Infrared transmission characteristic of indium-tin-oxide thin films prepared by femtosecond pulsed laser deposition

Indium tin oxide (ITO) films were deposited on sapphire substrates at temperatures ranging from 30°C to 700°C and oxygen background pressure changing from 0.05 Pa to 0.25 Pa by femtosecond pulsed laser deposition (PLD). The films were characterized using metallurgical microscope, film resistance meter and Fourier transform infrared spectrometer to study the effect of substrate temperature and oxygen background pressure on the surface topography, sheet resistance and infrared transmission. The photographs of metallurgical microscope show that substrate temperature plays a dominant role on the surface morphology of the films. The sheet resistance test suggests that the sheet resistance of the film decreases with increase of substrate temperature but increases with increase of oxygen background pressure. The results of infrared transmission show that the infrared transmission through the ITO film is about 40% at the wavelength of 1.5μm to 1.8μm and is very low at other infrared band. The films deposited at higher substrate temperatures show lower value of transmittance, and which at higher oxygen background pressure show higher value of transmittance.