STRESS-DISTRIBUTION IN HETEROEPITAXIAL CHEMICAL-VAPOR-DEPOSITED DIAMOND FILMS

The stress distribution in heteroepitaxial chemical vapor deposited di amond films has been investigated by Raman spectroscopy. A new method for stress determination based on polarized confocal micro-Raman is pr esented and used for the measurement of the stress evolution across th e film thickness in the center of the sample. The presence of highly i nhomogeneous stresses at a microscopic scale is first demonstrated. Th e interface appears to be under compressive stress which rapidly decre ases and then stabilizes, but remains compressive. The strain tensor i s also shown to vary. Near the interface, the common assumption of bia xial stress in the plane of the film has been confirmed. Near the grow th surface, the stress tensor appears to be more complicated. Grain bo undaries are suggested to be mainly responsible for the intrinsic stre ss generation when the grain boundary density is high. Inhomogeneous i mpurity distribution could be related to stress inhomogeneities near t he growth surface, where the grain boundary density becomes small. Agr eement has been obtained between micro- and macro-Raman stress measure ments. The average stress (over film thickness) as determined by macro -Raman is shown to increase by 30%-40% from the sample center to the e dge. (C) 1997 American Institute of Physics.