Enhancement of piezoelectric response in V doped LiNbO3 films deposited by RF magnetron sputtering
LiNbO3 films doped with vanadium (V) were deposited using RF magnetron sputtering technique. To realize doping with a wider range of V concentration, a 30 mm V metal inlaid target asymmetrically embedded in the 150 mm lithium niobate target was used. The V concentration in the deposited films was a decreasing function of the distance from the V target. The V/Nb ratio in the film decreased from 0.155 to 0.024. Surface and inner morphology and structure, phase and element composition, microstructure, and ferroelectric properties of the undoped and V doped LiNbO3 films were studied. The measured maximal d33 constant of the LiNbVO film with V/Nb ratio of 0.07 was about three times higher than that of the undoped LiNbO3 film, 13.5 pC/N and 4.76 pC/N, respectively. The optimal composition in the deposition geometry used was within the V/Nb ratio range of 0.05 to 0.13. Undoped and V doped LiNbO3 thin films were used as bulk acoustic wave ultrasonic transducers deposited on stainless steel plates to generate longitudinal waves and compare their ultrasonic performance.