Control of lithium-t-butoxide addition during chemical vapour deposition of Li-doped diamond films by optical emission spectroscopy

The potential of in situ lithium doping of diamond during microwave plasma chemical vapour deposition (MWPCVD) using a source of solid lithium-t-butox ide has been studied. It is shown that atomic lithium emission lines can be easily detected in the plasma by optical emission spectroscopy (OES). It w as found that for a fixed fraction of the Li precursor in the feed gas a va riation of the experimental conditions in the CVD reactor can drastically c hange the Li concentration in the plasma. The experimental results demonstr ate that an optical control of the Li concentration in the plasma is indisp ensible. Elastic recoil detection (ERD) measurements clearly established th at Li was incorporated into the diamond films in concentrations ranging fro m 40 up to 300 ppm. Etching of plasma exposed steel components in the react or due to Li addition and the subsequent incorporation of iron, cobalt, and nickel into the films could be strongly reduced by replacing these compone nts by graphite parts.