CH₃ and CH Densities in a Diamond Growth DC Discharge

Abstract

A highly sensitive multi-element optical absorption technique is used to measure the absolute column density of both CH, and CH radicals in a dc hollow cathode plasma-assisted chemical vapor deposition (CVD) system with CH, and H, used as the input gases. The plasma gas temperature is determined at different spatial points using the H, emission spectrum near 460nm. The spatial maps of the temperature and the radical densities provide information OA the chemical processes taking place in the discharge. The CH, and CH radical density measurements made in the dc discharge system are compared with similar measurements made in a hot filament CVD system. The [H]/[H,] ratio is derived from the CH, and CH densities using an analysis based on partial thermodynamic equilibrium of the single carbon hydrocarbon abstraction reactions.

Absolute transition probabilities for the a6D $\rightarrow$ y6P° multiplet (#8) of Fe II

“…Our experiment is now sensitive to fractional absorptions of 0.0003 using the 1 m spectrometer and PDA and is sensitive to fractional absorptions of 0.003 using the 3 m echelle spectrometer and CCD array. It has been possible to achieve sensitivities to fractional absorptions of 0.00001 with modest spectral resolving powers (Menningen et al 1995). We are optimistic that the experiment described here will ultimately achieve sensitivities to fractional absorptions of 0.0001 with a spectral limit of resolution of 0.03 cm −1 at wavelengths down to Lyman alpha.…”

“…When using this digital subtraction technique, the linearity of the detector arrays is especially important (Menningen et al 1995). We measure the fractional nonlinearity of our CCD array and find it to be less than 0.001 from 4% full well to 85% full well.…”

Ultraviolet reflection–absorption spectroscopy of benzene on metal surfaces

“…Sensitivities to fractional absorption of 3ϫ10 Ϫ6 have been achieved in our gas phase experiments. 15,16 Such sensitivities at modest spectral resolving powers of ϳ5000 require integration times of ϳ30 min using an arc lamp as a continuum source, but they are achieved in less than a minute using synchrotron radiation due to the far higher spectral radiance. A N min of 2.5 ϫ10 8 cm Ϫ2 is much less than a monolayer.…”

Radical density measurements in an oxyacetylene torch diamond growth flame

“…A series of spectra, recorded with the arc lamp either blocked or unblocked and with the flame either on or off, are digitally processed to subtract out the flame emission and determine the spectral transmittance of the flame. 9 Using the method described in Ref. 9, the absorbance correction due to the slightly nonlinear response of the diode array was determined to be negligible.…”

“…9 Using the method described in Ref. 9, the absorbance correction due to the slightly nonlinear response of the diode array was determined to be negligible. The transmittance spectra were recorded at different wavelength intervals and different experimental parameters in order to produce maps of the radical column densities as a function of distance from the substrate.…”