On-surface synthesis is a powerful method for fabricating atomically precise graphene nanoribbons (GNRs), but the products always include defective structures. In this study, scanning tunnelling microscopy and atomic force microscopy were used to determine the length distribution of armchair-edge GNRs with a width of seven carbon atoms (7-AGNRs) synthesised on Au(111) and to characterise defective structures. The product quality was improved by increasing the precursor deposition amount because of a preference for intermolecular polymerisation over intramolecular cyclodehydrogenation at a high coverage. However, the annealing rate had a complex effect on the quality, with a low rate elongating 7-AGNRs but degenerating the length uniformity. These insights advance the understanding of the critical parameters for obtaining high-quality products in high yield by on-surface synthesis.

中文翻译：

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表面合成的七原子宽扶手椅石墨烯纳米带的质量控制

表面合成是一种用于制造原子级精确的石墨烯纳米带（GNR）的有效方法，但产品始终具有缺陷结构。在这项研究中，使用扫描隧道显微镜和原子力显微镜来确定在Au（111）上合成的具有七个碳原子宽度的扶手椅边缘GNR（7-AGNRs）的长度分布，并表征缺陷结构。通过在高覆盖率下优先选择分子间聚合而不是分子内环脱氢，可以通过增加前体沉积量来提高产品质量。但是，退火速率对质量有复杂的影响，低速率可以延长7-AGNRs的长度，但会降低长度均匀性。