Probing the Thermodynamic Stability and Phonon Transport in Two-Dimensional Hexagonal Aluminum Nitride Monolayer

Discovery of graphene and its astonishing properties have drawn great interest in new two-dimensional (2D) materials for practical applications in micro- and nanodevices. 2D hexagonal aluminum nitride monolayer ( h -AlN), a III–V group wide-bandgap semiconductor, has promising applications in optoelectronics and energy conversion. Unfortunately, their high temperature thermodynamic stability and thermal transport properties have not been reported. Here we investigate these properties, for the first time, of monolayer h -AlN using both equilibrium and nonequilibrium molecular dynamics simulations. We find that h -AlN has a very high melting point in the range of 3500–4000 K due to the strong Al–N covalent bonding. On the basis of the kinetic theory of thermal transport and quantum corrections, the intrinsic in-plane thermal conductivity of ∼264.1 W m –1 K –1 and phonon mean free path of ∼154 nm of h -AlN are estimated at quantum-corrected room temperature. The analysis of phonon transport properties demonstrates that there is a notable frequency gap between acoustic and some optical modes. Moreover, we find that the low elastic stiffness (phonon group velocity) and missing phonon modes in such gap attribute to the lower thermal conductivity of h -AlN than that of its 2D III–V group counterpart, h -BN. Our computational work not only characterizes the thermal transport behavior of h -AlN for practical applications in electronics, but also inspires optimal selections of other 2D III–V group materials as more efficient high-temperature heat conductors.