Migration of point defects at charged Cu, Ag, and Au (100) surfaces

Müller, J. E.; Ibach, H.

doi:10.1103/physrevb.74.085408

Cited by 35 publications

(33 citation statements)

References 28 publications

(37 reference statements)

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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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confidence: 99%

Thiolate‐Induced Metal Adatom Trapping at Solid–Liquid Interfaces

2012

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“…For the adatom dipole moment, we use 0.05 eÅ. This is less than the 0.2 eÅ for a tungsten adatom on the most densely packed tungsten plane ͑110͒, reported by Besocke and Wagner, 19 and also smaller than the ϳ0.1 eÅ calculated by Müller and Ibach 16 for the ͑100͒ planes of the fcc materials Au, Cu, and Ag, which also have a higher packing density than the ͑100͒ plane of the bcc structure of tungsten. For W͑110͒, step line tension data are available 20 and range from 0.1 to 0.3 eV/ Å depending on the step orientation.…”

Section: Application To Schottky Emittersmentioning

confidence: 89%

“…Key to this approach is the change in the local charge density at the surface upon the creation of an adatom. 16 The charge redistribution induced by an adatom can be characterized with a dipole moment p and it changes the work function of the surface:…”

Section: Step Model Including the Effect Of An Extraction Voltagementioning

confidence: 99%

Effect of the electric field on the form stability of a Schottky electron emitter: A step model

Bronsgeest

Kruit

2008

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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The stability of the physical shape of an electron emitter ͑co͒determines the stability of the performance of electron-beam equipment. A typical short-term instability of the Schottky electron source is the instability of the ͑100͒ facet at the tip end known as "collapsing rings." This instability causes probe instabilities, but it is known from experiments that this can be prevented by applying high enough extraction voltages. The phenomenon of collapsing rings can be explained with a step-flow model, which is based on variations in equilibrium concentrations of adatoms on the surface. The effect of the extraction voltage can be incorporated by acknowledging the redistribution of the surface charge associated with adatom formation. For operation at constant extraction voltages the adatom formation energy becomes a function of the local charge density. The charge-density distribution on the emitter surface as a function of the applied extraction voltage can be calculated with boundary-element methods. It is shown that, provided the relevant material properties are known, it can be predicted if, for a given tip shape, a collapse is to be expected.

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“…However, simulations by Feibelman on Al(100) [2] as well as Yu and Scheffler on Au(100) [3] indicated that on both surfaces exchange diffusion is the predominant process for migration along terraces. The case of Au(100) has been reconsidered by Müller and Ibach, [4] who concluded that on an uncharged surface both mechanisms occur with comparable frequency.…”

Section: Introductionmentioning

confidence: 97%

Self‐Diffusion on Au(100): A Density Functional Theory Study

2010

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We used density functional theory to detail new self-diffusion mechanisms on perfect and imperfect Au(100) surfaces. Herein, we report binding energies of stable intermediates and transition states lying on the potential energy surface for these systems. We report migration pathways in the presence of a variety of surface defects and along different step edges, explaining their energetics in terms of chemical bonding. Furthermore, diffusion rate constants are deduced, which are useful for both experimental verification and for implementation into large-scale kinetic Monte Carlo simulations.

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Migration of point defects at charged Cu, Ag, and Au (100) surfaces

Cited by 35 publications

References 28 publications

Thiolate‐Induced Metal Adatom Trapping at Solid–Liquid Interfaces

Thiolate‐Induced Metal Adatom Trapping at Solid–Liquid Interfaces

Effect of the electric field on the form stability of a Schottky electron emitter: A step model

Self‐Diffusion on Au(100): A Density Functional Theory Study

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