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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 nonlayered 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 ultrathin 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 the {100} crystallographic plane and that of the {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 × 10 8 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 (V g ). Upon increasing the gate voltage from −30 to 30 V, the detector responsivity increases from 2.96 to 723 mA/W and the detector detectivity increases from 2.4 × 10 6 to 5.3 × 10 8 jones. Furthermore, upon increasing the thickness of SnTe nanoplate from 3.6 to 35 nm, the detector responsivity increases from 0.698 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 nonlayered materials into two-dimensional structure but also demonstrate the immense potential of SnTe nanoplates to be used in flexible near-infrared detectors.

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This work presents a review on the current progress, challenges, and potential future development opportunities for two-dimensional material-based heterostructures, including their fabrication techniques as well as their applications in various functional devices. The fabrication techniques for two-dimensional material-based vertical heterostructure are first reviewed and discussed, including artificial stacking, chemical vapor deposition, molecular beam epitaxy, and others. Then, twodimensional material-based lateral heterostructure growth techniques are reviewed, including chemical vapor deposition and others. Subsequently, various functional device applications based on twodimensional material-based heterostructures are systematically reviewed and discussed, including electronic devices, optoelectronic devices, electrochemical devices, and others. The advantages and disadvantages for each fabrication/growth technique are compared and analyzed, including those for both vertical and lateral heterostructures. In addition, the current primary challenges for further development of two-dimensional material-based heterostructures and their functional devices are discussed and analyzed, including lack of precise control, low interface/surface quality, surface passivation issue, low light absorption, lack of system integration and application, complex device fabrication process, as well as low device fabrication efficiency. Various potential solutions are proposed that have the potential to overcome these existing primary challenges to achieve better device performance and thus their ultimate industry applications for the two-dimensional material-based heterostructures.

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