Few-Layer Tin Sulfide: A New Black-Phosphorus-Analogue 2D Material with a Sizeable Band Gap, Odd–Even Quantum Confinement Effect, and High Carrier Mobility

Abstract

As a compound analogue of black phosphorus, a new 2D semiconductor of SnS layers is proposed. Based on state-of-the-art theoretical calculations, we confirm that such 2D SnS layers are thermally and dynamically stable and can be mechanically exoliated from α-phase SnS bulk materials. The 2D SnS layer has an indirect band gap that can be tuned from 1.96 eV for the monolayer to 1.44 eV for a six-layer structure. Interestingly, the decrease of the band gap with increasing number of layers is not monotonic but shows an odd−even quantum confinement effect, because the interplay of spin−orbit coupling and lack of inversion symmetry in odd-numbered layer structures results in anisotropic spin splitting of the energy bands. It was also found that such 2D SnS layers show high in-plane anisotropy and high carrier mobility (tens of thousands of cm 2 V −1 s −1 ) even superior to that of black phosphorus, which is dominated by electrons. With these intriguing electronic properties, such 2D SnS layers are expected to have great potential for application in future nanoelectronics.

Layer‐Dependent Optoelectronic Properties of 2D van der Waals SnS Grown by Pulsed Laser Deposition

“…Pan et al43 reported the band gap values of SnS all the way from one monolayer (ML) to the bulk material by relying on first principle calculation. The change of the values is not monotonously continuous, but has a parity quantum confinement effect because spin–orbit coupling results in splitting of the energy bands in the odd layers without inversion symmetry.…”

Facile Formation of Nanodisk‐Shaped Orthorhombic SnS Layers from SnS2 Particles for Photoelectrocatalytic Hydrogen Production

“…As a two‐dimensional (2D) material with an analogous structure as black phosphorus, yet with a finite band gap unlike graphene, tin sulfides have gained considerable attention among the family of two‐dimensional (2D) materials . Among tin sulfides, SnS (tin monosulfide, Herzenbergite) is known as a potential candidate for solar energy utilization due to its fascinating electronic properties such as direct optical band gap (1.4–1.7 eV) and a high absorption coefficient (>10 4 cm −1 ), in addition to the fact that it is earth‐abundant, non‐toxic and air stable .…”

“…This 2D nature of the SnS layer renders only a weak interaction between neighboring layers via van der Waals interactions, which allows easy separation and fabrication of layered composite structures with highly disparate atomic layers to create a wide range of van der Waals (vdWs) heterostructures without any constraints of lattice match and compatibility. Therefore, the processability of SnS combined with its extraordinary physical and chemical properties makes it a perfect model system in exploring new 2D properties …”

“…As at wo-dimensional (2D) material with an analogouss tructure as black phosphorus, yet with af inite band gap unlike graphene, tin sulfides have gained considerable attention among the family of two-dimensional (2D) materials. [1][2][3][4][5][6] Amongt in sulfides, SnS (tin monosulfide, Herzenbergite) is known as ap otentialc andidate for solar energy utilizationd ue to its fascinating electronic properties such as direct optical band gap (1.4-1.7 eV) and ah igh absorption coefficient (> 10 4 cm À1 ), in addition to the fact that it is earth-abundant, non-toxic and air stable. [7][8][9][10][11][12][13] SnS has as tructure with an orthorhombic unit cell, in which each tin atom is coordinated to six sulfur atoms in ah ighly distorted octahedral geometry.T wo corrugated tin sulfide double layers constitute as ingle unit cell and each SnS layer consists of ac ovalently bondedn etwork within the 2D lattice with no dangling bonds.…”

Synthesis of Submillimeter‐Scale Single Crystal Stannous Sulfide Nanoplates for Visible and Near‐Infrared Photodetectors with Ultrahigh Responsivity

“…Comparing to graphene, TMDs such as MoS 2 and WSe 2 have tunable bandgaps and have been receiving intensive attention owing to their remarkable electronic and optoelectronic properties. [17] It has large absorption coefficient (≈10 5 cm −1 ) [18] and predicted high carrier mobility, [19] rendering it a great potential applications in optoelectronic and electronic devices. [16] Among them, SnS is an intrinsic p-type layered semiconductor with an indirect band gap of 1.0-1.1 eV in orthorhombic crystal structure.…”