Investigation of the phase composition for TiO2-SiO2 composite films prepared by reactive ion-assisted coevaporation using atomic force microscopy

Abstract

Recently there has been a great deal of interest in studying TiO2-SiO2 composite films. These films can be produced by coevaporation,1 cosputtering,2 and sol-gel3 methods. Material studies have highlighted the novel properties of this composite films. From the x-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, structures of TiO2-SiO2 composite and their compositional component films deposited by reactive ion-assisted coevaporation (IAC) are completely amorphous, which is one of the favored properties for optical coating materials. However, it is difficult to identify whether the structure of the composite films is a mixture of their component phases or a solid solution, because their diffraction patterns are too close to be distinguished. It has been shown that the atomic force microscope (AFM) can be used for measuring not only the topography, but the lateral friction force. With the measurements of lateral friction forces, it is useful in detecting the different phases on a nanometer scale. The aim of this paper is to study the phase composition of TiO2-SiO2 composite films prepared by reactive IAC using AFM. In combination with the results of XRD and TEM analyses, it is possible to distinguish that the structure of the composite film is a mixture of their component phases or a solid solution. The surface roughness of these films is also presented.