Growth morphology and electronic structure of ultra-thin TaOx films on Ag(100)

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A study of the growth morphology and electronic structure of TaOx films on the Ag(100) substrate has been performed to determine the properties of ultra-thin TaOx films without the influence of a mixed interfacial oxide (i.e., a disordered SiO2/TaOx interface for growth on Si). The TaOx films were grown by thermal evaporation of Ta in an oxygen atmosphere of 1 × 10-6 Torr. Growth on a Ag(100) surface held at room temperature results in an amorphous TaOx overlayer, as determined by low energy electron diffraction. The onset of ordering of these films occurs for a post-anneal at ∼500 °C. A diffraction pattern that corresponds to a multi-domain overlayer structure is observed for anneals at ∼550 °C. Deposition of Ta without oxygen results in the formation of Ta islands. These results indicate that there is a very weak adsorbate-substrate interaction. Photoemission measurements of the TaOx films show the formation of a band gap with the valence band maximum residing at 3.5 eV below the Fermi level. Core level shifts of ∼3.5 eV are observed for the Ta with no indication of metallic Ta at the surface.

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Materials Research Society Symposium - Proceedings

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