DOUBLET PIEZOELECTRIC HYDROPHONE

RESEARCH TO DESIGN AND DEVELOP A DOUBLET PIEZOELECTRIC HYDROPHONE IS PROPOSED HERE. THE MAIN OBJECTIVE OF THE EFFORT IS TO DEVELOP MICRO-FABRICATION TECHNIQUES TO MAKE MINIATURE HIGH QUALITY HYDROPHONES. A SILICON WAFER IS CHEMICALLY ETCHED, AND A LAYER OF SILICON OXIDE IS GROWN TO FORM A DIAPHRAGM. NEXT, A LAYER OF ZNO IS DEPOSITED TO ACT AS A PIEZOELECTRIC TRANSDUCER TO SENSE THE DEFLECTION OF THE DIAPHRAGM UNDER ACOUSTIC PRESSURE. THE ZNO LAYER HAS ELECTRODES ON EITHER SIDE IN REGIONS WHERE THE HIGH STRESSES DEVELOP IN THE DIAPHRAGM. THESE ELECTRODES ARE USED FOR OUTPUT SIGNALS FROM THE DEVICE. A PAIR OF IDENTICALLY PROCESSED WAFERS IS ALIGNED AND BONDED TOGETHER BACK-TO-BACK TO YIELD A BATCH OF PIEZOELECTRIC HYDROPHONES. WHEN THE HYDROPHONE IS PLACE IN AN ACOUSTIC FIELD, THE SOUND WAVES PRODUCE DIFFERENT DEFORMATIONS IN THE TWO BACK-TO-BACK PLACED DIAPHRAGMS, HENCE, GENERATE A DIFFERENTIAL VOLTAGE ACROSS THE PIEZOELECTRIC. THE OUTPUT SIGNAL IS PROPORTIONAL TO THE PRESSURE GRADIENT ACROSS THE THICKNESS OF THE DIAPHRAGM.