title: Electronic and optical properties of oxygen vacancies in amorphous Ta2O5from first principles.
abstract: Oxygen vacancies are important defects considered to play a central role in the electronic and optical properties of tantalum pentoxide (Ta2O5) films and devices. Despite extensive experimental studies on oxygen vacancies in Ta2O5, the reported defect states are ambiguously identified due to the absence of accurate and conclusive theoretical evidence. Here we investigate the thermodynamic, electronic, and optical properties of oxygen vacancies in amorphous Ta2O5by first-principles calculations based on hybrid-functional density functional theory (DFT). The calculated thermodynamic and optical transition levels are in good agreement with a broad range of diverse measured properties with various experimental methods, providing conclusive evidence for the identification of the defect states observed in experiments as originating from oxygen vacancies. Our calculations also predict the formation of spin-polarized polarons. Our results elucidate the fundamental atomistic properties of oxygen vacancies in various oxidation states as a function of growth conditions and provide guidance to control the properties of Ta2O5films/devices.
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA. kioup@umich.edu and Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA. wluee@umich.edu.
authors.forename: Jihang
authors.identifier: http://orcid.org/0000-0001-8214-5905
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA. wluee@umich.edu.
authors.forename: Wei D
authors.identifier: http://orcid.org/0000-0003-4731-1976
authors.initials: WD
authors.lastname: Lu
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA. kioup@umich.edu.
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Kioupakis