Measurements of spatial and temporal sheath evolution for spherical and cylindrical geometries in plasma source ion implantation

Abstract

A comparison of experimental measurements and numerical calculations of temporal and spatial sheath evolution is presented. Spherical targets of copper and stainless steel (radius=2 cm) and a cylindrical target (radius=0.95 cm, height=18 cm) were immersed in an argon plasma with plasma densities of 2×108–8×109 cm−3 and biased negatively (20–50 kV). A Langmuir probe was used to detect the propagating sheath edge. Experimental measurements of sheath edge position were in good agreement with those determined by numerical calculations.