Effects of surface oxygen vacancies content on wettability of zinc oxide nanorods doped with lanthanum

This work highlights the wettability properties of La-doped ZnO sprayed thin films deposited on glass substrates at 460 degrees C in terms of oxygen vacancy induced by this doping element. First, X-ray diffraction (XRD) and scanning electron microscopy (SEM) observations reveal that all films exhibit vertically aligned ZnO nanorods crystallized in wurtzite ZnO phase and the crystallites are orientated towards (002) direction parallel to c-axis. Second, the shift of E-2H peak in Raman spectra reinforces the existence of compressive stress in such doped films which is consistent with XRD analysis. The changes in both A(1)(LO) and E-1(LO) peaks intensities show that the stress induced defects in terms of La doping. Moreover, to correlate between the evolution of oxygen vacancies concentration and the contact angle measurements, PL measurements were carried out at room temperature. Finally, a discussion has been made regarding the switching behaviors of ZnO:La film surfaces between hydrophobic and hydrophilic states showing that the variation of oxygen vacancy concentration leads effectively to a surface chemistry change which plays an important role in the wettability alteration phenomenon. (C) 2016 Elsevier B.V. All rights reserved.