Step-directed Epitaxy of Uni-directional Hexagonal Boron Nitride on Vicinal Ge(110)

TL;DR

This paper demonstrates the large-scale, monolayer, single-crystalline growth of hexagonal boron nitride on vicinal Ge(110) substrates via CVD, enabling high-quality dielectric films with controlled interfaces for electronic devices.

Contribution

It introduces a step-directed epitaxial growth method for uniform, monolayer hBN on Ge(110), advancing the fabrication of high-quality dielectric layers for electronics.

Findings

Successful large-scale monolayer hBN growth on Ge(110)

Epitaxial alignment guided by Ge atomic steps

Enhanced carrier transport in graphene and MoS2 devices

Abstract

Insulating hexagonal boron nitride (hBN) films with precisely controlled thickness are ideal dielectric components to modulate various interfaces in electronic devices. To achieve this, high-quality hBN with controlled atomic configurations must be able to form pristine interfaces with various materials in devices. However, previously reported large-scale hBN films with uniform thickness either are polycrystalline or are not suitable for atomically clean assembly via mechanical exfoliation, limiting their applications in device technology. Here, we report the large-scale growth of monolayer single crystalline hBN films on Ge(110) substrates by using chemical vapor deposition (CVD). Vicinal Ge(110) substrates are used for the step-directed epitaxial growth of hBN, where Ge atomic steps act as the hBN nucleation sites, guiding the uni-directional alignments of multiple hBN domains. Density functional theory (DFT) calculations reveal that the optimum hydrogen passivations on both hBN edges and Ge surfaces enable the epitaxial coupling between hBN and the Ge step edges and the single crystallinity of the final hBN films. Using epitaxially grown monolayer hBN films, we fabricate a few hBN films with controlled stacking orders and pristine interfaces through a layer-by-layer assembly process. These films function as high-quality dielectrics to enhance carrier transport in graphene and MoS₂ channels.