Synthesis of Hexagonal Boron Nitride Monolayer: Control of Nucleation and Crystal Morphology

Abstract

Monolayer hexagonal boron nitride (hBN) attracts significant attention due to the potential to be used as a complementary two-dimensional dielectric in fabrication of functional 2D heterostructures. Here we investigate the growth stages of the hBN single crystals and show that hBN crystals change their shape from triangular to truncated triangular and further to hexagonal depending on copper substrate distance from the precursor. We suggest that the observed hBN crystal shape variation is affected by the ratio of boron to nitrogen active species concentrations on the copper surface inside the CVD reactor. Strong temperature dependence reveals the activation energies for the hBN nucleation process of ∼5 eV and crystal growth of ∼3.5 eV. We also show that the resulting h-BN film morphology is strongly affected by the heating method of borazane precursor and the buffer gas. Elucidation of these details facilitated synthesis of high quality large area monolayer hexagonal boron nitride by atmospheric pressure chemical vapor deposition on copper using borazane as a precursor.

Boron Nitride Nanostructures: Fabrication, Functionalization and Applications

“…We proposed that the enhanced copper vapor pressure may play an important role here. The shape‐evolution from triangle to truncated‐triangle and further to hexagon was also observed with the increase of distance from Cu substrate to the precursor, and was attributed to the deficiency of nitrogen activate species farther to the precursor . This kind of substrate position effect was also observed on resolidified copper surface .…”

Role of hydrogen carrier gas on the growth of few layer hexagonal boron nitrides by metal-organic chemical vapor deposition

“…There are several reports on the evolution of h-BN crystal under different gas ambient with and without nitrogen (N), in which the carrier gas is considered as a source of N atoms. 20,21 M. Chubarov et al, claimed that pure hydrogen gas (H 2 ) ambient seems to be necessary for growth of rhombohedral BN layers by a hot wall MOCVD at the temperature of 1500 o C based on X-ray diffraction pattern. 22 However, there is a lack of systematic studies on the effect of carrier gas on the structural properties of MOCVD-grown h-BN, and explanation why H 2 carrier gas is more suitable for the growth of sp 2 -hybridized h-BN film.…”

Probing the Atomic Structures of Synthetic Monolayer and Bilayer Hexagonal Boron Nitride Using Electron Microscopy

“…Variations in the chemical potential of constituent elements can occur experimentally when different processes and substrates are used or when the Cu substrates are subjected to a pretreatment (i.e., oxidation) (Zhang et al, 2016), as in this scenario. To date, several other experimental approaches to obtaining similar hexagonal-shaped domains have been reported (Stehle et al, 2015;Tay et al, 2016b;Wang et al, 2015a;Wu et al, 2015;Yin et al, 2015b). The coexistence of ZZ N and ZZ B edges is further verified by the observation of truncated triangular-shaped domains (Fig.…”