Optical Properties and Oxidation of Evaporated Titanium Films*

Abstract

Measurements were made of the optical constants and of the reflectance and transmittance of titanium films evaporated onto fused quartz and glass. In order to prepare pure titanium films with normal density, all depositions were carried out at a pressure p 40 A/sec. The optical constants were determined by Drude’s polarimetric method from opaque films at the wavelengths 0.436 μ, 0.546 μ, 0.578 μ, and 0.650 μ. The reflectance values computed from n and k agreed well with the directly measured ones. The reflectance of titanium was measured from 900 A to 10 μ. 100 A to 300 A thick films of titanium were found to have quite uniform transmittance throughout the visible spectrum and can, therefore, be used as neutral density filters. Three optical principles were used to measure the oxidation of titanium in air. At room temperature the rate of oxidation of titanium was found to be almost equal to that of aluminum (about 35 A of oxide are formed in one month). With increasing temperature, however, the oxidation of titanium increases much more rapidly than that of aluminum.