Boundary Layer Profiles in Plasma Chemical Vapor Deposition
David S. Green 1,
Thomas G. Owano 2,
Skip Williams 1,
David G. Goodwin 3,
Richard N. Zare 1, and
Charles H. Kruger 2
1 Department of Chemistry, Stanford University, Stanford, CA 94305
2 High Temperature Gasdynamics Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, CA 94305
3 Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125
A nonlinear optical spectroscopy based on degenerate four-wave mixing has made possible direct measurements of species temperature and concentration profiles through the boundary layer of a reactive plasma at atmospheric pressure. Spectra were obtained for CH and C2 radicals over a range of conditions including those for the plasma chemical vapor deposition of diamond films. Numerical simulations based on a one-dimensional stagnation-point flow model are in good agreement with the measurements. The CH mole fraction is shown to rise and fall as a function of distance from the substrate, which is compelling experimental evidence for the complex chemistry that is occurring in the plasma boundary layer.
Submitted on October 26, 1992
Accepted on December 23, 1992
