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Nanostructure Science and Technology For other titles published in this series go to, http://www.springer.com/series/6331 Patrik Schmuki · Sannakaisa Virtanen Editors Electrochemistry at the Nanoscale 123 Editors Patrik Schmuki Sannakaisa Virtanen University of Erlangen-Nuernberg University of Erlangen-N¨urnberg Erlangen, Germany Erlangen, Germany schmuki@ww.uni-erlangen.de virtanen@ww.uni-erlangen.de ISSN 1571-5744 ISBN 978-0-387-73581-8 e-ISBN 978-0-387-73582-5 DOI 10.1007/978-0-387-73582-5 Library of Congress Control Number: 2008942146 c  Springer Science+Business Media, LLC 2009 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed on acid-free paper springer.com Preface For centuries, electrochemistry has played a key role in technologically important areas such as electroplating or corrosion. Electrochemical methods are receiving increasing attention in rapidly growing fields of science and technology, such as nanosciences (nanoelectrochemistry) and life sciences (organic and biological elec- trochemistry). Characterization, modification, and understanding of various electro- chemical interfaces or electrochemical processes at the nanoscale have led to a huge increase of scientific interest in electrochemical mechanisms as well as in applica- tion of electrochemical methods to novel technologies. Electrochemical methods carried out at the nanoscale lead to exciting new science and technology; these approaches are described in 12 chapters. From the fundamental point of view, nanoscale characterization or theoretical approaches can lead to an understanding of electrochemical interfaces at the molec- ular level. Not only is this insight of high scientific interest, but also it can be a pre- requisite for controlled technological applications of electrochemistry. Therefore, the book includes fundamental aspects of nanoelectrochemistry. Then, most important techniques available for electrochemistry on the nanoscale are presented; this involves both characterization and modification of electrochemi- cal interfaces. Approaches considered include scanning probe techniques, lithography-based approaches, focused-ion and electron beams, and procedures based on self-assembly. In classical fields of electrochemistry, such as corrosion, characterizing surfaces with a high lateral resolution can lead to an in-depth mechanistic understanding of the stability and degradation of materials. The nanoscale description of corrosion processes is especially important in understanding the initiation steps of local disso- lution phenomena or in detecting dissolution of highly corrosion-resistant materials. The latter can be of crucial importance in applications, where even the smallest amount of dissolution can lead to a failure of the system (e.g., release of toxic elements and corrosion of microelectronics). Since many electrochemical processes involve room-temperature treatments in aqueous electrolytes, electrochemical approaches can become extremely important whenever living (bio-organic) matter is involved. Hence, a strong demand for elec- trochemical expertise is emerging from biology, where charged interfaces play an important role. Interfacial electrochemistry is crucially important for understanding v vi Preface the interaction of inorganic substrates with the organic material of biosystems. Thus, recent developments in the field of bioelectrochemistry are described, with a focus on nanoscale phenomena in this field. Electrochemical methods are of paramount importance for fabrication of nano- materials or nanostructured surfaces. Therefore, several chapters are dedicated to the electrochemical creation of nanostructured surfaces or nanomaterials. This includes recent developments in the fields of semiconductor porosification, depo- sition into templates, electrodeposition of multilayers and superlattices, as well as self-organized growth of transition metal oxide nanotubes. In all these cases, the nanodimension of the electrochemically prepared materials can lead to novel prop- erties, and hence to novel applications of conventional materials. We hope that this book will be helpful for all readers interested in electrochem- istry and its applications in various fields of science and technology. Our aim is to present to the reader a comprehensive and contemporary description of electro- chemical nanotechnology. Contents Theories and Simulations for Electrochemical Nanostructures 1 E.P.M. Leiva and Wolfgang Schmickler SPM Techniques 33 O.M. Magnussen X-ray Lithography Techniques, LIGA-Based Microsystem Manufacturing: The Electrochemistry of Through-Mold Deposition and Material Properties 79 James J. Kelly and S.H. Goods Direct Writing Techniques: Electron Beam and Focused Ion Beam 139 T. Djenizian and C. Lehrer Wet Chemical Approaches for Chemical Functionalization of Semiconductor Nanostructures 183 Rabah Boukherroub and Sabine Szunerits The Electrochemistry of Porous Semiconductors 249 John J. Kelly and A.F. van Driel Deposition into Templates 279 Charles R. Sides and Charles R. Martin Electroless Fabrication of Nanostructures 321 T. Osaka Electrochemical Fabrication of Nanostructured, Compositionally Modulated Metal Multilayers (CMMMs) 349 S. Roy Corrosion at the Nanoscale 377 Vincent Maurice and Philippe Marcus vii viii Contents Nanobioelectrochemistry 407 A.M. Oliveira Brett Self-Organized Oxide Nanotube Layers on Titanium and Other Transition Metals 435 P. Schmuki Index 467 Contributors Rabah Boukherroub Biointerfaces Group, Interdisciplinary Research Institute (IRI), FRE 2963, IRI-IEMN, Avenue Poincar´e-BP 60069, 59652 Villeneuve d’Ascq, France, rabah.boukherroub@iemn.univ-lille1.fr Thierry Djenizian Laboratoire MADIREL (UMR 6121), Universit´ede Provence-CNRS, Centre Saint J´erˆome, F-13397 Marseille Cedex 20, France, thierry.djenizian@univ-provence.fr A. Floris van Driel Condensed Matter and Interfaces, Debye Institute, Utrecht University, P.O. Box 80000, 3508 TA, Utrecht, The Netherlands, a.f.vandriel@hotmail.com Steven H. Goods Dept. 8758/MS 9402, Sandia National Laboratories, Livermore, CA 94550, USA, shgoods@sandia.gov James J. Kelly IBM, Electrochemical Processes, 255 Fuller Rd., Albany, NY 12203, USA, mjklly@us.ibm.com John J. Kelly Condensed Matter and Interfaces, Debye Institute, Utrecht Univer- sity, P.O. Box 80000, 3508 TA, Utrecht, The Netherlands, J.J.Kelly@phys.uu.nl Christoph Lehrer Lehrstuhl f¨ur Elektronische Bauelemente, Universit¨at Erlangen- N¨urnberg, Cauerstr. 6, 91058 Erlangen, Germany, Christoph.Lehrer@brose.com Ezequiel P.M. Leiwa Universidad Nacional de Cordoba, Unidad de Matematica y Fisica, Facultad de Ciencias Quimicas, INFIQC, 5000 Cordoba, Argentina, eleiva@mail.fcq.unc.edu.ar Olaf M. Magnussen Institut f¨ur Experimentelle und Angewandte Physik, Christian-Albrechts-Universit¨at zu Kiel, 24098 Kiel, Germany, magnussen@physik.uni-kiel.de Philippe Marcus Laboratoire de Physico-Chimie des Surfaces, CNRS-ENSCP (UMR 7045) Ecole Nationale Sup´erieure de Chimie de Paris, Universit´e Pierre et Marie Curie, 11, rue Pierre et Marie Curie, 75005 Paris, France, philippe-marcus@enscp.fr ix x Contributors Charles R. Martin Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA, crmartin@chem.ufl.edu Vincent Maurice Laboratoire de Physico-Chimie des Surfaces, CNRS-ENSCP (UMR 7045), Ecole Nationale Sup´erieure de Chimie de Paris, Universit´e Pierre et Marie Curie, 11, rue Pierre et Marie Curie, 75231 Paris Cedex 05, France, vincent-maurice@enscp.fr Ana Maria Oliveira Brett Departamento de Quimica, Universidade de Coimbra, 3004-535 Coimbra, Portugal, brett@ci.uc.pt Tetsuya Osaka Department of Applied Chemistry, School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo, 169-8555, Japan, osakatets@waseda.jp Sudipta Roy School of Chemical Engineering and Advanced Materials, Newcastle University, Newcastle Upon Tyne NE1 7RU, UK, s.roy@newcastle.ac.uk Wolfgang Schmickler Department of Theoretical Chemistry, University of Ulm, D-89069 Ulm, Germany, Wolfgang.Schmickler@uni-ulm.de Patrik Schmuki University of Erlangen-Nuremberg, Department for Materials Science, LKO, Martensstrasse 7, D-91058 Erlangen, Germany, schmuki@ww.uni- erlangen.de Charles R. Sides Gamry Instruments, Inc., 734 Louis Drive, Warminster, PA 18974-2829, USA, Rsides@gamry.com Sabine Szunerits INPG, LEMI-ENSEEG, 1130, rue de la piscine, 38402 Saint Martin d’Her`es, France, sabine.szunerits@gmail.com Theories and Simulations for Electrochemical Nanostructures E.P.M. Leiva and Wolfgang Schmickler 1 Introduction Electrochemical nanostructures are special because they can be charged or, equiv- alently, be controlled by the electrode potential. In cases where an auxiliary elec- trode, such as the tip of a scanning tunneling microscope, is employed, there are even two potential drops that can be controlled individually: the bias potential between the two electrodes and the potential of one electrode with respect to the reference electrode. Thus, electrochemistry offers more possibilities for the genera- tion or modification of nanostructures than systems in air or in vacuum do. However, this advantage carries a price: electrochemical interfaces are more complex, because they include the solvent and ions. This poses a great problem for the modeling of these interfaces, since it is generally impossible to treat all particles at an equal level. For example, simulations for the generation of metal clusters typically neglect the solvent, while theories for electron transfer through nanostructures treat the solvent in a highly abstract way as a phonon bath. Therefore, a theorist investigating a par- ticular system must decide, in advance, which parts of the system to treat explicitly and which parts to neglect. Of course, to some extent this is true for all theoreti- cal research, but the more complex the investigated system, the more difficult, and debatable, this choice becomes. There is a wide range of nanostructures in electrochemistry, including metal clus- ters, wires, and functionalized layers. Not all of them have been considered by the- orists, and those that have been considered have been treated by various methods. Generally, the generation of nanostructures is too complicated for proper theory, so this has been the domain of computer simulations. In contrast, electron transfer through nanostructures is amenable to theories based on the Marcus [1] and Hush [2] type of model. There is little overlap between the simulations and the theories, so we cover them in separate sections. W. Schmickler (B) Department of Theoretical Chemistry, University of Ulm, D-89069 Ulm, Germany e-mail: Wolfgang.Schmickler@uni-ulm.de P. Schmuki, S. Virtanen (eds.), Electrochemistry at the Nanoscale, Nanostructure Science and Technology, DOI 10.1007/978-0-387-73582-5 1, C  Springer Science+Business Media, LLC 2009 1 [...]... coming to the substrate by atoms of the nanostructuring material In this way, the geometry at the beginning of the simulation should be approximately the same, apart from a slight stress that may be relaxed at the early stages of the simulation Figure 6 shows in snapshots of a GCMC simulation, the comparative behavior of pure Pd, and alloyed Pd/Au clusters upon dissolution In the case of the pure Pd... a surface of different nature The onset of the interaction between the tip and the surface produces an elongation of the tip at the atomic scale – the so-called jump to contact – that generates a connecting neck between the tip and the surface After this, the tip may approach further, and can be retracted at different penetration stages, with various consequences for the generated nanostructure Experiments... represents the energy necessary to embed atom i into the electronic density ρh,i This latter quantity is calculated at the position of atom i as the superposition of the individual atomic electronic densities ρi (ri j ) of the other particles in the arrangement as: Theories and Simulations for Electrochemical Nanostructures ρh,i = 7 ρi (ri j ) j =i The attractive contribution to the energy is given by the. .. equilibrium height depends on the applied overpotential, indicating that the surface energy of the growing cluster is balanced by the electrochemical energy The idea put forward by the authors was that the overpotential was related to the Gibbs energy change associated with the cluster growth From this hypothesis, the authors estimated that boundary energy amounts 0.5 eV/atom for the present system More... reflect atomic nature of matter, at least in a simplified way We shall return to this point below A typical atomistic computer simulation consists in the generation of a number of configurations of the system of interest, from which the properties in which we are 4 E.P.M Leiva and W Schmickler interested are calculated From the viewpoint of the way in which the configurations are generated, the simulations... ensemble that exhibits the same thermodynamic but different dynamic properties The second postulate refers to isolated systems, where the volume V , the energy E, and the number of particles N are fixed, and states that the systems in the ensemble are uniformly distributed over all the quantum states compatible with the N V E conditions Besides the N V E or microcanonical ensemble, some other popular... involves the generation of some species on the tip that further may react with the surface This is the basis of the technique denominated scanning electrochemical microscopy While it can be used to image regions of the surface with different electrochemical properties, it can also be applied to modify, at will, the surface if the latter reacts with the species generated at the tip Due to technical limitations,... metallic atoms, will give at least a qualitative idea of the leading contribution to the defect nanostructuring process Figure 9 shows results of such a simulation, where the chemical potential was stepped to simulate the negative polarization of the surface, together with snapshots of the simulation It can be seen that at chemical potentials μ close to the binding energy of bulk Cu (−3.61 eV), the Au... through the chemical potential of its constituting atoms Thus, since the stability of the cluster on the surface is given by the chemical potential of the atoms μ, a grand-canonical simulation with μ as control parameter appears as the proper tool to study cluster stability Further parameters in the experimental electrochemical systems are the temperature T and the pressure P, so that the proper simulation... changes in the energy Um As we have seen above, depending on the penetration of the tip into the surface, different degrees of mixing between the material of the tip and that of the substrate may be obtained, which can affect the stability of the clusters The behavior of pure and alloyed clusters could be in principle studied by comparing the behavior of the different clusters formed in the MD simulations . understanding the formation of the clusters. Figure 1b illustrates a different procedure, where a hole is generated by applying a potential pulse to the STM tip. Then the potential of the substrate is. monolayer of Pd. In the former case, rather pure Pd clusters are formed with the [110]-type tip. However, the structure of the tip also plays a role in the mixing between substrate and tip atoms. In. instability that generates the tip–surface contact. However, it must be noted that in the present case the surface atoms of the substrate participate actively in the processes, being lifted from their