Surface analysis of contamination layers in cold-cathode gauges

The influence of gas atmosphere on the long-term operation characteristics of a commercial cold-cathode gauge was studied. The changes of the electrode surfaces due to contamination effects of the so-called double-plasma gauge CF 2P by ALCATEL (double Penning system) were investigated by Auger-electron spectroscopy, X-ray photoelectron spectroscopy and scanning electron spectroscopy. Contrary to the widespread opinion that particular contamination is mainly caused by the polymerization of hydrocarbons in the discharge chamber of cold-cathode gauges, we found a contamination layer on the electrodes which consists only of sputtered cathode material. The distribution and thickness of the layer can give information about the preferred ion trajectories and convenient design features for a long life and stable operation of this type of gauge. Layer thickness seems to be a direct function of the pressure dose, independent of small changes in chemical composition of the layers and independent of the pressure itself.