Two-Dimensional SnS: A Phosphorene Analogue with Strong In-Plane Electronic Anisotropy

Abstract

We study the anisotropic electronic properties of two-dimensional (2D) SnS, an analogue of phosphorene, grown by physical vapor transport. With transmission electron microscopy and polarized Raman spectroscopy, we identify the zigzag and armchair directions of the as-grown 2D crystals. The 2D SnS field-effect transistors with a cross-Hall-bar structure are fabricated. They show heavily hole-doped (∼10 cm) conductivity with strong in-plane anisotropy. At room temperature, the mobility along the zigzag direction exceeds 20 cm V s, which can be up to 1.7 times that in the armchair direction. This strong anisotropy is then explained by the effective mass ratio along the two directions and agrees well with previous theoretical predictions. Temperature-dependent carrier density determined the acceptor energy level to be ∼45 meV above the valence band maximum. This value matches a calculated defect level of 42 meV for Sn vacancies, indicating that Sn deficiency is the main cause of the p-type conductivity.

The Optical Properties and Plasmonics of Anisotropic 2D Materials

“…Thus, the most critical value for determining the hyperbolic regime is not the effective mass ratio, but the anisotropy of the intraband and interband couplings along the two principle axes. In layered anisotropic semiconductor materials, such as BP, BP‐analog materials (e.g., SnSe, SnS, GeSe, and GeS), the 1T phase of TMDCs (e.g., ReSe 2 ), and the trichalcogenides (e.g., TiS 3 ), strong anisotropic in‐plane electronic properties have been demonstrated via anisotropic optical absorptions, polarization‐dependent PL, and anisotropic conductivities, while the low carrier densities (low intensity of intraband transitions) and relatively large bandgap (from the mid‐infrared to the visible spectrum) are against forming strong coupling between the intraband and interband excitations unless the plasmon frequencies are tuned to the vicinity of interband excitations. In such cases, the wave vector for plasmons would be extremely large, which is impractical in experiments.…”

Structural characterization of SnS crystals formed by chemical vapour deposition

“…However, this potential is currently unfulfilled, with record PCE of around 5% (Sinsermsuksakul et al, 2014), which is predominantly attributed to recombination at defects and grain boundaries. We are investigating SnS as a potential candidate for application as a p-type semiconductor in 2D Tunnel FETs and MOSFETs (Sucharitakul et al, 2016;Tian et al, 2017). SnS can take the form of several phases.…”

“…Several groups have previously used TEM to identify the crystal structure of SnS nanoparticles (Lu et al, 2015;Tarkas et al, 2017), nanosheets (Hori et al, 2014;Brent et al, 2015;Yang et al, 2015;Chao et al, 2016), nanorods (Suryawanshi et al, 2014;Chauhan et al, 2015) and micron-sized flakes (Xia et al, 2016;Tian et al, 2017) which were synthesised through various techniques. The TEM characterisation of the SnS nanosheets and flakes have been generally limited to plane view analysis and basic d-spacing measurements in cross section in order to confirm the phase of the material.…”

Phosphorene and Graphene Nanoribbons with Vacancies in Magnetic Field

“…But a problem appears here: generally, 2 2/ qs is a real multiple of q and the number of the magnetic factors (with real periods) is higher than 1. It means that they have not a common period, so, the magnetic elementary cell is infinite and we can do only an estimate of the solution.…”

“…In the last 5 years, the development has been enhanced with an additional research on the nanostructures based on phosphor, stannum, molybdenum, borum, silicium [1,2] etc. In this paper, we will be concerned with the carbon and phosphor planar nanostructures and their electronic properties.…”