Spectroscopic Studies of Diamond Growth

Abstract

Abstract : High Sensitivity Absorption Spectroscopy (HSAS) was used to study the C2 radical density in a hydrogen deficient Chemical Vapor Deposition (CVD) system for growing nanocrystalline diamond films. This work was performed in a collaboration between the University of Wisconsin group (supported by ARO) and Dr. Gruen's group at Argonne National Laboratory. The C2 radical density is important because it is the likely growth specie in the hydrogen deficient growth environment. The C2 radical density was measured over large range of parameter space in the CVD reactor. Research on the power balance of the plasma in the CVD reactor was performed. A microwave interferometer is being used to measure electron densities. Concentrations of benzene, C6H6, far higher than predicted by models of diamond CVD systems have been detected. This discovery is an important step toward a more quantitative understanding of the carbon balance of diamond CVD systems. We have extended the HSAS technique for use in a Reflection-Absorption mode to study molecules physisorbed on metal surfaces. The heterogenous chemistry and surface physics of many CVD, semiconductor etching, and other plasma processesing systems are poorly understood. New in-situ surface diagnostics are needed to advance the understanding of the surface science of these important systems. The Ultraviolet Reflection-Absorption Spectroscopy (UVRAS) method has important advantages for in-situ studies of processing environments. It has sensitivity to a small fraction of a monolayer. This high sensitivity is due to the fact that the oscillator strengths of electronic transitions in the UV are much larger than the oscillator strengths of vibrational transitions in the infrared which are probed using competing techniques.