Department of Materials Science and Engineering, National University of Singapore, 117575, Singapore;
Laboratoire National des Champs Magnétiques Intenses, CNRS-Université Grenoble Alpes-Université Paul Sabatier-Institut National des Sciences Appliquées Toulouse-European Magnetic Field Laboratory, 38042 Grenoble, France.
Proc Natl Acad Sci U S A. 2020 Jun 16;117(24):13214-13219. doi: 10.1073/pnas.2003895117. Epub 2020 Jun 1.
When serving as a protection tissue and/or inducing a periodic lateral modulation for/in atomically thin crystals, hexagonal boron nitride (hBN) has revolutionized the research on van der Waals heterostructures. By itself, hBN appears as an emergent wide-bandgap material, which, importantly, can be optically bright in the far-ultraviolet range and which frequently displays midgap defect-related centers of yet-unclear origin, but, interestingly, acting as single-photon emitters. Controlling the hBN doping is of particular interest in view of the possible practical use of this material. Here, we demonstrate that enriching hBN with carbon (C) activates an optical response of this material in the form of a series of well-defined resonances in visible and near-infrared regions, which appear in the luminescence spectra measured under below-bandgap excitation. Two, qualitatively different, C-related radiative centers are identified: One follows the Franck-Condon principle that describes transitions between two defect states with emission/annihilation of optical phonons, and the other shows atomic-like resonances characteristic of intradefect transitions. With a detailed characterization of the energy structure and emission dynamics of these radiative centers, we contribute to the development of controlled doping of hBN with midgap centers.
当六方氮化硼（hBN）作为一种保护组织和/或在原子层厚度晶体中诱导周期性侧向调制时，它彻底改变了范德瓦尔斯异质结构的研究。本身，hBN 表现为一种新兴的宽带隙材料，重要的是，它在远紫外范围内可以有很强的光学亮度，并且经常显示出与尚未清楚起源的带隙缺陷相关的中心，但有趣的是，它可以作为单光子发射器。考虑到这种材料可能的实际用途，控制 hBN 的掺杂具有特别的意义。在这里，我们证明了用碳（C）丰富 hBN 会激活这种材料的光学响应，表现为在低于带隙激发下测量的发光光谱中出现一系列明确定义的可见光和近红外区域的共振。已经确定了两种定性不同的 C 相关辐射中心：一种遵循描述两个缺陷态之间跃迁的 Franck-Condon 原理，其中伴随着光学声子的发射/湮没，另一种则表现出与缺陷内跃迁特征一致的原子样共振。通过对这些辐射中心的能量结构和发射动力学进行详细表征，我们为控制 hBN 中的带隙中心掺杂做出了贡献。
