Sharply defined lateral composition gradients of copper on gold by spatiotemporal control of the in-plane electrochemical potential distribution (original) (raw)
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Physical Review Letters, 2012
Homoepitaxial Cu electrodeposition on Cu(001) in chloride-containing electrolyte was studied by timeresolved in situ surface x-ray diffraction at growth rates up to 38 ML= min. With increasing Cu electrode potential, transitions from step-flow to layer-by-layer and then to multilayer growth are observed. This potential dependence is opposite to that expected theoretically and found experimentally for the Au(001) homoepitaxial electrodeposition [K. Krug et al., Phys. Rev. Lett. 96, 246101 (2006)]. The anomalous behavior is rationalized by a decisive influence of the ordered cð2 Â 2Þ-Cl adlayer on the surface energy landscape, specifically on the effective change in dipole moment during adatom diffusion.
Journal of Applied Electrochemistry, 1996
Electrochemical measurements were carried out simultaneously with acquisition of in situ STM images of copper electrodeposition at low cathodic overpotentials and subsequent dissolution from the underlying polycrystalline gold surfaces. The morphologies of the copper deposits were examined for correlation with features of the current-voltage diagram. Copper growth is by nucleation and formation of 3D islands. During the initial stages of
Electrochemical Cu Growth on MPS-Modified Au(111) Electrodes
The Journal of Physical Chemistry C, 2012
Au(111) electrodes have been modified with selfassembled monolayers (SAM) of 3-mercapto-1-propanesulfonic acid (MPS) and used as a substrate for Cu electrodeposition. Aqueous plating solutions contained 0.1 M H 2 SO 4 , low Cu concentrations (≤80 μM), and, optionally, 1.4 mM Cl ions. The deposition process was characterized by cyclic voltammetry (CV) and in-situ scanning tunneling microscopy (STM) as a function of the electrode potential. At potentials positive of Cu growth (≥0.7 V RHE), freshly modified electrodes are covered by an ordered (5√3 × √21) MPS adlayer (α) both in Cl-free and Cl-containing electrolytes. The α adlayer becomes disordered at more negative potentials prior to the onset of Cu deposition (≤0.65 V RHE). In the potential regime of Cu underpotential deposition (UPD) (≈0.2−0.65 V RHE), the surface morphology strongly depends on the presence of Cl. In the absence of Cl, a transient, ordered Cu/MPS adlayer phase (δ) forms via 2D growth and covers the entire Au(111) surface. Subsequently, the δ phase transforms into a disordered Cu/MPS phase (σ Cu) with small, embedded Cu islands. In Cl-containing electrolyte, a disordered Cu/MPS/Cl phase (γ) nucleates at Au step edges or surface defects and spreads laterally. Cu islands form simultaneously within the γ phase. Two-dimensional growth of these islands results in a pure Cu-UPD layer. Overpotential deposition (OPD) proceeds via layer-by-layer mode with second layer nucleations at surprisingly small critical coverages (θ C ≪ 0.5). Our observations differ significantly from those in previous studies, demonstrating that the Cu growth behavior critically depends on the concentrations of MPS, Cu, and Cl at the interface.
Electrochemical Cu deposition on thiol covered Au(111) surfaces
Surface Science, 1997
The electrochemical deposition of Cu on Au(111) surfaces covered by self-assembled thiol monolayers has been followed in situ by electrochemical STM. Monolayers formed by thiols of different chain length have been chemisorbed on gold electrodes. The thiol molecules are organized in a quasi-crystalline structure characterized by a multi-domain ordering. The presence of the organic layer strongly influences the Cu deposition process. Cyclovoltammetry shows the absence of the underpotential deposition peaks observed on bare gold as well as a decrease of the electrochemical current in the overpotential regime. Independently of the chain length, in the UPD region we observe the formation of Cu nanoparticles 2–5 nm in diameter, one Cu atomic layer in height, uniformly distributed at the surface. The Cu cluster density reaches its maximum in the UPD regime. In the OPD region a chain length dependent behaviour is observed. Long thiol monolayers prevent any further growth of already existing clusters while on short thiol covered surfaces an almost 2D growth of Cu is observed.
Surface Science, 2012
During selective etching (dealloying) surface-sensitive X-ray diffraction employing Synchrotron light has been used to in-situ monitor the potential-controlled formation of Au-rich films on the surface of Cu 3 Au (111) in iodide-containing electrolytes. Similar to the case in pure sulfuric acid we observed a sequence of structural transformations starting from a well-prepared pristine surface to a porous film consisting of substrateoriented Au ligaments. Also stacking-reversed ultrathin Au-rich films and Au islands form as intermediate steps but no passive-like behavior was observed in iodide-containing electrolytes, i.e. the surface quickly developed Au ligaments after reaching the Cu dissolution potential. At low overpotentials comparatively coarse Au islands point to a higher mobility of Au/electrolyte interfaces in iodide-containing solutions. At higher overpotentials and also with higher iodide concentrations an epitaxial Cu-iodide precipitate film showed an orientation relation of CuI (111) || CuAu (111) and two azimuthal domains ofb −2, 2, 0 > ||b −2, 2, 0 > and b −2, 2, 0 > || b 2, −2, 0>. This partially dissolution-inhibiting bulk CuI layer is observed to produce a bimodal pore size instead of usually obtained homogeneous porosity. The X-ray data and supporting ex-situ AFM and SEM images show marked differences in the morphology and connectivity of the forming nanoporous Au layer. Precipitation layers are thus suggested to provide means for controlling the nanoporosity for applications of dealloyed films and surfaces.
Surface Science, 1987
High resolution electron microscopy studies of the oxidation of vapor deposited Cu (< 30/~) on thin single crystal Au films are reported. The metal/metal and oxide/metal orientation relationships are obtained for both the diffraction and imaging modes, before and after the Cu oxidation is significant. For the oxidized overlayers, two cases are observed: Cu(lll) which transforms to three Cu20(110) variants and Cu(ll0) transforming to (211) oxide overgrowth. A lateral displacement of the top Cu layer in the (110) stacking sequence is detected in the first case and atomic layering is observed in the 6-layer lattice structure of the Cu20(211) orientation.
Surface Science, 1984
In the course of studies on the initial stages of electrochemical deposition of alloys, we sought a technique that would determine both the location and the composition of clusters consisting of only a few atoms. We utilized the only technique that is capable of sufficient resolution and sensitivity to solve this particular problem, the combination of field ion microscope (FIM) and imaging atom probe (lAP). For our first experiments we studied the underpotential deposition of Cu on Pt, since the electrochemical behavior of this deposition is well known [1-8] and because Cu should be easy to detect. In addition, Pt gives very sturdy and regular images in the FIM lAP used for the present studies.
Interface dynamics for copper electrodeposition: The role of organic additives in the growth mode
2002
An atomistic model for Cu electrodeposition under nonequilibrium conditions is presented. Cu electrodeposition takes place with a height-dependent deposition rate that accounts for fluctuations in the local Cu 2ϩ ions concentration at the interface, followed by surface diffusion. This model leads to an unstable interface with the development of protrusions and grooves. Subsequently the model is extended to account for the presence of organic additives, which compete with Cu 2ϩ for adsorption at protrusions, leading to a stable interface with scaling exponents consistent with those of the Edwards-Wilkinson equation. The model reproduces the interface evolution experimentally observed for Cu electrodeposition in the absence and in the presence of organic additives.
Physical Review Letters, 1998
The lateral extension of electrochemically induced surface modifications is usually determined by the macroscopic size of the electrodes and the diffusion length of the reacting species. To overcome this constraint, we conducted an electrochemical reaction far from equilibrium. We applied short voltage pulses (#100 ns, up to 64 V) to a scanning tunneling microscope tip while imaging a Au(111) surface in concentrated electrolytes. They lead either to hole formation by anodic dissolution of the Au or to cathodic deposition of Cu islands (in the Cu 21 containing electrolyte), both of nanometer extension. [S0031-9007(98)