Effect of Sr and La co-doping on structural and electrical properties of RF sputtered PZT thin films

Abstract

Doping in lead-zirconate-titanate (PZT) thin films is on the rise for next generation micro-electro-mechanical systems (MEMS) and energy harvesting applications, owing to their improved ferroelectric and piezoelectric properties. Strontium, lanthanum and neodymium like elements are the most exploited for such applications. This paper reports realization of a PZT thin film with strontium and lanthanum co-doping in tandem, Pb _1− _x _−3 _y _/2 Sr _x La _y (Zr _0.56 Ti _0.44 )O _3 x = 0.06, y = 0.03 (PSLZT), by RF sputtering process. Different process conditions like substrate temperature from 250 °C–350 °C and annealing temperature from 650 °C–750 °C are studied to achieve pyrochlore free PSLZT thin film. The structure, surface morphology, surface topography and ferroelectric characteristics are investigated using x-ray diffraction (XRD), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FE-SEM) and P-E analyser, respectively. Nanoscale polarization switching processes and the local surface displacements are studied to ascertain that the PSLZT thin film exhibits the ferroelectric and piezoelectric properties. Experimental results reveal that the present PSLZT thin film has a polarization of 5.5 μ C cm ^−2 , leakage current density of 10 ^−5 A cm ^−2 and piezoelectric charge coefficient, d _33 , of 87 pm V ^−1 , which are suitable for realization of various new piezoelectric MEMS sensors.

Keywords

• doped PZT
• thin film
• RF sputtering
• Sr and La doping