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The molecular hopping of a lone 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) molecule adsorbed on a Ge(001) surface is studied by density functional theory calculations and the climbing-ima...

Initial growth process of pentacene molecules on clean Si(001)-2 × 1 substrate was investigated by scanning tunneling microscopy. It is found that the wetting layer, which is not crystalline but disordered, forms before the growth of a first crystalline layer. The wetting layer consists of double layer of the flatly adsorbed pentacene molecules. The formation of the wetting double layer is discussed. The first crystalline layer that is grown on the disordered wetting layer with standing-up pentacene molecules consists of some domains that differ in their crystal structures. Among them, a new pentacene crystal structure is found that can form only on the first layer. In contrast, the second crystalline layer has only single domain. Moreover, we investigated the electronic properties of the pentacene layers by the current–voltage measurements. The pentacene layers are semiconducting with a band gap of about 4 eV.

Cu atom penetration through a defect in zero-layer graphene (ZLG) epitaxially grown on an SiC substrate was theoretically investigated, using density functional theory calculations, as a possible mechanism for pure single-layer graphene formation by Cu intercalation on an SiC surface. Our model calculation predicted that a Cu monolayer formed by Cu intercalation causes a lift of the graphene surface of about 0.2 nm, which supports our previous experimental observation. Our calculations on Cu intercalation through a graphene defect implied the possibility that a transition of the defect shape from a 5–8–5 to a double-vacancy model causes the timing of the passage of the Cu atom through the ZLG surface to reduce the potential barrier for the penetration. In addition, it was found that the SiC substrate stabilizes the Cu atom after penetration via an Si–Cu interaction. Furthermore, a preceding intercalated Cu atom was found to be capable of facilitating subsequent Cu penetration by suppressing its inverse re...

Adsorption of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on the Ge(001) surface was studied using scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and the density-functional theory (DFT) calculations. Only single adsorption configuration of the PTCDA molecule was observed at low coverages on the Ge(001) at room temperature, unlike on the Si(001) where several adsorption configurations were reported. This indicates that the PTCDA molecules on the Ge(001) were more mobile than those on the Si(001). Atomic structure of the adsorption configuration on the Ge(001) was determined by comparison between the STM experiments and the DFT calculations. Bias-dependent STM images, STS, and calculated projected density of state curves show nontrivial hybridization of molecular orbitals with surface states of the Ge substrate. Interactions of the PTCDA molecule with the Ge and the Si surfaces were in detail analyzed by the DFT calculation, considering five main competing contributions...