A method for predicting thickness of the unoriented layer in ZnO film using piezoelectricity distribution in depth direction

S. Takayanagi, Takahiko Yanagitani, M. Matsukawa

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2 Citations (Scopus)

Abstract

The crystalline orientation of thin films gradually improves as the growth proceeds. Especially in the non-epitaxial growth, its initial layer is often unoriented. Because the unoriented layer degrades the performance of the device, the degree of crystalline orientation in depth direction is a very important issue. We propose a non-destructive method for predicting the thickness of the unoriented layer, making use of piezoelectricity distribution of films. An electromechanical resonator consisting of the single highly oriented layer excites a fundamental mode, but does not excite a second-overtone mode. The unoriented layer, on the other hand, exhibits little piezoelectric effect. A bilayer resonator consisting of the highly oriented layer on the unoriented layer excites a second-overtone mode because of the deference of piezoelectricity in these layers. In this study, the electromechanical resonance characteristics of Cu/ZnO(0 0 0 1)/Ti(0 0 0 1)/SiO2, Cu/ZnO(0 0 0 1)/AZO(0 0 0 1)/Ti(0 0 0 1)/SiO2 and Cu/ZnO(112̄0) /Al/SiO 2 were experimentally observed. These results were compared with the theoretical estimations by a mechanical transmission line model to determine the thicknesses of the piezoelectrically inactive layers in the (0 0 0 1) or(112̄0) oriented ZnO films. The inactive layer thickness in(112̄0) the oriented ZnO film was in good agreement with the unoriented layer thickness observed by the cross-sectional transmission electron microscopy and electron diffraction.

Original languageEnglish
Article number315305
JournalJournal of Physics D: Applied Physics
Volume46
Issue number31
DOIs
Publication statusPublished - 2013 Aug 7
Externally publishedYes

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ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials
  • Acoustics and Ultrasonics
  • Surfaces, Coatings and Films

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