For the first time, Niobium-doped titanium dioxide (Nb:TiO2, NTO) and cadmium sulfide (CdS) are selected for building self-powered photodetectors for optimizing the performance. The p- or n-type NTO and the band structures of the heterojunctions can be controlled by doping Nb and tuning the sputtering power. A low sputtering power tends to produce pure anatase crystals and a high power induces additional rutile phase aligned in the (200) orientation. NTO films deposited at a sputtering power of 120 W show p-type behavior attributed to the compensation of oxygen vacancies. NTO films deposited at 180 W contain mixed anatase and rutile phases with lattice imperfections and show n-type semiconductor property after annealing. By measuring the energy band structure of n-n-type anatase-TiO2/CdS, p-n-type anatase-NTO/CdS, and n-n-type mix-NTO/CdS heterojunctions, we identify the interface carrier motion characteristics and tune the energy band structure to optimize the performance of the photodetectors. Without any external power supply, the responsivities reaches at least 0.125A/W in the mix-NTO/CdS (light source: 550 nm) and the response speed is lower than 10ms, which can be used for building a self-powered photodetector.

中文翻译：

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可调p型和n型Nb:TiO ₂和自供电Nb:TiO ₂ /CdS光电探测器的性能优化

首次选择掺铌二氧化钛 (Nb:TiO2, NTO) 和硫化镉 (CdS) 构建自供电光电探测器以优化性能。p 型或 n 型 NTO 和异质结的能带结构可以通过掺杂 Nb 和调整溅射功率来控制。低溅射功率往往会产生纯锐钛矿晶体，而高功率会导致额外的金红石相排列在 (200) 方向上。以 120 W 的溅射功率沉积的 NTO 薄膜显示出 p 型行为，这归因于氧空位的补偿。在 180 W 下沉积的 NTO 薄膜含有混合锐钛矿和金红石相，具有晶格缺陷，并且在退火后显示出 n 型半导体特性。通过测量nn型锐钛矿-TiO2/CdS、pn型锐钛矿-NTO/CdS的能带结构，和 nn 型混合 NTO/CdS 异质结，我们识别界面载流子运动特性并调整能带结构以优化光电探测器的性能。在没有任何外部电源的情况下，混合NTO/CdS（光源：550 nm）的响应率至少达到0.125A/W，响应速度低于10ms，可用于构建自供电光电探测器。