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PGI-1 Seminar: Dr. Predrag Lazic

Graphene on Ir(111), adsorption and intercalation of Cs and Li atoms - two tricks from surface science

21 Oct 2015 11:00
PGI Lecture Hall

Rudjer Boskovic Institute, Croatia


Experimental and theoretical study of Cs and Li atoms adsorption on graphene on Ir(111) will be presented. Graphene on Ir(111) surface is an interesting system because graphene has almost pristine electronic structure in it due to its weak bonding character to iridum surface. The bonding is almost exclusively of the van der Waals type. However adding Cs atoms graphene gets doped and nature of binding changes - especially in the case when the atoms intercalate. Density Functional Theory calculations with standard semilocal functionals (GGA) - fail to reproduce experimental findings even qualitatively. Only when the newly developed nonlocal correlation functional is used (vdW-DF) which includes van der Waals interactions, are the calculations in agreement with experiment, revealing the mechanism of graphene delamination and relamination which is crucial for intercalation and trapping of atoms under the graphene. Iridium (111) surface has a very well defined surface state (visible as a sharp peak in ARPES measurement). Addition of lithium atoms destroys the coherence of the surface state resulting in vanishing of the ARPES peak. This behavior is well known in surface science and is actually used as a test for surface states. Surprisingly addition of the graphene on top of lithium results in the restoration of the iridium of surface state. Using the DFT calculations we discovered the mechanism responsible for this, which seems to be quite general.


Dr. Nicolae Atodiresei
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