The Controllable Growth Of Two-Dimensional Hexagonal Boron Nitride And Its Heterostructures By Chemical Vapor Deposition

Two-dimensional(2D)materials have received a great deal of attention due to their unique structures,outstanding properties and huge potential in various applications.2D hexagonal boron nitride(h-BN)is a typical insulator with excellent thermal stability,chemical inertness,fascinating electronic and optical properties,combined with a wide band gap of about 5.97 eV.In addition,the surface of 2D h-BN is atomic level flat,without dangling band and trapped charge,which is considered to be a promising substrate for integration with other 2D materials.At present,chemical vapor deposition(CVD)is an effective,well-accepted method to realize large-size,high-quality and uniform 2D h-BN single crystal,however,the as-grown h-BN film is still suffering from the degradation of insulativity for the high density grain boundaries resulting from small domain sizes.Moreover,it is challenging to grow large-size single crystalline h-BN to date because of the ambiguous understanding of its growth mechanism.In this work,large-sized single crystalline h-BN was prepared by modifying the synthetic strategy and controlling the growth process.Besides,the graphene/h-BN heterostructures was synthesized by using h-BN as the substrate.The main research contents are as follows:In this study,we propose a novel in situ formed nanoparticle-assisted growth strategy for large-size single crystalline h-BN growth on conventional polycrystalline copper.We found that the areal nucleation density of h-BN can be suppressed from?10~5 nuclei per mm~2 to?10~2 nuclei per mm~2 by the in situ formed nanoparticles that were introduced by pre-oxidation.Thus,single crystalline h-BN with lateral length of up to?10~2?m wasreadily synthesized.Furthermore,for first time we discovered that the areal nucleation density of h-BN initially decreases and then increases under extreme annealing conditions,indicating that there is a competition-induced limit for suppressing the nucleation of h-BN on copper.This mechanism is universal for h-BN and graphene synthesis,which probably paves the way for large-size graphene/h-BN heterostructures synthesis in the future.Secondly,based on chemical vapor deposition(CVD)growth of large-sized 2D h-BN single crystals as the substrate,we use plasma-assisted growth of graphene/h-BN heterostructure to reduce the growth temperature of graphene.The existence of heterostructure was confirmed by Raman and UV-vis absorption spectra,and the etching occurred during the growth process was simply analyzed.