Capacitive transducers based ITO/polyimide/Al2O3 thin film structure

Abstract

It has been developed and approbated prototypes of thin-film capacitor transducers based on Al/ITO/polyimide/Al2O3 heterosystem for capacitive acoustic control in metal objects in the modes of simultaneous acoustic signal reception and generation by capacitive transducers and in certain modes of acoustic signal generating or receiving that can realize objects monitoring with sensitivity at the level of piezoelectric transducers. The developed prototype of thin film capacitive transducer for monitoring pipelines by longwave capacitive method allows increasing the maximum distance between the capacitive transducers up to 10 meters. At a substrate temperature of 300 oC and a specific power of the magnetron of 0.31 W/cm2 on Upilex polyimide films were obtained layers of capacitive transducers with a thickness of 0.2-0.3 μm with a surface resistance of 8 Ohm/, while the concentration of charge carriers was 8,3·1020 cm-3 and mobility - 44 cm2/(V·s). It has been engineered the thin film capacitive transducers which by using the polyamide film with 15 microns thickness of and alumina film with 1 micron thickness allow to increase the sensitivity of such method in 7-8 times, and the additional use of thin crystalline Al2O3 films deposited on a substrate of polyimide, allows to increase the value of the dielectric constant of the layer of the capacitive transduser from 3-4 relative units to 8.5-11.5 relative units. Experimental studies of the crystal structure of the developed transducers by X - ray diffractometry and research of their dielectric properties were carried out. The device was tested and the possibility of its use was shown along with the generally accepted methods of defectoscopy. It is shown that using the magnetron sputtering technology, which provides high adhesion to polyimide substrate layers, made possible produce the capacitive transducers for objects with various shape. Proposed and patented: capacitor method for receiving acoustic signals in non-destructive control and transducer of ultrasonic acoustic wave’s excitation and receiving.