Chianese Federico, Aversa Lucrezia, Verucchi Roberto, Cassinese Antonio
Dipartimento di Fisica, Università Degli Studi di Napoli Federico II, Piazzale Tecchio 80, 80125 Napoli, Italy.
CNR-SPIN, Unità di Napoli, Piazzale Tecchio 80, 80125 Napoli, Italy.
Nanomaterials (Basel). 2022 Nov 28;12(23):4239. doi: 10.3390/nano12234239.
Non-covalent π-π and dipolar interactions with small aromatic molecules have been widely demonstrated to be a valid option to tune graphene work functions without adding extrinsic scattering centers for charge carriers. In this work, we investigated the interaction between a CVD-graphene monolayer and a thermally evaporated sub-monolayer and the following few-layer thin films of similar perylene diimide derivatives: PDI8-CN2 and PDIF-CN2. The molecular influence on the graphene work function was estimated by XPS and UPS analysis and by investigating the surface potentials via scanning Kelvin probe force microscopy. The perfluorinated decoration and the steric interaction in the early stages of the film growth determined a positive work function shift as high as 0.7 eV in the case of PDIF-CN2, with respect to the value of 4.41 eV for the intrinsic graphene. Our results unambiguously highlight the absence of valence band shifts in the UPS analysis, indicating the prevalence of dipolar interactions between the graphene surface and the organic species enhanced by the presence of the fluorine-enriched moieties.
与小分子的非共价π-π和偶极相互作用已被广泛证明是一种有效的方法，可在不添加电荷载流子的外在散射中心的情况下调节石墨烯的功函数。在这项工作中，我们研究了化学气相沉积（CVD）石墨烯单层与热蒸发的亚单层以及随后几层类似苝二亚胺衍生物（PDI8-CN2和PDIF-CN2）薄膜之间的相互作用。通过X射线光电子能谱（XPS）和紫外光电子能谱（UPS）分析以及通过扫描开尔文探针力显微镜研究表面电位，估算了分子对石墨烯功函数的影响。在薄膜生长的早期阶段，全氟修饰和空间相互作用导致功函数正向偏移，对于PDIF-CN2，相对于本征石墨烯的4.41 eV值，功函数偏移高达0.7 eV。我们的结果明确表明，在UPS分析中不存在价带偏移，这表明石墨烯表面与有机物种之间的偶极相互作用占主导地位，而富氟基团的存在增强了这种相互作用。
