The possibility for white light emitting devices using carbon nitride (CNx) thin films has been studied. Microwave ECR-plasma CVD and RF-sputtering apparatuses have been used for the formation of CNx thin films. In both cases, CH4 was used as the source or sub-source of carbon in order to investigate the effect of hydrogenated carbon nitride for luminescence. The cathodeluminescence (CL) measurement of the film grown by ECR-plasma CVD method showed three peaks of R/G/B. The photoluminescence (PL) measurement of the film grown by RF-sputtering also showed the red peak, which could not be observed in the film without hydrogen. Together with the X-ray Photoelectron Spectroscopy (XPS) analysis data, we concluded that the red peak originates from C-H bonds and blue peak from C-N bonds.

We have carried out high-pressure X-ray structural studies of BeO and ZnO up to 200 GPa to find the phase transition of BeO from the wurzite to the NaCl structure and that of ZnO from the NaCl to the CsCl structure, which are expected theoretically. The phase transition of BeO occurred at 137 GPa, which is in good agreement with the theoretical value of 139 GPa. The wurzite phase persisted up to 175 GPa. The bulk modulus of BeO at zero pressure is determined to be 223 GPa by the Birch's equation. As previously reported, the ZnO sample transformed from the wurzite structure to the NaCl structure at 9.1 GPa. Extending the pressure range up to 202 GPa no phase transition to the CsCl structure occurred. The bulk modulus of the NaCl structure was determined to be 194 GPa.

We report results of investigations of electronic transport properties and lattice dynamics of Al-doped magnesium silicide (Mg2Si) thermoelectrics at ambient and high pressures to and beyond 15 GPa. High-quality samples of Mg2Si doped with 1 at. % of Al were prepared by spark plasma sintering technique. The samples were extensively examined at ambient pressure conditions by X-ray diffraction studies, Raman spectroscopy, electrical resistivity, magnetoresistance, Hall effect, thermoelectric power (Seebeck effect), and thermal conductivity. A Kondo-like feature in the electrical resistivity curves at low temperatures indicates a possible magnetism in the samples. The absolute values of the thermopower and electrical resistivity, and Raman spectra intensity of Mg2Si:Al dramatically diminished upon room-temperature compression. The calculated thermoelectric power factor of Mg2Si:Al raised with pressure to 2–3 GPa peaking in the maximum the values as high as about 8 × 10−3 W/(K2m) and then gradually decreased with further compression. Raman spectroscopy studies indicated the crossovers near ∼5–7 and ∼11–12 GPa that are likely related to phase transitions. The data gathered suggest that Mg2Si:Al is metallized under moderate pressures between ∼5 and 12 GPa.

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