Investigation of the unit cell parameter and dislocation structure of polycrystalline diamond films

Abstract

The values of the unit cell (UC) parameter were measured and elements of the internal structure were determined in polycrystalline diamond films (PDFs) using x-ray diffraction. It was established that the values of the UC parameter were connected with the dislocation densities in mosaic PDF crystallites. The dislocation density was calculated from measured microdistortions and dispersion in the blocks based on the surface stretch forces that arise on the boundaries between blocks. This allowed more precise computing of the dislocation density. A similar connection between the UC parameter and dislocation density also exists in epitaxial diamond films and in plastic deformed natural type IIb and Ic diamonds. A regular relationship between physical values of the UC parameter and dislocation density in mosaic diamond materials was determined using mathematical modelling. An increase in the dislocation density results in a decrease in the UC parameter from 0.356 689 nm in more pure and perfect type IIa diamonds to a limiting value of 0.356 42 nm in PDF samples.