Influence of Discharge Parameters on the Resultant Sputtered Crater Shapes for a Radio Frequency Glow Discharge Atomic Emission Source

A parametric study has been conducted on a radio frequency glow discharge atomic emission spectrometry (rf-GD-AES) source to evaluate the sputtering characteristics and resultant crater shapes for both metallic and nonconducting samples. These studies include a determination of how the operating parameters, namely, power and pressure, influence the sputtered crater's depth, the degree of convexity and/or concavity, and the crater bottom roughness. The results imply that many similarities exist between the rf mode of powering and the well-characterized dc powered devices. Some differences are noted, namely, differing crater shapes at low operating pressures and a lesser dependence of crater flatness on the applied voltage, i.e., dc-bias voltage. A new method of quantifying the degree of concavity/convexity is introduced which involves comparison of the calculated (ideal) cross-sectional area to the resultant crater area as measured by a diamond stylus profilometer. The studies indicate that the rf-GD is well suited for depth-resolved analysis under correctly chosen operating conditions, which fortuitously correspond to those used for optimum bulk elemental analyses.