Optical transmittance spectra for tin oxide films prepared by magnetron sputtering

Optical transmittance spectra of tin oxide films deposited on quartz substrates in the wavelength range 190-1100 nm have been investigated. Quartz substrates have been used because the quartz self-absorption band is shifted to the lower wavelength range relative to that for the glass. This circumstance permitted to obtain more correct data for thin films. By the way enough considerable number of maxima and minima for relatively low orders of interference is situated in the short-wave range. Measurements were performed for the films before and after annealing realized in different regimes. Considerable distinction between transmittance spectra for these two film groups was established. It will be noted that the results of optical measurements did not change significantly if the annealing duration was increased higher than 0.5 hour at temperature of 550 deg C. It can be noted that the annealing results in the considerable films enlightenment in the 200<λ<600 nm wavelength range. This process mechanism may be interpreted by the reconstruction of large cluster surface defects to more fine structure configurations. This process induces the decrease of diffuse reflection from the film surface and with results in increasing the transmittance. The transmittance spectra form is described well by the film low absorption model, when extinction coefficient k<<n (n- film refraction coefficient). The SnOx films optical parameters such as refraction and extinction coefficients, the film thickness, the optical band gap for as-deposited films and for films after the annealing were determined. In consequence of the annealing were mentioned the film thickness, extinction and refraction coefficients to decrease, but the optical band gap increased and was estimated to be equal that for bulk samples