Investigations of new samples of single-crystal CVD-diamond detectors

Single-crystal CVD diamond (scCVDD) for detector applications is grown on best quality HPHT single-crystal diamond substrates of (100) crystallographic orientation, because the incorporation of stacking faults or the creation of twin crystals is hereby more suppressed than, e.g., in the (111) growth direction. Any imperfection of the substrate may hand over in the CVD diamond film either as isolated bundle of threading dislocations or as an extended cluster defect. Both cases lead to crystal stress. After growth, the CVD plates are separated by laser cutting from the substrates and polished on both sides. In case of samples treated with diamond-coated scaifeor resin-wheels (Fig. 1, top-row), the AFM images of opposite surfaces (left and centre) show significant differences in morphology and roughness, e.g., 4-6nm rms and 1530nm rms, respectively. This is due to the initial brazing of the diamonds to the sample holder during polishing and the following chemical removal. The last fixed side remains amorphous (centre), whereas the opposite surface shows typical scratch line patterns (left). In contrast, ionbeam polished plates (Fig. 1, bottom-row) have almost atomically flat surface with roughness of ~ 0.5nm rms on both sides (left). The morphology and the ‘reconstruction’ of the diamond surface are important issues. Specific surface defects capable of accommodating excess electrons or holes by charge exchange between surface and bulk material [1]