The Effect of Water Vapor on the Sticking Coefficient of Lead on Silicon Monoxide

Abstract

Experiments have been conducted at a total pressure of 10−9−10−5 Torr while the partial pressure of water was varied from 10−10 to 10−6 Torr. A constant lead flux of 4.5×1014 atoms cm−2 sec−1 was utilized. Results indicated that a rapid decrease in the initial sticking coefficient reached an asymptote of approximately 0.6 as the partial pressure of the residual water vapor was increased. Also, the sticking coefficient did not approach unity as deposition continued but remained essentially constant. Competitive reactions between the lead and the water molecules with the surface are proposed as an explanation of this latter phenomenon. The sticking coefficient for this system can equal unity in a total pressure range of 10−6−10−5 Torr if the partial pressure of water is restricted to less than 1×10−8 Torr.