Thin films of titanium oxynitride were produced by ion assisted deposition of titanium using different nitrogen to oxygen ion ratios. X-ray, Raman, nuclear reaction analysis and Rutherford backscattering spectroscopies were used to study the film structure and to establish the relationship between deposition conditions, him composition, and electrical and optical properties of the films in the visible and infrared. This method of deposition appears to yield hard, amorphous; and uniform films with a restricted compositional range near the equistoichiometric composition. Nevertheless, variations in oxygen content of the films can result in changes in the electrical and optical properties that are sufficiently large to enable their use as selective surfaces.