OVIEDO OSCAR ALEJANDRO
Congresos y reuniones científicas
Título:
Computers simulations applied to study of electrochemically nanostructured systems
Autor/es:
E. P. M. LEIVA, S. A. DASSIE, N. LUQUE, P. VÉLEZ, M. MARISCAL, M. ROJAS, O. OVIEDO
Lugar:
Shanghai, China
Reunión:
Simposio; International Symposium on Functional Materials & Interfacial Electrochemistry; 2005
Resumen:
COMPUTERS SIMULATIONS APPLIED TO THE STUDY OF
ECTROCHEMICALLY NANOSTRUCTURED SYSTEMS
E.P.M. Leiva, S.A. Dassie , N. Luque, P. Vélez, M. Mariscal, M.Rojas, O. Oviedo.
Unidad de Matemática y Física, Facultad de Ciencias Químicas, Universidad Nacional
de Córdoba, INFIQC, Argentinae-mail: eleiva@fcq.unc.edu.ar
Nanoscale electrochemistry appears as a promising field in which scientists are beginning
to generate structures at the atomic and molecular scales in order to obtain surfaces and systems
with novel properties. In the particular case of electrochemistry, nanostructuring on solid surfaces
has been undertaken using different types of techniques, that share a common instrument for their
implementation - a scanning tunnelling microscope (STM). The exponential dependence of the
tunneling current on the tip-surface distance makes this device very sensitive to the topology of
the surface in the z direction. For this reason, in the origin of the STM techniques, the most
popular application was to get topological information, but soon an alternative application was
developed, consisting in the possibility of manipulation of matter at the atomic level.
Electrochemists have managed to employ the STM in several ways to nanostructure surfaces. In
one of them, denominated tip induced local metal deposition (TILMD), nanoclusters are
generated on the surface of a substrate by transfer of matter from the tip of the STM. The material on the tip is continuously renewed by deposition from a solution containing ions of the metal to be deposited (1). In a second method defects are generated on a metal surface, and the holes obtained in this way are later decorated through deposition of the foreign metal (2,3). In a third method the tip of an STM was used as an electrochemical nanoelectrode to generate
supersaturation conditions with respect to the bulk metal equilibrium potential, and nucleation
and growth of a single clusters is achieved (4,5). A fourth application of the STM consists in the
generation of nanowires. Moving a STM Au tip into and out of contact with a Au substrate in the
presence of molecules that interact strongly with gold, Xu and Tao (6) were able to generate
monomolecular junctions.
While many facts could be explained for the nanostructuring processes mentioned above,
an important number of question arose, leaving a fruitful field for theoretical modelling. Although
statistical mechanics cannot be applied directly due to the complexity of the problems mentioned,
computer simulations provide an alternative way towards the understanding of the atomistic
processes involved. In those cases where the electronic structure of the system plays an important
role, quantum mechanical calculations are required. On the other hand, for those system where
the behavior is the result of the collective interaction of the particles, some approximated
potential can be employed to describe the interacion between the constituents particles. It these
cases, a more complete statistical description of the system can be made.
In the present talk we will discuss on the application of quantum mechanical calculations
and classical simulation methods (molecular dynamics, Monte Carlo) to the problems mentioned
above. Some of the question to be addressed wll be the generation mechanisms of the
nanostructures and their stability, in relation to the nature of the materials involved.
Acknowledgement
The authors acknowledge financial support from CONICET, Agencia Córdoba Ciencia, Secyt
U.N.C., Program BID 1201/OC-AR PICT No. 06-12485
References
1. D.M.Kolb, R. Ullmann, T.Will, Science, 275, 1097 (1997)
2. W.Li, G.S. Hsiao, D. Harris, R.M. Nyffenegger, J.A. Virtanen, R.M. Penner, J. Phys. Chem.,
100, 20103 (1996).
3. X.H. Xia, R. Schuster, V. Kirchner, G. Ertl, J. Electroanal. Chem., 461, 102 (1999).
4. W. Schindler, D. Hoffmann, J. Kirschner, J. Appl. Phys. 87, 7007 (2000).
5. W. Schindler, P. Hugelmann, M. Hugelmann, F.X. Kärtner, J. Electroanal. Chem., 522, 49
(2002).
6. B.Xu and N. Tao, Science 301(2003)1123.
ECTROCHEMICALLY NANOSTRUCTURED SYSTEMS
E.P.M. Leiva, S.A. Dassie , N. Luque, P. Vélez, M. Mariscal, M.Rojas, O. Oviedo.
Unidad de Matemática y Física, Facultad de Ciencias Químicas, Universidad Nacional
de Córdoba, INFIQC, Argentinae-mail: eleiva@fcq.unc.edu.ar
Nanoscale electrochemistry appears as a promising field in which scientists are beginning
to generate structures at the atomic and molecular scales in order to obtain surfaces and systems
with novel properties. In the particular case of electrochemistry, nanostructuring on solid surfaces
has been undertaken using different types of techniques, that share a common instrument for their
implementation - a scanning tunnelling microscope (STM). The exponential dependence of the
tunneling current on the tip-surface distance makes this device very sensitive to the topology of
the surface in the z direction. For this reason, in the origin of the STM techniques, the most
popular application was to get topological information, but soon an alternative application was
developed, consisting in the possibility of manipulation of matter at the atomic level.
Electrochemists have managed to employ the STM in several ways to nanostructure surfaces. In
one of them, denominated tip induced local metal deposition (TILMD), nanoclusters are
generated on the surface of a substrate by transfer of matter from the tip of the STM. The material on the tip is continuously renewed by deposition from a solution containing ions of the metal to be deposited (1). In a second method defects are generated on a metal surface, and the holes obtained in this way are later decorated through deposition of the foreign metal (2,3). In a third method the tip of an STM was used as an electrochemical nanoelectrode to generate
supersaturation conditions with respect to the bulk metal equilibrium potential, and nucleation
and growth of a single clusters is achieved (4,5). A fourth application of the STM consists in the
generation of nanowires. Moving a STM Au tip into and out of contact with a Au substrate in the
presence of molecules that interact strongly with gold, Xu and Tao (6) were able to generate
monomolecular junctions.
While many facts could be explained for the nanostructuring processes mentioned above,
an important number of question arose, leaving a fruitful field for theoretical modelling. Although
statistical mechanics cannot be applied directly due to the complexity of the problems mentioned,
computer simulations provide an alternative way towards the understanding of the atomistic
processes involved. In those cases where the electronic structure of the system plays an important
role, quantum mechanical calculations are required. On the other hand, for those system where
the behavior is the result of the collective interaction of the particles, some approximated
potential can be employed to describe the interacion between the constituents particles. It these
cases, a more complete statistical description of the system can be made.
In the present talk we will discuss on the application of quantum mechanical calculations
and classical simulation methods (molecular dynamics, Monte Carlo) to the problems mentioned
above. Some of the question to be addressed wll be the generation mechanisms of the
nanostructures and their stability, in relation to the nature of the materials involved.
Acknowledgement
The authors acknowledge financial support from CONICET, Agencia Córdoba Ciencia, Secyt
U.N.C., Program BID 1201/OC-AR PICT No. 06-12485
References
1. D.M.Kolb, R. Ullmann, T.Will, Science, 275, 1097 (1997)
2. W.Li, G.S. Hsiao, D. Harris, R.M. Nyffenegger, J.A. Virtanen, R.M. Penner, J. Phys. Chem.,
100, 20103 (1996).
3. X.H. Xia, R. Schuster, V. Kirchner, G. Ertl, J. Electroanal. Chem., 461, 102 (1999).
4. W. Schindler, D. Hoffmann, J. Kirschner, J. Appl. Phys. 87, 7007 (2000).
5. W. Schindler, P. Hugelmann, M. Hugelmann, F.X. Kärtner, J. Electroanal. Chem., 522, 49
(2002).
6. B.Xu and N. Tao, Science 301(2003)1123.
