发表机构
National University of Singapore; Institute for Functional Intelligent Materials, National University of Singapore; University of Manchester; National Graphene Institute, University of Manchester; University of Southampton; National Institute for Materials Science（新加坡国立大学; 新加坡国立大学功能智能材料研究所; 曼彻斯特大学; 曼彻斯特大学国家石墨烯研究所; 南安普顿大学; 日本物质材料研究机构）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究发现高质量hBN中存在缺陷态，利用封装的单层石墨烯作为电荷传感器，证实位移场可诱导hBN缺陷电离，改变vdW异质结构电子响应，对器件设计和实验解读有直接意义。
AI 中文摘要
用六方氮化硼（hBN）封装二维（2D）材料被广泛用于制备超洁净范德华（vdW）异质结构，以开展光电和量子输运研究。这类器件常工作在强面外位移场下，该场可调控活性二维材料的电子性质，而周围的hBN通常被认为保持电惰性。然而，这一假设忽略了高质量hBN晶体中也存在的缺陷态。本文中，我们利用封装在hBN晶体之间的单层石墨烯作为灵敏电荷传感器，探测这些缺陷态对施加位移场的响应。增大位移场会诱导石墨烯与hBN之间发生显著电荷转移，即使在中等位移场（约0.5 V nm⁻¹）下，也会使石墨烯额外获得10-20×10⁹ cm⁻²的电子掺杂，同时增大石墨烯层的载流子密度不均匀性。这两种效应均与hBN带隙内缺陷态的电离一致，不同hBN晶体的缺陷态体密度约为1-7×10⁻⁵ nm⁻³，存在差异。我们的结果表明，hBN中位移场诱导的缺陷电离可改变vdW异质结构的电子响应，对器件设计和实验解读具有直接意义。
英文摘要
Encapsulation of two-dimensional (2D) materials with hexagonal boron nitride (hBN) is widely used to fabricate ultraclean van der Waals (vdW) heterostructures for optoelectronic and quantum transport studies. These devices are often operated under strong out-of-plane displacement fields that tune the electronic properties of the active 2D material, while the surrounding hBN is typically assumed to remain electronically inert. This assumption, however, neglects defect states that are present even in high-quality hBN crystals. Here, we probe their response to the applied displacement field using monolayer graphene encapsulated between hBN crystals as a sensitive charge sensor. Increasing the displacement field induces notable charge transfer between graphene and hBN, producing additional electron doping of 10-20x10^9 cm^(-2) even at the moderate displacement field (~0.5 V nm^(-1)), while simultaneously increasing carrier-density inhomogeneity of the graphene layer. Both effects are consistent with ionization of defect states within the hBN bandgap, with the bulk density ~1-7x10^(-5) nm^(-3) varying across different hBN crystals. Our results show that displacement-field-induced defect ionization in hBN can modify the electronic response of vdW heterostructures, with direct implications for device design and interpretation of experiments.
