The Directional and Interference Properties of Nanomaterial Based Surface Acoustic Wave Filters

Abstract

Nanotechnology is aimed to design and synthesis of novel nanoscale material. These materials are being used in the design of optical, biomedical, electronic devices, and acoustic devices. Surface Acoustic Wave (SAW) devices are microelectromechanical systems (MEMS) which uses piezoelectric substrate for propagation of surface wave. The propagation of surface acoustic wave is altered by chemicals in the ambient if the delay line spacing is coated with chemically sensitive material. Research work involves simulation, modelling, and fabrication of SAW devices. An algorithm is developed using the delta and impulse function model for quartz and ZnO based SAW device as filters, which are analyzed to qualitatively validate the proposed designs. Modelling of the devices are carried using finite element method (FEM). 2D plane-strain model simulations have been done to analyze the performance of the devices with or without sensitive material. newlineAnother aspect of the research involves the investigation of IDTs directionality and interference of the sensitive material in the delay line spacing. Quartz and ZnO based SAW devices are fabricated using lithography and liftoff technique with conventional and focused IDTs. Insertion losses of devices are measured to analyse their performance at centre frequency. Also the investigations of nano thin film in the delay line spacing are carried out to design SAW sensor to detect fluorine (F2) gas. This gas is a dangerous that may cause eyes and skin burns at high concentration. F2 is used in several industrial processes and chemical laboratories that need a sensor which can detect fluorine in ambient atmosphere with low as well as high concentration. Palladium (Pd) is a sensitive material for chemical detection. Absorption and desorption are revisable to produce changes in density, elastic properties, and conductivity of the film. Pd is investigated as sensitive material in quartz and ZnO based SAW sensor to detect F2 gas. The devices are tested for different concentration of the gas.