Preparation Of ZnO And TiO₂ Based Photocatalytic Thin Films And Their Properties

ZnO films doped with 0².0at% Gd and N doped TiO₂ films with deposition temperatures ranging from RT to 600℃were deposited by magnetron sputtering method.The structure,composition,surface morphology,optical and photocatalytic properties of Gd doped ZnO films,as well as N doped TiO₂ films are characterized by electron probe microscopy analysis（EPMA）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,scanning electron microscope（SEM）,atomic force microscopy（AFM）,X-ray photoelectron spectroscopy（XPS）,ultraviolet-visible spectroscopy and photoluminescence（PL）spectra,respectively.The conclusions are as follows:Ⅰ All Gd doped ZnO films were prepared by RF magnetron sputtering at 600℃.XRD and selected area diffraction results indicated that all Gd-doped ZnO films possessed the hexagonal wurtzite structure and the crystalline sizes were decreased with Gd doping.SEM images revealed that ZnO nanowires / film structures were grown with a lower Gd content or pure ZnO.XPS results confirmed that the Gd ion was +3 valence states.PL spectra demonstrated an immense enhanced deep-level emission which attributes to the increase in defects concentration due to Gd doping.With a critical doping concentration of 1.6 at.% Gd,the ratio of the deep-level emission and the nearband edge emission increases by a factor of almost five as compared with pure Zn O.The photocatalytic activities of the films were evaluated by the degradation of methylene blue in aqueous solutions under UV light.The photocatalytic results indicated that the 0.7at% Gd-doped ZnO nanowires / film structure performed the hightest photocatalytic activity.Ⅱ All N doped TiO₂ films with different deposition temperature were prepared by DC magnetron sputtering.Phase transformation of N doped TiO₂ thin films is from anatase（RT-400℃）to mixture of antase and rutile（600℃）.The crystallite size of films showed an increase tendency with the increase of the deposition temperature.Owing to N doped,the optical band gap value of N doped TiO₂ films at various deposition temperature higher than that of pure TiO₂ is 3.36±0.04eV（RT,200℃,400℃）,3.32eV（600℃）,respectively.With the temperature increased,the photocatalyic activity of N doped TiO₂ thin films was enhanced.The photocatalytic reaction rate constant k of N doped TiO₂ films at different temperature is 0.011 min^-1（RT）,0.012 min^-1（200 ℃）,0.014 min^-1（400 ℃）,and 0.021min^-1（600 ℃）,respectively.N doped TiO₂ film deposited at 600℃ performed the highest photocatalytic activity.