deep states. Low angle boundaries reveal high electrical activities. The EBIC contrast at low angle boundaries was found to increase with increasing misorientation angle up to 2° followed by an almost constant value. High electrical activity at low angle boundaries is probably attributed to a stress field of primary dislocations forming low angle boundaries.

We found the existence of hydrogen-induced luminescent states in the subsurface region of chemical-vapor-deposited homoepitaxial diamond films by means of cathodoluminescence (CL). A specific broad peak at around 540 nm is observed in both as-deposited diamond films and those treated by hydrogen plasma at 800 °C, but not in conventional oxidized films. The accelerating voltage dependence of the CL spectra indicates that the luminescent states related to the 540 nm peak exist in the surface region and decrease abruptly with increasing the depth from the surface, showing that the depth distribution of the states slightly depends on the hydrogenation duration. Although the 540 nm peak is not observed in the films hydrogenated at 500 °C, it appears once the films are irradiated by an incident electron beam. It indicates the existence of a metastable configuration of hydrogen or its complex forms in the diamond films hydrogenated at low temperatures and a relaxation occurs into a stable one which produces luminescent states by the electron-beam irradiation.