TlP₅: an unexplored direct band gap 2D semiconductor with ultra-high carrier mobility

Abstract

Two-dimensional materials with a proper band gap and high carrier mobility are urgently desired in the field of nanoelectronics. We propose a novel twodimensional crystal monolayer TlP5, which is dynamically and thermodynamically stable and possesses a direct band gap of 2.02 eV with high carrier mobilities (13960 cm 2 V -1 s -1 for electrons and 7560 cm 2 V -1 s -1 for holes), comparable to that of phosphorene. The band gap value and band characteristics of monolayer TlP5 can be adjusted by biaxial and uniaxial strains, and excellent optical absorption over the visible-light range is predicted. These properties, especially for the balanced high mobilities for not only the electrons but also the holes, render monolayer TlP5 an exciting functional material for future nanoelectronics and optoelectronic applications. 2 Since the successful mechanical exfoliation of graphene in 2004, 1,2 twodimensional (2D) materials such as silicene, 3 borophene, 4,5 phosphorene, 6,7 and transitional metal dichalcogenides (TMDCs) 8-11 have attracted intensive interests because of their extraordinary electrical, mechanical and thermal properties that enable extensive application potential in various fields. 9,12-18 For example, phosphorene, with a direct 2.0 eV band gap as well as a high carrier mobility of about 1.14×10 3 cm 2 V -1 s -1 -2.60×10 4 cm 2 V -1 s -1 , has been considered to be a candidate for high performance field effect transistors. 6 Yet, its chemical instability under ambient conditions and the low electron mobility still hinder its practical application. MoS2 possesses a suitable direct band gap (1.8 eV) for microelectronic and optoelectronic applications, but it suffers from the low carrier mobility (~200 cm 2 V -1 s -1 ). Nowadays, 2D materials with a proper band gap and high carrier mobilities for both electrons and holes are still urgently desired for logic and optoelectronic devices.Very recently, a series of 2D phosphides, such as InP3, 19 GeP3, 20 SnP3, 21 and CaP3, 22 have been theoretically proposed as novel 2D semiconductors with high carrier mobilities (~10 3 cm 2 V -1 s -1 -10 4 cm 2 V -1 s -1 ) that are comparable to those of phosphorene. In addition, their theoretical cleavage energy is relatively low (0.57~1.32 J m -2 ), indicating that they can be obtained through mechanical exfoliation from bulk.On the other hand, a layered material composed of P and Tl with the TlP5 stoichiometry

Recent Advances in 2D Layered Phosphorous Compounds

“…However, almost all of the reports about 2D group IIIA‐P compounds are theoretical predictions, mainly focusing on magnetism, electrical properties, catalysis and thermoelectricity. [ 43–52 ] There are very few experimental reports on 2D group IIIA‐P compounds. Therefore, in this section, we will highlight some representative crystal structures of 2D LPCs that have been widely reported experimentally, including GeP, SiP, b‐AsP, MPX 3 (M = Fe, Ni, Mn, X = S, Se), CuInP 2 S 6 and CrPS 4 .…”

Planar penta-transition metal phosphide and arsenide as narrow-gap semiconductors with ultrahigh carrier mobility

“…Recently, a series of phosphides such as GeP [21], GeP2 [22], GeP3 [23], InP3 [24], SnP3 [25][26][27], CaP3 [28], TlP5 [29] and so forth [30,31], have been reported to possess excellent electronic and optical properties. For instance, 2D InP3 undergoes a magnetic phase transition under hole doping [24]; single layer SnP3 was found to be a promising anode materials for Na-ion battery [27]; tetragonal-TlP5 shows a direct band gap of 2.02 eV with quite balanced carrier mobilities for electrons (1.396×10 4 cm 2 V -1 s -1 ) and holes (0.756×10 4 cm 2 V -1 s -1 ), even superior to that of phosphorene [29]. Notably, all of these predicted 2D phosphides are of buckling or muti-atomic layer structures.…”

Novel Braceletlike BiSbX3 (X = S, Se) Monolayers with an In-Plane Negative Poisson’s Ratio and Anisotropic Photoelectric Properties

“…The DFT-D3 method was used to correct the weak van der Waals (vdW) interaction . To get accurate results, the HSE06 hybrid functional was employed to calculate the electronic structures, and the spin–orbit coupling (SOC) effect was considered due to the existence of a heavy element in BiSbX 3 (X = S, Se) . The phonon dispersions were calculated using the PHONOPY code .…”