Lu Yang, Chen Jun, Chen Tongxin, Shu Yu, Chang Ren-Jie, Sheng Yuewen, Shautsova Viktoryia, Mkhize Nhlakanipho, Holdway Philip, Bhaskaran Harish, Warner Jamie H
Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK.
Adv Mater. 2020 Feb;32(7):e1906958. doi: 10.1002/adma.201906958. Epub 2020 Jan 1.
A chemical vapor deposition method is developed for thickness-controlled (one to four layers), uniform, and continuous films of both defective gallium(II) sulfide (GaS): GaS and stoichiometric GaS. The unique degradation mechanism of GaS with X-ray photoelectron spectroscopy and annular dark-field scanning transmission electron microscopy is studied, and it is found that the poor stability and weak optical signal from GaS are strongly related to photo-induced oxidation at defects. An enhanced stability of the stoichiometric GaS is demonstrated under laser and strong UV light, and by controlling defects in GaS, the photoresponse range can be changed from vis-to-UV to UV-discriminating. The stoichiometric GaS is suitable for large-scale, UV-sensitive, high-performance photodetector arrays for information encoding under large vis-light noise, with short response time (<66 ms), excellent UV photoresponsivity (4.7 A W for trilayer GaS), and 26-times increase of signal-to-noise ratio compared with small-bandgap 2D semiconductors. By comprehensive characterizations from atomic-scale structures to large-scale device performances in 2D semiconductors, the study provides insights into the role of defects, the importance of neglected material-quality control, and how to enhance device performance, and both layer-controlled defective GaS and stoichiometric GaS prove to be promising platforms for study of novel phenomena and new applications.
开发了一种化学气相沉积方法，用于制备厚度可控（一至四层）、均匀且连续的缺陷硫化镓（GaS）薄膜：GaS 和化学计量比的 GaS。利用 X 射线光电子能谱和环形暗场扫描透射电子显微镜研究了 GaS 独特的降解机制，发现 GaS 稳定性差和光信号弱与缺陷处的光致氧化密切相关。在激光和强紫外光下，化学计量比的 GaS 表现出增强的稳定性，通过控制 GaS 中的缺陷，光响应范围可从可见光到紫外光转变为紫外光分辨。化学计量比的 GaS 适用于大规模、对紫外光敏感的高性能光电探测器阵列，用于在大可见光噪声下进行信息编码，具有短响应时间（<66 毫秒）、优异的紫外光响应度（三层 GaS 为 4.7 A/W），与小带隙二维半导体相比，信噪比提高了 26 倍。通过对二维半导体从原子尺度结构到大规模器件性能的全面表征，该研究深入了解了缺陷的作用、被忽视的材料质量控制的重要性以及如何提高器件性能，层控缺陷 GaS 和化学计量比的 GaS 都被证明是研究新现象和新应用的有前途的平台。
