Project

graphene; surface x-ray diffraction; synchrotron radiation; nanomesh; interfacial physics

Lead
When an atomic layer of hexagonal boron-nitride (hBN) is deposited on the surface of rhodium, the hBN forms a structure reminiscent of chicken wire, with a periodicity of approximately 30 Angstrom. This so-called "nanomesh" can trap clusters or molecules in the hexagonal holes bordered by the nanomesh "wires". In this project, the prototypical system of Xe-clusters will be deposited on the nanomesh and their atomic structure investigated with synchrotron-based surface x-ray diffraction.
Lay summary
Das hBN/Rh(111)-System wird verwendet, um Xe bei kryogenischen Temperaturen zu deponieren. Fruehere Arbeit hat gezeigt, das wohldefinierte Strukturen gebildet werden koennen wenn man zuerst mehrere Monolagern Xe deponiert und danach das System langsam und kontrolliert aufwaermt bis etwa 77 K. Zuerst werden all die Xe ausser die letzte Monolage desorbiert und dan werden isolierte Klustern in den Nanomesh-Loechern gebildet. Letzlich werden Ringen von Xe an den Raendern den Nanomesh-Hexagons gebildet, wo die Absorptionsenergie am groessten ist. Nachdem das Prozedur identifiziert ist, wie man solche Ringe zuverlaessig produzieren kann, werden diese mittels Oberflaechen Roentgenbeugung untersucht werden, um die atomare Struktur mit sub-Angstrom-Aufloesung zu bestimmen. Xe/hBN/Rh ist eine prototypische System, die ausgewahlt wurde aus zwei Hauptgrunden: (a) Fruehere Experimente haben gezeigt, dass solche Xe-Ringe relative problemlos sythetiziert werden koennen; und (b) das Xe kann einfach vollstaendig desorbiert werden, in dem man auf etwa 100 K aufheizt. Dabei kann man mehrere Experimente augefuehrt werden, ohne dass man bei jedem neuen Versuch, die Nanomesh wiederholt praepaerieren muss. Das "Knowhow" gewonnen durch diese Experimente werden in zukunftigen Projekten verwendet werden, um Anordnungen von komplexeren, organischen- und biologischen Molekuelen zu untersuchen, vorallem die, die man schlecht in der Form von makroskopischen Kristallen produzieren kann.

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Last update: 26.09.2013

Number	Title	Start	Funding scheme

This document describes a research proposal for funding by the Swiss National Science Foundation for an extension to a fourth year of the PhD project 200021-132509 “Periodic strain fields in graphene and h-BN on transition-metal surfaces”, carried out by Mr. Irakli Kalichava, within the Surface Diffraction group of the Materials Science beamline of the Swiss Light Source, Paul Scherrer Institut. The PhD program began on 15th January, 2011, and has progressed satisfactorily to date. Four subprojects have been pursued. Two have produced high-quality and original results, presently being written up for publication. The other two unfortunately proved to be unsuccessful. This was through no fault of the PhD student, but was merely a fact of nature.The project is concerned with the investigation of the atomic structure and physical properties of single layers of graphene and hexagonal boron nitride (h-BN) grown on single-crystal transition metal surfaces. Particular emphasis has been on the experimental determination of the strain fields, i.e., the deviation of the atomic coordinates from a non-interacting, single-layer-substrate system, plus comparative studies with highly complex density functional theory (DFT) calculations, in a collaborative project.In the final part of the PhD, the ordered decoration of the nanomesh h-BN/Rh(111) with xenon atoms/clusters will be investigated in-situ using surface x-ray diffraction. This will serve as a prototypical system for future studies of regular nanoarrays of more complex species, in particular macromolecules and metallorganics. By depositing submonolayer doses of Xe on h-BN/Rh(111) at low temperatures, using our newly commissioned in-situ cryochamber, repeated measurements using the same template can be performed by simple heating/colling cycles. It is hoped that the knowledge gained here will be beneficial in future controlled nanoarray assemblages of, for example, membrane proteins, for studies using both synchrotron light and XFEL radiation.