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Effect of electron injection in copper-contacted graphene nanoribbons

Nano Research 2016年第9期9卷 2735-2746页

作者： Konstantin A.Simonov Nikolay A.Vinogradov Alexander S.Vinogradov Alexander V.Generalov Gleb I.Svirskiy attilio a.cafolla Nils Martensson Alexei B. Preobrajenski Department of Physics and Astronomy Uppsala UniversityUppsala Box 51675120Sweden MAX Ⅳ Laboratory Lund UniversityLund Box 11822100Sweden V.A.Fock Institute of Physics St.Petersburg State UniversitySt.Petersburg 198504Russia School of Physical Sciences Dublin City UniversityDublin 9Ireland

For practical electronic device applications of graphene nanoribbons (GNRs), it is essential to have abrupt and well-defined contacts between the ribbon and the adjacent metal lead. By analogy with graphene, these contacts can induce electron or hole doping, which may significantly affect the I/V characteristics of the device. Cu is among the most popular metals of choice for contact materials. In this study, we investigate the effect of in situ intercalation of Cu on the electronic structure of atomically precise, spatially aligned armchair GNRs of width N = 7 (7-AGNRs) fabricated via a bottom-up method on the Au(788) surface. Scanning tunneling microscopy data reveal that the complete intercalation of about one monolayer of Cu under 7-AGNRs can be facilitated by gentle annealing of the sample at 80 °C. Angle-resolved photoemission spectroscopy (ARPES) data clearly reflect the one-dimensional character of the 7-AGNR band dispersion before and after intercalation. Moreover, ARPES and core-level photoemission results show that intercalation of Cu leads to significant electron injection into the nanoribbons, which causes a pronounced downshift of the valence and conduction bands of the GNR with respect to the Fermi energy (ΔE ~ 0.5 eV). As demonstrated by ARPES and X-ray absorption spectroscopy measurements, the effect of Cu intercalation is restricted to n-doping only, without considerable modification of the band structure of the GNRs. Post-annealing of the 7-AGNRs/Cu/Au(788) system at 200 °C activates the diffusion of Cu into Au and the formation of a Cu-rich surface Au layer. Alloying of intercalated Cu leads to the recovery of the initial position of GNR-related bands with respect to the Fermi energy (E F), thus, proving the tunability of the induced n-doping.

关键词： graphene nanoribbons bottom-up method copper intercalation charge injection angle-resolved photoemission spectroscopy (ARPES) scanning tunneling microscopy

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Formation of Extended Covalently Bonded Ni Porphyrin Networks on the Au（lll） Surface

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Nano Research 2011年第4期4卷 376-384页

作者： Sergey A. Krasnikov Catherine M. Doyle Natalia N. Sergeeva Alexei B. Preobrajenski Nikolay A.Vinogradov Yulia N. Sergeeva Alexei A. Zakharov Mathias O. Senge attilio A. cafolla School of Physical Sciences Dublin City University Glasnevin Dublin 9 Ireland Centre tbr Research on Adaptive Nanostructures and Nanodevices （CRANN） School of Physics Trinity College Dublin Dublin 2 Ireland SFI Tetrapyrrole Laboratory School of Chemistry Trinity College Dublin Dublin 2 Ireland MAX-Lab Lund University Box 118 22100 Lund Sweden

The growth and ordering of {5,10,15,20-tetrakis（4-bromophenyl）porphyrinato}nickel（II）（NiTBrPP） molecules on the Au（111） surface have been investigated using scanning tunnelling microscopy, X-ray absorption, core-level photoemission, and microbeam low-energy electron diffraction. When deposited onto the substrate at room temperature, the NiTBrPP forms a well-ordered close-packed molecular layer in which the molecules have a flat orientation with the porphyrin macrocycle plane lying parallel to the substrate. Annealing of the NiTBrPP layer on the Au（111） surface at 525 K leads to dissociation of bromine from the porphyrin followed by the formation of covalent bonds between the phenyl substituents of the porphyrin. This results in the formation of continuous covalently bonded porphyrin networks, which are stable up to 800 K and can be recovered after exposure to ambient conditions. By controlling the experimental conditions, a robust, extended porphyrin network can be prepared on the Au（111） surface that has many potential applications such as protective coatings, in sensing or as a host structure for molecules and clusters.

关键词： Porphyrins covalently bonded networks scanning tunnelling microscopy X-ray photoemission spectroscopy near-edge X-ray absorption fine structure Au(111)

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