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Spectroscopic and catalytic probe characterization of oxygen and hydrogen plasmas

Inductively coupled plasma modification of surface is a well-established technique used in a wide variety of applications. Reactive and fast interaction between the plasma and sample shows the need for real-time plasma diagnostics. Optical emission spectroscopy and actinometry combined with the measurement of oxygen atom concentrations by the catalytic probe offer a relatively simple and efficient solution for that need. The combination of these methods was used for characterization of low pressure inductively coupled oxygen and hydrogen plasma in an afterglow chamber and the discharge tube. Plasma was created in a linear borosilicate glass tube by a 6 turn coil with an EM field oscillating at 13.56 MHz at the distance of 30 cm from the center of the afterglow chamber. Various plasma conditions were used: oxygen and hydrogen gas pressure (10-70 Pa), discharge powers (up to 260 W of applied power) and different plasma modes (E and H modes) . The spectrometer Avantes 3648 is calibrated for the spectral response and used for actinometry measurements. Ni-plated catalytic probe was used for measuring neutral oxygen atom concentrations, while Au probe was used for neutral hydrogen atoms. Oxygen atom concentrations were measured (by the catalytic probe and actinometry) to be in the range from 5•1018 m-3 (lowest pressure, furthest position) to 2•1021 m-3 (70 Pa, near the coil). Significant concentrations of oxygen atoms were measured even in the “dark” parts of the afterglow chamber.

optical emission spectroscopy; inductively coupled plasma; catalytic probes; actinometry

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