Low pressure chemical vapour deposition of BN: Relationship between gas phase chemistry and coating microstructure

Abstract

The structural and morphological characteristics of flat BN coatings processed by chemical vapour deposition, using BCl3−NH3−H2 gas mixtures at low pressure (P < 1 kPa), have been investigated as a function of the deposition temperature (ranging from 900 °C to 1400 °C) and the total gas flow rate. The resulting BN coatings are mainly turbostratic but with heterogeneous microstructures, i.e. mixtures of poorly and highly organized domains. The structural homogeneity and the degree of crystallization depend notably on the nature of the dilution gas (either H2 or Ar) and the depletion of gas species. The decrease of the apparent activation energy from 80 kJ.mol -1 below 1200 °C to 40 kJ.mol -1 above 1200 °C reflects a change in the deposition regime. Ex situ Fourier transform infrared analysis of the residual gas mixture allowed intermediate species leading to poorly or highly organized BN to be tracked and then connected with the main reaction paths leading to the different BN coatings.

Chemical vapor deposition of sp2-boron nitride on Si(111) substrates from triethylboron and ammonia: Effect of surface treatments

“…The carbidized surface showed a dendritic surface morphology (Figure 3(c and d) and S7). Etch pits are observed for both nitridation and carbidization (Figure 3 27,29 We suggest that this is due to the difference in chemistry, as the MOCVD process involves a significant amount of C while both halide-and borazine-based processes are essentially free from C. Our films were stable in ambient air for more than 24 months. Hence, the degradation process reported by Pedersen et al 25 for BN films deposited on Si(111) substrates in the temperature range 800 to 1200 °C was not observed in any of our deposited films.…”

“…Depositions performed below 1000 °C on Si, with several boron precursors such as diborane (B2H6) [18][19][20][21][22][23] , decaborane(14) (B10H14) 24 , triethylboron (TEB, B(C2H5)3) 25 and ammonia (NH3) or with single-source precursors such as ammonia-borane (H3NBH3) 10 and Btrichloroborazine (B3Cl3N3H3) 26 resulted in growth of amorphous BN. Turbostratic BN (t-BN) films was reported at 800 °C from borazine (B3N3H6) 27 , at 980 °C from Ntrimethyl borazine (B3H3N3(CH3)3) 28 and at 1200 °C using TEB 25 or BCl3 29 .…”

Oxidation/corrosion of BN-based coatings as prospective interphases for SiC/SiC composites

“…The apparatus used in this study to deposit the different coatings was the same as that used in the previous study by Carminati et al on CVD of BN [7]. It was a hot-wall CVD reactor working at low pressure.…”

“…The latter constituent is a sub-micrometric thin coating deposited by a method derived from chemical vapour deposition (CVD) on the fibres before the matrix. The t-BN deposited by CVD and used as an interphase can have different microstructures and degrees of crystallization depending on the processing conditions [4] [5] [6] [7] [8]. The role of the interphase is essential to the proper functioning of the CMC [9], it must be preserved during the use of the CMC in the oxidizing and corrosive environments of the aircraft engine [10].…”

Chemical Vapor Deposition of Sp2-Boron Nitride on Si(111) Substrates from Triethylboron and Ammonia: Effect of Surface Treatments

“…Depositions performed below 1000 °C on Si, with several boron precursors such as diborane (B2H6) [18][19][20][21][22][23] , decaborane (14) (B10H14) 24 , triethylboron (TEB, B(C2H5)3) 25 and ammonia (NH3) or with single-source precursors such as ammonia-borane (H3NBH3) 10 and B-trichloroborazine (B3Cl3N3H3) 26 resulted in growth of amorphous BN. Turbostratic BN (t-BN) films was reported at 800 °C from borazine (B3N3H6) 27 , at 980 °C from N-trimethyl borazine (B3H3N3(CH3)3) 28 and at 1200 °C using TEB 25 or BCl3 29 . Polycrystalline films were deposited from B2H6 and NH3 at 1200 °C on Si(100) 19 and nanocrystalline films from TEB and NH3 on Si(111) at 1350 °C 5 .…”