Metallic to insulating nature of (formula presented) Role of Ta and N vacancies

C. Stampfl, Arthur J Freeman

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2 Citations (Scopus)

Abstract

It has been demonstrated recently that the stoichiometry of rocksalt TaN can be tuned by (formula presented) pressure and temperature, yielding material that ranges from highly conductive to insulating. Using density functional theory, we investigate the atomic and electronic structure and formation energy of defective TaN structures. The calculations predict that Ta and N vacancies form under N-rich and N-poor conditions, respectively, where the presence of Ta vacancies reduce the density of states (DOS) around the Fermi level (formula presented) We also studied the (formula presented) and (formula presented) structures which occur in nature. The former phase, consisting of an ordered arrangement of Ta vacancies, also exhibits a notable decrease in the DOS at (formula presented) while the latter is a semiconductor with a band gap of 1.5 eV within the local density approximation. Our results suggest that the formation of Ta-deficient structures is directly related to the metal-to-insulator transition.

Original languageEnglish
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume67
Issue number6
DOIs
Publication statusPublished - Feb 28 2003

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Vacancies
Crystal atomic structure
Local density approximation
Fermi level
Stoichiometry
Electronic structure
Density functional theory
Energy gap
Metals
Semiconductor materials
energy of formation
atomic structure
stoichiometry
insulators
density functional theory
electronic structure
Temperature
approximation
metals
temperature

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

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abstract = "It has been demonstrated recently that the stoichiometry of rocksalt TaN can be tuned by (formula presented) pressure and temperature, yielding material that ranges from highly conductive to insulating. Using density functional theory, we investigate the atomic and electronic structure and formation energy of defective TaN structures. The calculations predict that Ta and N vacancies form under N-rich and N-poor conditions, respectively, where the presence of Ta vacancies reduce the density of states (DOS) around the Fermi level (formula presented) We also studied the (formula presented) and (formula presented) structures which occur in nature. The former phase, consisting of an ordered arrangement of Ta vacancies, also exhibits a notable decrease in the DOS at (formula presented) while the latter is a semiconductor with a band gap of 1.5 eV within the local density approximation. Our results suggest that the formation of Ta-deficient structures is directly related to the metal-to-insulator transition.",
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