Thermo-electric modeling and characterization of Carbon and silicon doped stanene nanostructures

Abstract

Stanene, a two dimensional buckled hexagonal allotrope of tin (Sn), exhibits very low thermal conductivity and high carrier mobility which make it a promising candidate for next generation thermoelectric (TE) applications. Significant improvement in thermoelectric figure of merit (zT) can be achieved in a system with simultaneously good electrical and low phonon transport. This fact urges the investigation of thermal as well as electrical transport characteristics of stanene and its nanostructures. In this work, equilibrium molecular dynamics simulation has been carried out for the thermal transport characterization of nanometer sized carbon and silicon doped stanene nanoribbon. We have investigated the impact of carbon and silicon doping concentrations as well as doping patterns namely single doping, double doping and edge doping on the thermal transport of nanometer sized zigzag stanene nanoribbon. The room temperature thermal conductivities of 15nm x 4nm doped zigzag stanene nanoribbon at 2 at. % carbon and silicon doping concentration are computed to be Wm-1K-1 and Wm-1K-1, respectively whereas the thermal conductivity for the pristine stanene nanoribbon of the same dimension is calculated to be Wm-1K-1. We find that the thermal conductivity of both carbon and silicon doped stanene nanoribbon increases with the increasing doping concentration for both carbon and silicon doping. The magnitude of increase in stanene nanoribbon thermal conductivity due to carbon doping has been found to be greater than that of silicon doping. Different doping patterns manifest different degrees of change in doped stanene nanoribbon thermal conductivity. Double doping pattern for both carbon and silicon doping induces the largest extent of enhancement in doped stanene nanoribbon thermal conductivity followed by single doping pattern and edge doping pattern respectively. The temperature and width dependence of doped stanene nanoribbon thermal conductivity has also been studied. Keeping a fixed carbon as well as silicon doping concentration, both temperature and nanoribbon width have been varied. For a particular doping concentration, the thermal conductivity of both carbon and silicon doped stanene nanoribbon shows a decaying trend at elevated temperatures while an opposite pattern is observed for width variation i.e. thermal conductivity increases with the increase in ribbon width. However, in spite of its intriguing prospect in thermoelectrics, pristine stanene has been found to have zero band gap with the p-orbitals of the tin atoms involved dominantly in both conduction and valence bands. This zero band gap feature limits the use of stanene in the high performance semiconductor based nanoelectronic devices. On the other hand, carbon doped stanene shows a band gap opening of ~82meV implying semiconducting nature of the system. On the other hand, silicon doping induces a small band gap of only ~14meV in the doped stanene leaving the electronic properties of the structure almost unaltered. In both types of doping, the formation of chemical bonding between the host atoms and the dopant atoms has been observed. Such comprehensive study on doped stanene would encourage further investigation on the proper optimization of thermal and electronic transport characteristics of stanene nanostructures and provide deep insight in realizing the potential application of doped stanene nanoribbon in thermoelectric as well as thermal management of stanene based nanoelectronic devices.