NbSe2, serving as a 2D metal electrode, has been proven to form a Schottky heterojunction with MoSe2 to realize a highperformance broadband photodetector. Here, we further investigated the effect of gate voltage on the optoelectronic characteristics of the device. The results revealed that NbSe2 exhibits a weak electrostatic screening effect similar to graphene, and due to the high-quality contact between the 2D metal and semiconductor, the rectification ratio of the device can be significantly modulated from 0.32 to 5.5×104. Regarding the photovoltaic response characteristics of the device, the gate voltage similarly achieves significant modulation of the short-circuit current (20 nA-1.6 μA), open-circuit voltage (0-0.32 V), maximum electrical power (0-210 nW). Furthermore, the response speed of the device is also influenced by the gate voltage. This work demonstrates that Schottky heterojunctions constructed based on 2D metals can achieve effective control of optoelectronic properties, and has encouraging prospects in the fields of optical communications, optical sensing, and imaging.
Influenced by the prominent progress of two-dimensional (2D) layered crystals, the fabrication of 2D nanostructures from non-layered materials has attracted more and more attention. Lead selenide (PbSe) is one of the superior candidate materials for photodetector with suitable bandgap and outstanding photoelectric properties. The growth and device preparation of PbSe supply great interest for the development of high-performance infrared photodetectors. Although a lot of efforts have been paid on preparing PbSe nanostructures for miniaturized detectors, it is challenging to synthesize excellent crystallinity and thin 2D PbSe nanosheets because of itsinherent rock salt nonlayered structure. In this work, we employ a catalyst-free facile physical vapor deposition (PVD) method for controllable synthesis of PbSe nanosheets by van der Waals epitaxy technology. By optimizing the growth temperature, PbSe nanosheets from triangular pyramid island to square 2D plane can be obtained. In addition, the 2D PbSe nanosheets detector has a responsivity of 3.03 A/W at the wavelength of 520 nm with the power density of 5.05 mW/cm2. This work provides a facile strategy to synthesize high-quality 2D PbSe nanosheets which have enormous potentials to fabricate high-performance miniaturized photodetector.
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