Papers by Author: Shigeru Tanaka

Abstract: Photoluminescence from epitaxial ZnO thin films deposited on R-plane sapphire substrates by RF magnetron sputtering was investigated. The intensity of the near band emission (NBE) of the ZnO thin film on R-plane sapphire was stronger than that of the film formed on C-plane sapphire at a low temperature. Some experimental results suggest that NBE depends on the polarization of the excitation light, which are considered to be related to the ZnO crystal orientation on the sapphire substrate.

Abstract: We have obtained Er-doped ZnO thin film in a micropattern of reverse trapezoids processed on Si substrate by sputtering and ultrafine polishing techniques. Near-infrared light emission was detected successfully from the thin film filling a single micropit with 10 μm square. Transmission electron microscopy (TEM) observation showed epitaxial growth of ZnO crystals along the curvature of the micropit.

Abstract: In order to clarify the fundamental luminescent mechanism of undoped and Er-doped ZnO thin films synthesized by sputtering method, cathodoluminescence (CL) from the samples formed on several kinds of substrate were measured. There was no explicit peak identified with luminescence from ZnO crystal defects in undoped sample, on the contrary, three sharp luminescent peaks were observed in the case of Er-doped ZnO film due to the internal transition of the additive Er ions in the CL spectrum. The mechanism was investigated in comparison with photoluminescence (PL).

Abstract: Er-doped ZnO thin films which emitted intense infrared light in the vicinity of 1.5 μm were investigated from points of view of the microstructure and electrical properties. The result of X-ray diffraction (XRD) pattern revealed that the crystal lattice of ZnO was apparently expanded by doping of Er ions. Electrical resistance in the direction of thickness of Er-doped ZnO film showed linear behavior, which was resemble to that of undoped ZnO film. Infrared light emission phenomenon of the film was related to the chemical / physical state of Er ions in ZnO matrix.