The values of the unit cell parameter were measured and elements of the internal structure were determined in polycrystalline diamond films using X-ray diffraction. It was established that the values of the unit cell parameter were connected with the dislocation densities in mosaic polycrystalline diamond film crystallites. The dislocation density was calculated from measured micro-distortions and dispersion in the blocks based on the surface stretch forces that arose on the boundaries between blocks. This allowed more precise computation of the dislocation density. A similar connection between the unit cell parameter and dislocation density also existed in epitaxial diamond films and in plastically deformed natural type-IIb and Ic diamonds. A regular relationship between physical values of the unit cell parameter and dislocation density in mosaic diamond materials was determined by using mathematical modelling. An increase in the dislocation density resulted in a decrease in the unit cell parameter, from 0.356689nm in purer and perfect type-IIa diamonds to a limiting value of 0.35642nm in polycrystalline diamond film samples.

Investigation of the Unit Cell Parameter and Dislocation Structure of Polycrystalline Diamond Films. N.D.Samsonenko, S.N.Samsonenko, V.N.Varyukhin, Z.I.Kolupaeva: Journal of Physics - Condensed Matter, 2006, 18, 5303-12