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Impedance analysis of amorphous and polycrystalline tantalum oxide sputtered films

Published online by Cambridge University Press:  09 March 2011

Guneet Sethi
Affiliation:
Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania 16802
Brian Bontempo
Affiliation:
Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania 16802
Eugene Furman
Affiliation:
Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania 16802
Mark W. Horn
Affiliation:
Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania 16802
Michael T. Lanagan
Affiliation:
Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania 16802
S.S.N. Bharadwaja
Affiliation:
Center for Dielectric Studies, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802
Jing Li
Affiliation:
Center for Dielectric Studies, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802
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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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Copyright © Materials Research Society 2011

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