Microstructure and surface topography of aluminum films deposited on glassmicrospheres in a fluidized bed CVD reactor

In this paper, we investigate the influences of deposition temperature and time on microstructure and surface topography of the aluminum films deposit ed on glass microspheres of higher refractive index by thermal decompositio n of tri-isobutyl aluminum in a fluidized bed CVD reactor at atmospheric pr essure, SEM examination of surface topography of the films shows that under the same conditions, the increase of deposition temperature causes the alu minum 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 grai ns become larger and surface roughness becomes distinct, The results demons trate that by means of thermal activation at appropriately elevated tempera tures (350 similar to 390 degrees C) for a certain period of time (about 30 min), it is possible to provide smooth and uniform aluminum films on the s urface of glass microspheres which may approximately conform with the requi rements of retro-reflective materials. Auger spectra for examining the surf ace chemical composition reveal that the preferred higher temperature used to obtain smooth topography does not introduce obvious contamination by car bon residues, but diffusion of Ti and Ba from substrates toward aluminum fi lm occurs to some extent, which may be another factor to cause the activati on of the substrate and to obtain smooth and uniform aluminum film on glass microspheres in this study. In order to further improve and control micros tructure and surface topography of the aluminum films, it is necessary to a dopt other appropriate activation process combined with thermal activation.