Chemical shifts and optical properties of tin oxide films grown by a reactive ion assisted deposition

Highly oriented nonstoichiometric tin oxide thin films were grown by a reactive ion assisted deposition onto Si(100) and glass substrates at room temperature as a function of relative ion (O)/atom (Sn metal) arrival ratio, and concurrently the deposited ion energy per atom (eV/atom) were changed from 10 to 100 eV/atom. As-deposited tin oxide films show preferred orientation along the SnO2[101]axis and the x-ray diffraction peak intensity appears maximum at an average energy of about 50 eV/atom. From quantitative Auger electron spectroscopy, characteristic transitional Auger peaks of Sn metal MNN transitions were shifted to lower kinetic energies by 4-6+/-1.0 eV as the Sn4+ component becomes dominant in the deposited tin oxide films and the position of O KL(1,2)L(2,3) transition line was also shifted to lower kinetic energy by 1-2+/-1.0 eV as the composition of deposited tin oxide films were changed from SnO to SnO2, respectively. On the basis of a tin 3d core level and O Is spectra analysis by x-ray photoelectron spectroscopy, the sizable chemical shift of different valencies between stannous tin (Sn2+:SnO) and stannic tin (Sn4+:SnO2) was 1.0+/-0.02 eV and that of O Is was 0.87+/-0.02 eV, and those values show larger shifts than previously reported ones. The refractive index n of as-deposited tin oxide films was evaluated from an ellipsometer, and spectrophotometric transmittances were measured in the wavelength range of 200-800 nm. In the luminous range, the refractive index varied from n = 2.36 to 2.04 as oxygen contents increased. (C) 1996 American Vacuum Society.