High-sensitivity white-light absorption

USES OF HIGH-SENSITIVITY WHITE-LIGHT ABSORPTION SPECTROSCOPY IN CHEMICAL VAPOR DEPOSITION AND PLASMA PROCESSING... 

II. High-Sensitivity White-Light Absorption Spectroscopy. 296... 

HIGH-SENSITIVITY WHITE-LIGHT ABSORPTION SPECTROSCOPY 297... 

Fig. 1. Schematic diagram of the hollow-cathode glow-discharge CVD and high-sensitivity white-light absorption spectroscopy apparatus. (Reprinted with permission from Menningen et ai, 1995a, Contrih. Plasma Phys. 35, 359, 1995 Wiley-VCH, Inc.)...

As stated in the introduction, high-sensitivity white-light absorption spectroscopy has been used more extensively in studying the gas-phase composition during the CVD of diamond films than in other applications of CVD. In this section we review the use of high-sensitivity white-light absorption for the measiuement of n for the various free radicals and molecules present in the CVD of diamond under different conditions. 

High-sensitivity white-light absorption spectroscopy was used in the detection of CH3 and C2H2 in the CVD of diamond by Childs et al. (1992) in a hot-filament... 

High-sensitivity white-light absorption spectroscopy has been used to measure the CH densities in various CVD reactors. These measurements show remarkable sensitivity. The CH and CH3 densities have been used to obtain the dissociation ratio [H]/[H2]. 

In this section, we have reviewed the use of high-sensitivity white-light absorption spectroscopy to study the C2H2 density during diamond growth in hot-filament CVD. Many interesting effects due to filament poisoning have been observed. 

The high-sensitivity white-light absorption spectroscopy of hydrogen-deficient microwave CVD used for nanocrystalline diamond growth done by Goyette et al. (1998a) used the (0,0) vibrational band of the cPYl — a II electronic transition of C2, known as the Swan system. Figure 20 shows a typical absorption spectrum from this band. The bandhead for the (0,0) Swan band is located at 516.5 nm. The... 

High-sensitivity white-light absorption spectroscopy has also been used in the determination of gas kinetic temperature in diamond CVD environments. The gas kinetic temperature is an important parameter in these reactive environments, since the rates and endpoints of chemical reactions are temperature-dependent, fri addition, knowledge of the gas kinetic temperature is necessary in order to calculate column or absolute densities of species from their measured absorbances. Absorption cross sections are temperature-dependent, and the relative populations of the various levels represented in the integrated equivalent width are also temperature-dependent. Determination of gas kinetic temperatures in reactive discharges is therefore important. 

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