Masatoshi Higuchi

Characteristics of Indium-Tin-Oxide/Silver/Indium-Tin-Oxide Sandwich Films and Their Application to Simple-Matrix Liquid-Crystal Displays

We developed low-resistivity transparent conductive films having the structure of indium-tin-oxide/silver/indium-tin-oxide (ITO/Ag/ITO). The thin silver film was sandwiched by ITO films. Our goal was to study the characteristics of the sandwich films and the display characteristics of simple-matrix liquid-crystal displays (LCDs) fabricated using the sandwich film. The electrical and optical characteristics of the sandwich films depended greatly on the thickness of the ITO and silver layers. Low resistivity and high transmittance were obtained when the film structure had a thickness of ITO/Ag/ITO: 40 nm/15 nm/40 nm. The simple-matrix LCD fabricated using a sandwich of ITO/Ag/ITO exhibited 27%–48% reduction in the level of crosstalk compared to the conventionally available simple-matrix LCDs fabricated using a single-layer ITO film; thus, the display performance was improved.

Microstructure and Electrical Characteristics of Sputtered Indium Tin Oxide Films

The relationship between microstructure and electron characteristics of indium tim oxide (ITO) films was investigated. The microstructure and resistivity were found to be dependent on the oxygen partial pressure in the sputtering ambient. Lower resistivity ITO films had a domain structure and a small amount of surface roughness. The small roughness and the large size domain structure caused a decrease in electron scattering, and hence an increase in mobility. Crystallinity was also affected by the oxygen partial pressure. For ITO films with a domain structure, the relative X-ray diffraction intensity of the (440) crystal plane increased.

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.

Electrical properties of ITO films prepared by tin ion implantation in In2O3 film

Abstract We have investigated the electrical characteristics of indium–tin–oxide (ITO) films prepared by implanting tin ions into In 2 O 3 films. In 2 O 3 films were deposited onto a glass substrate at 250°C by reactive DC magnetron sputtering in argon containing oxygen. Tin ions were implanted at an incident energy of −190 eV. The resistivity decreased with increasing tin ion dose, and the value of 1.39×10 −3 Ω cm was obtained at the dose of 6.1×10 15 cm −2 . It was confirmed that the carrier concentration increased from 6.93×10 19 cm −3 to 6.38×10 20 cm −3 . However, the Hall mobility decreased with increasing tin ion dose. The X-ray diffraction intensity of the (440) plane decreased, and broadened with increasing tin dose. The deterioration of crystallinity of the (440) plane is considered to be the cause of the reduced Hall mobility. By vacuum annealing at 500°C after tin ion implantation in order to improve the crystallinity of the (440) plane, the resistivity decreased from 1.39×10 −3 Ω cm to 4.46×10 −4 Ω cm for the In 2 O 3 film implanted with tin ion at the dose of 6.1×10 15 cm −2 .