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Bandgap tunable (AlGa)2O3 films were deposited on sapphire substrates by pulsed laser deposition (PLD). The deposited films are of high transmittance as measured by spectrophotometer. The Al content in films is almost the same as that in targets. The measurement of bandgap energies by examining the onset of inelastic energy loss in core-level atomic spectra using X-ray photoelectron spectroscopy is proved to be valid for determining the bandgap of (AlGa)2O3 films as it is in good agreement with the bandgap values from transmittance spectra. The measured bandgap of (AlGa)2O3 films increases continuously with the Al content covering the whole Al content range from about 5 to 7 eV, indicating PLD is a promising growth technology for growing bandgap tunable (AlGa)2O3 films.

Cu 2 ZnSnS 4 (CZTS) thin films were fabricated by co-evaporation of elemental sources on quartz glass substrates. The deposition was performed at the substrate temperature between 400 ºC and 600 ºC. From the results of electron probe microanalysis, it was confirmed that the nearly stoichiometric CZTS thin films were obtained in all substrate temperature. The X-ray diffraction patterns revealed that CZTS thin films have a kesterite structure with a strong preferred orientation. From the scanning electron microscope observation, the grain size becomes larger with increasing the substrate temperature. The CZTS thin films showed p-type conductivity.

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The composition dependence of the electrical properties of Cu2ZnSnSe4 thin films synthesized by coevaporation and the results of phase analyses are reported. We found that the hole concentration depends on the Cu/(Zn + Sn) ratio and is on the order of 1017 cm−3 for the ratio of 0.7 and increases to over 1020 cm−3 when the ratio exceeds 0.9. Raman spectra indicate the coexistence of semimetallic Cu2Se second phase in the thin films with Cu/(Zn + Sn) ratio above 0.9. In order to remove the Cu2Se phase selectively, we attempted a KCN etching. After the KCN etching for 30 min, the Raman peak attributed to the Cu2Se phase disappeared, and the hole concentration decreased to about 1018 cm−3.