(Ba/Pb) x Sr 1−x TiO 3 based capacitive sensor with LaNiO 3 electrode for higher tunability

The high tunability range of capacitive sensors can be achieved by the use of ferroelectric materials due to its perovskite structure. Thin films provide better utilization of properties comparative to bulk but greatly affect by the surface on which it deposited. In this work thin films of BaxSr1−xTiO3 (BST) and PbxSr1−xTiO3 (PST) are developed with x = 0.3 & 0.7. Thin films without doping of Sr are also developed for comparison. The capacitors Al/Si/BST/Al and Al/Si/PST/Al are fabricated in parallel plate structure using the sol–gel processing technique with Al as metal electrodes and BST/PST as the dielectric material. A new parallel plate capacitor with the introduction of Lanthanum Nickel Oxide (LNO) thin film with the preferred (100) orientation between Si substrate and BST/PST is proposed in this work. Crystallinity and orientation of BST/PST on Si and BST/PST over LNO are observed by X-ray diffraction (XRD). The average grain size and uniformity of thin films are confirmed by scanning electron microscopy (SEM) images. The capacitances are measured at 50 mV and 70 mV using LCR meter. The highest capacitance of 79.6pF is observed for Al/Si/LNO/BST/Al. Impedance spectroscopy reveals the decrement in impedance with doping of Sr and tunability range of LNO based BST/PST capacitor is much higher compared to non-LNO capacitors. Tunability with BST material reaches 57% at frequency 2.98 kHz and the PST attains a value of 33.8% at frequency 1.44 KHz.