Loss of Ga in sputtered deposits made from a Pu-4 at. % Ga alloy

Deposits of 5 to 500 μm thick coating were produced at rates from 0.025 to 2.5 μm/min on Al, Cu, Fe, and Kapton substrates in a triode system. Sputter parameters were as follows: Kr gas pressure (0.27--0.44 Pa), substrate temperature (21--1840C), target voltage (300--2000 V), substrate bias (-35 to -100 V), ion current density (60 to 120 A/m2). A minimum substrate temperature of 1000C was necessary to fully stabilize the fcc structure in the deposits. Chemical analyses and energy dispersive spectroscopy indicated that deposits, under certain conditions, contained substantially less Ga than the target. The loss of Ga was controlled by increasing the substrate temperature above 1800C. The angular distribution of Pu and Ga sputtered under normal Kr+ ion impingement on a flat polycrystalline target was also measured. The Pu distribution was found to be ''under cosine'' for 300 eV ions and ''cosine'' for 900 eV ions. The Ga atom distribution showed a wide variation at different angles (normal to the target) depending upon conditions. At 00 the ratio of Ga to Pu was higher than in the target