INVESTIGADORES
PATRITO Eduardo Martin
congresos y reuniones científicas
Título:
First Stages of Metal Junction Formation on Grafted Si(111) Surface
Autor/es:
M. F. JUÁREZ; F. A. SORIA; E. M. PATRITO; P. PAREDES OLIVERA
Lugar:
Niza
Reunión:
Congreso; The 61st Annual Meeting of the Internaternational Society of Electrochemistry; 2010
Institución organizadora:
Internaternational Society of Electrochemistry
Resumen:
Understanding the
interaction of metal atoms with organic surfaces at a molecular level is
becoming increasingly important as the number of applications involving
metal−organic interfaces grows. Of particular interest recently has been the
emergence of polymer and molecular electronic devices in which the issue of
optimizing top metal contacts is of critical importance [1]
The formation
of metallic islands on well-defined periodic arrays of organic molecules on
semiconductor surfaces is of fundamental importance in the development of
various technologies ranging from optical applications to magnetic devices. Metal
deposition on silicon has been investigated in various conditions and with
different surface functionalization. Recent studies have found that the
presence of alkyl monolayers on the surface of Si (111) alters the mechanism by
which metal atoms are deposited [2]. The factors that cause the desorption of the
monolayer on the semiconductor surface after the formation of metal deposits have
not yet been established.
The aim of this
paper is to study from a theoretical point of view the interaction of coinage metals
with different funtionalized Si(111) surfaces. We consider Au, Ag and Cu and silicon
surfaces functionalized with -H, -CH3, -CH2CH2CH3
and -CH2CH2SH. In the last two cases, we investigated the
influence of the terminal group on the penetration of metal atoms through the
monolayer.
To understand
the reactivity of grafted Si(111) surfaces toward metal atoms, we found that
the reaction path involves three different steps. First, the metal atom is adsorbed on the grafted
surface. In the second step the metal atom approaches
to a surface Si atom, breaking the Si-H or S-R bond to form a Si-Me-H or
Si-Me-R structure. The last step consists in breaking the Me-R or Me-H bond and
the release of the adsorbate attached to the metal. On the Si(111)-H surface, activation energy barriers for the second step
are 6.4, 15.2 and 9.2 kcal/mol for Au, Ag and Cu, respectively. When we replace
25% of the -H atoms by CH3, the activation energies increase to
18.7, 27.0 and 14.1 kcal/mol, respectively. The increase of more than 10 kcal/mol
in the activation energy for the detachment of a surface methyl group by the Ag
atom is in agreement with previous experimental studies showing that on functionalized
Si(111) surfaces, the deposition of Ag atoms does not cause the breakage of the
Si-C bond [2].