Large-area and low-temperature synthesis of few-layered WS 2 films for photodetectors

WS2-based photodetectors were fabricated by sputtering and electron beam irradiation (EBI), and the effect of EBI on the crystallization of WS2 films was investigated. EBI at 1 kV energy for 1 min transformed the as-deposited amorphous structure of WS2 film into a two-dimensional (2D) layered crystalline structure with high uniformity over a 50.8 mm diameter wafer. Additionally, EBI enhanced the photoelectrical properties of WS2-based photodetectors. The as-deposited WS2 film yielded a responsivity of 0.10 mA · W−1 under 450 nm laser irradiation, but showed no response under 532 and 635 nm laser wavelengths. However, after 1 kV and 3 kV EBI of the WS2 films, the responsivities under laser irradiation at 450, 532, and 635 nm were 0.36, 1.37, and 0.19 mA · W−1, and 1.68, 2.45, and 1.09 mA · W−1, respectively. The substrate temperatures after 1 min of 1 kV and 3 kV EBI were 102 °C and 591 °C, respectively. The WS2-based photodetectors exhibited high responsivity in the visible light region despite their unique process conditions of low temperature and fast EBI treatment. Such desirable performance of the EBI-treated WS2 films shows significant potential for future large-area and low-temperature photoelectronic applications. Thus, we demonstrated that EBI is an attractive method for synthesizing 2D materials as it is fast, simple, controllable, and compatible with sputtering processes.