A clean dry transfer of hexagonal boron nitride with improved oxidation resistance

Abstract

Hexagonal boron nitride (h-BN) is an outstanding two-dimensional material in terms of thermal stability and chemical inertness, enabling its versatile applications under harsh conditions. However, the oxidation resistance of h-BN is significantly reduced in the presence of metallic catalysts, which could be readily introduced during commonly adapted transfer methods of chemical vapor-deposited samples through the wet etching of metallic substrates. Here we propose a clean dry transfer method for monolayer h- BN film grown on the copper (Cu) surface. Thus, the mechanical delamination of the h-BN film from the substrates becomes feasible as their interfacial adhesion energy is significantly reduced because of the oxygen intercalation and surface oxidation of Cu during exposure to air. The drytransferred h-BN film is proven to be free of metallic (iron) contaminants, in sharp contrast to the wet-transferred h-BN film, which contains significant amounts of metallic residues. The clean transfer of h-BN considerably enhances its oxidation resistance by 50–100°C, yielding nearly the ideal performance of h-BN. As a result, graphene layers coated with drytransferred monolayer h-BN film exhibit enhanced robustness to temperatures in the air up to 700°C, indicating the advantage of the proposed dry transfer method.

摘要

六方氮化硼(h-BN)是一种具有出色热稳定性和化学惰性的二维 材料, 在苛刻条件下应用广泛. 然而, 表面金属催化剂会使其抗氧化性 显著降低. 对于通过化学气相沉积制备的样品, 常规通过湿法蚀刻金属 基底的转移方法不可避免地会引入金属残留. 我们这里提出了一种针 对铜表面生长的单层h-BN薄膜的洁净干转移方法. 空气环境下界面氧 插层和表面铜氧化导致界面粘附能量显著降低, 因而h-BN薄膜可以从 基底上被直接机械剥离开. 与湿法转移制备的薄膜形成鲜明对比, 干法 转移得到的h-BN薄膜几乎没有金属(铁)污染, 使其抗氧化性提高了 50–100°C, 甚至接近其本征性能. 在干法转移的单层h-BN薄膜保护下, 单层石墨烯在空气中的耐受温度提高到700°C, 展示了这一干转移方法 的优势.