Diamondlike carbon for infrared optics

Diamondlike Carbon (DLC), also known as amorphous hydrogenated carbon (or a:C-H), is a hard semitransparent material. Since it is amorphous and has no grain boundaries, it is proposed for use as a coating on infrared optical surfaces to protect them from the envi-ronmentally adverse chemicals such as the acids, salt water, etc., as well as particle impact. Moisture penetration studies of DLC, using the Variable Angle Spectroscopic Ellipsometry (VASE), have been presented elsewhere 1, 2. In this paper, we first briefly mention sample preparation, done using various combinations of RF power and gas pressure in a plasma deposition chamber. Then, results of using an ultraviolet-visible (UV-VIS) absorbance spectrometer are presented. From the absorbance we calculated the band gap using the Tauc plots, and found values ranging from 0.2 to 1.25eV, depending on deposition condition. Secondly, a series of DLC samples were prepared using a Kaufman type ion beam deposition system. Using VASE, we have studied these samples after bombarding them with various fluences of Fl, and analyzed the data using two Lorentz oscillators to represent the optical properties. We have also shown the correlation between the optical properties and the amount of hydrogen present within the samples, as measured by proton recoil experiments.