Evaluation of Local Stress Distributions and Dislocations Around Petal Patterns Observed in CVD Single Crystal Diamond Plates

Abstract

Diamond epitaxial films grown by plasma CVD often show petal-like patterns in places when observed by polarized light microscopy under crossed polarizers. In this study, we have comprehensively characterized shapes of the petal patterns, spatial distributions of local stress, and microstructures of the dislocation bundle around the pattern in CVD single crystal diamond plates, mainly using polarized optical microscopy, Raman scattering, and high-voltage transmission electron microscopy (HVTEM). Four-petal patterns observed in the film consisted of a set of high-intensity petals and a set of very low-intensity ones, which rotated with the rotation of crossed polarizers and changed to two higher intensity petals. It was found that there was local compressive stress around the center of the petal and local shear stress with weak tensile stress along the four directions of [110] equivalence. Cross-sectional Raman imaging showed that there was a funnel-shaped compressive stress region through the center of the petal pattern. HVTEM observations using a ∼1 μm thick foil revealed 17 dislocations in the funnel-shaped region, corresponding to the dislocation bundle. These dislocation types were determined based on Burger’s vectors obtained from gb analysis on the TEM images under two-beam conditions.