Analytical Sciences

Abstract − Analytical Sciences, 15(6), 517 (1999).

Application of a Bias-Current Modulation Technique to Radio-Frequency Glow Discharge Optical Emission Spectrometry
Kazuaki WAGATSUMA and Hideyuki MATSUTA
The Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai 980-8577, Japan
A 13.56-MHz Grimm-style glow discharge plasma in which pulsated bias currents are introduced was investigated concerning the analytical applications. The d.c. bias currents driven by a self-bias potential are conducted through the r.f. plasma body by using a low-pass filter circuit and a variable resistor. Excitation by a modified r.f. plasma can yield larger emission intensities. By modulating the bias current associated with phase-sensitive detection, the emission intensities can be measured at very low noise levels, enabling the detection limit to be improved more. A detection limit of 3x10-4 mass % was obtained for Mn determination in Fe-based binary alloy samples, whereas 1.4x10-2 mass % Mn was obtained in the conventional excitation of an 80-W r.f. discharge plasma. (Keywords: Radio-frequency Grimm glow discharge plasma, conduction of the bias current, current modulation, self-bias potential, detection limit, Fe-based alloys)