Surface-effects-dominated thermal and mechanical responses of zinc oxide nanobelts

Molecular dynamics (MD) simulations are carried out to characterize the mechanical and thermal responses of [0110]-oriented ZnO nanobelts with lateral dimensions of 21.22 A x 18.95 A, 31.02A x 29.42 A and 40.81 A x 39.89 A over the temperature range of 300-1000 K. The Young's modulus and thermal conductivity of the nanobelts are evaluated. Significant surface effects on properties due to the high-surface-to-volume ratios of the nanobelts are observed. For the mechanical response, surface-stress-induced internal stress plays an important role. For the thermal response, surface scattering of phonons dominates. Calculations show that the Young's modulus is higher than the corresponding value for bulk ZnO and decreases by ~33% as the lateral dimensions increase from 21.22 A x 18.95 A to 40.81 A x 39.89 A. The thermal conductivity is one order of magnitude lower than the corresponding value for bulk ZnO single crystal and decreases with wire size. Specifically, the conductivity of the 21.22 A x 18.95 A belt is approximately (31-18)% lowerthan that of the 40.81 A x 39.89 A belt over the temperature range analyzed. A significant dependence of properties on temperature is also observed, with the Young's modulus decreasing on average by 12% and the conductivity decreasing by 50% as temperature increases from 300 K to 1000 K.