Study of Sputtered Barium Strontium Titanate Films for Energy Harvesting Applications

Thin films of BaSrTiO3 (BST) were deposited by radio frequency (RF) sputtering with sputtering voltage varied between 0.5 and 0.7 kV. BaSrTiO3 films are investigated regarding their suitability for use in flexible energy harvesting devices. Analysis of the spectra and micrographs showed the piezoelectric features and the polycrystalline nature for the films grown at higher sputtering voltage. Meanwhile, the presence of an amorphous phase with a lack of characteristic bonds was found out for BaSrTiO3 films grown at the lower sputtering voltage. The electrical measurements of Al/BaSrTiO3/Al harvester on plastic substrate in the low-frequency range revealed superior piezoelectric voltage and 40% exceeding power density for the samples prepared at 0.7 kV as compared to the other thin films deposited at 0.5 kV. These results are achieved by simple architecture of single layer harvester with small size (0.4 cm 2 ) and small film thickness (0.5 µm), containing lead-free material. It was proved that the sputtered BaSrTiO3 films are suitable for thin film piezoelectric nanogenerators and their performance could be easily tuned by the sputtering voltage. Possible applications of the proposed element are low-frequency vibrational harvesting and a strain gauge.