Comprehensive characterization of ZnO thin films for surface acoustic wave applications

Burak Yildirim, Onur Tigli

Research output: Contribution to journalArticle

Abstract

This paper presents a comprehensive characterization of a very smooth, c-axis oriented, highly piezoelectric and electrically resistive 2.5 µm-thick ZnO thin film deposited by a radio frequency (RF) magnetron sputtering system on SiO2/Si substrate. Thin film properties such as surface roughness, crystallography, stoichiometry, and electrical resistivity are measured. Two-port surface acoustic wave (SAW) devices with bidirectional interdigital transducer (IDT) periods of 16 µm, 20 µm and 24 µm are fabricated on top of the ZnO thin film. A detailed finite element analysis (FEA) of the thin film is elaborated by varying ZnO thickness and IDT configuration. FEA results shows that acoustic wave velocities and resonance frequencies of the SAW devices are decreasing together with increasing ZnO thickness. Frequency response of the fabricated SAW devices are measured with a vector network analyzer (VNA) and compared to FEA results. First two wave modes, namely the Rayleigh and Sezawa waves, of the fabricated SAW devices on the ZnO thin films are interrogated. Resonance frequencies of the SAW devices with wavelengths of 16 µm, 20 µm, and 24 µm are measured as 204.8 MHz, 176.3 MHz, and 155.3 MHz for the Rayleigh mode, 335.9 MHz, 275.3 MHz, and 235.1 MHz for the Sezawa mode, respectively. In addition, omnidirectional wave propagation of ZnO thin film is shown with 45° rotated IDTs. Overall, experimental results are in good agreement with simulation results, demonstrating ZnO thin film fabrication is successfully carried out, and FEA is an appropriate method for modeling SAW devices on thin films.

Original languageEnglish (US)
JournalJournal of Materials Science: Materials in Electronics
DOIs
StatePublished - Jan 1 2019

Fingerprint

Acoustic surface wave devices
Surface waves
surface acoustic wave devices
Acoustic waves
Thin films
acoustics
thin films
Finite element method
interdigital transducers
electrical resistivity
Transducers
Crystallography
Electric network analyzers
Rayleigh waves
Acoustic wave velocity
Thick films
Stoichiometry
Magnetron sputtering
Wave propagation
frequency response

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

Cite this

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abstract = "This paper presents a comprehensive characterization of a very smooth, c-axis oriented, highly piezoelectric and electrically resistive 2.5 µm-thick ZnO thin film deposited by a radio frequency (RF) magnetron sputtering system on SiO2/Si substrate. Thin film properties such as surface roughness, crystallography, stoichiometry, and electrical resistivity are measured. Two-port surface acoustic wave (SAW) devices with bidirectional interdigital transducer (IDT) periods of 16 µm, 20 µm and 24 µm are fabricated on top of the ZnO thin film. A detailed finite element analysis (FEA) of the thin film is elaborated by varying ZnO thickness and IDT configuration. FEA results shows that acoustic wave velocities and resonance frequencies of the SAW devices are decreasing together with increasing ZnO thickness. Frequency response of the fabricated SAW devices are measured with a vector network analyzer (VNA) and compared to FEA results. First two wave modes, namely the Rayleigh and Sezawa waves, of the fabricated SAW devices on the ZnO thin films are interrogated. Resonance frequencies of the SAW devices with wavelengths of 16 µm, 20 µm, and 24 µm are measured as 204.8 MHz, 176.3 MHz, and 155.3 MHz for the Rayleigh mode, 335.9 MHz, 275.3 MHz, and 235.1 MHz for the Sezawa mode, respectively. In addition, omnidirectional wave propagation of ZnO thin film is shown with 45° rotated IDTs. Overall, experimental results are in good agreement with simulation results, demonstrating ZnO thin film fabrication is successfully carried out, and FEA is an appropriate method for modeling SAW devices on thin films.",
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