Abstract
IrO2 thin films were prepared by laser ablation using an Ir target at substrate temperatures (Tsub) from room temperature (RT) to 873 K in an oxygen atmosphere. A small amount of Ir metal was contained in IrO2 films prepared at Tsub = RT. The lattice parameters particularly a-axis values decreased with increasing Tsub, and the values were a = 0.452 nm, c = 0.315 nm at Tsub = 873 K in agreement with those of bulk IrO2. The surface roughness increased from 1.2 to 5.2 nm with increasing Tsub. These values imply that the IrO2 films were far smoother than those prepared by MOCVD and sputtering. The electrical conductivity of IrO2 films prepared at Tsub = RT changed from semiconductor-like to metallic behavior after a heat-treatment; on the other hand, those prepared at Tsub > 573 K were metallic without changing after heat-treatment. The IrO2 films prepared at Tsub = 873 K showed the highest electrical conductivity of 37 × 10−8 Ωm at RT. The optical transmittance of IrO2 thin films were mainly dependent on thickness and surface roughness, and were around 10% at a wavelength range from 300 to 800 nm.
