Two-Dimensional Gold Halides: Novel Semiconductors with Giant Spin–Orbit Splitting and Tunable Optoelectronic Properties

Abstract

We introduce a new family of 2D materials with unique structure and optoelectronic properties, namely, single-layer gold(I) halides (AuHals). We propose their stability as well as structural, electronic, and optical properties using first-principles calculations. The cleavage energy is found to be similar to that of graphene from graphite, indicating the possibility for mechanical exfoliation. We show that AuHals are stable and have tunable direct (AuBr) and indirect (AuI) band gaps depending on the number of layers. We discuss the possible origin of the giant spin−orbit coupling (SOC) induced conduction band splitting in terms of orbital-decomposed band structure to guide future investigations on the design of materials with highly effective SOC. Exceptionally high excitonic binding energy, high hole mobility, and tunable band gaps indicate that AuHals are promising candidates for optoelectronic devices with excellent performance.

Single-Layer MX2 (M = Zn, Cd and X = Cl, I): Auxetic Semiconductors with Strain-Tunable Optoelectronic Properties

“…The low-dimensional effect introduces a variety of compelling properties, which lays the foundation for the application of two-dimensional (2D) materials in the fields of nanoelectronics, microelectromechanical devices, catalysis, sensors, and superconductors. − Over the past few decades, 2D transition metal halides (TMHals) have drawn considerable attention owing to their intriguing properties, including quantum anomalous Hall effect, magnetic properties, − high carrier mobility, and excellent optical properties. − Particularly, CrI 3 monolayer exhibits unique tunable magnetic properties related to the number of layers, with the monolayer showing ferromagnetism and the bilayer showing antiferromagnetism . Moreover, RhI 3 monolayer displays significant thickness-dependent band gap tunability .…”

High Anisotropic Optoelectronics in Two Dimensional Layered PbSnX2 (X = S/Se)

“…Our calculations show that the band gap decreases from a single layer (1.50 eV) to three layers (0.50 eV) of PbSnS 2 by PBE, which is in excellent agreement with ref 28. In order to further understand the strong layer-dependent band structure of PbSnS 2 , we systematically calculate the indirect band gaps with and without SOC from 1 to 8 layers of PbSnX 2 (X = S/Se) by HSE level, 51,52 as shown in Figure 5 and Figure S3. Clearly, the band gap decreases (down to 0.08/0.05 eV with SOC) with an increasing number of layers, and the slope reduces (for more than 4 layers) which suggests that the layer dependence will weaken with increased film thickness.…”