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

采用TiCl_4+O_2混合气体和双二极管衬底偏置电路，在600℃下采用50Hz等离子体增强气相沉积技术在氧化铝衬底上制备了TiO_2薄膜。衬底偏置电压为-50(V)， TiO_2/O_2气体混合比为0.05。折射率约为2.7，介电常数约为120，光能隙约为3.0。采用TiO_2/氧化铝结构制备了薄膜辐射探测器。采用等离子体气相沉积技术在厚度为1mm的氧化铝板上沉积了厚度为100 nm ~ 1 μm的TiO_2。TiO_2的厚度对探测器的信噪比有一定的影响。探测器在TiO_2厚度为200（nm）的TiO_2/氧化铝结构上施加10(V)电压时暗电流为几十pA， 1（μm）厚度的TiO_2/氧化铝时暗电流为nA电流。因此，我认为TiO_2的厚度最好小于100（nm）左右。在TiO_2/氧化铝结构上设置金薄膜两个电极，并在两个电极之间加1 ~ 100(V)。薄膜探测器分别以2 ~ 8（C/kg/min）和5 ~ 33×10^<-4>(C/kg/min)照射γ射线和x射线。在施加电压10(V)时，用静电计测量辐照电流I=5 （pA）至300（pA）。测量的辐照电流与辐照强度呈线性关系。辐射检测灵敏度约为60（nA/ (C/kg/min)）。因此，TiO_2/氧化铝结构的薄膜辐射探测器可以测量γ射线和x射线的强度。此外，探测器的尺寸可以小到5×5×1（mm）。SiC/氧化铝结构比TiO_2/氧化铝结构具有更低的暗电流。因此，与TiO_2/氧化铝结构相比，SiC/氧化铝结构是较好的探测器。

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.