High-Resolution Electrochemical Scanning Tunneling Microscopy (EC-STM) Flow-Cell Studies

Lay, Marcus D.; Sorenson, Thomas A.; Stickney, John L.

doi:10.1021/jp0358782

Cited by 13 publications

(17 citation statements)

References 35 publications

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“…In-situ scanning tunneling microscopy studies were performed using a Nanoscope III (Digitial Instruments, Veeco), equipped with W tips that were electrochemically etched (15 V ac in 1 M KOH) from 0.25 mm wires. The tip was coated with transparent nail polish to minimize faradaic currents from the tip sides. , The electrodes used were gold single-crystal beads made in-house using a variation of the Clavilier method. , Imaging was performed on one of the resulting large Au(111) planes. Experiments were begun with a clean Au(111) surface in a H 2 GeO 3 solution (depending on the pH) at a potential positive of H 2 GeO 3 reduction.…”

Section: Methodsmentioning

confidence: 99%

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Aqueous Electrodeposition of Ge Monolayers

et al. 2009

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The electrodeposition of germanium on Au(111) in aqueous solutions has been investigated by means of cyclic voltammetry, Auger electron spectroscopy, and in situ scanning tunneling microscopy (STM). The data yield a picture of germanium deposition, which starts with the formation of two well-ordered hydroxide phases, with 1/3 ML and 4/9 ML coverages upon initial reduction of the Ge(IV) species (probably H(2)GeO(3) at pH 4.7). Those structures appear to result from a three-electron reduction to form surface-limited structures with (square root(3) x square root(3))R30 degrees or (3 x 3) unit cells, respectively. Further reduction, probably in a two-electron process from the hydroxide structures, resulted in a germanium hydride structure, again surface-limited, with a coverage of close to 0.8 ML. The hydride structure is very flat, though with the periodic modulation characteristic of a Moiré pattern. Longer deposition times and lower potentials resulted in increased coverage of Ge in some cases, but with apparently limited coverage as a function of pH. The maximum Ge coverage, about 4 ML, was observed using a pH 9.32 deposition solution. At potentials negative of the Moiré pattern, about -850 mV versus Ag/AgCl, a "corruption" of the smooth Moiré pattern occurred. This roughening appears to mark the initial formation of a Au-Ge alloy, accounting for the observation of coverage in excess of that needed to form the Moiré pattern at some pH values.

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Section: Methodsmentioning

confidence: 99%

“…The tip was coated with transparent nail polish to minimize faradaic currents from the tip sides. 33,41 The electrodes used were gold single-crystal beads made in-house using a variation of the Clavilier method. 42,43 Imaging was performed on one of the resulting large Au(111) planes.…”

Section: Methodsmentioning

confidence: 99%

Aqueous Electrodeposition of Ge Monolayers

et al. 2009

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“…A single peristaltic pump (0.9 mL/min) was used to maintain equivalent flow rates in and out of the cell, ensuring a constant solution level, as previously described. 9,35 The supporting electrolyte contained 0.05 M doubly distilled H 2 SO 4 (Aldrich Chemicals, Milwaukee, WI) in 18 MΩ-cm water. The Pd solution consisted of 0.1 mM ultrapure-grade PdCl 2 (Aldrich Chemicals) in 50 mM HCl.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Hydrogen Adsorption, Absorption, and Desorption at Palladium Nanofilms formed on Au(111) by Electrochemical Atomic Layer Deposition (E-ALD): Studies using Voltammetry and In Situ Scanning Tunneling Microscopy

et al. 2013

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Pd nanofilms were grown on Au(111) using the electrochemical form of atomic layer deposition (E-ALD). Deposits were formed by repeated cycles of surface-limited redox replacement (SLRR). Each cycle produced an atomic layer of Pd, allowing the reproducible formation of Pd nanofilms, with thicknesses proportional to the number of cycles performed. Pd deposits were formed with up to 30 cycles, in the present study, and used as a platform for studies of hydrogen sorption/desorption as a function of thickness. The SLRR cycle involved the initial formation of an atomic layer of Cu by underpotential deposition, followed by its galvanic exchange with PdCl4 2– ions at open circuit. The first three cycles were studied using in situ electrochemical scanning tunneling microscopy (EC-STM), which showed a consistent morphology from cycle to cycle and the monatomic steps indicative of layer-by-layer growth. Cyclic voltammetry was used to study the hydrogen sorption/desorption properties as a function of thickness in 0.1 M H2SO4. The results indicated that the underlying Au structure greatly influenced hydrogen adsorption, as did film thickness for deposits formed with fewer than five cycles. No hydrogen absorption occurred for the thinnest films, although it increased linearly for thicker films, producing an average H/Pd molar ratio of 0.6. Electrochemical annealing was shown to improve surface order, producing CVs that strongly resembled those characteristic of bulk Pd(111).

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“…For the STM studies, Au single crystal beads were formed using the method developed by Clavilier [23], and imaging was performed on one of the resulting large (1 1 1) planes of the single crystal bead. The electrochemical cell was designed to allow solution to pass over the electrode so that the solutions could be exchanged without loss of potential control during imaging [24].…”

Section: Methodsmentioning

confidence: 99%