Controlled Growth of a Large-Size 2D Selenium Nanosheet and Its Electronic and Optoelectronic Applications

TL;DR

This paper reports the successful synthesis of large, high-quality 2D selenium nanosheets with anisotropic properties and demonstrates their potential in electronic and optoelectronic devices, including transistors and photodetectors.

Contribution

The study introduces a physical vapor deposition method to produce large 2D selenium nanosheets, enabling exploration of their electronic and optoelectronic applications.

Findings

Synthesized 2D selenium nanosheets as thin as 5 nm.

Demonstrated p-type field-effect transistors with 20 mA/mm current density.

Achieved phototransistors with 263 A/W photoresponsivity.

Abstract

Selenium has attracted intensive attention as a promising material candidate for future optoelectronic applications. However, selenium has a strong tendency to grow into nanowire forms due to its anisotropic atomic structure, which has largely hindered the exploration of its potential applications. In this work, using a physical vapor deposition method, we have demonstrated the synthesis of large-size, high-quality 2D selenium nanosheets, the minimum thickness of which could be as thin as 5 nm. The Se nanosheet exhibits a strong in-plane anisotropic property, which is determined by angle-resolved Raman spectroscopy. Back-gating field-effect transistors based on a Se nanosheet exhibit p-type transport behaviors with on-state current density around 20 mA/mm at Vds = 3 V. Four-terminal field effect devices are also fabricated to evaluate the intrinsic hole mobility of the selenium nanosheet, and the value is determined to be 0.26 cm2 Vs at 300 K. The selenium nanosheet phototransistors show an excellent photoresponsivity of up to 263 A/W, with a rise time of 0.1 s and fall time of 0.12 s. These results suggest that crystal selenium as a 2D form of a 1D van der Waals solid opens up the possibility to explore device applications.