The first stages of oxide growth at the low index Al surfaces (100), (110), (111): clusters and stripes <i>vs.</i> homogeneous growth

Lousada, Cláudio M.; Korzhavyi, Pavel A.

doi:10.1039/c8cp04519d

Cited by 8 publications

(3 citation statements)

References 60 publications

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“…2 ) shows that with increasing number of H-atoms, absorption sites that were initially preferred for single H-atom are no longer preferred when more H-atoms are in the vicinity, and vice versa. This is due to neighboring or cooperative effects and has been previously observed for H at Cu GBs and H and other atoms at Al surfaces 37 , 79 , 80 . These cooperative neighboring effects are known to occur for some adsorbates at surfaces and depending on geometric and electronic structure effects can lead to either weaker or stronger adsorption with increasing coverage 81 .…”

Section: Resultssupporting

confidence: 64%

Hydrogen at symmetric tilt grain boundaries in aluminum: segregation energies and structural features

Lousada

Korzhavyi

2022

Sci Rep

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Aluminum is envisioned to be an important material in future hydrogen-based energy systems. Here we report an ab initio investigation on the interactions between H-atoms and common grain boundaries (GBs) of fcc Al: Σ9, Σ5, Σ11 and Σ3. We found that upon segregation to the GBs, single H-atoms can cause displacement of Al-atoms. Increasing their concentration revealed large cooperative effects between H-atoms that favor the segregation when other H-atoms are bound at neighboring sites. This makes these GBs able to accommodate high concentrations of H-atoms with considerable segregation energies per atom. Structural analyses derived from Laguerre–Voronoi tessellations show that these GBs have many interstitial sites with higher symmetry than the bulk tetrahedral interstitial site. Many of those sites have also large volumes and higher coordination numbers than the bulk sites. These factors are the increased driving force for H-atom segregation at the studied GBs in Al when compared to other metals. These GBs can accommodate a higher concentration of H-atoms which indicates a likely uniform distribution of H-atoms at GBs in the real material. This suggests that attempting to mitigate hydrogen uptake solely by controlling the occurrence of certain GBs may not be the most efficient strategy for Al.

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Section: Resultssupporting

confidence: 64%

Hydrogen at symmetric tilt grain boundaries in aluminum: segregation energies and structural features

Lousada

Korzhavyi

2022

Sci Rep

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“…They extended our knowledge down to the “atomistic” level for the mechanisms involved during oxidation. (See, for example, refs − for the specific case of Al oxidation.) Nevertheless, modern theoretical works aim to bridge the gap with the key parameters of the CM model.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, gas-phase oxidation studies have greatly benefitted from implementing in situ, real-time techniques such as NAP-XPS. − As a prerequisite to XPS measurements, we first had to clarify the model’s thermodynamic grounds and discriminate what spectroscopic proxies should be monitored. We have considered Al oxidation in O 2 because of its historical role in establishing the oxidation models ,, and because it keeps attracting considerable attention both experimentally − and theoretically. ,,− ,, Aluminum is also the material of choice in the fabrication of Josephson junction qubits, for which the oxidation of the metal is a vital issue . The Al/AlO x /Al junctions are often fabricated by exposing the metallic surface to O 2 (at room temperature in the mbar range) .…”

Section: Introductionmentioning

confidence: 99%

Testing the Cabrera–Mott Oxidation Model for Aluminum under Realistic Conditions with Near-Ambient Pressure Photoemission

et al. 2022

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Using the nascent band theory of solids, Cabrera and Mott designed in the late 1940s a model for the lowtemperature oxidation of metals that still stands today as a landmark. The core assumption is that an electric field set up in the growing oxide at thermodynamic equilibrium drives the transport of the ionic species responsible for the oxidation process. The existence of an electrostatic potential has long been sought experimentally by in situ measurement of the work function changes in the presence of gaseous O 2 . Here, we demonstrate that the work function measurement is insufficient to test the model. Instead, the oxide band structure characteristics (surface dipole energy barrier and band bending) should be followed. We exemplify this for the paradigmatic case of the Al(111) surface oxidation at room temperature using near-ambient pressure X-ray photoemission spectroscopy (operated up to a pressure of 1 mbar). Using an in situ spectroscopic tool, we monitor the oxide growth in real time and obtain detailed energetic information on the metal/oxide/gas system. This allows us to validate the central hypothesis of the Cabrera−Mott model (i.e., the existence of the Cabrera−Mott potential). The original assumption that oxygen anions are adsorbed at the oxide/gas interface is also discussed. The concept of "realistic conditions" also means that the issue of water coadsorption (inherent to near-ambient O 2 conditions) is addressed. The specific consequences of the Cabrera−Mott regime of oxidation are also discussed with respect to the functioning of aluminum-based superconducting qubits. The in situ, real-time spectroscopic methodology used here is effective and can be generalized far beyond the specific case of aluminum oxidation.

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Oxide growth characteristics on Al (100), (110), and (111) surfaces: A chemo-mechanical evaluation

Kim

Choi

2021

Materials Today Communications

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The first stages of oxide growth at the low index Al surfaces (100), (110), (111): clusters and stripes vs. homogeneous growth

Abstract: The oxide growth at Al(100), Al(110) and Al(111) involves formation of structures that depend on the surface and O-atom coverage.

Cited by 8 publications

References 60 publications

Hydrogen at symmetric tilt grain boundaries in aluminum: segregation energies and structural features

Hydrogen at symmetric tilt grain boundaries in aluminum: segregation energies and structural features

Testing the Cabrera–Mott Oxidation Model for Aluminum under Realistic Conditions with Near-Ambient Pressure Photoemission

Oxide growth characteristics on Al (100), (110), and (111) surfaces: A chemo-mechanical evaluation

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