Koichi Haga

Effects of silver deposition on 405nm light-driven zinc oxide photocatalysta)

A silver-loaded zinc oxide (Ag∕ZnO) photocatalyst was fabricated by chemical deposition, followed by an annealing process using a 405-nm-light-driven ZnO fiber. Silver oxide (Ag2O) was deposited on the ZnO fiber with the same method of chemical deposition using a silver-nitrate solution. Ag2O was also decomposed to Ag by annealing at 600°C in a N2 flow. The authors found that the Ag∕ZnO photocatalyst had a fiber structure and that there was 405-nm-light activity. The Ag∕ZnO photocatalyst containing 0.02at.% Ag obtained via a 3.7×10−3mol∕l AgNO3 solution had the highest photocatalytic activity of all the samples.

Fabrication of Organic Light-Emitting Devices with Indium–Tin-Oxide Anode Prepared by Spray Chemical Vapor Deposition

Organic light-emitting devices (OLEDs) were fabricated using an indium–tin-oxide (ITO) anode and a small molecular light-emitting material, tris(8-hydroxyquinolinato) aluminum (Alq3). The ITO anode (thickness, 120 nm) was prepared inexpensively by spray chemical vapor deposition using ethanol solution consisting of indium chloride and tin chloride onto a glass substrate at 270 °C, which is 80 °C lower than the temperature previously reported by the present authors. The work function and lowest resistivity of the as-deposited anode containing 6.6 at. % Sn were respectively 4.7 V and 3.7×10-4 Ωcm. The luminance and turn-on threshold voltage of the OLED were respectively 6500 cd/m2 and 3.5 V. These values agreed with those of an OLED with the same layer structure but without the commercial ITO anode deposited by physical vapor deposition. The effects of tin concentration in the present ITO anode on the work function and device performance were also investigated.

Fabrication of ZnO thin film transistor by MO-CVD using Bis(acetylacetonato)zinc (II) Fiber and Ozone

C-axis oriented high resistance ZnO(100) thin films were prepared on Pyrex glass and SiO2/p-type Si (Si(p)) substrate by MO-CVD method using fibrous bis(acetylacetonato) zinc (II) (Zn(C5H7O2)2) formed by a novel process, and ozone (O3) gas. Compared to the introduction of oxygen (O2) gas, the introduction of high-active O3 gas mixed in O2 gas reduced oxygen defect in ZnO thin film and realized high resistance ZnO thin film of 1×103 Ωcm resistivity. Bottom-gate-type zinc oxide thin film transistor (ZnO-TFT) was fabricated on the SiO2/Si(p) substrate with the 8 nm-thick ZnO film as an active layer. The electron field-effect mobility was 53 cm2V−1s−1, and TFT characteristic of 106 on/off ratio was obtained.

Preparation of ZnO thin films by MO-CVD using fibrous bis (acetylacetonato) zinc (II) and ozone

The fibrous bis (acetylacetonato) zinc (II) (Zn(C5H7O2)2·xH2O) was prepared with novel apparatus involved the vaporization and the recrystallization, and was investigated by differential thermal analysis (DTA), flourier transform infrared spectroscopy (FT-IR) with attenuated total reflection (ATR), and the inductively coupled plasma optical emission spectroscopy (ICP-OES). The zinc oxide (ZnO) films were prepared by the low-pressure CVD (LP-CVD) using the fibrous Zn(C5H7O2)2·xH2O and ozone(O3). The DTA curve of the fibrous material with a wide-ranging endothermic peak under 100°C according to desorption of the hydrated water separated to two peaks decreasing in the evaporation temperature. The resistivity of the ZnO films has changed widely from 104 to 108 Ωcm by the fibrous material with a different preparation condition.