Study on transmittance spectra of ITO thin films by ellipsometric method

ITO films with thicknesses (134 +/- 8) nm, grown on glass substrates by sputtering method, were post-annealed at the temperatures of 100, 200, 300 and 400A degrees C for 1 h, respectively. The as-deposited ITO film was amorphous, but crystallized with annealing at elevated temperatures, as demonstrated by X-ray diffraction. The transmittance spectra of all samples were obtained and subsequently simulated by means of spectroscopic ellipsometry. The optical constants n and k of the films were extracted. With the annealing temperature increasing, the optical constants n and k of the films firstly decreased then increased in the whole investigated wavelength range. The optical band gaps of all films were evaluated and they varied between 3.74 and 3.93 eV.