Title: CHARACTERIZATION STUDIES OF PHYSICAL VAPOR-DEPOSITED BERYLLIUM.

The increase in grain size (to a final constant value) during deposition is a well known occurrence in physical vapor deposition. Columnar grain structures result as the coating thickens beyond the point of constant grain size (in general, for those thicknesses greater than approximately 25 ..mu..m). As the deposition is taking place, the grain size of the Ti coating increases from that on the order of 0.01 ..mu..m to that greater than 1.0 ..mu..m. At a certain critical thickness during deposition, t/sub c/, the grain size stabilizes. In this study, the minimum coating thickness required to produce the ultimate grainmore » size is sought. The effect of coating texture and deposition conditions on coating to substrate bond strength has been established in earlier work. Purpose of this investigation is then to relate the critical thickness to achieve a stable grain size with the texture of the coating. The distribution of grain size within the coating may provide a qualitative characterization of the stress relief driven growth in grain size which produces enhanced bonding of the Ti coating to its Be substrate.« less

Physical vapor deposition of films through an opening in an obscuring body, such as a mechanical deposition mask, will demonstrate a distinct ramp at the edges of the deposit zone as defined by the mask opening. This ramp is a direct function of the size, shape, and location of the vapor source. Evaporation sources using electron beam guns result in minimum ramping; however, some does occur and must be considered in process development. This ramping is modeled in a simplified manner and discussed to provide some understanding of the considerations necessary for natural design limits, particularly in thicker films usedmore » in the preparation of some bridge wire devices by evaporation deposition techniques.« less

Chemical and physical properties of vapor-deposited niobium carbide and zirconium carbide have been determined by the fabrication of thick-wall tubes of each carbide under varying deposition conditions. The effects studied included coefficient of thermal expansion, density, impurity level, carbon-to-metal ratio, and metallographic structure. The niobium carbide coatings contained less than 3,000 parts per million impurities, and the impurity level decreased when the deposition temperature was increased. Some of the zirconium carbide coatings contained four percent oxygen and chlorine, and the impure coatings were unstable when heated above the deposition temperature of 1,100°C. The amount of instability was primarily related tomore » the oxygen and chlorine content; an increased deposition temperature reduced the impurity contents to less than 500 ppm. The higher-temperature process conditions produced coatings with a predictable and consistent coefficient of thermal expansion value which could be repeatedly heated to 2,000°C (~ 700°C above the deposition temperature) without any detrimental effects such as weight and volume changes. The weight and volume changes were related to the impurities being evolved when the coatings were heated to temperatures of 1,600 to 1,800°C.« less