Index of refraction versus oxygen partial pressure for tantalum oxide and silicon dioxide films produced by ion beam deposition
Description: Tantalum oxide and silicon oxide films were made using an ion beam sputtering system. It was found that even though these films were deposited from oxide targets, additions of oxygen were necessary to achieve stoichiometry and hence index of refraction. It was observed that the tantalum oxide target changed color from white to gray, indicating that the oxygen was being depleted from the target. The addition of oxygen to the chamber during deposition replenished the target and improved film stoichiometry. The deposition rate decreased with increasing oxygen partial pressure. It was experimentally determined that by varying the oxygen partial pressure and keeping all other variables fixed, the index of refraction of the film changed in a predictable manner. That is, as the oxygen partial pressure was increased, the index decreased rapidly initially and then reached a saturation point where it stayed fixed with oxygen content. With this data a coating process can be set up using the minimum amount of oxygen (thus increasing filament lifetime) to produce a fully stoichiometric film that has a fixed index. This paper will present the details of these observations and results.
Date: April 30, 1998
Creator: Goward, W.D.; Petersen, H.E.; Dijaili, S.P. & Walker, J.D.
Partner: UNT Libraries Government Documents Department