The influence of grain-boundaries on the electronic performance of CVD diamond films

CVD diamond shows interesting perspectives for the production of high-performance radiation detectors and electronic devices. However, due to a polycrystalline structure, the performance of CVD diamond-based devices may be hampered by the low signal-to-noise ratio associated with high level of conductivity. We consider that the level of conductivity correlates with the presence of graphitic impurities within the polycrystalline samples. Assuming that this graphitic phase is concentrated in the free volume of the interfacial crystal grain-boundaries, we show that the graphitic contamination and bulk leakage conductivity can be reduced by increasing the nucleation density. This effect is mainly due to a better filling of the interfacial space by smaller grains induced during the first stage of CVD deposition process. The 60 μm-thick films were structurally characterized, using Raman spectroscopy and X-ray diffraction (XRD), and electrically by the analysis of room temperature (RT) conductivity and charge collection efficiency, extracted from low-energy X-ray irradiation (8.05 keV).