Impedance analysis of amorphous and polycrystalline tantalum oxide sputtered films

Guneet Sethi, Brian Bontempo, Eugene Furman, Mark William Horn, Michael T. Lanagan, S. S.N. Bharadwaja, Jing Li

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Abstract

Impedance spectroscopy studies were conducted on amorphous tantalum oxide thin films prepared using pulsed-DC reactive sputtering, which were post-annealed to crystallize the films. X-ray diffraction results showed that crystallization to Ta2O5 β phase occurs for samples annealed above 650 °C, with a crystallite size of ∼40 nm. The film microstructure was studied by electron microscopy, and remnants of the columnar amorphous microstructure were found in the polycrystalline films. Complex impedance analyses revealed significant differences in dielectric behavior between the amorphous and crystalline films. Lumped circuit models were conducted on the films using resistors, capacitors, and constant phase elements. Amorphous films exhibited a single relaxation with Arrhenius activation energy of 1.1-1.3 eV. Crystallized films exhibited two relaxations with activation energies equal to 1.1 ± 0.08 and 0.6 ± 0.03 eV. The relative permittivity of the bulk crystalline grain in tantalum oxide films is close to the established permittivity of the β phase (εr = 40) of Ta 2O5.

Original languageEnglish (US)
Pages (from-to)745-753
Number of pages9
JournalJournal of Materials Research
Volume26
Issue number6
DOIs
StatePublished - Mar 28 2011

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All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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