Physical vapour deposition of beryllium films

Conditions have been optimized for obtaining adherent films of Beryllium on zircaloy substrates. Tantalum boats are found suitable for small scale evaporation. For large scale evaporation water cooled copper crucible with bent electron beam source is recommended. A source temperature of 1500deg C and substrate temperature of 400-550deg C gives adequate vapour density and film adherence. Basic vacuum in chamber should be 1 x 10-6 Torr or better. A rough surface helps in adherence of film but it is detrimental to dense, pin hole free, films. For obtaining dense adherent films free from pin holes, ion plating is the preferred method. The rate of evaporation and coating thickness measured were not in agreement with theoretical values obtained from Langmuir equations. Actual evaporation was found to be lower and thickness higher than theoretical values. (author)