Cathode Sputtering in Glow Discharges

The analysis and interpretation of experiments on cathode sputtering in glow discharges requires definite knowledge of the behaviour of the metal atoms after they leave the cathode. Previous theoretical investigations of this neglect important factors, or are based on imperfectly realizable assumptions, and are not in good agreement with experiment. In particular, application of these theories leads to qualitative and order-of-magnitude discrepancies with low-pressure experiments. We have now attempted to make a more precise description of the behaviour of the metal atoms. It has been shown that hitherto largely neglected effects of initial scattering, lateral boundaries, distribution of current over the cathode, high emission velocities and the difference in mass between metal atoms and gas molecules, are of fundamental importance. The new formulation removes most of the old difficulties and discrepancies. It also shows definitely, however, that the phenomena are so complex that it will probably never be possible to develop a theory of sufficient accuracy to permit of exact conclusions being drawn from the experimental data.