Ultra-thin high-quality SnTe nanoplates for fabricating flexible near-infrared photodetectors.

This work demonstrates a controlled Van-der Waals growth of two-dimensional SnTe nanoplates on mica substrates and their applications in flexible near-infrared photodetectors. The growth of non-layered rock-salt structured SnTe crystals into two-dimensional SnTe nanoplate structures is mainly caused by the two-dimensional nature of the mica surface, which also results in the ultra-thin nanoplates obtained (3.6 nm, equivalent to 6 monolayers). Furthermore, it is found that the shape of the SnTe nanoplates can be well engineered by changing their growth temperature due to the competition between the surface energy of {100} crystallographic plane and that of {111} plane. As a result of the favorable physical properties of topological crystalline insulators such as metallic surface (high electron mobility) and narrow bandgap, near-infrared photodetectors based on single SnTe nanoplate with the thickness of 3.6 nm present excellent device performance with a responsivity of 698 mA/W, a specific detectivity of 3.89 × 108 Jones and an external quantum efficiency of 88.5% under the illumination of a 980 nm laser at room temperature (300 K) without applying a gate voltage (Vg). With increasing the gate voltage from -30 V to 30 V the detector responsivity increases from 2.96 mA/W to 723 mA/W). and the detector detectivity increases from 2.4 × 10 Jones to 5.3 × 10 Jones. Furthermore, with increasing the thickness of SnTe nanoplate from 3.6 nm to 35 nm, the detector responsivity increases from 0.698 A/W to 1.468 A/W. The device performance measured after bending for 300 times as well as after bending with different radii presents no obvious degradation, which exhibits the excellent flexibility of the SnTe nanoplate detectors. These results not only contribute to a deep understanding of the mechanisms of the Van-der Waals growth of non-layered materials into two-dimensional structure, but also demonstrate the immense potential of SnTe nanoplates to be used in flexible near-infrared detectors.