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

Abstract

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.

Bias-Enhanced Formation of Metastable and Multiphase Boron Nitride Coating in Microwave Plasma Chemical Vapor Deposition

“…Boron nitride is not found naturally; it has to be produced from boron and nitrogen precursors. Different methods and experimental conditions have been used to synthesize BN from a variety of boron and nitrogen precursors [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Preparation of boron nitride (BN) was reported from high pressure/high temperature synthesis using diamond anvil cell/laser heating.…”

“…However, high pressure/high temperature synthesis can be expensive and often only generates very little amounts of material. In contrast, chemical vapor deposition (CVD) has proven to be a scalable technology for synthesizing a wide range of coating materials including BN coatings with large area uniformity and at the same time it is also very cost effective [ 17 , 18 , 19 , 20 , 24 , 25 ]. Laser chemical vapor deposition was also used to high yield synthesis of cubic and hexagonal boron nitride [ 26 ].…”

Improving Formation Conditions and Properties of hBN Nanosheets Through BaF2-assisted Polymer Derived Ceramics (PDCs) Technique

“…However, for hBN to reach its ultimate practical application in the optoelectronic and dielectric industry, synthesis of large-area high-quality single crystals of hBN, at cost effective conditions, is a very crucial issue. Consequently, numerous techniques have been developed and employed to produce hBN; these include processes such as mechanical exfoliation [5,27,28], sputtering [29,30], pulsed laser deposition (PLD) [31,32], atomic layer deposition (ALD) [33][34][35], and chemical vapor deposition (CVD) [36,37]. For instance, with graphene, mechanical exfoliation has been widely used to produce high-quality hBN nanosheets.…”

“…Additionally, other techniques basically require extremely sophisticated equipment using high temperatures and pressures [13]. Therefore, in an attempt to circumvent these drawbacks, the use of the polymer derived ceramics (PDCs) [36][37][38][39][40] process coupled with the addition of a crystallization agent such as lithium nitride (Li 3 N) has been reported to provide an alternative approach for preparing large-scale and high-quality single crystals of hBN nanosheets for further applications in next-generation electronics. During the PDCs method, a polymeric precursor is synthesized from its monomers, after which it is then converted into ceramic after shaping.…”

“…During the PDCs method, a polymeric precursor is synthesized from its monomers, after which it is then converted into ceramic after shaping. Among the various precursors that have been used for the PDCs-synthesis of hBN nanosheets, polyborazylene (PBN) has shown to lead to the production of large-area highly crystallized hBN at temperatures as low as~1400 • C [36][37][38][39][40]. This is owing to its relatively high ceramic yield and high purity.…”