Growth and Contrast of Hexagonal Boron Nitride: From Submonolayer Islands to Multilayer Films

Strong interest in hexagon boron nitride (h-BN) as a substrate for graphene devices [1] or as a template for growth of other layered compounds [2] has motivated recent attempts to synthesize large scale h-BN by chemical vapor deposition (CVD). We synthesize h-BN by low pressure CVD on polycrystalline Cu foil in a hot wall tube furnace with a heated ammonia borane precursor carried downstream by Ar and H$_{\mathrm{2}}$ gas. Transmission electron microscopy (TEM) diffraction patterns show that the resulting growths are highly crystalline, with several layers obtained for longer growth times. Short growth times show that the h-BN nucleates in triangular islands at a higher precursor temperature than previously reported in [3] and a lower temperature than reported in [4]. In-air calcination of the Cu foils after partial h-BN growth allows optical contrast of the previously transparent h-BN islands on the Cu foil. This observed resistance to oxidation suggests that grown h-BN films can serve as an insulating anti-corrosion layer. \\[4pt] [1] J. Xue, et al., Nat. Mater. 10, 282 (2011).\\[0pt] [2] P. Gehring, et al., Nano Lett. 12, 5137 (2012).\\[0pt] [3] K.K. Kim, et al., \textit{Nano Lett.} 12, 161 (2012).\\[0pt] [4] N. Guo, et al., Nanotechnology. 23, 415605 (2012).