Bottom-up synthesis of graphene nanoribbons (GNRs) may open new possibilities in future electronic devices owing to their tunable electronic structure, which depends strongly on their well-defined width and edge geometry. For instance, armchair-edged GNRs (AGNRs) exhibit width-dependent bandgaps. However, the bandgaps of AGNRs synthesized experimentally so far are relatively large, well above 1 eV. Such a large bandgap may deteriorate device performance due to large Schottky barriers and carrier effective masses. Here, we describe the bottom-up synthesis of AGNRs with smaller bandgaps, using dibromobenzene-based precursors. Two types of AGNRs with different widths, namely 17 and 13 carbon atoms, were synthesized on Au(111), and their atomic and electronic structures were investigated by scanning probe microscopy and spectroscopy. We reveal that 17-AGNRs have the smallest bandgap, as well as the smallest electron/hole effective mass, among bottom-up AGNRs reported so far. The successful synthesis of 17-AGNRs is a significant step toward the development of GNR-based electronic devices.

石墨烯纳米带（GNR）的自下而上合成可能由于其可调电子结构而在未来的电子设备中开辟了新的可能性，这在很大程度上取决于其明确定义的宽度和边缘几何形状。例如，扶手椅边缘的GNR（AGNR）表现出与宽度有关的带隙。但是，到目前为止，实验上合成的AGNR的带隙相对较大，远高于1 eV。由于较大的肖特基势垒和载流子有效质量，如此大的带隙可能会使器件性能下降。在这里，我们描述了使用基于二溴苯的前体，以较小的带隙自下而上地合成AGNRs。在Au（111）上合成了两种宽度不同的AGNR，即17和13个碳原子，并通过扫描探针显微镜和光谱法研究了它们的原子和电子结构。我们发现，在迄今为止报道的自下而上的AGNR中，17-AGNR具有最小的带隙以及最小的电子/空穴有效质量。17-AGNRs的成功合成是向基于GNR的电子设备发展的重要一步。