Suprun O. Regularities of the dislocation structure formation and the physical and mechanical properties of structurally perfect diamond single crystals grown at high pressures and temperatures

The thesis is devoted to solution of the actual scientific and technical problem of studying of the dislocation structure of diamond single-crystals of Ib, IIa and IIb types depending on the growth temperature, growth rate and growth medium composition in the diamond thermodynamic stability region and determination of their physical and mechanical properties. Dislocations observation method is developed, the density of dislocations of diamond single crystals obtained at temperatures 1240 - 1500 °C with growth rates 1-25 mg/h is studied. The microhardness is studied, yield strength, the degree of diamond single crystals deformation in experiments on indentation at high temperatures 900 - 950 °C were determined. It was established that with increasing of growth temperature the density of dislocations decreases, while the growth rate increasing leads to increasing of density of dislocations. Critically low growth temperatures lead to the formation of bulk defects in the crystal structure. It is established that at indentation temperatures of 900 - 950 °С diamond is characterized by significant deformation hardening due to high shear modulus and low mobility of dislocations.