Effect of LPHT annealing on interface characteristics between HPHT Ib diamond substrates and homoepitaxial CVD diamond layers

To study the interface characteristics between substrates and homoepitaxially grown single crystalline diamond layers, the high-pressure/high-temperature Ib diamond seeds with homoepitaxial diamond layers were annealed by low-pressure/high-temperature treatment in a hydrogen environment. The stress evolution and related impurity transformation near the interface were characterized by Raman spectroscopy, photoluminescence, and micro-infrared spectroscopy before and after annealing. It is found that the stress is the smallest in a 100 mu m wide zone near the interface, accompanying with the similar change in substitutional nitrogen (Ns) concentration. After annealing at 1050 degrees C, 1250 degrees C, and 1450 degrees C, the local compressive stress is released gradually with temperature change. It is decreased by 1.03 GPa in maximum after annealing at 1450 degrees C. The concentration of nitrogen-vacancy (NV) complexes in the chemical vapor deposition (CVD) layer is dramatically reduced at 1450 degrees C. The value of INV-/I-diamond decreases much more than I-NV0/I-diamond in the CVD layer, which is due to the lower stability of NV- compared with NV0 at high temperature.