Langmuir-Blodgett Ultrathin Films Composed of ZnO Nanoparticles: Fabrication and Characterization

By the Langmuir-Blodgett(LB) technique, the zinc ion containing multilayer was prepared by transferring the zinc acetate, spread on the surface of subphase of ultrapure water and stearic acid-chloroform mixtures, onto a hydrophilic silicon wafer or glass plate. Then the multilayer was converted into ZnO ultrathin films after pre-heating and annealing. The optimized parameters for monolayer formation, such as concentration of subphase, barrier speed and spreading volume, were determined by the measurement of the surface pressure-surface area (Π-A) isotherms. The expended areas after deposition with zinc ions inferred the interaction of stearic acid with zinc ion during the formation of monolayer at air-water interface. The optimized parameters for multilayer deposition, such as surface pressure and lifting speed were determined by the measurement of the transfer coefficient. The X-ray diffraction(XRD) was used to investigate the crystal structures of ZnO nanoparticles and ultrathin film. The surface morphologies of the LB multilayer and ultrathin film were observed by the atomic force microscopy (AFM). A uniform and flat surface of ZnO ultrathin film within nanometer ranges(<35nm) were obtained.