Prediction of a two-dimensional S3N2 solid for optoelectronic applications

Abstract

Two-dimensional materials have attracted tremendous attention for their fascinating electronic, optical, chemical and mechanical properties. However, the band gaps of most 2D materials reported are smaller than 2.0 eV, which greatly restricted their optoelectronic applications in blue and ultraviolet range of the spectrum. Here, we propose a new stable sulfur nitride (S3N2) 2D crystal that is a covalent network composed solely of S-N σ bonds. S3N2 crystal is dynamically stable as confirmed by the computed phonon spectrum and ab initio molecular dynamics simulations in the NPT ensemble. Hybrid density functional calculations show that 2D S3N2 crystal is a wide, direct band-gap (3.17 eV) semiconductor with good hole mobility. These fascinating electronic properties could pave the way for its optoelectronic applications such as blue or ultra-violet light-emitting diodes (LEDs) and photodetectors.Keywords: Sulfur nitride, S3N2, 2D material, wide band gap, direct band gap October 2004 marked the discovery of graphene [1], the first stable and truly 2D material. This epic discovery has opened up the possibility of isolating and studying the intriguing properties of a whole family of 2D materials including the 2D insulator boron nitride (BN) [2][3][4], graphane analogues of group IV elements, i.e. semimetallic silicene, germanene, and stanene [5][6][7][8][9][10][11], 2D transition-metal dichalcogenides [12][13][14][15][16], such as molybdenum disulfide [2,17,18] and tungsten disulfide [19], and very recently, 2D phosphorus, i.e. phosphorene [20], which extend the 2D material family into the group V. These 2D free-standing crystals exhibit unique and fascinating physical and chemical properties that differ from those of their 3D counterparts [21,22], opening up possibilities for numerous advanced applications. For example, MoS2, MoSe2, and WS2 are able to achieve 1 order of magnitude higher sunlight absorption than traditional photovoltaic materials such as GaAs and Si [23]. Two-dimensional materials offer novel opportunities for fundamental studies of unique physical and chemical phenomena in 2D systems [24,25].In this work, we propose a new two-dimensional sulfur nitride (S3N2) solid ( Fig. 1(a)) with space group Pmn21. The ground state structure of S3N2 was obtained using the evolutionary algorithm driven structural search code USPEX [26][27][28] combined with the ab initio code Quantum Espresso [29]. The S3N2 structure was further geometry optimized with density functional calculations with Perdew-Burke-Ernzerhof (PBE) [30] exchange-correlation functional using the Cambridge series of total-energy package (CASTEP) [31,32]. A plane-wave cutoff energy of 700 eV is used, and a 12 × 6 × 1 Monkhorst-Pack [33] k-point mesh was used. The convergence test of cutoff energy and k-point mesh has been conducted. Because the band gaps are dramatically underestimated by the GGA level DFT [34,35], band structures of S3N2 solid were calculated with HSE06 [36] hybrid functional, which has been demonstrated to be able to predict accu...

First-principles investigations on a two-dimensional S3N2/black phosphorene van der Waals heterostructure: mechanical, carrier transport and thermoelectric anisotropy

“…The optimized lattice constants of BP and S monolayers), respectively, in accordance with previous theoretical results [14,38]. In order to construct a lattice-matched model, A 3 × 1 periodicity of BP supercell and a S 3 N 2 primitive cell are combined to form the S 3 N 2 /BP vdW heterostructure (containing 12 P, 6 S and 4 N atoms).…”

“…We consider that the material lying on the BP is stable and does not completely mask the physical properties of the BP. Therefore, in our view, we find a recently reported S 3 N 2 monolayer with low symmetric heart-shaped structure [14]. The monolayer S 3 N 2 is not only a wide bandgap semiconductor (3.92 eV), but also a promising flexible material, which has the same mechanical property of out-of-plane negative Poisson's ratio as BP.…”

Predicting a two-dimensional P2S3 monolayer: A global minimum structure

“…For example, a novel 2D Be2C monolayer, with each carbon atom binding to six Be atoms to form a quasi-planar hexacoordinate carbon moiety, was discovered by Li et al [32]. And in our previous work [33], we discovered a novel light-emitting 2D crystal with a wide direct band gap, namely S3N2 monolayer, using the evolutionary crystal structure search method. The amazing properties of the S3N2 2D crystal inspired us to explore the possibility of other group V-VI 2D crystals.…”

“…For example, a novel 2D Be2C monolayer, with each carbon atom binding to six Be atoms to form a quasi-planar hexacoordinate carbon moiety, was discovered by Li et al [32]. And in our previous work [33],…”

Mono- and Bi-Molecular Adsorption of SF6 Decomposition Products on Pt Doped Graphene: A First-Principles Investigation

“…To obtain the 2D material with global minimum total energy or to get the adsorption structure with the global minimum total energy rather than the local minimum, several initial structures should be considered and several optimized structures were obtained. By comparing the final total energy or other physical properties, the final structure of materials or adsorption structure can be obtained [14,15]. It has been proved that single-layer graphene without any defects has very week chemical interactions with most of the gas molecules [16].…”