Atomic layer deposition of ultrathin and conformal Al2O3 films on BN particles

Abstract Ultrathin and conformal Al2O3 films were deposited on BN particles using alternating exposures of Al(CH3)3 and H2O. Transmission Fourier transform infrared spectroscopy performed in vacuum on high surface area BN particles was used to monitor the surface chemistry during the sequential exposures. The initial vibrational modes were consistent with BOH* and BNH2* surface species on the BN particles. These species were converted to AlCH3* species during Al(CH3)3 exposure. Subsequently, H2O exposure was used to convert the AlCH3* species into AlOH* species. Alternating Al(CH3)3 and H2O exposures yielded AlCH3* and AlOH* species, respectively, that sequentially deposited aluminum and oxygen with atomic layer control. The repetition of the Al(CH3)3 and H2O exposures in an ABAB… reaction sequence led to the appearance of bulk Al2O3 vibrational modes. The intensity of these bulk vibrational modes increased with the number of AB reaction cycles. Following Al2O3 deposition, the BN particles were also examined with transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM studies revealed extremely uniform and conformal Al2O3 films on the BN particles with a thickness of ∼90 A after 50 AB reaction cycles. The absence of observable B and N photoelectron signals during XPS analysis was consistent with a continuous and conformal Al2O3 coating. These ultrathin Al2O3 films should help to increase BN particle loading in composite materials for thermal management applications without degrading the high thermal conductivity of the BN particles.