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Impedance analysis of amorphous and polycrystalline tantalum oxide sputtered films

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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 Ta2O5.

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ACKNOWLEDGMENTS

This research was conducted under MURI grant from Office of Naval Research under the contract number N000140510541. The authors thank Dr. Matthew Olszta for his help with the TEM analysis, Jennifer Sloppy and Elizabeth Dickey for their discussions on tantalum anodization, and Sean Pursel for his help with SEM analysis.

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Authors and Affiliations

  1. Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA

    Guneet Sethi, Brian Bontempo, Eugene Furman, Mark W. Horn & Michael T. Lanagan

  2. Center for Dielectric Studies, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA

    S.S.N. Bharadwaja & Jing Li

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  1. Guneet Sethi
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Sethi, G., Bontempo, B., Furman, E. et al. Impedance analysis of amorphous and polycrystalline tantalum oxide sputtered films. Journal of Materials Research 26, 745–753 (2011). https://doi.org/10.1557/jmr.2010.77

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