The importance of singly charged oxygen vacancies for electrical conduction in monoclinic HfO2

Michael P. Mueller, Felix Gunkel, Susanne Hoffmann-Eifert, Roger A. De Souza*

*Corresponding author for this work

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Abstract

The point-defect structure of monoclinic HfO 2 (m-HfO 2) was studied by means of equilibrium electrical conductance measurements as a function of temperature 1050 ≤ T / K ≤ 1200 and oxygen partial pressure - 20 ≤ log (p O 2 / bar) ≤ - 2. The total conductivity σ displayed similar behavior at each temperature examined. In oxidizing conditions (p O 2 ≥ 10 - 7 bar), the total conductivity increased with increasing oxygen partial pressure and was assigned to hole conduction. Around 10 - 10 bar, a region of almost constant conductivity was found; this is ascribed to ionic conduction by means of doubly charged oxygen vacancies. In reducing conditions (p O 2 ≤ 10 - 16 bar), the total conductivity surprisingly decreased with decreasing oxygen partial pressure. Defect-chemical modeling indicates that this behavior is consistent with the conversion of mobile doubly charged oxygen vacancies into less mobile singly charged vacancies by electron trapping. Point-defect concentrations at the oxygen partial pressures relevant to resistive switching devices are predicted and discussed.
Original languageEnglish
Article number025104
JournalJournal of Applied Physics
Volume129
Issue number2
Number of pages8
ISSN0021-8979
DOIs
Publication statusPublished - 2021

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