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Title: Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying

The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at. %. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms are not located in a TiO{sub 2} unit in the oxide layer, but rather in a mixed Ti-Al oxide layer. The optical band gap energy of the anodic oxide layers was determined by vacuum ultraviolet spectroscopy in the energy range from 4.1 to 9.2 eV (300–135 nm). The results indicate that amorphous anodic Al{sub 2}O{sub 3} has a direct band gap of 7.3 eV, which is about ∼1.4 eV lower than its crystalline counterpart (single-crystal Al{sub 2}O{sub 3}). Upon Ti-alloying, extra bands appear within the band gap of amorphous Al{sub 2}O{sub 3}, mainly caused by Ti 3d orbitals localized at the Ti site.
Authors:
;  [1] ; ;  [2] ;  [3] ; ;  [4] ; ;  [5]
  1. Department of Photonics Engineering, Technical University of Denmark, 4000 Roskilde (Denmark)
  2. Danish Technological Institute, Kongsvang Alle 29, 8000 Aarhus (Denmark)
  3. Paul Scherrer Institute, 5232 Villigen (Switzerland)
  4. ISA, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus (Denmark)
  5. Department of Mechanical Engineering, Technical University of Denmark, 2800 Kongens Lyngby (Denmark)
Publication Date:
OSTI Identifier:
22258583
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 12; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; ALLOYS; ALUMINIUM OXIDES; BAND THEORY; ELECTRONIC STRUCTURE; LAYERS; MONOCRYSTALS; THIN FILMS; TITANIUM OXIDES; ULTRAVIOLET RADIATION; X-RAY SPECTROSCOPY