Nanocoating Individual Silica Nanoparticles by Atomic Layer Deposition in a Fluidized Bed Reactor


  • This work was funded by the National Science Foundation (Grant NER-0210670), the Department of Education GAANN Program in Functional Materials, and the University of Colorado Engineering Excellence Fund. The authors thank Jarod McCormick at the University of Colorado at Boulder for performing the XPS analysis as well as Geoff Courtin and William Kroenke at the Center for Micro-Engineered Materials at the University of New Mexico for performing the FESEM-EDS studies on coated nanoparticles.


Silica nanoparticles (40 nm) were individually and conformally coated with alumina films using atomic layer deposition (ALD) in a fluidized bed reactor. Films were deposited using self-limiting sequential surface reactions of trimethylaluminum and water. Alumina vibrational modes were observed using Fourier-transform infrared spectroscopy (FTIR). X-ray photoelectron spectroscopy (XPS) indicated complete coverage on the surface as the silica features were completely attenuated. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) showed high uniformity of the deposited films. Transmission electron microscopy (TEM) revealed extremely conformal films with an average growth rate of 0.11 nm per cycle. Self-limiting characteristics of ALD allowed primary nanoparticles to be coated as they fluidized as dynamic aggregates.