Ultrathin metal films and particles on oxide surfaces: structural, electronic and chemisorptive properties

In the light of recent experimental as well as theoretical studies, we summarize our present understanding of polar oxide surfaces and examine fundamental issues regarding their stability. The focus is on the surface atomic configurations (relaxations, reconstructions, non-stoichiometry, etc) obtained under specific preparation conditions and their associated electronic structure. We discuss several mechanisms at work on polar surfaces, such as relaxation effects, change of covalency in the surface layers, partial filling of surface states, and stoichiometry variations, and try to assess their actual efficiency for cancelling the polarity.

https://iopscience.iop.org/article/10.1088/0953-8984/12/31/201/pdf

Polar oxide surfaces

Interaction of nanostructured metal overlayers with oxide surfaces

The photophysics and electron injection dynamics of Ru(dcbpy)2(NCS)2 [dcbpy = (4,4‘-dicarboxy-2,2‘-bipyridine)] (or Ru N3) in solution and adsorbed on nanocrystalline Al2O3 and TiO2 thin films were studied by femtosecond mid-IR spectroscopy. For Ru N3 in ethanol after 400 nm excitation, the long-lived metal-to-ligand charge transfer (3MLCT) excited state with CN stretching bands at 2040 cm-1 was formed in less than 100 fs. No further decay of the excited-state absorption was observed within 1 ns consistent with the previously known 59 ns lifetime. For Ru N3 absorbed on Al2O3, an insulating substrate, the 3MLCT state was also formed in less than 100 fs. In contrast to Ru N3 in ethanol, this excited state decayed by 50% within 1 ns via multiple exponential decay while no ground-state recovery was observed. This decay is attributed to electron transfer to surface states in the band gap of Al2O3 nanoparticles. For Ru N3 adsorbed onto the surface of TiO2, the transient mid-IR signal was dominated by the IR abs...

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Femtosecond IR Study of Excited-State Relaxation and Electron-Injection Dynamics of Ru(dcbpy)2(NCS)2 in Solution and on Nanocrystalline TiO2 and Al2O3 Thin Films

Auger parameter and Wagner plot in the characterization of chemical states by X-ray photoelectron spectroscopy: a review

Modifications of α-Al2O3(0001) surfaces induced by thermal treatments or ion bombardment

Influence of the Al2O3(0001) surface reconstruction on the Cu/Al2O3 interface

We follow the cluster formation when depositing less than 2 monolayers Cu onto a monocrystalline αAl2O3 (0001) stoichiometric surface, by combining XPS and X-ray absorption spectroscopy at the Cu K edge (EXAFS, XANES). An estimate of the evolution of cluster size with copper deposition is given from XANES and EXAFS data. The variation of the Cu Auger parameter, measured from the XPS spectra, shows a continuous increase, attributed to the continuous increase of cluster size with copper deposition.

https://iopscience.iop.org/article/10.1209/0295-5075/18/2/015/pdf

M. Gautier

Papers

Modifications of α-Al2O3(0001) surfaces induced by thermal treatments or ion bombardment

Influence of the Al2O3(0001) surface reconstruction on the Cu/Al2O3 interface

Copper Clusters Formation on Al2O3 Surfaces: An XPS and SEXAFS Study

Surface science letterInfluence of the Al2O3(0001) surface reconstruction on the Cu/Al2O3 interface