Thermal-enhanced field emission from CuO nanowires due to defect-induced localized states

The temperature dependence of the field emission properties of CuO nanowires was studied from 163 to 453 K. Large current increases were observed with increasing temperature, which cannot be explained by band to band excitation or emission from the valence band. Two distinct sections were observed from the Arrhenius plot. Activation energies of 100 meV for the high-temperature range (273 to 453 K) and 26.4 meV for the low-temperature range (163 to 273 K) were obtained. Phonon-assisted and defect-assisted thermal field emission mechanisms from p-type CuO NWs were proposed to explain the observed phenomena in the two temperature ranges, which relate to the defect-induced localized states. Numerical simulation using the proposed mechanism was carried out and a good fit with the experimental results was achieved. The results suggest that defect-induced localized states play an important role in field emission from nanowires.