Synthesis of zinc oxide nanosheet thin films and their improved field emission and photoluminescence properties by annealing processing

ZnO nanosheet thin films have been synthesized through a solvothermal route. These obtained nanosheets disperse quasi-vertically and homogenously on the copper substrates and range in thickness from 80 nm to 250 nm. The as-grown nanosheet thin films were then annealed in the oxygen-presented atmosphere. Field emission plots indicate that the value of turn-on field is reduced from 2.86 V/μm to 1.52 V/μm and the corresponding value of threshold field decreases from 7.19 V/μm to 4.45 V/μm after annealing processing. Room temperature photoluminescence spectrum from the sample annealed at 850 °C in almost pure oxygen atmosphere shows only UV emission and a blue shift while the visible light band is unobservable compared with those of the other two samples, indicating that the crystalline quality of the obtained zinc oxide nanosheet thin films is greatly improved through annealing treatment. This solution approach combined with annealing treatment can, therefore, be regarded as a convenient route to fabricate high-quality crystalline ZnO nanomaterials.