INFLUENCE OF ANODE GEOMETRY ON ELECTRIC-FIELD DISTRIBUTION AND CRATER PROFILE USING A GLOW-DISCHARGE LAMP

Depth resolution in glow discharge surface analysis depends on the shape of the crater and on the roughening of the new sputtered surface. The deviation from flatness of the crater bottom (convexity) and the surface roughening increase with time and, therefore, the depth resolution decreases. The crater depth and the electric potential have an exponential dependence on the radius of the anode cylinder and can be described by the same type of function. The anode geometry has a considerable influence on the crater profile, which can be explained by the variation in the electric potential. The exponential character of the potential function decreases with increasing diameter of the anode cylinder. The larger the diameter of the anode cylinder the flatter the middle of the crater bottom becomes. By using a ceramic tube as a spacer for the anode tube, in order to restrict the burning spot, optimization of the discharge voltage and pressure results in an almost flat crater profile being obtained.