a1 Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802
As the technology for diamond film preparation by plasma-assisted CVD and related procedures has advanced, Raman spectroscopy has emerged as one of the principal characterization tools for diamond materials. Cubic diamond has a single Raman-active first order phonon mode at the center of the Brillouin zone. The presence of sharp Raman lines allows cubic diamond to be recognized against a background of graphitic carbon and also to characterize the graphitic carbon. Small shifts in the band wavenumber have been related to the stress state of deposited films. The effect is most noticeable in diamond films deposited on hard substrates such as alumina or carbides. The Raman line width varies with mode of preparation of the diamond and has been related to degree of structural order. The Raman spectrum of hexagonal diamond (lonsdaleite) is distinct from that of the cubic diamond and allows it to be recognized.
(Received August 12 1988)
(Accepted November 09 1988)