Low temperature wafer-scale synthesis of hexagonal boron nitride by microwave assisted surface wave plasma chemical vapour deposition

Here, we report on the large-area synthesis of hBN layer at a comparatively lower temperature using ammonia borane as precursor by microwave assisted surface wave plasma (MW-SWP) chemical vapour deposition (CVD). The solid precursor was sublimed inside the CVD chamber and decomposed to form plasma radicals, which allowed the growth of hBN layer at a lower temperature (∼500 °C). The growth of hBN on Cu catalyst and Si wafer was confirmed by X-ray photoelectron spectroscopy, ultraviolet absorption spectroscopy, Fourier-transform infrared spectroscopy and transmission electron microscopy analysis. The hBN film synthesized on Cu catalyst showed a sharp absorption peak at 276 nm wavelength corresponding to an optical band gap of ∼4.1 eV, owing to the incorporation of carbon and oxygen doping impurities. The reduction of optical band gap of the hBN film with impurity doping can be significant to tune its optoelectronic properties. Thus, the demonstrated MW-SWP-CVD process can be significant to synthesize hBN layers independent of the catalytic behaviour of the substrate, thereby opening enormous possibilities of transfer-free application for device fabrication and as transparent coating on various surfaces.