2024-03-29T01:41:24Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/1698852020-05-27T09:27:33Zcom_10261_89com_10261_3col_10261_468
The mechanism of vacancy formation on the surface of Pt(111) upon C60 deposition
Pinardi, Anna Lisa
Otero, Gonzalo
Gardonio, Sara
Lizzit, Silvano
Merino-Mateo, Pablo
van De Ruit, Kees
Flipse, C. F. J.
Méndez, Javier
López, María Francisca
Martín-Gago, José A.
Trabajo presentado en Fuerzas y Túnel, celebrada en San Lorenzo de El Escorial del 12 al 14 de septiembre de 2012.
It has been recently shown that the interaction of fullerenes with
transition metal surfaces leads to the formation of one vacancy per C60 molecules
in the metal [1]. We show by a combination of Scanning Tunneling Microscopy
(STM), and real time-X-ray Photoelectrons Spectroscopy (XPS) that a charge
transfer from the surface towards the molecule precedes the vacancy formation.
As this charge is returned to the surface, the ejection of a surface atom takes
place.
At RT (Fig. 1-a), all the molecules were observed by STM to have an
Apparent Height (AH) of 6.6 ± 0.3 Å (they will be called M molecules from now
on), and to be oriented in different position [2]. However, at about 500 K (Fig. 1-
c) something drastic happens to the sample: brighter molecules (named B, AH
= 7.5 ± 0.3 Å) and dimmer molecules (called D, AH = 4.8 ± 0.5 Å) were observed,
together with M molecules. B and D fullerenes are all sitting on a hexagon (as it
can be seen by the molecular orbital resolution in Fig. 1-c) and all are oriented
in the same way. Further annealing to 600 K allowed no more M molecules, and
all the fullerene were either B or D. Moreover, above 675 K all the fullerenes
were of type D. Therefore, an overall decrease in AH occurs (from M to D),
which is compatible with the vacancy formation. However, this change is not
direct, all the molecules pass through a B phase first.
In order to explain this process, fast-real time XPS has been performed,
to track the changes of the core level C1s peak at different temperatures on 0.6
ML of C60 on Pt(111) (Fig. 2). The intensity of the C1s peak is plotted in terms
of the temperature (Y axis) and of the binding energy (bottom X axis). A shift
towards lower Binding Energy (BE) of the main C1s peak of 0.16 eV occurs at
450 K, which is consistent with charge transfer to the molecule, the same which is
observed by STM.
Thus, charge accumulation on the molecules, starting at about 450 K,
could be a precursor stage to the vacancy formation as observed in the STM as
an increase of the apparent height of the molecule and by XPS as a shift in
binding energy of the C1s peak.
No
2018-09-19T09:41:24Z
2018-09-19T09:41:24Z
2012-09
comunicación de congreso
http://purl.org/coar/resource_type/c_5794
Fuerzas y Túnel (2012)
http://hdl.handle.net/10261/169885
en
Sí
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