Low-Temperature Deposition of Hexagonal Boron Nitride via Sequential Injection of Triethylboron and N-2/H-2 Plasma

Hexagonal boron nitride (hBN) thin films were deposited on silicon and quartz substrates using sequential exposures of triethylboron and N-2/H-2 plasma in a hollow-cathode plasma-assisted atomic layer deposition reactor at low temperatures (450 degrees C). A non-saturating film deposition rate was observed for substrate temperatures above 250 degrees C. BN films were characterized for their chemical composition, crystallinity, surface morphology, and optical properties. X-ray photoelectron spectroscopy (XPS) depicted the peaks of boron, nitrogen, carbon, and oxygen at the film surface. B 1s and N 1s high-resolution XPS spectra confirmed the presence of BN with peaks located at 190.8 and 398.3eV, respectively. As deposited films were polycrystalline, single-phase hBN irrespective of the deposition temperature. Absorption spectra exhibited an optical band edge at similar to 5.25eV and an optical transmittance greater than 90% in the visible region of the spectrum. Refractive index of the hBN film deposited at 450 degrees C was 1.60 at 550nm, which increased to 1.64 after postdeposition annealing at 800 degrees C for 30min. These results represent the first demonstration of hBN deposition using low-temperature hollow-cathode plasma-assisted sequential deposition technique.