Phase-Controllable Growth of Air-Stable SnS Nanostructures for High-Performance Photodetectors with Ultralow Dark Current

The epitaxial growth of low-dimensional tin chalcogenides SnX (X = S, Se) with a controlled crystal phase is of particular interest since it can be utilized to tune optoelectronic properties and exploit potential applications. However, it still remains a great challenge to synthesize SnX nanostructures with the same composition but different crystal phases and morphologies. Herein, we report a phase-controlled growth of SnS nanostructures via physical vapor deposition on mica substrates. The phase transition from a-SnS (Pbnm) nanosheets to fi-SnS (Cmcm) nanowires can be tailored by the reduction of growth temperature and precursor concentration, which originates from a delicate competition between SnS-mica interfacial coupling and phase cohesive energy. The phase transition from the a to fi phase not only greatly improves the ambient stability of SnS nanostructures but also leads to the band gap reduction from 1.03 to 0.93 eV, which is responsible for fabricated fi-SnS devices with an ultralow dark current of 21 pA at 1 V, an ultrafast response speed of <= 14 mu s, and broadband spectra response from the visible to near-infrared range under ambient condition. A maximum detectivity of the fi-SnS photodetector arrives at 2.01 x 108 Jones, which is about 1 or 2 orders of magnitude larger than that of a-SnS devices. This work provides a new strategy for the phase-controlled growth of SnX nanomaterials for the development of highly stable and high-performance optoelectronic devices.

Automated summary

In this work, we demonstrate the phase-controlled growth of SnS nanostructures by physical vapor deposition on mica substrates. The phase transition from a-SnS nanosheets to fi-SnS nanowires can be achieved by reducing the growth temperature and precursor concentration, which is attributed to the competition between SnS-mica interfacial coupling and phase cohesive energy. The resulting fi-SnS devices exhibit improved ambient stability, a reduced band gap, and enhanced optoelectronic properties compared to a-SnS devices.