In-situ STM study of the initial stages of corrosion of Cu(100) electrodes in sulfuric and hydrochloric acid solution

Vogt, Monika; Lachenwitzer, A.; Magnussen, Olaf M.; Behm, R. J.

doi:10.1016/s0039-6028(97)00811-x

Cited by 205 publications

(149 citation statements)

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“…It has been reported for chlorine adlayers under UHV conditions [18][19][20][21][22][23][24][25] as well as in chloride-containing electrolytes. 6,7,[26][27][28][29][30][31] However, at the electrochemical interface the c͑2 ϫ 2͒ structure was observed only positive of a critical potential ͑−0.4 V Ag/AgCl at a Cl concentration of 10 −3 M͒ by in situ STM, whereas at more negative potentials the ͑1 ϫ 1͒ substrate lattice was visible, suggesting a potential-induced order-disorder phase transition into a dilute adlayer of highly mobile chloride. 28,30 More recently, the surface-normal interface structure of the c͑2 ϫ 2͒ adlayers of Cl and Br on Cu͑001͒ was studied by in situ SXRD, focusing on the halide-copper interlayer spacing.…”

Section: Introductionmentioning

confidence: 96%

Reversal of chloride-induced Cu(001) subsurface buckling in the electrochemical environment: Anin situsurface x-ray diffraction and density functional theory study

et al. 2010

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The interface of Cu͑001͒ electrode surfaces in 10 mM HCl solution was studied by in situ surface x-ray diffraction and density functional theory, focusing on the precise structure of the c͑2 ϫ 2͒ Cl adlayer formed at positive potentials. Crystal truncation rod measurements in this adsorbate phase at a potential of −0.20 V Ag/AgCl reveal distinct differences to corresponding data by Tolentino et al. ͓Surf. Sci. 601, 2962 ͑2007͔͒ for the c͑2 ϫ 2͒ Cl structure formed at the Cu͑001͒-vacuum interface. Although in both environments, the atoms in the second Cu layer exhibit a small vertical corrugation, the sign of this corrugation is reversed. Furthermore, also the Cu-Cl bond distance and the average Cu interlayer spacings at the surface differ. Ab initio calculations performed for this adsorbate system reproduce these effects-specifically the reversal of the subsurface second-layer buckling caused in the presence of coadsorbed water molecules and cations in the outer part of the electrochemical double layer. In addition, studies at more negative potentials reveal a continuous surface phase transition to a disordered Cl adlayer at −0.62 V Ag/AgCl , but indicate a substantial Cl coverage even at the onset of hydrogen evolution.

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Section: Introductionmentioning

confidence: 96%

Reversal of chloride-induced Cu(001) subsurface buckling in the electrochemical environment: Anin situsurface x-ray diffraction and density functional theory study

et al. 2010

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“…We have focused on the potential range in which the Cu surface is covered by the well-known c(22) chloride adsorbate layer, [16][17][18] where the adsorbate motion was sufficiently low to be observed directly. After describing our method of preparing Cu(100) electrodes with the required, low S ad coverage and demonstrating that the dynamic behavior of these adsorbates is not significantly altered by the STM measurement, we describe the tracer diffusion of isolated S ad in the undistorted c (22) adlayer and the influence of the S ad ÀS ad interactions on the adsorbate dynamics.…”

Section: Introductionmentioning

confidence: 99%

In Situ Video‐STM Studies of Adsorbate Dynamics at Electrochemical Interfaces

2010

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The dynamic behavior of individual adsorbates at electrochemical interfaces was studied directly by in situ high-speed scanning tunneling microscopy, using sulfur adsorbed on Cu(100) electrodes in 0.01 M HCl solution as an example. By dosing from diluted Na(2)S solutions S(ad) coverages of a few percent can be prepared, with the sulfur adsorbates occupying positions within the c(2x2) lattice of coadsorbed chloride. S(ad) tracer diffusion occurs via hopping between neighboring c(2x2) lattice sites at considerably higher rates than those of sulfur on Cu(100) under UHV conditions, indicating a pronounced influence of the electrochemical environment on the adsorbate surface dynamics. The diffusion barrier linearly increases by 0.5 eV per V with potential and is strongly affected by neighboring S(ad) and surface defects. The S(ad)-S(ad) interactions extend over approximately 7 A. They are repulsive between nearest-neighbor and attractive between next-nearest-neighbor sites, respectively, and result in significantly reduced diffusion barriers. S(ad) on the upper terrace side of steps are transiently trapped and exhibit lower diffusion rates, leading to the formation of small metastable p(2x2) domains. Attractive interactions between S(ad) and domain boundaries in the c(2x2) adlayer result in boundary pinning as well as transient trapping and enhanced diffusion of S(ad) along the boundary.

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“…To assess the effect of the potential f in the second case, we consider the adatom formation energy, which has a potential-dependent electrostatic contribution of p Z e 0 À1 C d f, where C d is the differential capacitance and p Z the dipole moment of the metal adatom. [14] Using p Z = 0.092 e , calculated for Cu adatoms on bare Cu(100) [15] and C d = 25 mC cm À2 , [16] this energy contribution is 0.26 eV V À1 . The corresponding change in the Cu ad surface concentration for a potential increase Df is exp (p Z e 0 À1 C d Df/ k B T), which would result in a 125 % increase for Df = 80 mV at room temperature.…”

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confidence: 99%

Thiolate‐Induced Metal Adatom Trapping at Solid–Liquid Interfaces

2012

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Organosulfur compounds, in particular thiolates, are one of the most important classes of surface-active species and have very diverse applications. On the one hand, they are extensively employed in molecular self-assembly, for which they may be considered as the archetypal system, with wide ranging applications in nanoscience (for example molecular electronics, immobilization of biomolecules, and stabilization of nanoparticles). [1][2][3] On the other hand, organosulfur species have been empirically developed and used as additives for a long time in various areas of chemical engineering, including corrosion inhibition and modern galvanic plating, such as the damascene plating process used for the formation of copper interconnects on ultra large-scale integrated microchips. [4] While the structure of ordered self-assembled thiolate monolayers has been studied in great detail, [1][2][3] much less is known on thiolate adsorbates at low surface coverage, where these species are highly mobile on the metal surface at room temperature. Clarifying the dynamic behavior of thiolates in the low-coverage regime is of great importance for understanding the elementary mechanisms of both molecular selfassembly as well as their influence on the surface chemistry in additive applications, where the surface coverages likewise are often well below saturation densities. Atomic-scale studies of thiolates at low coverage, performed in ultrahigh vacuum (UHV) at cryogenic temperatures, revealed a much more complex behavior than previously anticipated, involving pronounced interactions with metal adatoms. [5][6][7] Herein,we present studies on the surface dynamics at solid-liquid interfaces and room temperature; that is, under conditions typically employed in applications, for the most simple organosulfur adsorbate, methyl thiolate, on Cu(100) electrode surfaces in 0.01m HCl solution. The use of this system not only is interesting in view of the importance of thiol-bound species in an electrochemical environment (for example in copper electroplating), but also allows the dynamic behavior to be influenced by the applied potential, thus providing additional information on the molecular mechanisms. As will be shown by our quantitative in situ high-speed scanning tunneling microscopy (video-STM) studies, interactions with metal adatoms also play a significant role under these conditions, which may have important implications for the surface chemistry of these species.In the studied potential range, the chloride coadsorbate forms a well-ordered square c(22) lattice on the Cu(100) electrode surface (lattice spacing a 0 = 3.6 ), which is clearly visible in high-resolution STM images. [8,9] Upon addition of dimethyl disulfide to the solution, distinct isolated adsorbates gradually emerge on the surface, which occupy sites of the c(22) lattice (Figure 1 a). Based on their small size and their similar appearance in the STM images as adsorbed sulfide, [10,11] these species are identified as methyl thiolate adsorbates (CH 3 S ad ), formed by dissoc...

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In-situ STM study of the initial stages of corrosion of Cu(100) electrodes in sulfuric and hydrochloric acid solution

Cited by 205 publications

References 50 publications

Reversal of chloride-induced Cu(001) subsurface buckling in the electrochemical environment: Anin situsurface x-ray diffraction and density functional theory study

Reversal of chloride-induced Cu(001) subsurface buckling in the electrochemical environment: Anin situsurface x-ray diffraction and density functional theory study

In Situ Video‐STM Studies of Adsorbate Dynamics at Electrochemical Interfaces

Thiolate‐Induced Metal Adatom Trapping at Solid–Liquid Interfaces

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