Application of Pulsed Voltage to d.c. Glow Discharge Plasma for Controlling the Sputtering Rate in Glow Discharge Optical Emission Spectrometry

摘要

The application of a pulsed voltage to a Grimm-style glow discharge lamp was investigated to control the sputtering rate in d.c. glow discharge optical emission spectrometry. This purpose is to reduce the sampling depth so that thin film-like samples can be measured with a better spatial resolution and a better analytical precision. While the sputtering rate decreases by using a pulsed voltage due to the reduction in the effective discharge power, the emission signals from the glow discharge plasma are modulated by a cyclic variation of the discharge voltage so that only the desired signals can be detected without any noises with a lock-in amplifier. Whereas the sputtering rate could be more than 50 percent reduced when the duty ratio of the pulsed voltage was down to 20 percent compared to the rate in the corresponding continuous discharge, the emission intensities could be estimated with much better signal-to-noise ratios.