Abstract: In this paper, we investigate the influences of deposition temperature and time on microstructure and surface topography of the aluminum films deposited on glass microspheres of higher refractive index by thermal decomposition of tri isobutyl aluminum in a fluidized bed CVDreactor at atmospheric pressure. SEMexamination of surface topography of the films shows that under the same conditions, the increase of deposition temperature causes the aluminum films to change from 3-dimensional hillock formation to non specular, rough structure with steep peeks and valleys to uniform and smooth surface; and while extending the deposition time at certain temperatures, the grains become larger and surface roughness becomes distinct. The results demonstrate that by means of thermal activation at appropriately elevated temperatures(350~390 ℃) for a certain period of time(about 30 min), it is possible to provide smooth and uniform aluminum films on the surface of glass microspheres which may approximately conform with the requirements of retro-reflective materials. Auger spectra for examining the surface chemical composition reveal that the preferred higher temperature used to obtain smooth topography does not introduce obvious contamination by carbon residues, but diffusion of Ti and Ba from substrates toward aluminum film occurs to some extent, which may be another factor to cause the activation of the substrate and to obtain smooth and uniform aluminum film on glass microspheres in this study. In order to further improve and control microstructure and surface topography of the aluminum films, it is necessary to adopt other appropriate activation process combined with thermal activation.

Key words: Fluidized bed CVD reactor, Triisobutyl aluminum, Aluminum deposition, Microstructure and surface topography, Glass microspheres of high refractive index, Thermal activation