Monitoring oxygen species in diamond hot-filament CVD by zircon dioxide sensors

Electrochemical zircon dioxide oxygen sensors were applied to measure oxygen in diamond hot-filament CVD (HFCVD) coating atmospheres. These low-pressure hydrogen environments are highly reductive and methane containing. Under industrial coating conditions there is the possibility that oxygen from ambient air enters the reactor by leakages. This leads to a tremendous influence on coating conditions by lowering the active carbon content in the gas phase and by decarburizing the gas activating filaments in HFCVD. In order to ensure process stability, a monitoring of an oxygen-related value is desired. This work displays the possibility to measure oxygen in HFCVD with potentiometric and amperometric ZrO2 sensors. The dependency of the sensor signals on process parameters is investigated and the possibility of monitoring an oxygen-related value during a coating process is shown. The sensor signals allow a comparison of plants and processes regarding the seal tightness condition. The employed zircon dioxide sensors offer a cost effective and feasible method to monitor air leakage and ensure process reproducibility.