Hideo ISSHIKI (一色 秀夫)

This study investigates the effects of different fabrication and annealing atmospheres on the properties of samarium (Sm)‐doped titanium dioxide (TiO₂:Sm) thin films, with a focus on luminescence and electrical conductivity. TiO₂:Sm thin films are deposited by laser ablation and annealed at 700 °C in O₂ and H₂ + N₂ atmospheres. X‐ray diffraction analysis shows that fabrication and annealing in the H₂ + N₂ atmosphere significantly inhibit crystal growth. PL spectra reveal that films fabricated and annealed in O₂ exhibit the strongest luminescence, while those in the H₂ + N₂ show quenched luminescence. X‐ray absorption fine structure results indicate that Sm³⁺ ions in the non‐luminescent samples have a high‐symmetry oxygen coordination, which is unfavorable for luminescence. C–V and I–V measurements reveal a substantial increase in electrical conductivity for films fabricated and annealed in H₂ + N₂, attributed to the incorporation of hydrogen and the formation of oxygen vacancies. This study concludes that while the fabrication and annealing in the H₂ + N₂ atmospheres enhance the electrical conductivity of TiO₂:Sm thin films, they also degrade luminescence. Balancing luminescence intensity and electrical conductivity is crucial for the optical device application of TiO₂:Sm thin films. It is necessary to carefully adjust the fabrication and annealing conditions to enhance electrical conductivity while maintaining strong luminescence.

Abstract

Sm-doped TiO₂ thin films were synthesized by pulsed laser deposition. The luminescence and donor-generation properties of thin films annealed at various temperatures were investigated. The results showed that Sm-related emissions occurred in the temperature range 500 °C–800 °C. The donor densities in this temperature range were two orders of magnitude higher than that of the undoped TiO₂ thin film. The effect of annealing within the temperature window indicates a local fine structural transition of the ligands around Sm³⁺ ions from T_d symmetry to the lower C_4v one; these ions are effective luminescence centers in TiO₂:Sm thin films. This local structural distortion also increases defect generation, and this increases the donor density in the same temperature region.

Abstract

A CuAlO₂ (CAO) bottom gate top contact p-type thin film transistor (TFT) is demonstrated. The CAO thin film is synthesized through a digitally processed DC sputtering (DPDS) technique, employing a precise layer-by-layer (LBL) deposition strategy. X-ray diffraction analysis exhibited distinct peaks beyond 600 °C. The CAO film shows a dominant phase along the (004) plane at the elevated temperature of 990 °C. The fabricated CAO p-TFT exhibits field effect mobility of 4.1 cm² V⁻¹ s⁻¹. In addition, the p-TFT characteristics were observed even in the as-deposited CAO film. The DPDS-assisted LBL approach offers a promising pathway for controlled stacking deposition routes in the growth of CAO thin films, enabling enhanced performance and device integration.