Numerical Investigation of Rayleigh, Sezawa and Love Modes in C-Axis Tilted ZNO/SI for Gas and Liquid Multimode Sensor

• Published in: Journal of mechanics Vol. 36; no. 1; pp. 7 - 18
• Main Authors: Laidoudi, F., Boubenider, F., Caliendo, C., Hamidullah, M.
• Format: Journal Article
• Language: English
• Published: Taipei Oxford University Press 01-02-2020
• Subjects: Computer simulation; Coupling; Dispersion curve analysis; Finite element method; Free surfaces; Gas sensors; Gases; Half spaces; Phase velocity; Piezoelectricity; Polyisobutylene; Room temperature; Sensitivity; Sensors; Thin films; Zinc oxide
• ISSN: 1727-7191; 1811-8216
• DOI: 10.1017/jmech.2019.14

ABSTRACT
Finite element analysis is carried out to investigate the characteristics of Rayleigh, Sezawa and Love surface acoustic modes travelling along c-axis tilted ZnO layer on Si (001) half-space. The phase velocity dispersion curves, electromechanical coupling, reflectivity and mass loading sensitivity are studied for different electroacoustic coupling configurations and c-axis tilt angles θ. The behavior of Rayleigh and Sezawa modes operating as gas sensor, was simulated under the hypothesis that the ZnO free surface is covered with a thin polyisobutylene (PIB) film, 0.2 μm thick, able to selectively adsorb volatile gases at atmospheric pressure and room temperature. The sensor sensitivity to gas concentration in air, i.e. the frequency shifts per unit gas concentration, is studied and compared to some common materials used in literature. The obtained results, demonstrate the feasibility of high-frequency multimode micro-sensor based on the c-axis tilted ZnO piezoelectric thin film and operating in both liquid and gaseous environments.