Ag/AgCl/KCl micro-electrodes as O2-insensitive reference tips for dynamic scanning Kelvin probe measurement

Ehahoun, H.; Stratmann, M.; Rohwerder, Michael

doi:10.1016/j.electacta.2004.11.011

Cited by 10 publications

(7 citation statements)

References 17 publications

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“…The measured CPD values show a variation of almost 0.20 V between different alloys in the Hf–Nb–Ta system. This variation is significantly larger than the normal CPD noise of approximately ±5 mV measured above a homogeneous metallic surface [35,36]. The Volta potential of individual alloys across the library depends mainly on the Hf concentration.…”

Section: Resultsmentioning

confidence: 99%

Basic properties mapping of anodic oxides in the hafnium–niobium–tantalum ternary system

Mardare

Kollender

et al. 2018

Science and Technology of Advanced Materials

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A thin film combinatorial library deposited by co-sputtering of Hf, Nb and Ta was employed to characterise fundamental properties of the Hf-Nb-Ta system. Compositional mappings of microstructure and crystallography revealed similarities in alloy evolution. Distinct lattice distortion was observed upon addition of hexagonal Hf, leading to amorphisation of alloys containing more than 32 at.% Hf and less than 27 and 41 at.% Nb and Ta, respectively. Volta potential and open circuit potential mappings indicated minimal values for the highest Hf concentration. Localised anodisation of the library by scanning droplet cell microscopy revealed valve metal behaviour. Oxide formation factors above 2 nm V−1 were identified in compositional zones with high amounts of Nb and Ta. Fitting of electrochemical impedance spectroscopy data allowed electrical permittivity and resistivity of mixed oxides to be mapped. Their compositional behaviours were attributed to characteristics of the parent metal alloys and particularities of the pure oxides. Mott–Schottky analysis suggested n-type semiconductor properties for all Hf–Nb–Ta oxides studied. Donor density and flat-band potential were mapped compositionally, and their variations were found to be related mainly to the Nb amount. Synergetic effects were identified in mappings of Hf-Nb-Ta parent metals and their anodic oxides.

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Section: Resultsmentioning

confidence: 99%

Basic properties mapping of anodic oxides in the hafnium–niobium–tantalum ternary system

Mardare

Kollender

et al. 2018

Science and Technology of Advanced Materials

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“…Initially the SKP was commonly calibrated against a Cu/Cu 2+ reference electrode in humid air (rh ≈ 95%). Then the three reference electrodes, Cu/CuSO 4 , Ag/AgCl/KCl (referring to ref ), and Ag/AgCl/KCl/Paraffin were measured alternatingly in a long-term measurement while changing the atmospheric conditions. First the measurements were realized with a bare SKP-tip (Figure a–c), and then the same samples were measured at the same locations with a paraffin coated SKP-tip (Figure d,e).…”

Section: Results and Discussionmentioning

confidence: 99%

“…Ehahoun et al have described the fabrication of a Ag/AgCl/KCl SKP-tip, extending the earlier work of Atanasoski et al The presented reference tips for the use in Kelvin probe applications are based on Ag/AgCl and especially insensitive for O 2 adsorption (see ref ) and have been evaluated for relative humidity (rh) between 40% and ∼100% (see ref ).…”

Section: Introductionmentioning

confidence: 90%

“…The samples were polarized first at −0.1 V vs Ag/AgCl for 30 s and subsequently at +0.1 V vs Ag/AgCl for 120 s using a Solatron Schlumberger 1286 potentiostat. The samples polarized in 1 M KCl electrolyte solution were just dried carefully under a nitrogen stream after removal in order to form KCl crystals on the surface (according to ref ). The paraffin coatings were produced as described for the stainless steel samples, but the Ag surface was connected with a piece of copper tape (one-sided sticky, purchased from Plano GmbH) before.…”

Section: Methodsmentioning

confidence: 99%

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Fabrication of Robust Reference Tips and Reference Electrodes for Kelvin Probe Applications in Changing Atmospheres

et al. 2017

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The scanning Kelvin probe (SKP) is a versatile method for the measurement of the Volta potential difference between a sample and the SKP-tip (Δψ). Based on suitable calibration, this technique is highly suited for the application in corrosion science due to its ability to serve as a very sensitive noncontact and nondestructive method for determining the electrode potential, even at buried interfaces beneath coatings or on surfaces covered by ultrathin electrolyte layers, which are not accessible by standard reference electrodes. However, the potential of the reference (i.e., the SKP-tip) will be influenced by variations of the surrounding atmosphere, resulting in errors of the electrode potential referred to the sample. The objective of this work is to provide a stable SKP-tip which can be used in different or changing atmosphere, e.g., within a wide range of relative humidity (approximately 0-99%-rh) or varying O partial pressure, without showing a change of its potential (note that the work functions measured in non-UHV atmospheres are electrochemical in nature [Hausbrand et al. J. Electrochem. Soc. 2008, 155 (7), C369-C379], and hence in the following we will refer to the potential of the SKP-tip instead of its work function). In that regard, the SKP-tip is in a first approach modified with self-assembled monolayers (SAMs) in order to create a hydrophobic barrier between the metallic surface and the surrounding atmosphere. The changes in potential upon varying relative humidity (ΔE) of different bare metallic substrates are quantified, and it is shown that these potential differences cannot be minimized by SAMs. On the contrary, the ΔE increases for every examined material system modified with SAMs. The major explanation for this observation is the dipole layer at the interface metal|SAM, causing an interfacial adsorption of water molecules even in a preferred orientation of their dipole moments, which leads to a changed work function and consequently to the correlated electrode potential. However, thin paraffin coatings were found to lead to a strongly reduced ΔE, finally validated with novel robust Ag/Ag reference electrodes. It is also shown that nickel as SKP-tip material is seemingly more stable in varying atmospheric conditions compared to widely used Ni/Cr, stainless steel, or gold as SKP-tip material.

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“…Thus, gold, platinum, and chromium-nickel have often been selected as pseudo-REs 17,18 because these metals do not corrode. However, their electrode potential is influenced by external environmental conditions, 19 which is problematic because a stable potential is very important for the RE during electrochemical measurements. To accurately measure the electrode potentials during atmospheric corrosion, several types of miniaturized REs have been developed.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Electrochemical Corrosion of Copper under a Micrometric Electrolyte Droplet Using a Three-Electrode System

Qing-Li¹,

中国石油化工有限公司青岛安全工程研究院²,

Zhang³

et al. 2015

Acta Physico-Chimica Sinica

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Owing to its high impedance, studying atmospheric corrosion using a traditional reference electrode (RE) is difficult. To obtain more accurate information on the electrochemical processes involved in atmospheric corrosion, it is necessary to improve the traditional RE. In this paper, the corrosion behavior of copper under an electrolyte droplet containing (NH4)2SO4 was investigated by electrochemical impedance spectroscopy (EIS) and polarization measurements using a three-electrode system with a modified RE. The average corrosion rate increased with decreasing electrolyte volumes (from 1 to 20 μL) and with decreasing heights of the droplet at heights below 850 μm. The EIS and polarization results were in agreement, thereby demonstrating that the modified RE could be effectively used to study atmospheric corrosion under an electrolyte droplet.

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Ag/AgCl/KCl micro-electrodes as O2-insensitive reference tips for dynamic scanning Kelvin probe measurement

Cited by 10 publications

References 17 publications

Basic properties mapping of anodic oxides in the hafnium–niobium–tantalum ternary system

Basic properties mapping of anodic oxides in the hafnium–niobium–tantalum ternary system

Fabrication of Robust Reference Tips and Reference Electrodes for Kelvin Probe Applications in Changing Atmospheres

Investigation of the Electrochemical Corrosion of Copper under a Micrometric Electrolyte Droplet Using a Three-Electrode System

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