Pitting corrosion of polycrystalline annealed copper in alkaline sodium perchlorate solutions containing benzotriazole

The pitting corrosion of copper in alkaline solutions in the presence of benzotriazole (BTA) was investigated. The presence of BTA shifts the breakdown (Eb) and the repassivating (Ep) potentials positively with respect to the blanks. However, the shift of Eb becomes smaller than that ofE b, particularly at pH9 and 11. Pitting corrosion involves the formation of crystallographic pits. The kinetics of the process fits a nucleation and growth mechanism involving instantaneous nucleation and 3D growth under charge transfer control. The spatial distribution of pits indicates that there is no marked influence of a pit on the nucleation and growth of other pits.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Synergistic Effects in the Inhibition of Copper Corrosion

Benzotriazole (BTA), thiourea (TU), and potassium ethylxanthate (KEX), behave as copper (Cu) corrosion inhibitors under certain conditions. These chemicals have been investigated to establish whether they provide synergistic effects. The Cu corrosion inhibition was followed through changes in electrochemical characteristics. Cu specimens were tested at 25°C in two aggressive media, 0.1 M NaCl and 1 M NaClO4, using the linear potential sweep technique at 0.001 V s–1 and by scanning electron microscopy of Cu specimens subjected to potentiodynamic and potentiostatic routines. A comparative behavior of the different substances for Cu was presented in the 6.6 ≤ pH ≤ 11 range. For KEX-BTA mixtures, synergistic inhibition effects were found in 0.1 M NaCl (7 ≤ pH ≤ 11). The apparent synergistic inhibition was explained tentatively by an increase in the compactness of the polymer-like passivating layer of KEX-Cu, which formed in the presence of BTA and Cl– ions.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Morphological stabilization and KPZ scaling by electrochemically induced co-deposition of nanostructured NiW alloy films

We have assessed the stabilizing role that induced co-deposition has in the growth of nanostructured NiW alloy films by electrodeposition on polished steel substrates, under pulsed galvanostatic conditions. We have compared the kinetic roughening properties of NiW films with those of Ni films deposited under the same conditions, as assessed by Atomic Force Microscopy. The surface morphologies of both systems are super-rough at short times, but differ at long times: while a cauliflower-like structure dominates for Ni, the surfaces of NiW films display a nodular morphology consistent with more stable, conformal growth, whose height fluctuations are in the Kardar-Parisi- Zhang universality class of rough two-dimensional interfaces. These differences are explained by the mechanisms controlling surface growth in each case: mass transport through the electrolyte (Ni) and attachment of the incoming species to the growing interface (NiW). Thus, the long-time conformal growth regime is characteristic of electrochemical induced co-deposition under current conditions in which surface kinetics is hindered due to a complex reaction mechanism. These results agree with a theoretical model of surface growth in diffusion-limited systems, in which the key parameter is the relative importance of mass transport with respect to the kinetics of the attachment reaction.Facultad de Ciencias Exacta

Roughening kinetics of chemical vapor deposited copper films on Si(100)

The roughening kinetics of copper films synthesized by low pressure chemical vapor deposition (LPCVD) on Si(100) substrates was investigated by scanning tunneling microscopy (STM). By applying the dynamic scaling theory to the STM images, a steady growth roughness exponent α=0.81±0.05 and a dynamic growth roughness exponent β=0.62±0.09 were determined. The value of a is consistent with growth model predictions incorporating surface diffusion. The value of β, while higher than expected from these models, can be related to LPCVD processing conditions favoring growth instabilities.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Morphological stabilization and KPZ scaling by electrochemically induced co-deposition of nanostructured NiW alloy films

We have assessed the stabilizing role that induced co-deposition has in the growth of nanostructured NiW alloy films by electrodeposition on polished steel substrates, under pulsed galvanostatic conditions. We have compared the kinetic roughening properties of NiW films with those of Ni films deposited under the same conditions, as assessed by Atomic Force Microscopy. The surface morphologies of both systems are super-rough at short times, but differ at long times: while a cauliflower-like structure dominates for Ni, the surfaces of NiW films display a nodular morphology consistent with more stable, conformal growth, whose height fluctuations are in the Kardar-Parisi- Zhang universality class of rough two-dimensional interfaces. These differences are explained by the mechanisms controlling surface growth in each case: mass transport through the electrolyte (Ni) and attachment of the incoming species to the growing interface (NiW). Thus, the long-time conformal growth regime is characteristic of electrochemical induced co-deposition under current conditions in which surface kinetics is hindered due to a complex reaction mechanism. These results agree with a theoretical model of surface growth in diffusion-limited systems, in which the key parameter is the relative importance of mass transport with respect to the kinetics of the attachment reaction.Facultad de Ciencias Exacta

Mechanisms of defect generation and clustering in CH 3S Self-assembled monolayers on Au(111)

Periodic density functional calculations probe that step edges play a key role as source of defects during self-assembly. It is shown that the self-assembly process strongly reduces the energy required to strip an atom from the gold surface, locally increasing the concentration of surface defects. The thermodynamic driving force for the atom stripping is considerably more favorable along step-edge lines within the self-assembly than on the higher-coordinated terrace sites. Furthermore, the clustering of surface defects is considered, and we probe that the formation of aggregates of vacancies in the form of vacancy pits significantly stabilizes the self-assembly on the terraces of gold, where the role of the step edges is expected to be less significant. The high stability of pit-like structures arises from a balance between the corrugation and the enhanced bonding of defect-rich substrates. Our results demonstrate the important role that step edges play during assembly and could be very valuable for discovering defect-free assembled structures.Fil: Carro, P.. Universidad de La Laguna; EspañaFil: Torres, D.. Universidad de Barcelona; EspañaFil: Diaz, R.. Instituto IMDEA Energía; EspañaFil: Salvarezza, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Illas, F.. Universidad de Barcelona; Españ

Electrodeposition of gold nanoparticles on aryl diazonium monolayer functionalized HOPG surfaces

Gold nanoparticle electrodeposition on a modified HOPG surface with a monolayer organic film based on aryl diazonium chemistry has been studied. This organic monolayer is electrochemically grown with the use of 2,2-diphenyl-1-picrylhydrazyl (DPPH), a radical scavenger. The electrodeposition of gold on this modified surface is highly favored resulting in an AuNP surface density comparable to that found on glassy carbon. AuNPs grow only in the areas covered by the organic monolayer leaving free clean HOPG zones. A progressive mechanism for the nucleation and growth is followed giving hemispherical AuNPs, homogeneously distributed on the surface and their sizes can be well controlled by the applied electrodeposition potential. By using AFM, C-AFM and electrochemical measurements with the aid of two redox probes, namely Fe(CN)64−/Fe(CN)63− and dopamine, relevant results about the electrochemical modified surface as well as the gold nanoparticles electrodeposited on them are obtained.Fil: Gonzalez, M. C. R.. Universidad de La Laguna; EspañaFil: Orive, A. G.. Universidad de La Laguna; EspañaFil: Salvarezza, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Creus, A. H.. Universidad de La Laguna; Españ

A mechanistic approach to the electroformation of anodic layers on copper and their electroreduction in aqueous solutions containing NaHCO₃ and Na₂ CO₃

The electrochemical behaviour of Cu in solutions containing Na2CO3 + NaHCO3 (8.8 2O layer followed by the growth of a CuO/Cu(OH)2-Cu(HO)3 complex outer layer. Soluble Cu(II) species were detected in the entire anodization potential range . Kinetic models devised for phase change electrochemical processes have been applied to explain the characteristics of anodic and cathodic current transients.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Surface nanopatterning of hard and soft thin films by a replica-molding approach

In this work, we report on our recent results obtained by a replica-molding approach for large-scale surface nanopatterning. Two materials with quite different mechanical properties have been naopatterned, namely: titanium nitride (TiN) films deposited by reactive sputtering and polystyrene films deposited by the casting procedure. In order to explore the capabilities of this strategy we have used in both cases as master surfaces to be replicated silicon surfaces previously nanostructured by low-energy ion-beam sputtering. The original template pattern was formed by an array of silicon lenticular nanodots, 6 nm of average height and 40-50 nm of lateral size, displaying short-range hexagonal order.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada