Direct Synthesis of Ultrathin Hexagonal Boron Nitride Films on Si(001)

Synthesis of hexagonal boron nitride (hBN) on CMOS-compatible substrates is desirable for large-scale fabrication of hBN-based micro- and optoelectronic devices. However, growth of well-oriented, high-quality hBN films via chemical vapor deposition (CVD) on silicon substrates is still challenging. We report a new method to synthesize ultrathin, well-oriented hBN films on Si(001) substrates, based on a continuous flow CVD process using borazine as a single-source precursor. In addition, spectroscopic ellipsometry is explored as a fast, nondestructive method to determine the thickness, refractive index, and optical bandgap of the grown hBN films. The resulting hBN films exhibit a thickness of 7 ± 1 layers, near perfect stoichiometry, a surface roughness of 1.1 nm, a refractive index of 2.17 at 633 nm, and an optical bandgap of 5.89 eV. The use of borazine precursor avoids the availability of reactive nitrogen species and thus prevents the formation of an amorphous SiN_x interlayer at the Si interface.