Highly anisotropic thermal conductivity of arsenene: An ab initio study

Highly Anisotropic Thermal Conductivity of Arsenene: an ab initio Study Majid Zeraati, 1 S. Mehdi Vaez Allaei, 1, 2, ∗ I. Abdolhosseini Sarsari, 3 Mahdi Pourfath, 4, 5 and Davide Donadio 6, 7, 8, 9, † Department of Physics, University of Tehran, Tehran 14395-547, Iran School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran Department of Physics, Isfahan University of Technology, Isfahan 84156-83111, Iran School of Electrical and Computer Engineering, University of Tehran, Tehran 14395-515, Iran Institute for Microelectronics, TU Wien, Gushausstrase 27–29/E360, 1040 Vienna, Austria Department of Chemistry, University of California Davis, One Shields Ave. Davis, CA, 95616 Max Planck Institut f¨ ur Polymerforschung, Ackermannweg 10, D-55128 Mainz, Germany Donostia International Physics Center, Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastian, Spain IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain (Dated:) Elemental 2D materials exhibit intriguing heat transport and phononic properties. Here we have investigated the lattice thermal conductivity of newly proposed arsenene, the 2D honeycomb struc- ture of arsenic, using ab initio calculations. Solving the Boltzmann transport equation for phonons, we predict a highly anisotropic thermal conductivity, of 30.4 and 7.8 W/mK along the zigzag and armchair directions, respectively at room temperature. Our calculations reveal that phonons with mean free paths between 20 nm and 1 µm provide the main contribution to the large thermal con- ductivity in the zigzag direction, mean free paths of phonons contributing to heat transport in the armchair directions range between 20 and 100 nm. The obtained anisotropic thermal conductivity and feasibility of synthesis, in addition to high electron mobility reported elsewhere, make arsenene a promising material for nano-electronic applications and thermal management. I. INTRODUCTION The discovery of graphene as a stable atomically thin material has led to extensive investigation of similar 2D systems. Its properties such as high electron mobility 1 , and very high thermal conductivity 2–5 make graphene very appealing for applications in electronics, for packag- ing and thermal management 6–11 . The successful iso- lation of single-layer graphene fostered the search for further ultra-thin 2D structures, such as silicene, ger- manene, phosphorene, and transition metal dichalco- genides, e.g. MoS 2 and WS 2 12,13 . These materials are now considered for various practical usages due to their distinguished properties stemming from their low dimen- sionality. Thermal transport in 2D materials has recently attracted the attention of the scientific community, as anomalous heat conduction has been predicted to oc- cur in systems with reduced dimensionality 14 . Phononic properties and thermal conductivity vary significantly from one 2D system to another 5,15–18 . For example, sil- icene has a buckled structure and a much lower thermal conductivity 19,20 compared to graphene 12,21,22 . 2D structures of arsenic and phosphorous have been recently investigated 23–27 . Arsenic and phosphorus are in the 5th group of the periodic table and both have different allotropes. Black phosphorus is a layered al- lotrope of phosphorus similar to graphite, and the stabil- ity of its single layer form, named phosphorene has been probed both theoretically and experimentally 13,28 . Gray arsenic is one of the most stable allotropes of arsenic with a buckled layered structure 27,29 . In addition, arsenic has an orthorhombic phase (puckered) similar to black phosphorus 23,25,26 , and its monolayer is called arsenene (see Fig. 1). Experimental observations have shown that gray arsenic undergoes a structural phase transition to the orthorhombic precursor of arsenene at temperatures of about T = 370 K 30 . As a monolayer arsenene can have a direct band gap of the order of 1 eV, as opposed to the multilayer allotrope, which exhibits an indirect band gap 23,26 . According to our calculations, arsenene is stable as a puckered monolayer also near zero temper- ature, in agreement with previous reports 23,25,26 . Both phosphorene and arsenene exhibit diverse polymorphs, with electronic properties that vary from semiconduct- ing to semimetallic and metallic as a function of struc- ture and strain 23,27,31 . Low dimensionality and the versa- tility of their electronic structure make two-dimensional 5th group elemental systems very appealing, not only for fundamental studies, but also for practical applications in nano electronics. For the latter applications, it is how- ever essential to characterize thermal transport and heat dissipation, to predict their operating temperatures. In this Article we investigate heat conduction in ar- senene and we elucidate the anisotropy of its thermal con- ductivity. We consider “puckered” unstrained arsenene, which is a semiconductor 23 . Since in semiconductors phonons are the predominant heat carriers, we use first- principles anharmonic lattice dynamics calculations and the Boltzmann transport equation to compute phonon dispersion relations and thermal conductivity. Accord- ing to electronic structure calculations 23 , arsenene has a band gap of the order of 1 eV, thus we expect a negligible electronic contribution to κ, unless the system is doped or strained. For this reason we restrict our study to the phononic contribution to thermal transport.