Band structure effects in Auger neutralization of He ions at metal surfaces

Goebl, D.; Valdés, Diego; Abad, E.; Monreal, R.; Primetzhofer, Daniel; Bauer, Péter

doi:10.1103/physrevb.84.165428

Cited by 21 publications

(27 citation statements)

References 52 publications

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“…This behavior indicates that in this regime, neutralization is exclusively due to Auger neutralization (AN). The characteristic velocity v c is significantly higher for Pt (220.000 m/s) than for Ag (140.000 m/s); this can be understood as a band structure effect in Auger neutralization [28]. For Pt, E th is considerably lower than for Ag, i.e., 700 eV for Pt, compared to 1200 eV for Ag.…”

Section: Resultsmentioning

confidence: 95%

Role ofdelectrons in electronic stopping of slow light ions

2013

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In recent energy loss measurements, band structure effects in electronic stopping have been observed for materials with finite excitation thresholds, for example, noble metals such as Cu and Au. To further investigate the influence of the position of the d band relative to the Fermi edge, electronic stopping of hydrogen and helium ions in Ag and Pt was determined. For Ag, the electronic stopping power exhibits a velocity dependence similar to Cu and Au. No particular effect due to the comparatively large d-band offset in Ag is found. In the case of Pt, the electronic stopping power is virtually velocity proportional for H + ions and exhibits a distinct velocity dependence for He + ions. For hydrogen the results are compatible with modeling the conduction band as a free electron gas with an energy-dependent effective number of electrons. For He + , however, the observed effects point towards an additional energy loss mechanism, e.g., by charge-exchange processes.

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Section: Resultsmentioning

confidence: 95%

Role ofdelectrons in electronic stopping of slow light ions

2013

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“…Several such calculations have been performed for jellium-model wave functions, but this approach would in turn not provide a good description for a semiconductor, nor does it allow us to include the electronic structure of the chosen surface. Gloebl et al [21,22] and Valdès et al [23] did calculate the Auger neutralization rate by considering the matrix elements for the neutralization using a linear combination of atomic orbitals (LCAO) and various distances and positions of an incoming He + ion on several metals and Ge. The electronic response of the surface was modeled using the response function, once again calculated from the jellium model.…”

Section: A Hagstrum's Modelmentioning

confidence: 99%

Quantitative modeling of secondary electron emission from slow-ion bombardment on semiconductors

2019

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When slow ions incident on a surface are neutralized, the excess potential energy is passed on to an electron inside the surface, leading to emission of secondary electrons. The microscopic description of this process, as well as the calculation of the secondary electron yield, is a challenging problem due to its complexity as well as its sensitivity to surface properties. One of the first quantitative descriptions was articulated in the 1950s by Hagstrum, who based his calculation on a parametrization of the density of states of the material. In this paper, we present a model for calculating the secondary electron yield, derived from Hagstrum's initial approach. We use first-principles density functional theory calculations to acquire the necessary input and introduce the concept of electron cascades to Hagstrum's model in order to improve the calculated spectra, as well as remove its reliance on fitting parameters. We apply our model to He + and Ne + ions incident on Ge(111) and Si(111) and obtain yield spectra that match closely to the experimental results of Hagstrum.

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“…Fig. 13 shows the Auger rates for He on Cu(111), Ag (111) and Au(111) surfaces on-top position [140,141]. The qualitative behavior of the three metals is very similar.…”

Section: Results: Noble Metal Surfacesmentioning

confidence: 94%

“…29 ion fractions for three crystal orientations of Cu are compared [140]. In the simulations, the He level was set to -20.5 eV with respect to the Fermi level which results in almost perfect agreement with the experimental data for the polycrystalline surface.…”

Section: Leis Regimementioning

confidence: 88%

Auger neutralization and ionization processes for charge exchange between slow noble gas atoms and solid surfaces

Monreal

2014

Progress in Surface Science

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Electron and energy transfer processes between an atom or molecule and a surface are extremely important for many applications in physics and chemistry. Therefore a profound understanding of these processes is essential in order to analyze a large variety of physical systems. The microscopic description of the two-electron Auger processes, leading to neutralization/ionization of an ion/neutral atom in front of a solid surface, has been a long-standing problem. It can be dated back to the 1950s when H. D. Hagstrum proposed to use the information contained in the spectrum of the electrons emitted during the neutralization of slow noble gas ions as a surface analytical tool complementing photoelectron spectroscopy. However, only recently a comprehensive description of the Auger neutralization mechanism has been achieved by the combined efforts of theoretical and experimental methods. In this article we review the theoretical models for this problem, stressing how their outcome compare with experimental results. We also analyze the inverse problem of Auger ionization. We emphasize the understanding of the key quantities governing the processes and outline the challenges remaining. This opens new perspectives for future developments of theoretical and experimental work in this field.

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Band structure effects in Auger neutralization of He ions at metal surfaces

Cited by 21 publications

References 52 publications

Role ofdelectrons in electronic stopping of slow light ions

Role ofdelectrons in electronic stopping of slow light ions

Quantitative modeling of secondary electron emission from slow-ion bombardment on semiconductors

Auger neutralization and ionization processes for charge exchange between slow noble gas atoms and solid surfaces

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