High-performance ultra-violet phototransistors based on CVT-grown high quality SnS2 flakes.

Haoting Ying,Zhiwei He,Yutong Wu,Junhua Xi,Weitao Su,Chengchao Jin,Qi Zhang,Xin Li,Yi Yao,Minxuan Xu

doi:10.1039/c9na00471h

Abstract

van der Waals layered two-dimensional (2D) metal dichalcogenides, such as SnS2, have garnered great interest owing to their new physics in the ultrathin limit, and become potential candidates for the next-generation electronics and/or optoelectronics fields. Herein, we report high-performance UV photodetectors established on high quality SnS2 flakes and address the relatively lower photodetection capability of the thinner flakes via a compatible gate-controlling strategy. SnS2 flakes with different thicknesses were mechanically exfoliated from CVT-grown high-quality 2H-SnS2 single crystals. The photodetectors fabricated using SnS2 flakes reveal a desired response performance (Rλ ≈ 112 A W−1, EQE ≈ 3.7 × 104%, and D* ≈ 1.18 × 1011 Jones) under UV light with a very low power density (0.2 mW cm−2 @ 365 nm). Specifically, SnS2 flakes present a positive thickness-dependent photodetection behavior caused by the enhanced light absorption capacity of thicker samples. Fortunately, the responsivity of thin SnS2 flakes (e.g. ∼15 nm) could be indeed enhanced to ∼140 A W−1 under a gate bias of +20 V, reaching the performance level of thicker samples without gate bias (e.g. ∼144 A W−1 for a ∼60 nm flake). Our results offer an efficient way to choose 2D crystals with controllable thicknesses as optimal candidates for desirable optoelectronic devices.

Highlights

Two-dimensional (2D) materials, such as graphene since its rst isolation from bulk crystals, have created opportunities to access novel features at reduced dimensionality.[1,2,3] Inspired by this, there has been growing interest to nd new 2D structures, because fundamentally and technologically interesting properties have been identi ed in the ultrathin limit, but most attention so far has been paid to layered transition metal dichalcogenides (TMDs).[4,5,6,7] graphene shows a zero-band gap which traditionally has limited its application in optoelectronic devices.[8]
Recent evidence has already pointed out the fascinating progress in applying 2D SnS2 structures in lithium ion batteries,[22] eld-effect devices[23] and photodetectors,[24] bene tting from the simple exfoliation from bulk crystals and the controlled bottom-up synthesis.[25,26]
To get SnS2 samples with varied thicknesses, we employed tapeassisted mechanical isolation from raw crystals synthesized via a chemical vapour transport (CVT) approach

Summary

Introduction

Two-dimensional (2D) materials, such as graphene since its rst isolation from bulk crystals, have created opportunities to access novel features at reduced dimensionality.[1,2,3] Inspired by this, there has been growing interest to nd new 2D structures, because fundamentally and technologically interesting properties (charge carriers and photons are con ned in a 2D plane, etc.) have been identi ed in the ultrathin limit, but most attention so far has been paid to layered transition metal dichalcogenides (TMDs).[4,5,6,7] graphene shows a zero-band gap which traditionally has limited its application in optoelectronic devices.[8]. SnS2 akes with different thicknesses (that can be thinned to $7 nm in the work) were mechanically exfoliated from CVT-grown high-quality 2H-SnS2 single crystals.

Results

Conclusion