We report on the scanning tunneling microscopy/spectroscopy (STM/STS) study of cobalt phthalocyanine (CoPc) molecules deposited onto a back-gated graphene device. We observe a clear gate voltage (V_g) dependence of the energy position of the features originating from the molecular states. Based on the analysis of the energy shifts of the molecular features upon tuning V_g, we are able to determine the nature of the electronic states that lead to a gapped differential conductance. Our measurements show that capacitive couplings of comparable strengths exist between the CoPc molecule and the STM tip as well as between CoPc and graphene, thus facilitating electronic transport involving only unoccupied molecular states for both tunneling bias polarities. These findings provide novel information on the interaction between graphene and organic molecules and are of importance for further studies, which envisage the realization of single molecule transistors with non-metallic electrodes.

中文翻译：

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扫描隧道显微镜探测单分子晶体管中的电荷传输†

我们报告沉积在背栅石墨烯装置上的钴酞菁（CoPc）分子的扫描隧道显微镜/光谱学（STM / STS）研究。我们观察到清晰的栅极电压（V _g）对源自分子态的特征的能量位置的依赖性。基于对分子特征的能量转移进行调谐V _g的分析，我们能够确定导致间隙电导差的电子状态的性质。我们的测量表明，在CoPc分子和STM尖端之间以及CoPc和石墨烯之间存在相当强度的电容耦合，因此有利于电子传输，这两个隧穿偏置极性仅包含未占据的分子态。这些发现为石墨烯与有机分子之间的相互作用提供了新颖的信息，并且对于进一步研究具有重要意义，这些研究设想了具有非金属电极的单分子晶体管的实现。