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Instruments / Technical Area	Publication Details	Published	Actions
I09-Surface and Interface Structural Analysis	Using polycyclic aromatic hydrocarbons for graphene growth on Cu(111) under ultra-high vacuum Benedikt P. Klein , Matthew A. Stoodley , Matthew Edmondson , Luke A. Rochford , Marc Walker , Lars Sattler , Sebastian Weber , Gerhard Hilt , Leon B. S. Williams , Tien-Lin Lee , Alex Saywell , Reinhard J. Maurer , David A. Duncan Applied Physics Letters 121 DOI: 10.1063/5.0122914 Diamond Proposal Number(s): [25379] Open Access Show Abstract ▼ Abstract: Ultra-high vacuum deposition of the polycyclic aromatic hydrocarbons azupyrene and pyrene onto a Cu(111) surface held at a temperature of 1000 K is herein shown to result in the formation of graphene. The presence of graphene was proven using scanning tunneling microscopy, x-ray photoelectron spectroscopy, angle-resolved photoemission spectroscopy, Raman spectroscopy, and low energy electron diffraction. The precursors, azupyrene and pyrene, are comparatively large aromatic molecules in contrast to more commonly employed precursors like methane or ethylene. While the formation of the hexagonal graphene lattice could naively be expected when pyrene is used as a precursor, the situation is more complex for azupyrene. In this case, the non-alternant topology of azupyrene with only 5- and 7-membered rings must be altered to form the observed hexagonal graphene lattice. Such a rearrangement, converting a non-alternant topology into an alternant one, is in line with previous reports describing similar topological alterations, including the isomerization of molecular azupyrene to pyrene. The thermal synthesis route to graphene, presented here, is achievable at comparatively low temperatures and under ultra-high vacuum conditions, which may enable further investigations of the growth process in a strictly controlled and clean environment that is not accessible with traditional precursors.	Nov 2022
	Topological Stone-Wales Defects enhance bonding and electronic coupling at the graphene/metal interface Benedikt P. Klein , Alexander Ihle , Stefan R. Kachel , Lukas Ruppenthal , Samuel J. Hall , Lars Sattler , Sebastian M. Weber , Jan Herritsch , Andrea Jaegermann , Daniel Ebeling , Reinhard J. Maurer , Gerhard Hilt , Ralf Tonner-Zech , André Schirmeisen , J. Michael Gottfried Acs Nano 9 DOI: 10.1021/acsnano.2c01952 Show Abstract ▼ Abstract: Defects play a critical role for the functionality and performance of materials, but the understanding of the related effects is often lacking, because the typically low concentrations of defects make them difficult to study. A prominent case is the topological defects in two-dimensional materials such as graphene. The performance of graphene-based (opto-)electronic devices depends critically on the properties of the graphene/metal interfaces at the contacting electrodes. The question of how these interface properties depend on the ubiquitous topological defects in graphene is of high practical relevance, but could not be answered so far. Here, we focus on the prototypical Stone–Wales (S–W) topological defect and combine theoretical analysis with experimental investigations of molecular model systems. We show that the embedded defects undergo enhanced bonding and electron transfer with a copper surface, compared to regular graphene. These findings are experimentally corroborated using molecular models, where azupyrene mimics the S–W defect, while its isomer pyrene represents the ideal graphene structure. Experimental interaction energies, electronic-structure analysis, and adsorption distance differences confirm the defect-controlled bonding quantitatively. Our study reveals the important role of defects for the electronic coupling at graphene/metal interfaces and suggests that topological defect engineering can be used for performance control.	Aug 2022

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