Instrumentation and fundamental studies on glow discharge-microwave-induced plasma (GD-MIP) tandem source for optical emission spectrometry

Instrumentation and fundamental studies on glow discharge-microwave-induced plasma (GD-MIP) tandem source are described in this paper. Mutual effects among parameters, vacuum pressure, discharge current, voltage, and microwave power are examined with different cathode materials. Sputtering rates with and without microwave boost are measured under various experimental conditions. The experimental results demonstrate that the introduction of a microwave plasma will significantly decrease the sampling rate. A possible mechanism for the more uniform erosion obtained with microwave plasma boosting is suggested and discussed. Excitation temperatures are measured with the line-pair method and Boltzmann plot. A considerable increase in the excitation temperature (from about 3500 to 4200 K by using the line-pair method) is found with the addition of microwave plasma boosting. A comparison of the behavior of glow discharge alone and the GD-MIP tandem source is made. Significant enhancements in signal intensities are observed. The experimental results suggest that the excitation temperature plays an important role in signal enhancement.