XAFS Study of Epitaxial CoxTi1-xO₂-x Anatase

Conference · Sat Jan 01 04:00:00 EST 2005

OSTI ID:919719

Heald, Steve M.; Chambers, Scott A.; Droubay, Timothy C.

Co doped TiO₂-anatase is a promising candidate for a room-temperature ferromagnetic semiconductor. XAFS measurements have been used to investigate the local Co environment and Co valence for several Co-anatase films. The samples were grown on LaAlO₃(001) by oxygen plasma assisted molecular beam epitaxy and on SrTiO₃ by atomic oxygen assisted MBE. Co concentrations were about 5%. The measurements were made at the PNC-CAT bending magnet and undulator beamlines at the Advanced Photon Source. For the films on LaAlO₃, the near edge clearly shows the presence of only Co(₂⁺), and no evidence for metallic Co, while the films on SrTiO₃ showed significant metallic Co. Analysis of the extended fine structure for the LaAlO₃ films finds that the Co substitutes for Ti with some distortion of the lattice. Both in-plane and out-of-plane Co-O bonds are expanded from the Ti-O bonds in anatase. The in-plane bonds are expanded approximately twice as much. A deficit in the oxygen coordination number suggests a correlation of oxygen vacancies with Co sites.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 919719
• Report Number(s): PNNL-SA-38914
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
43 PARTICLE ACCELERATORS
ABSORPTION
ADVANCED PHOTON SOURCE
BENDING
COORDINATION NUMBER
FINE STRUCTURE
MAGNETS
MOLECULAR BEAM EPITAXY
OXYGEN
PLASMA
VACANCIES
VALENCE
spintronics magnetic semiconductors XAFS