Fabrication Of Periodic SnO₂-based Nanostructure Arrays By Glancing Angle Sputter Deposition

As the most popular fabrication method of films, magnetron sputter deposition hasadvantages in its good homogeneity and reproducibility, and the ease and flexibility ofdoping, which is extensively used to adjust the composition. On the other hand, themorphology of films can be tuned by Glancing Angle Deposition （GLAD） technique,in which the oblique incident vapor flux causes atomic shadow effects and thus resultsin special morphological nanostructures. With GLAD and magnetron sputter depositioncombined, periodic arrays of SnO₂-based nanostructures with modulated compositionsand morphology were fabricated. The glancing angle sputter deposition technique ismuch simpler and cheaper compared to lithography techniques, and thus shows greatpotentials in device applications.First, regular arrays of Ti_xSn_1-xO₂nanostructures were prepared by glancing anglesputter deposition onto self-assembled close-packed arrays of polystyrene microspheres.The morphology of the nanostructures could be modulated by the variation of thesputtering power of Ti target and the size of polystyrene microspheres templates.Accordingly, the performance of reflection which was dependent on the morphology ofnanostructures could be tuned by optimizing the parameters. After annealing in air, thefilms were crystallized to TiO2/SnO₂composite and maintained good thermal stabilityin the morphology and antireflection property.Secondly, the wetting behaviors of Ti_xSn_1-xO₂nanostructures were studied. Theanisotropic nanoflakes grown on200-nm-diameter polystyrene microspheres exhibitedmacroscopic-wetting anisotropy, which is ascribed to the difference of the three-phasecontact line structure in different directions, resulting from the anisotropic topography.On the other hand, it was shown that the “spheric shells” deposited on1-μm-diameterpolystyrene microspheres can be reversibly switched between hydrophobicity andsuperhydrophilicity by alternating visible light illumination and dark storage. Therealization of special wettability on antireflective films is of great significance and canbe employed to develop coatings for various substrates with simultaneous antireflective,self-cleaning and antifogging behavior.Thirdly, periodic arrays of Fe_xSn_1-xO₂nanostructures were fabricated by glancingangle sputter deposition. Compared with Fe_xSn_1-xO₂flat films, arrays of Fe_xSn_1-xO₂ nanostructures processed larger saturation magnetic moment, and exhibited bothperpendicular magnetic anisotropy and in-plane magnetic anisotropy. The EPR signaloriginating from the oxygen vacancies significantly varied with the Fe concentrationand reached the strongest at x=0.059, which is consistent with the saturationmagnetization. It demonstrates that the oxygen vacancies are an important factor forthe ferromagnetism of Fe_xSn_1-xO₂films.