Kazuhiko Yokogawa

Micrograin structure influence on electrical characteristics of sputtered indium tin oxide films

The relationship between micrograin structures and electrical characteristics of sputtered indium tin oxide (ITO) films was investigated. Micrograin structures were observed by a high resolution scanning electron microscope. Electrical characteristics were evaluated by four point probe resistance measurement and Hall effect measurement. Low resistivity ITO films had domain structures. One domain consisted of many sputter grains having the same orientation. The resistivity decreased with increasing domain size. The domain boundary might cause scattering for conduction electrons. Therefore, larger domain ITO films had a higher Hall mobility. The minimum resistivity was 1.8×10−4 Ω cm, deposited at a sputtering voltage of −250 V and a 250 °C deposition temperature. The electron conduction mechanism in domain structured ITO films was taken into consideration.

Postdeposition Annealing Influence on Sputtered Indium Tin Oxide Film Characteristics

The influence of postdeposition annealing on sputtered indium tin oxide (ITO) film characteristics were investigated. The annealing experiments were carried out in air or vacuum atmosphere. Both air and vacuum annealing decreased the resistivity up to heat treatment of 200° C. Over 300° C treatment, air annealing increased resistivity whereas vacuum annealing decreased it. It was clarified that the resistivity depended on the carrier concentration. The lowest resistivity attained was 1.3×10-4 Ωcm, with film deposited on a 250° C heated substrate and annealed in vacuum atmosphere at 300° C. Transmittance was improved in both air and vacuum annealing. In air and vacuum annealing, crystallinity improved with increasing annealing temperature. The surface topography showed no changes with air or vacuum annealing.