Al O and SiO were deposited on BN particles with atomic layer control using alternating exposures of Al CH rH O 2 3 2 3 3 2 and SiCl rH O, respectively. The sequential surface chemistry was monitored in vacuum using transmission Fourier 4 2 Ε½ . transform infrared FTIR spectroscopy studies on high surface area BN particles. The initial BN particles displayed ) ) Ε½ . vibrational modes consistent with BOH and BNH surface species. These species reacted with Al CH or SiCl and 2 3 3 4 were converted to AlCH ) or SiCl ) surface species. The subsequent reaction with H O converted the surface species to 3 2 AlOH ) or SiOH ) . By repeating the sequential surface reactions, the absorbance of Al O and SiO bulk vibrational modes 2 3 2 Ε½ . on the BN particles increased vs. the number of reaction cycles. Transmission electron microscopy TEM studies revealed Ε½ . extremely uniform and conformal Al O coatings on the BN particles. X-ray photoelectron spectroscopy XPS analysis was 2 3 consistent with conformal Al O coatings. In contrast, TEM investigations observed fairly uniform SiO coatings on the 2 3 2 edge planes of the BN particles and only patches of SiO on the basal planes. XPS measurements were consistent with some 2 uncovered regions on the SiO -coated BN particles. These results illustrate the capability of sequential surface reactions to 2 deposit ultrathin Al O and SiO films on BN particles.