Boron precursors include boron hydrides, like diborane (B2H6) , or organoboranes, like triethylborane B(C2H5)3 (TEB), and trimethylborane B(CH3)3 (TMB). Numerous reports in the literature show that temperatures around 1500 °C are required for epitaxial growth of h-BN and r-BN, limiting the substrates that can be used in thermal CVD. Sapphire (Al2O3) and silicon carbide (SiC) are the two most common substrates. While the CVD for both epitaxial films and monolayers of crystalline BN have been reported, the deposition process is poorly understood at an atomic scale.