Tadao Kaneko

Improved design of inverted magnetrons used for deposition of thin films on wires

Abstract The inverted type of cylindrical magnetron sputtering has not been widely used, although this system is useful for only certain types of applications such as fibre coatings. This paper presents two types of electrode configurations which improved the complicancy of target assembly by using positive voltage power supply. One is a simple type which has no endplate (type I), and the other is a modified type which has a target constructed with a large cylindrical part, a conical part and a small cylindrical part (type II). When positive voltage was applied to an anode for both types, a stable glow discharge was established and a high deposition rate was obtained. The substrate bias current was monitored to estimate the effect of ion bombardment. As a result, it was found that the substrate current was larger in type II than in type I. Microstructure and morphology of titanium films deposited on thin wires were investigated by scanning electron microscopy in relation to preparation conditions. High level ion bombardment was found to be effective in obtaiing a good adhesion for wire coatings.

Structural Features of Black Ti Films Prepared by Cylindrical Magnetron Sputtering

In preparation for the fabrication of porous thin-film TiO2 semiconductors, the microstructure and morphology of titanium films deposited under higher Ar gas pressures than usual were observed. Black titanium films were deposited at a pressure of around 12 Pa on stainless steel wires and Cu thin plates, although glossy films were obtained at lower pressures. The black titanium films had a larger apparent thickness than the glossy films. Scanning electron microscopic observation of the films showed that the black films have an extremely porous structure, consisting of separated columns with periodic steps on the lateral surfaces. This morphology indicates that the nuclei formed on the substrate grow periodically to form steps due to the shadowing effect. The surface areas of the black films on the Cu thin plates varied with bias potential. A small negative bias was found to be effective for increasing the surface area of black titanium films. These results suggest that porous TiO2 films can be prepared by applying a suitable oxidation process to the black titanium film which consists of separated columns.