Masami Miyazaki

Properties of Ga-doped ZnO films

Abstract Transparent conductive films of Ga-doped ZnO (GZO) were deposited on glass substrates by dc magnetron sputtering using a ZnO target with Ga 2 O 3 content of 3 to 10 wt%. The dependence of electrical properties on substrate temperature, Ga 2 O 3 contents in the sputtering target and magnetic field strength at the target surface were investigated. It was found that the resistivity depended on both substrate temperature and Ga 2 O 3 content. At substrate temperatures of 100°C, resistivity decreased with increasing Ga 2 O 3 content and 6.5 × 10 −4 ω cm was obtained for a Ga 2 O 3 content of 7.5–10.0 wt%. When the substrate temperature was increased to 300°C, GZO films deposited using 4.5 to 5.7 wt% Ga 2 O 3 targets had a resistivity of 2.7 × 10 −4 ω scm. In addition, the resistivity was found to decrease with increasing magnetic field strength. When the substrate temperature and Ga 2 O 3 content were 100°C and 7.5 wt%, respectively, the resistivity decreased from 6.5 × 10 −4 to 2.9 × 10 −4 ω cm by increasing the magnetic field strength from 3.0 × 10 −2 to 6.5 × 10 −2 T. The minimum resistivity of 2.2 × 10 −4 ω cm was obtained at 250°C (Ga 2 O 3 content:5.7 wt%) for a magnetic field strength of 6.5 × 10 −2 T. The decrease in resistivity was due to the increase both in carrier concentration and mobility.

Development of Silver-Based Multilayer Coating Electrodes with Low Resistance for Use in Flat Panel Displays

Multilayer coatings consisting of thin silver layers sandwiched between layers of transparent conducting metal oxides were investigated from the view-point of low-resistance electrodes for use in flat panel displays. Optimization of the multilayer coatings resulted in a five-layer coating composed of indium and zinc oxide composite material (IZO) and silver containing 1 wt% of palladium (Ag–Pd). The coatings had satisfactory properties of low resistance, high transmittance, high moisture and alkali resistance, and good patterning.

Improvement of Alkali Durability of Silver-Based Multilayer Coatings for Use in Flat Panel Displays

Silver-based multilayer coatings are well known to be transparent films with low electrical resistivity. In particular, indium and zinc composite oxide (IZO)/silver containing palladium (AgPd) multilayer coatings have good pattering properties and durability. However, the IZO/AgPd multilayer coatings do not have sufficient alkali durability as transparent electrodes of flat panel displays (FPDs). In order to solve this problem, coatings covered with a protective layer of tin-doped indium oxide (ITO) were investigated. Over-coating of an ITO layer degraded the patterning properties of the multilayer coatings because the etching rates of ITO, IZO and AgPd layer were very different. From the viewpoint of controlling the etching rate of each layer independently, the etching solution composed of hydrobromic acid and iron chloride was adjusted, so that the ITO/IZO/AgPd/IZO/AgPd/IZO/substrate multilayer coatings could be fabricated into fine patterns for electrodes. The multilayer coatings thus prepared are more tolerable for alkali detergents used in the production process of FPDs.