Impacts of phase transformation on the thermoelectric properties of ZnO nanowires

Impacts of phase transformation from regular wurtzite phase to a graphitic polymorph hexagonal phase under tensile loading, on the thermoelectric properties of Zinc oxide nanowires (ZnO NWs), which is oriented in the [0001] direction, are studied by combining the first-principles simulation with one-dimensional (1D) Boltzmann transport equation (BTE). Our results show that this phase transformation has greatly influenced the thermoelectric properties of the ZnO NWs. We also find that the largest value of figure of merit ZT achieved for hexagonal phase (H phase) is larger than that for wurtzite phase (W phase) in the temperature range (200 K-1000 K), which means that hexagonal phase may become the optimal choice for ZnO nanowires in thermoelectric applications.