Rousseau Adrien, Ren Lei, Durand Alrik, Valvin Pierre, Gil Bernard, Watanabe Kenji, Taniguchi Takashi, Urbaszek Bernhard, Marie Xavier, Robert Cédric, Cassabois Guillaume
Laboratoire Charles Coulomb, UMR5221 CNRS-Université de Montpellier, 34095 Montpellier, France.
Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077 Toulouse, France.
Nano Lett. 2021 Dec 8;21(23):10133-10138. doi: 10.1021/acs.nanolett.1c02531. Epub 2021 Sep 16.
The optical response of 2D materials and their heterostructures is the subject of intense research with advanced investigation of the luminescence properties in devices made of exfoliated flakes of few- down to one-monolayer thickness. Despite its prevalence in 2D materials research, hexagonal boron nitride (hBN) remains unexplored in this ultimate regime because of its ultrawide bandgap of about 6 eV and the technical difficulties related to performing microscopy in the deep-ultraviolet domain. Here, we report hyperspectral imaging at wavelengths around 200 nm in exfoliated hBN at low temperature. In monolayer boron nitride, we observe direct-gap emission around 6.1 eV. In marked contrast to transition metal dichalcogenides, the photoluminescence signal is intense in few-layer hBN, a result of the near unity radiative efficiency in indirect-gap multilayer hBN.
二维材料及其异质结构的光学响应是一个深入研究的课题，人们对由几层至单层厚度的剥离薄片制成的器件中的发光特性进行了深入研究。尽管六方氮化硼（hBN）在二维材料研究中很常见，但由于其约6 eV的超宽带隙以及在深紫外领域进行显微镜观察的技术困难，在这种极限情况下仍未得到探索。在这里，我们报告了在低温下对剥离的hBN在200 nm左右波长处的高光谱成像。在单层氮化硼中，我们观察到约6.1 eV的直接带隙发射。与过渡金属二卤化物形成鲜明对比的是，在少层hBN中光致发光信号很强，这是间接带隙多层hBN中接近单位辐射效率的结果。
