In Situ Growth of GeS Nanowires with Sulfur-Rich Shell for Featured Negative Photoconductivity

• Published in: The journal of physical chemistry letters 2021-04, Vol.12 (12), p.3046-3052
• Main Authors: Zhao, Shuai, Sun, Jiamin, Yin, Yanxue, Guo, Yanan, Liu, Dong, Miao, Chengcheng, Feng, Xiao, Wang, Yiming, Xu, Mingsheng, Yang, Zai-xing
• Format: Article
• Language: English
• Subjects: Physical Insights into Light Interacting with Matter
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.1c00540

The negative photoconductivity (NPC) effect originating from the surface shell layer has been considered as an efficient approach to improve the performance of optoelectronic nanodevices. However, a scientific design and precise growth of NPC-effect-caused shell during nanowire (NW) growth process for achieving high-performance photodetectors are still lacking. In this work, GeS NWs with a controlled sulfur-rich shell, diameter, and length are successfully prepared by a simple chemical vapor deposition method. As checked by transmission electron microscopy, the thickness of the sulfur-rich shell ranges from 10.5 ± 1.5 to 13.4 ± 2.5 nm by controlling the NW growth time. The composition of the sulfur-rich shell is studied by X-ray photoelectron spectroscopy, showing the decrease of S in the GeS x shell from the surface to core. When configured into the well-known phototransistor, a featured NPC effect is observed, benefiting the high-performance photodetector with high responsivity of 105 A·W–1 and detectivity of 1012 Jones for λ = 405 nm with ultralow intensity of 0.04 mW·cm–2. However, the thicker-shell NW phototransistor shows an unstable photodetector behavior with smaller negative photocurrent because of more hole-trapping states in the thicker shell. All results suggest a careful design and controlled growth of an NPC-effect-caused shell for future optoelectronic applications.