Repeated and Controlled Growth of Monolayer, Bilayer and Few-Layer Hexagonal Boron Nitride on Pt Foils

Abstract

Atomically thin hexagonal boron nitride (h-BN), as a graphene analogue, has attracted increasing interest because of many fascinating properties and a wide range of potential applications.However, it still remains a great challenge to synthesize high-quality h-BN with predetermined number of layers at a low cost. Here we reported the controlled growth of h-BN on polycrystalline Pt foils by low-cost ambient pressure chemical vapor deposition with ammonia borane as the precursor. Monolayer, bilayer and few-layer h-BN domains and large-area films were selectively obtained on Pt by simply changing the concentration of ammonia borane. Moreover, using a bubbling method, we have achieved the nondestructive transfer of h-BN from Pt to arbitrary substrates and the repeated use of the Pt for h-BN growth, which not only reduces environmental pollution but also decreases the production cost of h-BN. The monolayer and bilayer h-BN obtained are very uniform with high quality and smooth surfaces. In addition, we found that the optical band gap of h-BN increases with decreasing number of layers. The repeated growth of large-area, high-quality monolayer and bilayer h-BN films, together with the successful growth of graphene, opens up the possibility for creating various functional heterostructures for large-scale fabrication and integration of novel electronics.

Synthesis of large single-crystal hexagonal boron nitride grains on Cu–Ni alloy

“…Figure 4e shows the AFM image of a corner of a triangularshaped h-BN grain transferred on the SiO 2 /Si substrate. The height of the transferred film is B0.455 nm, consistent with that reported for single-layer h-BN 23,24,28,29 . Figure 4f shows a typical TEM image obtained at the edge of the h-BN film on a TEM grid, confirming that the h-BN prepared is monolayered.…”

“…However, the flakes are obtained through a highly skilled manual process-mechanical exfoliation and transferring, which is not a scalable method for practical applications. So far, many efforts have been taken on various substrates such as Ni [16][17][18][19][20][21] , Cu 3,[21][22][23][24][25][26][27] , Pt 28,29 , Ru 30,31 and Co 32 to obtain large h-BN crystals via the chemical vapour deposition (CVD) process. However, those grains in h-BN films are very small (usually o50 mm 2 ) because of high nucleation density at the early growth stages 10,11,[15][16][17]19,22 .…”

Spin transport in two-layer-CVD-hBN/graphene/hBN heterostructures

“…For this purpose, the recently proposed dry transfer technique for CVD-grown materials [40] could be adopted to greatly improve the quality of graphene spin-valve devices. Furthermore, we expect that a controlled growth of bilayer-CVD-hBN [26] tunnel barriers followed by dry transfer on top of recently obtained high-045411-7 quality CVD graphene [41] could help to expand the role of CVD-grown materials for spintronics in van der Waals heterostructures.…”

“…In addition, the spin-injection efficiency is expected to be higher for a bilayer hBN barrier than for a single-layer hBN barrier [25]. However, practically, controlled and direct growth of bilayer or multilayer (>1 layer) CVD-hBN is difficult [26]. Therefore, for our samples, we prepare a two-layer-CVD-hBN tunnel barrier via layer-by-layer stacking of two individual monolayers of CVD-hBN.…”

Layer- and strain-dependent optoelectronic properties of hexagonal AlN

“…Furthermore, Kim et al showed that 2D h-BN layers display very high transparency (transmittance over 99%) in the wavelength range of 250-900 nm, with a sharp absorption peak below 250 nm, where the optical gap was calculated as 6.07 eV [13]. Gao et al indicated that the optical gap of h-BN increases with decreasing number of layers [14]. On the other hand, no cathodoluminescence or photoluminescence measurements of monolayer or few-layer h-BN structures have yet been reported.…”