Electrical and optical properties of IrO₂ thin films prepared by laser-ablation

IrO₂ thin films were prepared by laser ablation using an Ir target at substrate temperatures (T_sub) from room temperature (RT) to 873 K in an oxygen atmosphere. A small amount of Ir metal was contained in IrO₂ films prepared at T_sub, = RT. The lattice parameters particularly a-axis values decreased with increasing T_sub, and the values were a = 0.452 nm, c = 0.315 nm at T_sub = 873 K in agreement with those of bulk IrO₂. The surface roughness increased from 1.2 to 5.2 nm with increasing T_sub. These values imply that the IrO ₂ films were far smoother than those prepared by MOCVD and sputtering. The electrical conductivity of IrO₂ films prepared at T_Sub = RT changed from semiconductor-like to metallic behavior after a heat-treatment; on the other hand, those prepared at T_sub > 573 K were metallic without changing after heat-treatment. The IrO₂ films prepared at T_sub = 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.