Thermoluminescent response of thin(2 [micro sign]m) polycrystalline diamond films grown by pulsed and continuos microwave plasmas

Polycrystalline diamond films with a thickness of about 2 mu m were deposited by chemical vapour deposition on silicon substrates in continuous and pulsed wave regimes with duty cycle between 25% and 100%. The thermoluminescent behaviour of these films was analysed in the temperature range 323-723 K after beta irradiation with doses in the range 7-107 Gy. All the films exhibit a dosimetric peak centred at about 592 K, showing a good linearity in the whole investigated dose range. The thermoluminescence analyses show that the intensity of the dosimetric peak is maximum for the continuous wave film, while it decreases for the pulsed wave samples. The variation of the crystalline quality and the purity of the films with the employed duty cycle, investigated via micro-Raman spectroscopy and room-temperature photoluminescence, indicates that the continuous wave (duty cycle = 100%) film has the best quality, corresponding to the highest thermoluminescence efficiency.