Whiskers in indium tin oxide films obtained by electron beam evaporation

Indium tin oxide thin films consisting mainly of whiskers have been deposited on glass by electron beam evaporation. Low deposition rates (35 Å/min) and substrate temperatures in the 120–400 °C range were used. Morphology by scanning electron microscopy, crystal structure, energy dispersive analysis of x-rays, and x-ray photoelectron spectroscopy compositions, optical and conducting properties of films have been studied as a function of temperature of growth and further annealing in air. Whiskers associate and produce flatter surfaces, the grain size increases from ≈390 Å to ≈790 Å, keeping however its fibrous structure after 400 °C-30 min annealing. In films deposited at temperatures below 200 °C, next to cubic In2O3, tetragonal Sn and cubic In2Sn2O(7−x) appear. During growth and after air annealing Sn4+ segregates to the surface, attaining Sn/In concentration ratios of 4.6. On air annealing the optical transmittance and electrical resistance increase, in some cases from 2% to 90% and by a factor of about 4, respectively.