Electronic structures of ZnO(10 1̄ 0) under electric fields

Wide band gap semiconductors are considered as the potential materials for the vacuum nanoelectronic devices, such as field emission device. ZnO micro- and nano-structures with their high aspect ratios are selected as one of candidates for the field emission.The field emission currents from ZnO would enhance with strengthened external electric field, which have been interpreted in terms of the Fowler-Nordheim equation. However, little is known, for the relationship between the electronic structures and field emission properties of ZnO´s. In this report, we present the density functional calculations to investigate the relationship of the electronic structures of the ZnO and the field emission. Especially, we focus on the changes of the energy between the Fermi level and lowest unoccupied molecular orbital (LUMO) under electric fields. The Mulliken charge populations show that the field emission is dependent on the charges on surface of ZnO.