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Engineering epitaxial graphene by adsorption, intercalation and strain

Speaker: 
Marko Kralj (Institute of Physics Zagreb, Croatia)
Date: 
Wed, 03/06/2015 - 11:00am to 12:00pm
Location: 
Physics Conference Room (S13-M01-11)
Host: 
Slaven Garaj
Event Type: 
Seminars

Abstract

The properties of graphene can be exploited in various applications e.g. by controlling the density of states at the Fermi energy or the strain and related pseudomagnetic fields. Besides electric field, a chemical adsorption either "on top" or "underneath" graphene, where typically charge transfer processes take place, is a suitable tool for the charge carrier and many-body interaction modifications. In epitaxial graphene systems deposition of atoms and molecules often leads to intercalation where species are pushed between graphene and its support. Besides the charge donation, the intercalation can affect the binding interaction and more subtle properties of graphene, e.g. spin-polarization. In fact, properties of many layered materials, including copper- and iron-based superconductors, dichalcogenides, topological insulators, graphite and epitaxial graphene, can be manipulated by intercalation. Another direction of graphene electronic structure tailoring is related to a precise stress control which can be realized by graphene growth on flat or specifically on stepped surfaces and we focus to such systems in order to exploit uniaxial strain engineering.

We studied the intercalation and entrapment of alkali atoms under epitaxal graphene on Ir(111) in real and reciprocal space by means of LEEM, STM, ARPES, LEED and vdW-DFT. The microscopic mechanism and dynamics of intercalation process is explained, where we find that the intercalation is adjusted by the van der Waals interaction, with the dynamics governed by defects anchored to graphene wrinkles. Graphene wrinkles, their structure, ordering and formation dynamics are characterized in great detail on relevant nano- and micrometer scales. Finally, the way to obtain uniaxially strained graphene by growing it on a stepped single crystal substrate and subsequently transferring it to a dielectric support by preserving uniaxial pattern will be presented.

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