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.

中文翻译：

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单层氮化硼：深紫外区的高光谱成像

2D 材料及其异质结构的光学响应是深入研究的主题，对由很少到单层厚度的剥落薄片制成的器件的发光特性进行了深入研究。尽管六方氮化硼 (hBN) 在 2D 材料研究中很流行，但由于其约 6 eV 的超宽带隙以及与在深紫外域中进行显微术相关的技术困难，六方氮化硼 (hBN) 在这种最终状态下仍未被探索。在这里，我们报告了低温下剥离 hBN 中波长约为 200 nm 的高光谱成像。在单层氮化硼中，我们观察到约 6.1 eV 的直接间隙发射。与过渡金属二硫属化物形成鲜明对比的是，在少层 hBN 中光致发光信号很强，