Initial stages of growth and electronic properties of epitaxial SrF2 thin films on Ag(1 1 1)

Mauro Borghi, Andrea Mescola, Guido Paolicelli, Monica Montecchi, Sergio D'Addato, Simone Vacondio, Luca Bursi, Alice Ruini, Bryan P. Doyle, Tibor Grasser, Luca Pasquali

Research output: Contribution to journalArticlepeer-review

Abstract

Molecular beam epitaxy (MBE) is used to grow ultrathin SrF2 layers at different temperatures on Ag(1 1 1) epitaxial films prepared on mica. The electronic properties, structure and morphology of the films are probed by ultraviolet and x-ray photoelectron spectroscopies (UPS and XPS) supported by ab-initio calculations, reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM). The SrF2 films are composed of crystallites with their [1 1 1] direction parallel to the substrate normal, thereby reproducing the symmetry of the substrate. Twinned domains are also observed. At the Ag/SrF2 interface, fluoride molecules do not dissociate and the interaction with the substrate is weak. At room temperature, fluoride crystallites merge together, resulting in a continuous film covering the entire substrate when it reaches a nominal thickness of 5 nm. Growth at higher temperature induces the formation of triangular 3D islands, leaving sizable portions of the Ag substrate uncovered. At 400 °C, also a small fraction of SrF2(0 0 1)-oriented crystallites are observed, with their [1 −1 0] axis rotated by about 30° with respect to the [1 −1 0] substrate direction.

Original languageEnglish
Article number159724
JournalApplied Surface Science
Volume656
DOIs
Publication statusPublished - 30 May 2024

Keywords

  • Atomic force microscopy
  • Ionic fluorides
  • Molecular beam epitaxy
  • Photoelectron spectroscopy
  • Projected density of states
  • Reflection high energy electron diffraction

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

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