Atomic layer deposition of SiO2 films on BN particles using sequential surface reactions

Alternating SiCl4 and H2O exposures were used to deposit SiO2 films with at omic layer control on BN particles. The high surface area of the BN particl es facilitated the use of transmission Fourier transform infrared (FTIR) sp ectroscopy to monitor the sequential surface reactions. The BN particles in itially displayed vibrational modes consistent with BOH* and BNH2* surface species. SiCl4 exposure at 700 K converted these species to SiClx* surface species. The subsequent H2O exposure at 700 K converted the SiClx* species to SiOH* surface species. Alternate exposures of SiCl4 and H2O yielded SiCl x* and SiOH* species, respectively, sequentially depositing silicon and oxy gen with atomic layer control. By repeating the sequential surface reaction s, the absorbance of SiO2 bulk vibrational modes on the BN particles increa sed versus the number of SiCl4 and H2O reaction cycles. Transmission electr on microscopy studies revealed fairly uniform SiO2 films of similar to 28-3 8 Hi on the edge planes of the BN particles after 32 reaction cycles at 700 K. SiO2 films on the basal planes of the BN particles were thinner and occ urred in patches. X-ray photoelectron spectroscopy analysis was consistent with some uncoated regions on the BN particles. These ultrathin SiO2 films on BN particles may be useful to enhance the loading of BN particles in com posite materials.