On the influence of the top and bottom electrodes—A comparative study between Pt and LNO electrodes for PZT thin films

Platinum (Pt) and lanthanum nickelate LaNiO3 (LNO) nanocrystalline films have been grown by r.f.magnetron sputtering as both bottom and top electrodes to investigate their effect on the dielectric, ferroelectric and piezoelectric properties of 600 nm PZT thin films. XRD measurements showed that by using LNO or Pt as bottom electrode it is possible to change the PZT film orientation. Laser doppler vibrometry is used to characterize the electromechanical performance. Dielectric constant, piezolectric coefficient d33 and polarization-electric field hysteresis loops were measured on Pt/PZT/Pt, LNO/PZT/LNO, Pt/PZT/LNO and LNO/PZT/Pt structures. The dielectric constant and the piezoelectric response are significantly increased and the average coercive fields are strongly lowered when LNO is used as the top electrode. There is also a general trend for the maximum polarization to increase by up to around 20%, while the remnant one increases only slightly, when Pt is replaced by LNO as the top electrode. The nature of the bottom electrode, however, was found to only influence the dielectric properties of the structure, whilst the top electrode affects the device properties too.