Thermal transport characterization and bandgap opening through electronic functionalization in stanene nanostructure

Abstract

In this study, equilibrium molecular dynamics simulation has been performed to characterize the thermal properties of stanene nanoribbons (STNRs). The room temperature thermal conductivities of pristine 10-nm x 3-nm zigzag and armchair stanene nanoribbon were estimated to be 0.95 ± 0.024 W/m-K and 0.89 ± 0.026 W/m-K, respectively. Thermal conductivity as a function of temperature and width of the ribbon was also studied. The thermal conductivity was found to decrease with increasing temperature within the temperature range of 100 K to 600 K. The thermal conductivity tends to increase with increasing width that range from 2 nm to 6 nm for both the configurations. In all cases, the zigzag STNR exhibited a higher thermal conductivity than its armchair counterpart. However, despite its intriguing prospect in thermoelectrics, stanene (Sn) is reported to have zero bandgap and this feature would certainly limit its use in the semiconductor based nanoelectronic devices. In this context, with a view to opening a bandgap in stanene, the structural and electronic properties of stanene/hexagonal boron nitride heterobilayer with different stacking patterns have been studied using first principle calculations within the framework of density functional theory. The electronic band structure of different stacking patterns shows a direct band gap of ~30 meV at Dirac point (without considering spin orbital coupling) and at the Fermi energy level with a Fermi velocity of ~0.53 x 106 ms-1. The obtained band gap value is ~100 meV considering spin orbital coupling. Linear Dirac dispersion relation is nearly preserved and the calculated small effective mass in the order of 0.05 mo suggests high carrier mobility. Density of states and space charge distribution of the considered heterobilayer structure near the conduction and the valence bands show unsaturated P orbitals of stanene. This indicates that, electronic carriers are expected to transport only through the stanene layer thereby leaving the hexagonal boron nitride (h-BN) layer to be a good choice as substrate for the heterostructure. We have also explored the modulation of the obtained band gap by changing the interlayer spacing between h-BN and Sn layer from 3.3 Å to 4.2 Å and by applying tensile biaxial strain upto 7% to the heterostructure. A small increase in the band gap is observed with the increasing percentage of strain. With the increasing percentage of strain, a downward shifting of Fermi level is observed. Our results suggest that, Sn/h-BN heterostructure can be a potential candidate for Sn-based nanoelectronic device applications.