High performance visible photodetectors based on thin two-dimensional Bi₂Te₃ nanoplates

Two-dimensional (2D) nanostructures, bismuth telluride (Bi₂Te₃), as represented by one of the topological insulators (TI) materials, have attracted tremendous interests from world-wide scientists due to their potential applications in electronic devices. However, the growth mechanism especially chemical vapour deposition (CVD) and the optoelectronic device applications of these Bi₂Te₃ nanostructures have barely been investigated and reported. In this work, we present a detailed study on the controlled CVD growth of 2D Bi₂Te₃ nanostructures and explore their applications in high performance visible photodetectors. With increasing the precursor material temperature from 470 °C to 510 °C, it is observed that the lateral size of Bi₂Te₃ nanoplates first increases and then becomes saturated when the precursor material temperature over 490 °C, which is mainly due to the competition between the transportation and diffusion of precursor molecules onto the substrate surface and the reaction consumption of precursor atoms on the substrate surface. In addition, it is also observed that the lateral size of Bi₂Te₃ nanoplates decreases with increasing the total inner tube pressure as a result of the reduced diffusion rate of Bi₂Te₃ precursor molecules. 2D Bi₂Te₃ nanoplates with a lateral size over 10 μm can be obtained with applying proper precursor material temperature and total inner tube pressure. Furthermore, a visible photodetector is fabricated using few-layered 2D Bi₂Te₃ nanoplates grown in this work. This visible photodetector demonstrates a high responsivity of 23.43 AW⁻¹ and a high detectivity of 1.54 × 10¹⁰ Jones, outperforming some visible detectors based on traditional 2D nanomaterials. Tche intensity-dependent photo-responsivity measurements show stable photoswitching behavior. This 2D Bi₂Te₃ nanoplate photodetector also presents high flexibility by showing no obvious performance degradation after being bent for 50 times. The results presented in this work will not only contribute to a comprehensive understanding of the CVD growth mechanism of Bi₂Te₃ nanostructures, but open up novel optoelectronic device applications for 2D Bi₂Te₃ nanostructures.