Role of the film texturing on the response of particle detectors based on CVD diamond

Recent improvements in the quality of diamond films grown by Chemical Vapour Deposition (CVD) have made synthetic diamond a very attractive material for detection applications. In this paper, polycrystalline diamond films synthesised by microwave plasma enhanced CVD using a CH4-CO2 gas mixture, previously investigated as particle detectors, have been characterised by X-ray diffraction and Raman spectroscopy. The detector response was measured in vacuo under irradiation with 5.5 MeV α-particle from a 241Am source. A systematic study of the influence of the film structural properties on the detector performance has been carried out by changing the methane concentration in the growth plasma and the deposition temperature. The existence of a correlation between growth conditions, film texturing and detector performance has been demonstrated. Independently of the substrate temperature, (100) orientated films exhibit the lowest detection efficiencies. The meas ured collection distances are smaller than the average grain sizes and seem to be limited by trapping centres within the grains. These results are confirmed by Raman analysis.