铁催化表面合成基底解耦石墨二炔单层
Iron-mediated on-surface synthesis of substrate-decoupled graphdiyne monolayers
AI总结：
通过添加微量铁原子，在Au(111)上成功合成了共价有序的石墨二炔单层，实现了结构解耦和约1.6 eV的带隙。
摘要：
石墨二炔构成了一类新兴的二维sp-sp2碳同素异形体，具有石墨烯无法实现的可调电子性质。尽管已尝试通过表面合成方案实现石墨二炔网络的无缺陷单层生长，但由于金属化中间体和反应副产物的持续存在，限制了长程共价有序所需的结构自组织，因此完全共价且结构有序的石墨二炔网络的实验实现仍然具有挑战性。在这里，我们证明在生长过程中向表面添加微量Fe原子可以显著改善Au(111)上共价二维石墨二炔单层框架的合成。通过低温扫描隧道显微镜和光谱学，结合密度泛函理论，我们揭示了反应的原子级表面动力学。我们展示了Fe原子的关键作用，它们与Br副产物键合，形成Fe-Br物种，促进Au吸附原子的去除，并在温和退火条件下驱动从金属化网络向纯共价框架的转化。此外，我们展示了共价石墨二炔网络在结构和电子上与底层金属基底解耦，显示出由p_z前沿轨道位置定义的约1.6 eV的有限带隙。这些结果为原子精确表面合成全碳石墨二炔建立了可行路线，并为补充石墨烯的半导体二维碳材料开辟了道路。
英文摘要：
Graphdiynes are emerging two-dimensional sp-sp$^2$ carbon materials with electronic structures complementing those of graphene, yet their on-surface synthesis is limited by the persistence of metalated intermediates or yields disordered covalent networks. Here, we report an iron-assisted route to covalent hydrogenated graphdiyne monolayers on Au(111) from 1,3,5-tris(bromoethynyl)benzene. Low-temperature scanning tunnelling microscopy, X-ray photoelectron spectroscopy and density functional theory show that Fe scavenges chemisorbed Br byproducts forming FeBr$_2$, in turn promoting the removal of Au adatoms from the organometallic network, thus enabling its metalated-to-covalent conversion under mild thermal treatment. Subsequent annealing removes FeBr$_2$ and yields covalent, ordered domains weakly coupled to the substrate. Scanning tunnelling spectroscopy, combined with density functional theory, reveals a semiconducting gap of about 1.6 eV associated with carbon p$_z$ frontier orbitals. This Fe-mediated on-surface synthesis strategy provides a route to atomically precise, weakly substrate-coupled graphdiyne networks and offers a design principle for two-dimensional carbon semiconductors.
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