A study of barium ultra-thin films on the SrTiO3(1 0 0) surface by soft X-ray photoelectron spectroscopy
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peer reviewed
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Όνομα περιοδικού
Journal of Electron Spectroscopy and Related Phenomena
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Περιγραφή
The growth and the electronic properties of Ba ultra-thin films (coverage ? 2 ML) on the SrTiO3(1 0 0) surface was studied using synchrotron radiation facilities. The investigation was carried out mainly by soft X-ray photoelectron spectroscopy measurements at low core levels and the valence band region. The results show that the Ba overlayer develops in a layer-by-layer mode. The first two layers do not create any states in the band gap, thus leaving intact the insulating character of the substrate. This is due to the oxidation of Ba through transfer of O2? anions from the substrate into the Ba overlayer. It is observed that the valency of the Ti atoms at the interface does not change. This is attributed to an outwards diffusion of O2? anions from deeper layers promoted by substrate annealing. Within the coverage examined, no evidence for Ba metallization is found, contrary to what happens on metallic substrates. Comparing the results of this work with previous ones on similar metal SrTiO3(1 0 0) adsorption systems, it is concluded that a single factor such as charge transfer or thermodynamic stability is not always sufficient to determine the oxidation process of the adsorbate layer. Kinetics on surfaces as well as substrate doping and defects can also play a decisive role.
Περιγραφή
Λέξεις-κλειδιά
Strontium titanate, Barium, Adsorption, Barium oxide, X-ray photoemission spectroscopy, Valence band
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http://www.sciencedirect.com/science/article/pii/S0368204812001375
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Γενική Περιγραφή / Σχόλια
Ίδρυμα και Σχολή/Τμήμα του υποβάλλοντος
Πανεπιστήμιο Ιωαννίνων. Σχολή Επιστημών και Τεχνολογιών. Τμήμα Βιολογικών Εφαρμογών και Τεχνολογιών