Fabrication of scalable and ultra low power photodetectors with high light/dark current ratios using polycrystalline monolayer MoS2 sheets

During the last decade an unprecedented amount of funding has been invested on the study of the fundamental properties of two dimensional (2D) materials. Most of these studies have been mainly developed using research oriented techniques, such as mechanical exfoliation and electron beam lithography. Despite the large amount of information gained, these methods are not scalable, which impedes the mass production of electronic devices. The raising pressure for recovering the investment has shifted the global interest towards scalable routes of growing and manipulating the 2D materials, aiming to build up devices with realistic possibilities of commercialization. Here we show the fabrication of MoS2 photodetectors using an entirely scalable process, which is based on chemical vapor deposition (CVD), photolithography, electron beam evaporator and plasma ion etching. The devices show strikingly low power consumption (3.25×10−9 W under illumination) and high light/dark current ratios (up to 170) which, to the best of our knowledge, are the best ever reported in the literature for MoS2 phototransistors. These performances are related to the small domain size of the polycrystalline monolayer MoS2 sheets (164±54 nm in diameter). We also successfully minimized the hysteresis by introducing an annealing step during the fabrication process. The different parameters to be selected during the CVD growth process (precursor, gas carrier, pressure, temperature and time) offer a unique framework for tuning the properties of these devices. These results should be of interest to the entire community working on 2D materials based electronic devices.