Two‐dimensional thermoluminescence of CVD diamond films

Diamond crystals can be used as thermoluminescent (TL) detectors due to their high sensitivity to the ionizing radiation. Passive diamond detectors exposed to the radiation cumulate the dose in their trap structure, which can be read out by a photomultiplier during heating of the diamond. The replacement of photomultiplier by a CCD camera gives the possibility to register the dose distribution over the surface of a CVD wafer and control the homogeneity of the diamond layer. The aim of the work was to use two-dimensional (2-D) TL system consisting of a planar reader with a CCD camera for the quick estimation of the homogeneity of CVD diamond surface prepared in different conditions. Diamond films were deposited using a microwave plasma enhanced chemical vapor deposition method with methanehydrogenoxygen gas mixture. Growth conditions such as gas composition mixture and substrate temperature strongly affect morphology and structure of polycrystalline diamond, which results in different local TL properties. Samples were exposed to Co-60 gamma radiation. The appearance of inhomogeneous dose distribution of the CVD diamond wafers was correlated with structure, morphology and phase purity. Diamond layers were investigated by scanning electron microscopy, Raman spectroscopy and X-ray diffraction. Large area 2-D TL system seems to be a promising tool for testing CVD diamonds and can be the basis for the analysis of the diamond coatings for TL synthesized in conditions, which provide reproducibility.