Emission spectroscopy during direct-current-biased, microwave-plasma chemical vapor deposition of diamond

Publisher Website
Google Scholar
Abstract
Optical emission spectroscopy was used to investigate dc biasing during diamond film synthesis in a microwave plasma. These measurements show that biasing produces significant changes near the substrate (i.e., close to the sheath region). Increasing the negative bias voltage (Vb) from 0 to −180 V in a CH4/H2/Ar (4/496/30 sccm) mixture increases the intensities of the hydrogen Balmer α and β lines. The relative concentrations of neutral atomic hydrogen were estimated by using an Ar(750.4 nm) emission line as an actinometer. At 38 Torr, increasing Vb from 0 to −150 V increased the concentration of atomic hydrogen by more than 20%. In addition, increasing Vb also increased the electron temperature near the substrate. These effects are likely to play an important role in the enhanced diamond nucleation that has been observed after negative-biased pretreatment.