Field effect transistor photodetector based on two dimensional SnSe<sub>2</sub>

Abstract

Two dimensional materials have been attracting intensive interest due to their unique physical and optoelectronic properties. As an emerging two dimensional materials, SnSe<sub>2</sub> have shown a considerable potential for next-generation electronic and optoelectronic. Herein, SnSe<sub>2</sub> bulk crystals have been prepared by a chemical vapour transport method with high purity tin and selenium powder as precursors. Then SnSe<sub>2</sub> multilayers has been successfully prepared by a micromechanical exfoliation method from the SnSe<sub>2</sub> bulk crystals. The phase structures and elemental composition of the bulk crystal are investigated using an X-Ray diffractometer, an X-ray photoelectrons spectrometer and a Raman spectrometer. And the morphologies are observed using an optical microscope, an atomic force microscope and a transmission electron microscope. The measurement results show that the SnSe<sub>2</sub> bulks are single crystals with a high crystallization and purity. The SnSe<sub>2</sub> multilayers have a size of 25–35 μm and a thickness of 1.4 nm. To detect the electronic and photoresponse characteristics of the SnSe<sub>2</sub> multilayers, a field effect transistor based on such SnSe<sub>2</sub> are fabricated via a photolithographic-pattern-transfer method. The transistor has a smooth surface without wrinkles and bubbles, and also has a good contact with Au electrodes. The transistor shows a linear output characteristic and an obvious rectification. The on/off ratio of the device is 47.9 and the electron mobility is 0.25 cm<sup>2</sup>·V<sup>–1</sup>·s<sup>–1</sup>. As a photodetector, the field effect transistor exhibits obvious photoresponse to three visible lights with the wavelengths of 405, 532, and 650 nm. As the lasers are turned on and the device is under illuminations of three visible lights, the current increase rapidly to a saturation state. Then as the lasers are switched off, the current decrease and recover to the original state. The drain-source current can alternate between high and low states rapidly and reversibly, which demonstrates photoresponse characteristics of the devices are stable and sensible. Notably, it shows a strongest response to the 405 nm light at an intensity of 5.4 mW/cm<sup>2</sup> with a high responsivity of 19.83 A/W, a good external quantum efficiency of 6.07 × 10<sup>3</sup>%, a normalized detectivity of 4.23 × 10<sup>10</sup> Jones, and a fast response time of 23.8 ms. The results of this work demonstrate that layered SnSe<sub>2</sub> can be a suitable and excellent candidate for visible light photodetector and has a huge potential for high-performance optoelectronic devices.