On the preparation of thin metal oxides by Langmuir-Blodgett film deposition

Abstract

An attempt at forming thin ZnO films by the thermal decomposition of Zn stearate Langmuir-Blodgett (LB) films is described. The stearate films were prepared by spreading stearic acid on a water subphase containing ZnCl 2. To ensure maximum conversion of the acid to salt, a high pH is required, but owing to micellar formation the maximum practical pH for stable monolayer formation was found to be 7.2. The monolayer was transferred to a solid substrate by vertical dipping with dipping ratios close to unity. The uniformity of the deposited LB multilayers was investigated by scanning surface potential measurements, phase contrast microscopy and surface plasmon resonance spectroscopy. Conversion of the acid to the Zn salt was confirmed by electron beam microanalysis and Rutherford backscattering, the latter suggesting that a fraction of the Zn ions may be incorporated into the monolayer as lower valence complexes. Despite the initial uniformity of the films, upon heating, the multilayers broke up into a myriad of microscopic droplets, the size of which increased with increasing film thickness.