Wettability conversion on ZnO nanowire arrays surface modified by oxygen plasma treatment and annealing

The ZnO nanowire arrays were synthesized by a simple vapor-solid process. Wettability of nanowire arrays was studied by measuring contact angle. Under both oxygen plasma treatment and annealing at O2 atmosphere, the wettability of nanowire arrays changed from hydrophobic to super-hydrophilic. By measuring the photoluminescence spectra of modified samples, we affirm that the wettability conversion is not due to oxygen vacancies. It is thought that the oxygen related surface defect is the main reason to make this kind of change.