Optical Measurement of Oxide Thickness on Titanium*

Reflectance of thermally oxidized, mechanically polished titanium surfaces was measured with a spectrometer at 5889–5895 A. The principal aim of the experiments was to furnish an optical means of measuring the thickness of thermal oxide layers on titanium. These measurements also provided a method for determining the optical constants of the metal and the thermal oxide. The system was found to be an absorbing base with an absorbing film. The optical constant of titanium was found to be nˆ3=2.41−3.24i and the optical constant of the thermal oxide film was nˆ2=2.40−0.17i. From these constants, the oxide growth curve at 482°C was determined. The curve is of the same type found by other workers, and indicates that the growth rate can be expressed as a combination of a simple parabolic law and a linear law.