Development of Thin Film Radiation Detectors using TiO_2 film by plasma CVD method

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The TiO_2 film have been deposited on alumina substrate by the 50Hz plasma-enhanced CVD at 600℃ using TiCl_4+O_2 gas mixture with a substrate bias circuit using two diodes. Substrate bias voltage was -50(V), and the gas mixture ratio (TiO_2/O_2) was 0.05. The refractive index, dielectric constant and optical energy gap were about 2.7, 120 and 3.0, respectively.Thin film Radiation detector was made by TiO_2/alumina structure. TiO_2 on alumina plate (1mm in thickness) was deposited 100(nm) to 1(μm) in thickness by the plasma CVD. It seems that thickness of TiO_2 influence upon detector S/N characters. Detector dark current at TiO_2 thickness 200(nm) of TiO_2/alumina structure by 10(V) applied voltage was few tens pA, 1(μm) thickness TiO_2/alumina was few nA current. Therefore, I think so that the thickness of TiO_2 is better than less about 100(nm). Gold thin film two electrodes were set on TiO_2/alumina structure, and add 1 to 100(V) between two electrodes. The film detector was irradiated γ-ray and X-ray of exposure rate 2〜8(C/kg/min) and 5〜33×10^<-4>(C/kg/min), respectively. Irradiation current of I=5 (pA) to 300(pA) was measured with an electrometer at applied voltage 10(V). The measured irradiation current has linearity against radiation intensity. And detection sensitivity of radiation was about 60(nA/ (C/kg/min)). Accordingly, it appears that the thin film radiation detector of TiO_2/alumina structure can be measuring intensity of γ-ray and X-ray. Moreover, the detector was made possible small size as 5×5×1(mm). Moreover, SiC/alumina structure has lower dark current than that of TiO_2/alumina structure. Therefore, it seems that SiC/alumina structure was good detector in comparison with TiO_2/alumina structure.