Ma Chuanxu, Xiao Zhongcan, Puretzky Alexander A, Wang Hao, Mohsin Ali, Huang Jingsong, Liang Liangbo, Luo Yingdong, Lawrie Benjamin J, Gu Gong, Lu Wenchang, Hong Kunlun, Bernholc Jerzy, Li An-Ping
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States.
ACS Nano. 2020 Apr 28;14(4):5090-5098. doi: 10.1021/acsnano.0c01737. Epub 2020 Apr 16.
Solid-state narrow-band light emitters are on-demand for quantum optoelectronics. Current approaches based on defect engineering in low-dimensional materials usually introduce a broad range of emission centers. Here, we report narrow-band light emission from covalent heterostructures fused to the edges of graphene nanoribbons (GNRs) by controllable on-surface reactions from molecular precursors. Two types of heterojunction (HJ) states are realized by sequentially synthesizing GNRs and graphene nanodots (GNDs) and then coupling them together. HJs between armchair GNDs and armchair edges of the GNR are coherent and give rise to narrow-band photoluminescence. In contrast, HJs between the armchair GNDs and the zigzag ends of GNRs are defective and give rise to nonradiative states near the Fermi level. At low temperatures, sharp photoluminescence emissions with peak energy range from 2.03 to 2.08 eV and line widths of 2-5 meV are observed. The radiative HJ states are uniform, and the optical transition energy is controlled by the band gaps of GNRs and GNDs. As these HJs can be synthesized in a large quantity with atomic precision, this finding highlights a route to programmable and deterministic creation of quantum light emitters.
固态窄带发光体是量子光电子学所需要的。目前基于低维材料中缺陷工程的方法通常会引入广泛的发射中心。在此，我们报告了通过分子前驱体的可控表面反应将共价异质结构融合到石墨烯纳米带（GNR）边缘而实现的窄带发光。通过依次合成GNR和石墨烯纳米点（GND），然后将它们耦合在一起，实现了两种类型的异质结（HJ）态。扶手椅状GND与GNR扶手椅边缘之间的HJ是相干的，并产生窄带光致发光。相比之下，扶手椅状GND与GNR锯齿状末端之间的HJ是有缺陷的，并在费米能级附近产生非辐射态。在低温下，观察到峰值能量范围为2.03至2.08 eV、线宽为2 - 5 meV的尖锐光致发光发射。辐射性HJ态是均匀的，并且光学跃迁能量由GNR和GND的带隙控制。由于这些HJ可以以原子精度大量合成，这一发现突出了一条可编程和确定性地创建量子发光体的途径。
