Abstracts from the
7 th International Workshop on Electrodeposited Nanostructures
22 nd -24 th April 2010, Bristol U.K.
2
Scientific Programme Thursday 22
ndApril
09.00 - 09.10 Welcome to Bristol
1st Plenary Session: Nanostructures I: Chair Walther Schwarzacher
09.10 - 09.40 Giovanni Zangari
Materials Science and Engineering, University of Virginia, Charlottesville, USA Synthesis of Gold nanostructures by electrodeposition on modified substrates and their applications
Page 8
09.40 - 10.10 Patrick Fricoteaux
LACM-DTI, LRC-CEA, University of Reims Champagne-Ardenne, Reims, France Copper core - Silver shell nanoparticles elaboration
Page 9
10.10 - 10.40 Manon Lafouresse
LEPMI, CNRS, Grenoble-INP-UJF, Saint Martin d’Hères, France Hydrogen adsorption and absorption in nanosized Pd/Pt(111) films
Page 10 10.40 - 11.15 Tea/coffee break and poster session
2nd Plenary Session: Magnetoelectrodeposition I: Chair Margitta Uhlemann
11.15 - 11.45 Anne-Lise Daltin
LACM-DTI, LRC-CEA, University of Reims Champagne-Ardenne, Reims, France Evolution of Cuprous Oxide crystal morphology by magnetic field convection
Page 11
11.45 - 12.15 Kristina Tschulik
Institute for Metallic Materials, IFW Dresden, Dresden, Germany Electrodeposition of patterned metal layers in gradient magnetic fields
Page 12
12.15 - 12.45 Dámaris Fernández
School of Physics and CRANN, Trinity College Dublin, Dublin, Ireland
Magnetoconvective effect on current distribution and roughness during copper electrodeposition
Page 13
12.45 - 14.00 Lunch break and poster session
3
3rd Plenary Session: Alloys and multilayers: Chair Imre Bakonyi
14.00 - 14.30 Tsvetina Dobrovolska
Institute of Physical Chemistry, Bulgarian Academy of Science, Sofia, Bulgaria ALSV characterization of electrodeposited Cd-Co alloy coatings
Page 14
14.30 - 15.00 László Péter
Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Budapest, Hungary
Calculation of the transport coefficient of Fe2+ in the electrolyte from the composition depth profile of electrodeposited Fe-Co-Ni alloys
Page 15
15.00 - 15.30 Nicoleta Lupu
National Institute of Research and Development for Technical Physics, Iasi, Romania Magnetization processes and magnetotransport phenomena in electrodeposited NiFe/Cu multilayered nanowires
Page 16 15.30 - 16.00 Tea/coffee break and poster session
4th Plenary Session: Ionic liquids/ Nanostructures II: Chair Wolfgang Hansal
16.00 - 16.30 Reinhard Boeck
FEM - Research Institute for Precious Metals & Metals Chemistry, Schwaebisch Gmuend, Germany
Electrodeposition of morphologically selected micro- and nanodeposits from ionic liquids
Page 17
16.30 - 17.00 Luca Magagnin
Department of Chemistry, Materials and Chemical Engineering, Politecnico di Milano, Milan, Italy
Choline Chloride based ionic liquids for the electrodeposition of metals and alloys Page 18
17.00 - 17.30 Subir Ghosh
Department MTM, Katholieke Universiteit Leuven, Leuven, Belgium In-situ electrodeposition of nanostructured MoSx films
Page 19
4
Friday 23
rdApril
5th Plenary Session: Electrochemical surface science: Chair Nikolay Dimitrov
09.00 - 09.30 Klaus Krug
Institute for Experimental and Applied Physics, Christian-Albrechts-University Kiel, Kiel, Germany
In-situ surface X-ray scattering studies of electrochemical deposition and dissolution processes
Page 20
09.30 - 10.00 Natasa Vasiljevic
H. H. Wills Physics Laboratory, University of Bristol, Bristol, U.K.
Electrochemical in-situ STM, stress and OIRD studies of Pb deposition on Au(111) Page 21
10.00 - 10.30 David Fermin
School of Chemistry, University of Bristol, Bristol, U.K.
Electrochemical deposition of Te adlayers on 3D networks of metal nanostructures Page 22
10.30 - 11.00 Tea/coffee break and poster session
6th Plenary Session: Nano-composites/ Magnetoelectrodeposition II: Chair Sudipta Roy
11.00 - 11.30 Wolfgang Hansal
Happy Plating GmbH, Leobersdorf, Austria
Electrochemical pulse deposition of functional nano-dispersion coatings
Page 23
11.30 - 12.00 Paula Cojocaru
Department of Chemistry, Materials and Chemical Engineering, Politecnico di Milano, Milan, Italy
Novel plating cell geometry for Gold composites with nanodiamond
Page 24
12.00 - 12.30 Jakub Koza
Institute for Metallic Materials, IFW Dresden, Dresden, Germany
Influence of external homogeneous magnetic fields superposed during the electrodeposition of thin CoFe films on their properties
Page 25
12.30 - 14.00 Lunch break and poster session (and meeting of EDNANO Board)
5
7th Plenary Session: Nanowires: Chair Giovanni Zangari
14.00 - 14.30 Eugenia Toimil Molares
GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany
Electrochemical deposition in nanopores: metal, semimetal, and alloy semiconductor nanowires
Page 26
14.30 - 15.00 Veronika Haehnel
Institute for Metallic Materials, IFW Dresden, Dresden, Germany
Electrodeposition of Fe-Pd nanowires for magnetic shape memory application
Page 27
15.00 - 15.30 Célia Sousa
IN-IFIMUP and Department of Physics, University of Porto, Porto, Portugal Pulsed electrodeposition in nanoporous alumina: Control of barrier layer
Page 28 15.30 - 16.00 Tea/coffee break and poster session
8th Plenary Session: Solder issues and additives: Chair László Péter
16.00 - 16.30 Nikolay Dimitrov
Department of Chemistry, SUNY-Binghamton, Binghamton, U.S.A.
Understanding, controlling and minimizing the voiding, sporadically occurring in solder joints with electroplated Copper
Page 29
16.30 - 17.00 Yuriy Yanson
Leiden University, Leiden, Netherlands
Effect of additives on Cu electrodeposition: in-situ STM study
Page 30
17.00 - 17.30 Naray Pewnim
School of Chemical Engineering, Newcastle University, Newcastle upon Tyne, U.K.
Electrochemical analysis for electrodeposited Tin-Copper solder alloys from Methanesulphonic electrolytes
Page 31 17.30 Closing remarks
6
Posters
Ina Alber
GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany Electrochemical deposition of Au and Au/Ag alloy nanostructures
Page 32
Imre Bakonyi
Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Budapest, Hungary
Modelling the magnetoresistance vs. field curves of GMR multilayers with various couplings and anisotropies
Page 33
Meritxell Cortes
Department of Physical Chemistry and IN2UB, University of Barcelona, Barcelona, Spain
Electrodeposition of Magnetite (Fe3O4) thin films for single-molecule spintronics
Page 34
José García-Torres
Department of Physical Chemistry and IN2UB, University of Barcelona, Barcelona, Spain
Enhanced giant magnetoresistance in Co-Ag electrodeposits
Page 35
Jeerapat Nutariya
H. H. Wills Physics Laboratory, University of Bristol, Bristol, U.K.
Surface alloying during Pb underpotential deposition on Au(111)
Page 36
Mariana Proença
IN-IFIMUP and Department of Physics, University of Porto, Porto, Portugal Potentiostatic electrodeposition of Nickel nanowires inside nanoporous Alumina templates
Page 37
Ralph Süptitz
Institute for Metallic Materials, IFW Dresden, Dresden, Germany
The impact of a superimposed magnetic field on the free corrosion of iron
Page 38
Bence Tóth
Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Budapest, Hungary
Giant magnetoresistance study of electrodeposited Co-Ni/Cu multilayers
Page 39
7 Bence Tóth
Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Budapest, Hungary
Structure and electrical transport properties of electrodeposited Ni-Co alloys
Page 40
Margitta Uhlemann
Institute for Metallic Materials, IFW Dresden, Dresden, Germany
Magnetoelectrodeposition of CoFe nanowires in ordered alumina template
Page 41
Sarah Ward Jones
H. H. Wills Physics Laboratory, University of Bristol, Bristol, U.K.
Alloys by precision electrodeposition
Page 42
8
Synthesis of Gold Nanostructures by Electrodeposition on Modified Substrates and their Applications
G. Zangari1, J. Zhu2, G. Pattanaik1
1Materials Science and Engineering and 2Electrical and Computer Engineering University of Virginia, Charlottesville VA, 22904, USA
Inhibition of the nucleation process by substrate modification results in the formation of a small number of nuclei only at high overpotentials, leading to diffusion-limited growth and to the formation of dendrites. While in many applications conditions are sought to avoid dendritic growth, the nanostructuring provided by this growth mode can provide for interesting surface effects.
In this talk, we will show that electrochemical growth of Au onto Au substrates covered with self-assembled monolayers (SAMs) occurs in correspondence of defects in the SAMs. The resulting Au films exhibit a microstructure that depends strongly on the applied potential: at low overpotentials the films grow as an assembly of hemispherical clusters, while at high overvoltage the films become dendritic (Fig. 1).
A similar dendritic growth mode is observed when growing Au onto porous Si. In this case we show how conformal growth into the substrate pores vastly increases the adhesion of the resulting films.
Finally, we demonstrate the control of wettability (from hydrophilic to super- hydrophobic) of Au dendritic structures by modification of the Au surface with carboxyl- or methyl-terminated SAMs.
Figure 1. Morphology of Au films electrodeposited onto dodecanethiol-modified Au substrates from a TechniGold 25 soft gold electrolyte: left, -0.6 VSCE, right -0.75 VSCE.
9
COPPER CORE-SILVER SHELL NANOPARTICLES ELABORATION Patrick Fricoteauxa, Valérie Manciera, Céline Roussea, Jean Dilleb, Jean Michelc
a LACM-DTI, LRC-CEA 0534/EA 4302, UFR Sciences, BP 1039, F-51687 Reims Cedex 2, France b Service Matières et Matériaux, U L B Avenue F.D. Roosevelt, 50,CP 194/03, B-1050 Bruxelles, Belgium
c INSERM UMR-S926, LMEA, 21, rue Clément Ader, F-51685 Reims, France
Nanoparticles have been extensively studied in the last decade because of their high surface- to-volume ratios and their potential applications in magnetic recording, catalysis or medical, etc. Around 1950 a new synthesis method was appeared associating electrodeposition and ultrasound named “sonoelectrochemistry” [1]. Recently, new type of nanoparticles, composed of a core and a shell of two different materials, has been synthesized. Because of the nanoscale size of the layers, such bimetallic materials may have better or different chemical [2], magnetic [3], optical [4] and catalytic [5] properties comparing to the pure metals. To our knowledge, only Au/Ag particles have been obtained by electrochemical method [6] but no bimetallic nanoparticles have been elaborated by using sonoelectrochemistry. Our results concern the preparation of Cu/Ag core-shell nanopowders by ultrasound-assisted electrochemistry followed by a displacement reaction [7].
Cu/Ag system has been chosen because of the bactericidal properties of the external silver allowing potential interesting medical applications ("smart textiles" as wound dressings, contraceptive devices, surgical instruments and bone prostheses) and the lower cost compared with particles of massive silver. The work deals only with the feasibility of core-shell nanoparticles associating the sonoelectrosynthesis with chemical displacement method.
The X-ray diffraction and energy dispersive X-ray spectroscopy confirm the presence of copper and silver in the particles. These two techniques show three stages in the displacement kinetic. This point is attributed to the copper surface accessibility to silver chemical displacement. Transmission electron microscopy observations indicate that the powders consist mainly of isolated particles with different nanometric diameters but also with some small agglomerates. Elemental mapping obtained by electron energy-loss spectroscopy (EELS) underlines the core-shell structure and consequently the possibility to synthesize Cu- Ag core-shell nanostructures by electrolysis following by a chemical displacement.
[1] O. Lindstrom, Acta Chemica Scandinavica 6 (1952) 1313-1323
[2] S. Sao-Joao, S. Giorgio, J.M. Penisson, C. Chapon, S. Bourgeois, C. Henry, Journal of Physical Chemistry B 109(1) (2005) 342-347
[3] L. Favre, S. Stanescu, V. Dupuis, E. Bernstein, T. Epicier, P. Melinon, A. Perez, Applied Surface Science 226(1-3) (2004) 265-270
[4] S. Basu, D. Chakravorty, Journal of Non-Crystalline Solids 352(5) (2006) 380-385 [5] D.R. Rolison, Science 299 (2003) 1698-1702
[6] J. Zhu, Y. Wang, L. Huang, Y. Lu, Physics Letters A 323(5-6) (2004) 455-459.
[7] V. Mancier, C. Rousse, J. Dille, J. Michel, P. Fricoteaux, Ultrasonics Sonochemistry, DOI 10.1016/j.ultsonch.2009.12.009
10
Hydrogen adsorption and absorption in nanosized Pd/Pt(111) films Manon Lafouresse, Yvonne Soldo-Olivier, Eric Sibert
LEPMI, CNRS, Grenoble-INP-UJF,38402 Saint Martin d’Hères, France
The hydrogen-palladium system is a model system for analysing the insertion/desorption of hydrogen in metals and alloys. While hydrogen insertion into bulk Pd has been extensively studied, nanosized Pd overlayers electrodeposited onto single crystals offer an interesting alternative for studying both hydrogen adsorption and hydrogen insertion.
Pseudomorphic Pd films 1 to 30 monolayer thick were grown by electrodeposition on single crystal Pt(111). Hydrogen adsorption was used as a probe to characterise the Pd films. An increase of the temperature of the bath, a decrease of the concentration of chloride ions in the electrolyte or a decrease of the potential of deposition lead to a more layer by layer growth.
Electrochemical impedance spectroscopy (EIS) measurements were carried out to study the kinetics of hydrogen adsorption on the Pd overlayers and thereby study the influence of the substrate. In addition, the effects of the hydrogen electroinsertion on the structure of the Pd deposits were characterised at the ESRF by in situ Surface X-Ray Diffraction (SXRD). The pseudomorphism of the Pd overlayers was confirmed up to 20 monolayers (MLs). No hydrogen insertion was observed in the first two Pd overlayers. For a 20 ML film, a gradient for the hydrogen insertion rate was measured in the direction perpendicular to the surface.
11 EDNANO-7
EVOLUTION OF CUPROUS OXIDE CRYSTAL MORPHOLOGY BY MAGNETIC FIELD CONVECTION
Anne-Lise Daltin, Jean-Paul Chopart
LACM-DTI, LRC CEA, Université de Reims Champagne-Ardenne, B.P. 1039, 51687 Reims Cedex 2. France al.daltin@univ-reims.fr
Interest in cuprous oxide has been grown due to abondant non-toxic materials sources and its numerous properties and potential applications in electronics, solar energy conversion or catalysis. It is well known that shape and size of crystals have great effects on the properties of this oxide.
In this study, morphological development during electrocrystallization of cuprous oxide crystals is reported. The effects of magnetohydrodynamic convection generated by superimposition of high magnetic field up to 12 T have been observed. Variation of the crystal morphology from dense to labyrinthine and finally very high porous structure with magnetic field has been obtained, whereas no change in the crystallization growth envelope has been seen. Crystals grown under microconvection induced by magnetic field are different due to changes in the diffusion process. These results are evidence that magnetic field acts principally on branching growth without crystal habit modification.
Magnetic field is a convective tool that acts on electrodeposition processes and our present work has established that it governs the branching growth of Cu2O microcrystals. This is a promising result to obtain nanopowders with controlled shape.
12
Electrodeposition of patterned metal layers in gradient magnetic fields
Kristina Tschulik*, Jakub Koza, Ralph Sueptitz, Margitta Uhlemann, Annett Gebert, Ludwig Schultz
Institute for Metallic Materials, IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany With regard to surface finishing, in terms of functionalization or decoration, electroplating is a very common industrial method. Electrochemical deposition is also suitable when specific metallic structures are to be produced. One example is the damascene process, which is widely utilized for production of interconnections in semiconductor industry, where the conducting paths of copper are electrodeposited. Yet, although electrodeposition is in general very cost-efficient the whole process is quite complex, because obtaining metal deposits of a certain structure is very complicated. Consequently, a non-invasive method to simplify structuring of electrodeposits would be a matter of interest, not only for basic researchers, but also for electroplaters.
As it is known, that by superposition of magnetic fields during metal electrodeposition increased deposition rates and better deposit qualities can be obtained [1]. The application of magnetic gradient fields might as well be a possibility of influencing the deposit topography.
In non-homogenous magnetic fields paramagnetic species are attracted to regions of high gradients of magnetic flux density, which affects electrochemical reactions significantly [2].
As many commercially electrodeposited metals form ions of this kind in aqueous solution, e.g. Cu2+, Ni2+, Co2+, Fe2+, Fe3+, remarkable effects of non-homogenous magnetic fields on metal electroplating processes can be expected. Despite this, very little studies focused on the ability of using patterned magnetic fields in order to deposit patterned layers, up to now [3].
Hence this work is dedicated to this topic.
It has been shown, that the distribution of magnetic flux density gradients at the working electrode can be transferred to the topography of electrodeposited metal layers.
Furthermore it has been demonstrated, that the aspect ratio of the patterned deposits can be adjusted by means of electrochemical processes.
Fig. 1: Optical image of a magnetic field template (a) used to generate a patterned magnetic field (b) at the working electrode. An optical image of the resulting deposit (c) reveals the same pattern (c).
References
[1] J. M. D. Coey, G. Hinds, J. Alloys compds. 326 (2001) 238.
[2] S. R. Ragsdale, K. M. Grant, H. S. White, J. Am. Chem. Soc. 120 (1998) 13461.
[3] K. Tschulik, J. A. Koza, M. Uhlemann, A. Gebert, L. Schultz, Electrochem. Commun. 11 (2009) 2241.
13
Magnetoconvective effect on current distribution and roughness during copper electrodeposition
D. Fernandez a, W. Schwarzacher b, JMD Coey a
a School of Physics and CRANN, Trinity Colege Dublin
b HH Wills Physics Laboratory, University of Bristol
It is well known that magnetic fields enhance mass transport-limited reactions in electrochemistry. In particular, during copper electrodeposition at overpotentials related to the diffusion plateau, fields increase the reaction rate, reflected in enhanced measured currents [1]. Also well known is an associated effect on deposit morphology, with changes in fractal growth direction and density [2] or even increased smoothness [3]. However most of the reports related to morphology are not quantitative and thus difficult to extrapolate from case to case. We have studied copper electrodeposition in vertical electrodes under homogeneous magnetic fields up to 5 Tesla. As expected, for potentiostatic deposition, the thickness increases as current density increases. However, the thickness varies across the sample in accord with the Lorentz force direction, a similar effect to that produced by natural convection force, as shown in Fig. 1, A and B. When deposition is performed galvanostatically, the field does not increase the average thickness of the deposit, but dramatic reductions in particle size and roughness are observed, as can be seen from Fig. 1, C and D. In this work we report quantitatively on roughness measurements of this system.
Fig. 1: Effect of magnetic fields up to 5 T on copper deposits obtained from 0.3 M CuSO4 solution. Under potentiostatic mode, deposits grown for 300 s at η=200 mV exhibit changes in thickness across the Lorentz force direction (A) and also across the natural convection force (B). Under galvanostatic mode, deposits grown at a fixed rate of 0.06 /cm2 during 5 seconds exhibit changes in particle size from 0 T (C) to 5 T (D).
[1] G. Hinds, F.E. Spada, J.M.D. Coey, T.R. Ní Mhíocháin, M.E.G. Lyons, J. Phys.
Chem. B 105 (2001) 9487.
[2] T.R. Ní Mhíocháin, J.M.D. Coey, J. Magn. Magnet. Mat. 226-230 (2001) 1281.
[3] T.Z. Fahidy, Prog. Surf. Sci. 68 (2001) 155.
14
ALSV characterization of electrodeposited Cd-Co alloy coatings
B.M. Jovića, , Ts. Dobrovolskab, U. Lačnjevaca, I. Krastevb, V.D. Jovića,
a Institute for Multidisciplinary Research, 11030 Belgrade, P. O. Box 33, Serbia,
b Institute of Physical Chemistry, Bulgarian Academy of Science, 1113 Sofia, Bulgaria
Abstract
According to the literature data several attempts were made in order to obtain phase diagram for the system Cd-Co and none of them was successful, because it was not possible to prepare alloys with less than 94 wt.% and more than 10 wt.% Co. In the case of melts with up to 10 wt.% Co cooling curves showed only eutectic arrests at 316 oC. By the structural analysis of this melt it was stated that an intemetallic phase is present in eutectic matrix. Some authors claimed that Cd23Co3 intermetallic compound (having structure of γ-brass) was identified in this system, but it could not be proven by immersion of Co in a Cd melt at 700
oC. Hence, at the moment no convincing data concerning the phase diagram for the system Cd-Co are available in the literature.
Concerning the electrodeposition of Cd-Co alloy coatings the literature data are very limited. There is practically only one paper dealing with the electrolyte for Cd-Co alloy coatings electrodeposition.
Although it is known that electrodeposited alloys very often possess slightly different characteristics than those predicted by the phase diagram, in this work an attempt was made to characterize electrodeposited Cd-Co alloy coatings by using ALSV technique in order to define are there some intermediate phases or/intermetallic compounds present, or the system corresponds to the eutectic type alloy.
The electrodeposited Cd-Co alloys were characterized by the anodic linear sweep voltammetry technique (ALSV) in the solution of 1M NaCl (pH 2). It is shown that Cd-Co alloys could be deposited with high current efficiency (> 90%) from the solution containing 0.2M boric acid, low concentration of cadmium sulfate (0.01M and 0.02M) and high concentration of cobalt sulfate (0.2M and 0.4M) under the conditions of convective diffusion (RPM = 1000). The ALSVs were characterized by the presence of three peaks: one corresponding to the dissolution of pure Cd, one corresponding to the dissolution of pure Co and one corresponding to the dissolution of unknown phase formed in the system Cd-Co (since the phase diagram of the Cd-Co system does not exist in the literature). Depending on the charge and on the alloy composition (amount of Cd and Co) the peak of the unknown phase can either be hardly seen, or can prevail on the ALSV. This phase is formed mainly on the account of Co, but certain limiting amount of Cd must be deposited for the unknown phase to be formed and seen on the ALSV.
15
Calculation of the transport coefficient of Fe
2+in the electrolyte from the composition depth profile of electrodeposited Fe-Co-Ni alloys
László Péter1, Attila Csik2, Kálmán Vad2, György Molnár3
1: Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences 1525 Budapest, P. O. Box 49, Hungary
2: Institute of Nuclear Research of the Hungarian Academy of Sciences 4001 Debrecen, P. O. Box 51, Hungary
3: Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, 1525 Budapest, P. O. Box 49, Hungary
Electrodeposition of Fe-Co-Ni alloys is an important technique in the preparation of thin films for magnetic data storage devices. Several reports were published in this field, but most of the publications report the average composition of the deposits only. Magnetic properties of thin electrodeposited (ED) Fe-Co-Ni films represent a particularly controversial issue.
Hereby we present the electrodeposition and composition depth profile of ED Fe-Co-Ni films.
Deposits of 1-2 µm thickness were obtained by using Si/Cr(5nm)/Cu(20nm) substrates. For sake of the depth profile analysis, the Fe-Co-Ni layers were covered successively with a Zn and a Ni layer, the thickness of both covering layers ranging to 1-3 µm. These additional layers enabled us to peel off the deposit from the substrate and to start the depth profile analysis from the substrate side (reverse sputtering mode). The mean initial roughness during the depth profile measurements was 1 nm. Depth profile measurements were performed with a secondary neutral mass spectrometer (SNMS) of the type INA–X (SPECS GmbH, Berlin).
It was found that the growth of ED Fe-Co-Ni alloys starts with a zone that is rich in Fe (see right). The fast depletion of the electrolyte for Fe2+ leads to the decrease in the molar fraction of Fe in the alloy and to the increase in the deposition rate of Co and Ni.
The molar fraction of Co (i.e., the next metal in the row of deposition preference) increases first but starts to decrease after about 40 nm deposit thickness. The molar fraction of both Fe and Co achieves a minimum after 90-150 nm deposit thickness, depending on the deposition conditions.
This initial zone with drastic changes of the molar
fractions is followed by the bulk deposit in which there is no systematic change in the molar fractions.
The decay of the molar fraction of Fe in the initial zone made it possible to calculate the transport coefficient of Fe2+ in the electrolyte. This calculation was based on the Cottrell equation. It was found that the effective transport coefficient of Fe2+ is an order of magnitude higher than the diffusion coefficient, which can be measured with various techniques when no deposition at a relatively high rate takes place.
0 500 1000 1500
0.0 0.2 0.4 0.6 0.8 1.0
Cu
Fe Co
Ni
Molar fraction
Sputtering depth /nm
0.0 0.2 0.4 0.6 0.8 1.0
0.0 0.2 0.4
0.6 Steady-state deposition
Cottrell zone
Nucleation zone
Molar fraction of Fe
tDEP.-1/2 / s-1/2
16
Magnetization processes and magnetotransport phenomena in electrodeposited NiFe/Cu multilayered nanowires
H. Chiriac1, S. Krimpalis1,2, O. Dragos1, M. Grigoras1, G. Ababei1, and N. Lupu1
1National Institute of Research and Development for Technical Physics, Iasi, Romania
2Faculty of Physics, “Alexandru Ioan Cuza” University, Iasi, Romania
Magnetic nanowires were extensively studied in the last decade in order to understand and clarify a number of fundamental aspects or for potential applications [1,2]. A special emphasis is laid on the nanowires prepared by electrochemical deposition in the nanopores of different templates, due to the efficiency of this preparation method [2]. Additionally, the magnetotransport properties (both d.c. and a.c.) are behaving in a very specific manner in the multilayered nanowires structures, recommending them for applications in spintronics [3]. On the other hand, the high frequency properties (mainly the magnetoimpedance) are extremely important for developing new systems of microsensors arrays, to be used both in technical and biomedical applications.
[NiFe/Cu] x n multilayered nanowires were electrodeposited into the nanopores of the anodic aluminum oxide (AAO) templates by switching between the deposition potentials of the two constituents (respectively -1.4 V and -0.3 V for permalloy (NiFe) and Cu deposition). The aspect ratio (length/diameter) of the magnetic segments was varied from 0.1 to 1.42. The influence of the aspect ratio of the magnetic and non-magnetic layers on the orientation of the magnetization easy axis was investigated. Calculations were made for the magnetization orientation depending on the thickness of the magnetic NiFe layer for different non-magnetic Cu layer thicknesses. The magnetization direction is determined by a competition between the demagnetizing fields and the dipole-dipole fields between the adjacent ferromagnetic layers, and can be tuned parallel or perpendicular to the wires’ axis by varying the thickness of the magnetic and non-magnetic layers. Two formulas are proposed in order to calculate the saturation fields for applied field parallel and perpendicular to the nanowires axis, taking into account the magnetostatic interactions between the nanowires and, respectively, between adjacent ferromagnetic layers in each nanowire. The variation of the saturation field on the thickness of the NiFe and Cu layers for applied fields parallel and perpendicular to the nanowire axis was also calculated.
The magnetotransport properties of single multilayered nanowires have been measured. The MR curve is symmetrically anhysteretic, independent of the thickness of the non-magnetic Cu layer.
The MR ratio can reach values of 2-2.5%, depending on the thickness of the non-magnetic Cu layer. The presence of non-magnetic Cu layers produces a decrease of the axial magnetic anisotropy in the multilayered nanowires, and consequently the magnetic permeability increases at the surface of the nanowires leading to the enhancement of the d.c. magnetic field effect over the MI response, which can go up to 100%. The obtained results are discussed taking into account the considerations made for the MR effect, observed previously in such multilayered nanowires [4]. The results reported in the present work open up the possibility of realization of nanosensors arrays with enhanced sensitivity in a narrow range of frequencies.
Support from the Romanian PN II – Partnerships Programme (Project NANOBIODET, Contract No. 11-072/2007), NUCLEU PN 09-43 01 02, and from the European Community under the Sixth Framework Programme for the Marie Curie Research Training Network “SPINSWITCH”
Contract Number MRTN-CT-2006-035327 is highly acknowledged.
[1] R. Cowburn and D. Petit, Nature Mater. 4 (2005) 721-722.
[2] A. Fert, L. Piraux, J. Magn. Magn. Mater. 200 (1999) 338-358.
[3] L.-P. Carignan, C. Lacroix, A. Ouimet, M. Ciureanu, A. Yelon, and D. Ménard, J. Appl.
Phys. 102 (2007) 023905.
[4] L. Piraux, K. Renard, R. Guillemet, S. Matefi-Tempfli, M. Matefi-Tempfli, V.A. Antohe, S.
Fusil, K. Bouzehouane, and V. Cros, Nano. Lett. 7 (2007) 2563.
17
Electrodeposition of morphological selected micro- and nanodeposits from ionic liquids Reinhard Boeck a,*
a fem - Research Institute for Precious Metals & Metals Chemistry, Dep. of Electrochemistry, Katharinenstraße 17, D-73525 Schwaebisch Gmuend, Germany
* Corresponding author. Tel. +49(0)7171-1006 58, Fax +49(0)7171-1006 54, E-mail: boeck@fem-online.de
Nanoparticles and nanodeposits have been widely studied in a wide range of technical applications and in fundamental research. For instance, catalysis and electrocatalysis by nanoparticles have been a subject of continuously growing interest.
The size and shape of electrodeposited submicron particles/electrodeposits are important factors in determining their optical, electric, magnetic and catalytic properties.
Electrodeposition is an economical and convenient choice for the preparation of functional metal coatings. Furthermore, plating on odd-shaped surface is possible and controlling of size and morphologies of the deposits is assessable by special electrochemical techniques.
In addition, ionic liquids were discussed as promising non-aqueous electrolytes for metal deposition. These liquids have interesting physical and chemical properties. One very interesting aspect of ionic liquids is that the deposition of nanocrystalline deposits is enabled.
In a recent study at the fem, the nano- and microcrystalline electrodeposition of various metals (Au, Pd and Ni) from ionic liquids were investigated. The effects of deposition current, deposition temperature on the morphology of the electrodeposits was examined. The surface morphology of the electrodeposits was characterized by a scanning electron microscope (SEM) and the crystalline phases of the deposits were studied with a X-ray diffractometer (XRD).
The results show that it is possible to electrodeposit micro- and nanocristalline deposits from ionic liquids with different morphologies and partly with high crystallographic orientation on innovative substrates (open cell metal foams, carbon gas diffusion layers).
18
Choline Chloride Based Ionic Liquids for the Electrodeposition of Metals and Alloys Stefania Costovici 1, Teodor Visan 2, Paula Cojocaru3, Luca Magagnin3
1FELIX IT SA - Bucharest, Romania
2POLITEHNICA University of Bucharest - Bucharest, Romania
3Dip. Chimica, Materiali e Ing. Chimica G. Natta, Politecnico di Milano – Milano, Italy
In the last years, the metals and alloys electrodeposition involving an innovative class of electrolytes based on ionic liquids (room temperature molten salts) has proved to be very attractive due to the possibility either to perform metallic coatings that are hardly or impossible to be obtained in classical aqueous solutions or to apply these coating layers with a suitable adherence on water sensitive metallic substrates such as Al, Mg, Ti and their alloys, stainless steels, other alloys containing high contents of refractory or rare earth metals. Recently it has been shown the possibility of formation of ionic liquids from eutectic mixtures of quaternary ammonium salt such as choline chloride (2-hidroxy-ethyl-trimethyl ammonium chloride) with a hydrogen bond donor species such as amides, glycols or carboxylic acids. These media have been further used to electrodeposit a large range of metals and alloys including Zn and Zn alloys, Cr, Sn, Cu and Ag.
In this work, we report about the electrodeposition of metals, e.g. nickel and alloys, copper, palladium and silver from choline chloride based electrolytes. Adherent and uniform Ni based coatings have been evidenced for the first time onto Mg and Al substrates, when the ionic liquids has been prepared using sulfate as Ni based salt. To evaluate the resistance against corrosion, several accelerated corrosion tests have been performed, respectively: (i) continuous immersion in 0.5M NaCl for 240 hours with intermediary visual examinations and recording of corrosion potential; (ii) potentiodynamic polarization curves and (iii) impedance spectra at open circuit potential, in 0.5M NaCl. Cu deposits with low roughness were obtained onto brass substrate.
According to XRD investigations all investigated electrochemical coatings showed a nanocristalline structure, with average sizes of the cristallites between 6-25 nm. Preliminary results on palladium and silver deposition will be also reported.
19
In-situ Electrodeposition of Nanostructured MoS
xFilms
S.K. Ghosh1,2 and J. P. Celis2
1,2Materials Processing Division Bhabha Atomic Research Centre Trombay, Mumbai-400085, India
2Department of MTM, Kathilieke University Leuven,
Leuven, B-3000, Belgium
Abstract
In this presentation, we report on the deposition of MoSx films on various substrates by in-situ electrolysis in aqueous solutions containing molybdate (MoO4 2-
) and sulphide (S2-) ions. X-ray diffraction (XRD) revealed that as-deposited films are x- ray amorphous in nature. Upon annealing, they transformed into crystalline films. The structural transformation was monitored via high temperature XRD analyses which showed that the crystallization process starts beyond 400 0C with the appearance of a (0002) peak and progresses with time and becomes more evident at higher temperatures. XRD line broadening of the (0002) peak on post-annealed MoSx films confirmed the formation of nanosize crystallites within the films. A surface topography investigation by scanning electron microscope (SEM) revealed the featureless morphology of as-deposited films. However, the formation of a nanotube/nanorod structure along with numerous outward smaller nodules was noticed on post-annealed sample surfaces. Further investigation by transmission microscope (TEM) unearthed the presence of nanoballs, nano-ribbons, and nanotubes inside the nanostructured films. The nanotubes have a diameter of 10-400 nm and are several micrometers in length as evidenced by SEM. The diameter of the nano-balls was in the range of 5 to 10 nm. A large lowering of the coefficient of friction was noticed on post-annealed MoSx films deposited on NiP and CoW substrates tested against a corundum counter ball in fretting tests.
20
In-situ surface X-ray scattering studies of electrochemical deposition and dissolution processes
Klaus Krug
Institute for Experimental and Applied Physics, Christian-Albrechts-University Kiel, Kiel, Germany
I will talk about gold homoepitaxial deposition on Au(100) single crystal electrodes as well as about electrodissolution at Au(100) and Au(111) electrodes. All experiments were performed in chloride containing acidic solution of pH 1. The SXS data and simultaneously recorded electrochemical data reveal information about the growth/dissolution behavior on the atomic scale in dependence on central system parameters, i.e. electrode potential and deposition/dissolution rate.
21
Electrochemical In-situ STM, Stress and OIRD Studies of Pb deposition on Au(111)
Natasa Vasiljevic, Jeerapat Nutariya, Jonathan Velleuer and Walther Schwarzacher H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue,
Bristol BS8 1TL
The advancement of new electrochemical techniques gives unprecedented opportunity to study complex details of atomic scale processes that have not been studied before. In-situ STM has been shown to be invaluable tool for the surface structure characterisation during deposition. An understanding of stages of metal electrodeposition has been extended in last ten years by in-situ surface stress technique based on the beam bending curvature measurements. Most recently the in-situ oblique incidence reflectivity difference (OIRD) has been introduced in electrodeposition studies as a useful tool for characterisation of morphological changes in real time during film growth.
Metal systems with large misfit that feature surface/bulk alloying are becoming subjects of increased interest. The need for new nano-materials and new ways to control structure/properties motivate more extensive research in this particular area. Until now it has been recognized that many systems (both mixable and immiscible) feature surface confined alloying/dealloying transformation during initial stages of growth. Since the foundation work on Pb alloying kinetics on Ag electrode there has not been much research done on other systems. In this talk we will present a comprehensive study on one such system of interest, Pb on Au(111) in perchlorate solution using combination of the electrochemical, STM, surface stress and OIRD measurements.
Pb deposition proceeds in Stranski-Krastanov growth mode characterised by formation of an epitaxial UPD layer followed by three dimensional bulk (OPD) deposition. Even though Pb UPD monolayer formation on Au(111) has been the subject of numerous studies, a quantitative analysis of alloying/dealloying during this process has not yet been carried out. More recent surface stress measurements by a number of research groups raised questions regarding the role of surface alloying/dealloying transitions in the stress behaviour (Figure). Here we will present the first electrochemical study of alloying kinetics at different stages of Pb UPD growth and the effect on surface structure changes monitored by in-situ STM, stress and OIRD techniques. We also studied the changes of the surface stress during Pb bulk deposition. The large compressive stress evolution during growth at constant overpotentials is related to nucleation and growth of low density of three-
dimensional islands. This has been unambiguously illustrated by in-situ STM and OIRD changes. The most remarkable STM finding was the localized alloying observed at the Pb/Au island interface. The STM also showed preferential nucleation of three-dimensional islands on areas of higher surface defect density.
Figure. (A) Cyclic voltammetry of Pb UPD and corresponding surface stress evolution in 10-3 M Pb(ClO4)2+ 0.1 M HClO4, scan rate 20mV/s . (B) In-situ STM image (93×93)nm of Au (111) surface after striping of Pb UPD layer.
A B
22
Electrochemical deposition of Te adlayers on 3D networks of metal nanostructures María G. Montes de Oca and David J. Fermín*
School of Chemistry University of Bristol Cantocks Close, Bristol BS8 1TS, United Kingdom david.fermin@bristol.ac.uk www.chm.bris.ac.uk/pt/electrochemistry
Metal nanostructures can exhibit rather complex electrochemical reactivity depending on their size and shape. Surface sensitive electrochemical probes, e.g. H and CO adsorption, provide an interesting approach to the reactivity of these systems [1]. In the present contribution, we examine the surface properties of Au and Au-Pd core-shell nanostructures by analysing the electrochemical responses associated with the formation of Te atomic adlayers, commonly referred to as underpotential deposition (upd). Water-soluble Au nanoparticles with an average diameter of 19.2±1.2 nm were synthesized by reduction of AuCl4- in the presence of sodium citrate. Epitaxial Pd layers with thickness between 1 and 10 nm were grown onto Au cores by chemical reduction of PdCl42- using ascorbic acid. The size and structure of core-shell nanostructures were investigated by transmission electron microscopy and electron diffraction patterns. Two- and three-dimensional networks of nanoparticles were assembled via electrostatic layer-by-layer adsorption employing poly-L- Lysine (PLL) on In-doped SnO2 (ITO) electrodes. Atomic force microscopy (AFM) and electrochemical measurements showed that the 3D assemblies consist of an open network of electrically interconnected nanoparticles. Electrochemical studies of Au-modified electrodes in the presence of TeO2 in HClO4 electrolyte show two distinct features associated 1 and 2 upd layers of Te selectively deposited onto the Au nanocrystals. Detailed analysis of the electrochemical responses as a function of the surface corrugation showed that the average Te coverage on a single Au nanoparticle is close to those observed at extended Au surfaces [2,3].
The results demonstrate that each individual particle in the 3D assembly can be electrochemically addressed. The responses associated Te upd on Au-Pd core-shell exhibited a systematic dependence on the Pd shell thickness. These effects are rationalised in terms of the structure of the Pd shells as revealed from electron diffraction patterns.
(1) J. Solla-Gullon, P. Rodriguez, E. Herrero, A. Aldaz and J.M. Feliu, Phys. Chem. Chem.
Phys., 10 (2008) 1359-1373.
(2) J.Y.Y. W. Zhu, D.X. Zhoub, S.Q. Bao, X.A. Fan, X.K. Duan, Electrochim. Acta, 52 (2007) 3660–3666.
(3) K.V. Thomas A. Sorenson, D. Wayne Suggs, John L. Stickney, Surf. Sci., 470 (2001) 197 - 214.
23 Abstract
EDNANO VII Bristol 2010
Electrochemical pulse deposition of functional nano-dispersion coatings W.E.G. Hansal, S. Hansal, G. Sandulache, M. Halmdienst
Happy Plating GmbH, Aumühlweg 17-19, 4F, A 2544 Leobersdorf, Austria
This presentation will introduce and critically discuss several systems combining both pulse deposition and (nano) dispersion coatings for tribological wear applications. Engineered tribocoatings of all kinds are under increasing interest due to their capability of enhancing component reliability and reducing life-cycle cost. Beside the emerging physical methods electrochemical techniques have still their relevancy in industrial production although the fact that the introduction of new technology in the field of galvanic is slow especially for this field of application. The substitution of hard chromium processes, which suffer from severe environmental problems due to the emission of carcinogenic hexavalent chromium ions, would push the importance of galvanic process routes. An environmentally friendly electrodeposited tribocoating having properties similar to those of hard chrome with dense, stable and uniform coatings even on complexly shaped parts would provide a major improvement in surface finishing. One possible way of realising this is the use of dispersion coatings.
While dispersion coatings including micro particles and using DC or electroless plating processes are industrially widely used, nano-dispersion coatings using either nano particles or the benefits of modern pulse plating techniques are on the edge of their industrial implementation. The combination of both methods pulse plating and dispersion coatings offer a broad variety of new surface functionality. The embedment of nano particles within a metal matrix can offer the desired hardness, the friction and wear characteristics, the pulse deposition will provide the erosion and corrosion resistance and an excellent thickness distribution. Comparing pulse plated nano dispersion coatings with especially hard chromium coatings will reveal the capability of such layer systems. The electrochemical development, the surface layer characterisation and the tribological testing will be presented. The embedment of nano particles during a pulse plating process will lead to a different composite coating with an average grain size in the order of magnitude of the nano particles. While as well regular chromium coatings as direct current using dispersion coatings will produce a micro crystalline metal matrix, the nanocrystalline matrix of the pulse plated layer systems lead to a much tighter incorporation of the (nano) particles.
24
Novel plating Cell Geometry for Gold composites with nanodiamond Paula Cojocaru1, Luca Magagnin1, Thomas Lampke2, Dagmar Dietrich 2
1Dip. Chimica, Materiali e Ing. Chimica G. Natta, Politecnico di Milano – Milano, Italy
2Institute of Materials Science and Engineering, Chemnitz University of Technology, D-09107 Chemnitz, Germany.
Composite layers were produced using a particular electrolytic cell where electrolyte is pumped into a circuit and then is reintroduced into the cell by little holes situated in front of the substrate. Gold nanodiamond composites have been prepared by using sulphite electroplating bath. Different concentration of microparticles of nanodiamond (0 - 20 gl-1) in the bath were used. The electrolytic cell used in these experiments is showed in the Fig. 1, and its functioning is described below.
Fig. 1. Scheme of the Forced Flow Cell
To describe how the cell works it’s useful to analyze the path that the electrolyte is forced to follow during the deposition. The electrolyte is pumped out from the cell, and then is reintroduced into it by a pipe, fixed on the bottom of the cell, with holes which allows the solution to return in the electrolytic cell; the holes are situated in a particular zone of the pipe: they are just in front of the substrate, this is important because a flow of electrolyte heads towards the substrate, generating a better interaction between electrolyte and substrate with obvious benefits to the electrcodeposition process; this particular configuration helps the particles to be suspended in the bath, but this effect is not sufficient and there is the necessity to add to the cell a mechanical stirrer in order to obtain a good suspension of the particles in the electrolyte.
Changes in the microstructure, mechanical and magnetic properties were studied in correlation with the percentage of particles incorporated in the gold matrix.
25
Influence of external homogeneous magnetic fields superposed during the electrodeposition of thin CoFe films on their properties
Jakub Adam Koza, Franziska Karnbach, Kristina Tschulik, Margitta Uhlemann, Jeffrey McCord, Christine Mickel, Annett Gebert, Stefan Baunack, Ludwig Schultz
Leibniz Institute for Solid State and Materials Research IFW Dresden, P.O. Box 270116, D- 01171 Dresden, Germany
The Fe-group alloys are characterized by their excellent soft magnetic properties. Especially the CoFe system, which possesses the highest, among others, saturation magnetisation of 2.45 T and a relatively low coercivity of about 2 Oe [1], is of interest. These properties are crucial for the further development in the storage technology, i.e. for the hard drive’s writing head.
A superposition of an external magnetic field during the electrodeposition has gained a considerable attention during the past decade [2,3], since it can affect the deposit properties.
Mainly the morphology of the deposited layers is influenced. But it has also been reported that a magnetic field applied during the deposition could texture the deposit, affect its phase composition and reduce the internal stress of the layer. Additionally, when magnetic alloy layers are deposited under the influence of an external magnetic field, an in-plane anisotropy could be induced [1,3], which is of commercial importance [1].
The aim of this study was to investigate the influence of homogeneous magnetic fields with flux density up to 1 T superposed during the deposition of CoFe thin films on their properties.
The deposition of alloy films has been carried out potentiostatically from low concentrated sulphate electrolytes without and with the addition of boric acid. The resulting layers
morphology has been investigated by means of SEM, TEM and AFM techniques. The crystal structure and texture was investigated by means of XRD and TEM. It has been clearly
demonstrated that the superposition of magnetic fields influences the resulting layer properties significantly. A pronounced impact on the layer morphology has been observed. The layers deposited under the influence of the parallel-to-electrode magnetic field appear denser and more homogenous than those obtained without a magnetic field. On the contrary, the layers deposited in the perpendicular-to-electrode magnetic field appeared more diverse. A scaling analysis [4] revealed a smoothing effect of a parallel- and a roughening effect of a
perpendicular-to-electrode magnetic field. No influence of magnetic fields neither on the deposited layers chemical composition nor the structure and texture has been found, whereas the internal stress state of the layer is affected by the superposition. The effects are discussed with respect to the Lorentz force driven convection, which increases the electrochemical reactions rates and improves desorption of hydrogen from the electrode surface. The alterations of magnetic properties of the CoFe thin films correlate well with the observed microstructural changes. Moreover, an in-plane magnetic anisotropy is induced by a parallel magnetic field superposition. This phenomenon origins from a preferential next neighbour atomic pair-ordering in the direction of the magnetic field, e.g. magnetization, during deposition of the ferromagnetic alloy.
[1] E.I. Cooper, C. Bonhote, J. Heidmann, Y. Hsu, P. Kern, J.W. Lam, M.
Ramasubramanian, N. Robertson, L.T. Romankiw, H. Xu, IBM. J. Res. Develop. 49 (2005) 103.
[2] R.A. Tacken, L.J.J. Janssen, J. Appl. Electrochem. 25 (1995) 1.
[3] I. Tabakovic, S. Riemer, V. Vas’ko, V. Sapozhnikov, M. Kief, J. Electrochem. Soc.
150 (2003) C635.
[4] S. Huo, W. Schwarzacher, Phys. Rev. Lett. 86 (2001) 256.
26
Electrochemical deposition in nanopores: metal, semimetal, and alloy semiconductor nanowires
I. Alber1, S. Müller1, R. Neumann1, O. Picht1, M. Rauber1,2, M.E. Toimil Molares1
1 GSI Helmholtz Center for Heavy Ion Research, Planckstr. 1, 64291 Darmstadt
2 TU-Darmstadt, Material Analytik, Petersenstrasse 23, D-64287 Darmstadt, Germany
Over the last two decades, investigations of nanostructures and, in particular, nanowires have attracted large interest due to their novel properties and promising applications in various fields such as electronics, optoelectronics, thermoelectrics, and sensorics. The properties of nanoscale materials strongly depend on their size and crystallinity. Nanowire synthesis using the ion-track technique in combination with electrodeposition enables independent and simultaneous control over size (diameter and length), morphology, crystalline structure, and composition of the nanowires. Templates with nanochannels (length of several tens of µm length and diameter from 20 nm to some µm) are produced by irradiating polymer foils with high-energy heavy ions at the linear accelerator of GSI. Each single ion produces a cylindrical damage trail which is converted into a nanochannel and enlarged by chemical etching. Recent results on the electrochemical synthesis of nanowires of different materials in the channels will be presented: metals such as gold and platinum, semimetals such as bismuth and semiconductor alloys such as bismuth antimony and bismuth telluride. In this presentation, it will be reported how composition and morphological and crystallographic characteristics (surface roughness, crystallinity, and texture) are controlled by the electrolyte, and by the voltage and temperature applied during the deposition process.
27
Electrodeposition of Fe-Pd nanowires for magnetic shape memory application Veronika Haehnel1,2, Sebastian Fähler1, Ludwig Schultz1,2, Heike Schlörb1
1IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany
2TU Dresden, Faculty of Mechanical Engineering, 01062 Dresden, Germany
Fe-Pd alloys are especially promising candidates for smart and intelligent materials. At about 30 at.% Pd these alloys exhibit the magnetic shape memory effect (MSM). This effect allows obtaining strains, length changes, in the percent range [1]. By either applying an external magnetic field or heat, MSM materials convert undergoing a reversible fcc to fct structure transition. Alloys near this composition show approximately 2/3 of the saturation magnetization of pure Fe and are appropriate for fast length changes by applying an external magnetic field. By down scaling the dimensions nano- and microsystems such as magnetically driven nanoactuators are conceivable. Using now electrodeposition within self- organised nanoporous templates FePd nanowires of different length are producible. This is a very time and cost efficient method compared to top down approaches. Although the electrodeposition process is realizable it gains major obstacles as finding an effective and stable plating bath.
In this study we have investigated the electrochemical preparation of Fe-Pd nanowires in nanoporous alumina membranes using a pulsed potential electrodeposition regime. To allow the codeposition of both Fe and Pd their deposition potentials are controlled by complexing [2]. The Fe-Pd ratio was adjusted by the electrolyte composition and pulse parameters toward Fe70Pd30. Structural and magnetic characterization (Figure 1) of electrodeposited FePd nanowire arrays are presented and discussed in terms of the MSM effect.
[1] R. D. James, M. Wuttig, Magnetostriction of martensite, Philosophical Magazine A, 77, 1998, 1273 [2] P. Juzikis, M.U. Kittel, Ch.J. Raub, Electrolytic Deposition of Palladium-Iron Alloys, Plating and Surface Finishing, 81, 1994, 59
Figure 1 a) Crosssectional SEM micrograph; b) bright-field TEM micrograph; c) selected area diffraction pattern; d) corresponding magnetisation curve of Fe69Pd31 nanowires deposited into alumina template.
28
Pulsed electrodeposition in nanoporous alumina:
Control of barrier layer
C.T. Sousa1*, D.C. Leitão1, A.M.Pereira1,A.Apolinário1, M.P. Proença1, J. G. Correia2, J. Ventura1, J.P. Araújo1
1IN-IFIMUP and Dep. Física, Rua do Campo Alegre 687, 4169-007 Porto, Portugal
2ITN, Estrada Nac. N10, Apartado 21 – 2686-953 Sacavém, Portugal
*celiasousa@fc.up.pt
The great advances in nanoscience and nanotechnology in the last decade have lead to the development of new platforms where all physical properties like size, porosity, geometry and surface functionalization can be controlled at the nanoscale.
The research devoted to this field is pushed by the potential applications offered by such structures in several areas, ranging from spintronics to nanomedicine.
Particularly, high aspect ratio inorganic nanoparticles have arouse great interest and shown many potentialities. Among the different approaches to the fabrication of these high aspect ratio nanoparticles, alumina template-based synthetic methods have received considerable attention due to their several unique structural properties, such as controllable pore diameter, extremely narrow pore size distribution, and an ideally cylindrical shape. Especially, template electrodeposition has been proved to be an effective way to fabricate metallic nanowires. Until now, three different methods have been developed to obtain uniforme and complete filling of template pores by electrodeposition: direct current (DC), alternating current (AC) and pulsed electrodeposition (PED). The PED method usually consists on the application of DC pulses with square or other complex electronic waves. Contrary, to DC deposition, AC deposition and PED can be performed if a thin barrier layer is present in the pore bottom. Since aluminium substrate and alumina barrier layer do not need to be removed for AC deposition and PED, pore filling is simple and nanowires with very small length can be fabricated. PED can thus be a reliable alternative method for the deposition of metals into high aspect ratio forms. However, pre-treatment of the alumina template before PED is needed because the resistance during the electrodeposition varies depending on the thickness of the bottom of the pores. This influences the deposition behaviour, since electrodepostion preferably occurs in those pores exhibiting a thinner (less resistive) barrier layer. Therefore, the barrier layer is thinned by decreasing the voltage at the end of the anodization process. The nanowires are straightforwardly electrodeposited on the bottom of nanohole and the procedure is very simple.
In this work we will describe the PED stages of growth of metallic nanowires into anodic nanoporous alumina. After a two step anodization process, an exponential voltage was applied leading the formation of dendrites at the pore bottom. Metal deposition was achieved without removing the aluminum substrate because a PED method in the microsecond range with an intermittent asymmetric square pulse was used. We further present an optimization of the type and the thickness of the barrier layer to control the homogeneity and the length of the nanowires.
29
Understanding, Controlling and Minimizing the Voiding, Sporadically Occurring in Solder Joints with Electroplated Copper
N.DIMITROV1,Y.LIU1,F.WAFULA1,S.BLIZNAKOV1, E.J.COTTS2,L.YIN3,P.BORGESEN3 1) Department of Chemistry, and 2) Department of Physics, SUNY at Binghamton, P.O. Box
6000, Binghamton, NY 13902
3) Unovis Solutions, PO Box 5304, Binghamton, NY 13902
The present work offers generic remedies for a problem that is known to have cost the industry billions of dollars. When an interconnect is made between typical Sn containing solder and Cu pads, metallurgical reactions lead to the formation of Cu6Sn5 and Cu3Sn intermetallic compounds (IMC), as seen in the Figure. On many occasions the Cu3Sn intermetallic compound formed with specific electroplated Cu samples has been seen to develop voids and weaken to a catastrophic extent over time near or at room temperature. This would eventually cause wear out or fatigue life degradation in board level testing.
The first view of the voiding phenomenon invokes the commonly known “Kirkendall voiding”. Another view identifies a fundamentally different mechanism of void formation in which, interfacial vacancies are mostly produced by “vacancy injection” mechanisms associated with the phase transformation/ consumption at the interfaces. Vacancy super- saturation, necessary for void formation, may result from vacancy sinks, e.g. dislocations or
interfaces, being blocked by impurity molecules. In general, the level of impurity incorporation is found to depend greatly on interactions between the plating additive chemistry and the plating process parameters. A major effort is therefore aimed at learning how to properly control the acid Cu electroplating process in order to minimize the propensity for voiding.
An overview of the effort to establish a general picture that accounts for the propensity for voiding in the Cu3Sn IMC is presented in this work. With the reported experimental activity we demonstrate our ability to turn the voiding problem on and off at will, pointing to a generic remedy. In initially surveyed samples plated from a commercial Cu plating additive systems the voiding propensity was seen to be greatly dependent on the additive chemistry and bath age. The effect of bath chemistry and age as well as deposition rate and temperature was further studied in a rotating disc electrode (RDE) configuration in plating bath with known bath constituents. Thus, besides the Cu sulfate, sulfuric acid, and chloride ions, two generic organic additives: polyethylene glycol (PEG) as carrier and bis(3-sulfopropyl) disulfide (SPS) as brightener were used. Samples were at different current densities, for different times and at different temperatures. Potential evolution, surface morphology, voiding behavior and composition of plated samples were quantified and compared. The effect of multiple brightener replenishments was also investigated. Plots of plating overpotential as a function current density and temperature at fixed solution composition were analyzed with respect to the voiding behavior of accordingly deposited Cu layers. Based on this analysis conditions generating either only void-proof or only void-prone Cu were identified. Further confirmation of the proposed analysis is obtained by scaling experiments in a Hull Cell layout where regions of void prone and void proof Cu co-exist on the same sample in a perfectly controlled way. Based on the above analysis, empirically derived means are proposed for controlling (and possibly avoiding) the sporadic voiding in solder joints with Cu electroplated under manufacturing relevant conditions.
Figure: SEM cross section image of (SAC405) solder joint with electroplated Cu pad after reflow and aging for1000 hours at 175°C.
Cu Cu3Sn
Sn-Ag-Cu (solder) Cu6Sn5
Voids 20 µm
