Thickness-dependent microstructure, resistive switching, ferroelectric, and energy storage properties of pulsed laser deposited 0.85[0.6Ba(Zr0.2Ti0.8)O3-0.4(Ba0.7Ca0.3)TiO3]-0.15SrTiO3 thin films

In this work, we have studied the effect of thickness on structural, morphological, resistive switching (RS), ferroelectric, and energy storage properties of 0.85[0.6Ba (Zr0.2Ti0.8)O3-0.4(Ba0.7Ca0.3)TiO3]-0.15SrTiO3 (BZCT-STO) thin films deposited by the pulsed laser deposition technique. X-ray diffraction (XRD) analysis suggests that BZCT-STO thin films exhibit a polycrystalline tetragonal structure. The lattice parameters and tetragonality ratio approaching to bulk value with an increase of thickness, confirm strain relaxation in thicker films. SEM analysis reveals a dense columnar structure with a different grain size that varies from 3 nm to 60 nm as thickness increased from 160 to 360 nm. The P-E loops suggest that the relaxor behaviour increases with a decrease of thickness due to interface low dielectric layer, substrate clamping effect, small grain size, and high back switching ratio. The RS effect observed in Pt/BZCT-STO/Au capacitors is attributed to polarization modulation of the Schottky barrier and is found to be significant at low thickness. The effect of electric field and frequency on energy storage properties of BZCT-STO films is also investigated. The Pt/BZCT-STO/Au capacitor with a thickness of 160 nm exhibited 6.0 J/cm3 with an efficiency of 72% at a field of 800 kV/cm. It also exhibited a robust energy storage performance in the frequency range of 50–2000 Hz and also up to 108 cycles passing through the capacitor.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding Contract UIDB/04650/2020. This work has received funding from the Eu ropean Union’s Horizon 2020 research and innovation program under grant agreement No 958174 (M-ERA-NET3/0003/ 2021—NanOx4EStor). The author KK acknowledges DST –SERB for the financial support through grant no: SPG/2021/003797. The authors would also like to thank Jos´e Santos for technical support in the Thin Film Laboratory at CF-UM-UP