Microwave plasma characteristics during bias-enhanced nucleation of diamond: An optical emission spectroscopic study

Abstract

A negative bias applied to a nondiamond substrate at the initiation of microwave plasma-enhanced chemical-vapor deposition of thin-film diamond can lead to diamond nucleation, high crystalline density, and an improved level of crystallographic alignment. In this work, optical emission spectroscopy has been used to study changes in the chemical species within the plasma that occur as a result the applied bias to a tungsten substrate. The ratio of C2 to CH species detected changes considerably as does the atomic hydrogen intensity as the bias is applied. Both effects appear to be greatest near the substrate surface. The results are discussed in terms of possible origins for the bias-enhanced nucleation process.

Effects of Radical Species on Structural and Electronic Properties of Amorphous Carbon Films Deposited by Radical-Injection Plasma-Enhanced Chemical Vapor Deposition

“…Further investigation based on more precise and quantitative analyses of radical density is necessary for the detailed discussion. However, as reported by M. Heintze and coworkers and Don Rodway and coworkers, this method is useful to evaluate qualitative behaviors of radicals in the plasma. Also in this study, the changes in density ratios of radical species with decreasing the residence time are indicated.…”

“…[34,35] Based on these prior studies, the plot of deposition rate as a function of residence time in Figure 1 suggests that the dominant radical species contributing to the deposition of the a-C film undergo a compositional transition at a residence time of approximately 6 ms. intensity of the Ar emission line at 811.5 nm was used as a reference, for the calibration of the emission originated from H a , H b , C 2 , and CH. [35,36] Figure 2( [37,38] this method is useful to evaluate qualitative behaviors of radicals in the plasma. Also in this study, the changes in density ratios of radical species with decreasing the residence time are indicated.…”

Optical emission spectroscopy study of positive direct current bias enhanced diamond nucleation

“…Emission intensities of (a) H α and H β and (b) C 2 and CH as a function of methane content at a bias of +300 V. [26]. The variation in the H β /H α ratio with negative bias and pressure during bias-enhanced growth of diamond nuclei or positive bias in hot filament chemical vapor deposition was reported by several researchers [16][17][18]27]. In the present study, the variation in the intensity ratio of H β /H α as a function of positive bias voltage, methane content and working pressure in MPCVD was also studied.…”

“…For the methane flow range used in this study (35-50 sccm), a little variation in the H α signal was observed by increasing methane content, and a rather high value was measured at the highest methane content of more than 50% when a + 300 V bias was applied on the substrate. This may be due to the positiondependent in deposition as proposed by Jackman [17]. It was shown that this effect was not significant at some distances from the substrate surface (N10 mm) and suggested that near surface a higher atomic hydrogen concentration was obtained at a higher methane concentration and − 200 V bias.…”