Wafer-scale single-crystal hexagonal boron nitride film via self-collimated grain formation

Abstract

Although polycrystalline hexagonal boron nitride (PC-hBN) has been realized, defects and grain boundaries still cause charge scatterings and trap sites, impeding high-performance electronics. Here, we report a method of synthesizing wafer-scale single-crystalline hBN (SC-hBN) monolayer films by chemical vapor deposition. The limited solubility of boron (B) and nitrogen (N) atoms in liquid gold promotes high diffusion of adatoms on the surface of liquid at high temperature to provoke the circular hBN grains. These further evolve into closely packed unimodal grains by means of self-collimation of B and N edges inherited by electrostatic interaction between grains, eventually forming an SC-hBN film on a wafer scale. This SC-hBN film also allows for the synthesis of wafer-scale graphene/hBN heterostructure and single-crystalline tungsten disulfide.

Vapor‐phase growth of high‐quality wafer‐scale two‐dimensional materials

“…The most prevailing one is to suppress nucleation or even allow only one nucleus to grow into a wafer‐scale 2D film . Another vital approach is to “seamless stitch” multiple aligned islands into single‐crystal 2D materials over wafer scale . The third one is triggering the ESG to achieve the nearly single‐crystal 2D materials .…”

“…Another vital factor is controlling the grain orientation in the CVD progress to obtain well‐aligned islands. It is an important and effective route to “seamless stitch” multiple aligned islands into uniform wafer‐scale 2D materials . It should be noted that this method strongly relies on the availability of substrates rather than the control over nucleation density.…”

“…The past decade has witnessed various breakthroughs in two‐dimensional (2D) materials . Academia and industry have paid tremendous attention and high expectations on 2D materials, as they have broad prospects in various fields owing to their remarkable and tunable physical and chemical properties .…”

“…Their practical applications in high‐performance electronics and optoelectronics, such as touch screen, radio frequency devices, photovoltaic devices, solar cell, and so on, are hampered by their poor crystalline quality and limited size. Wafer‐scale and high‐quality 2D materials with few or even without grain boundaries will exhibit excellent electronic performance with high charge mobility, and low interface scattering, which is beneficial in modern electronics . Therefore, routes toward the synthesis of high‐quality (especially single‐crystal) wafer‐scale 2D materials that are compatible with current semiconductor microfabrication processes are essential for exploring the full potential of them in the practical applications.…”

“…A straightforward route is to grow up from a single seed, which is similar to silicon ingot growth . Another thoroughgoing approach is to make the multinucleation domains with identical orientation seamless coalesce into a wafer‐scale single‐crystal film, which can usually be achieved on a single‐crystal substrate or liquid substrate . The third effective one is the evolutionary selection growth (ESG) that can eliminate the formation of undesired seeds to get large‐area single‐crystal 2D materials, even on a polycrystalline substrate .…”