PIEZOELECTRIC PROPERTIES OF SOL-GEL DERIVED ZNO THIN-FILMS

ZnO films exhibit a wide range of interesting material properties. Rec ently, ZnO films have been studied for sensing applications based. on their piezoelectric and pyroelectric behaviors. Reported literature va lues of piezoelectric and pyroelectric coefficients of ZnO films are i n the range of 11-12 pm/V and 1.0-1.4 nC/cm(2)-K respectively. In this study, the piezoelectric properties of sol-gel derived ZnO thin films were measured. These films were prepared on platinized Si wafers and fired to temperatures ranging from 550 degrees C to 750 degrees C. Mul tiple spincoating was performed with an intermediate firing at 400 deg rees C between coatings to obtain films up to 6000 A thick. Top Pt ele ctrodes were sputtered to form monolithic capacitors. XRD indicated th at the films consisted of crystalline wurtzite at firing temperatures as low as 400 degrees C, and that the c-axis orientation increased wit h increasing firing temperature. A dielectric constant of 10 was obtai ned, while piezoelectric characterization indicated d(33) values as la rge as 12 pm/V i.e., values similar to those of bulk ZnO.