Study on the crystalline and ferroelectric properties on PZT thin films deposited by pulsed laser deposition

Abstract

Preferentially [h00]-oriented LaNiO3 (LNO) thin films were prepared on Si (100) wafers using KrF excimer pulsed-laser deposition. Microstructures of the deposited films were investigated using X-ray q-2q scan and pole figure or j scan. The effects of substrate temperatures from 400 to 700A?C as well as oxygen pressure from 50 to 200mTorr were also studied. LNO thin film deposited at 600A?C at 50mTorr was found to exhibit the best quality. Deposition at temperatures below 500A?C resulted in an amorphous LNO while those deposited at temperatures above 600A?C induced the formation of mixed [110] and [h00] out-of plane orientation. High O2 pressures were observed to manifest similar effects.Surface morphologies of the deposited LNO films examined using atomic force microscopy and scanning electron microscopy showed that the films had been grown with extremely smooth and crack free surfaces.Investigations done on the LNO films reveal a co-relation between the orientation and crystallinity of the LNO films and their resistivities. Highly oriented films display lower resistivity. Increasing the substrate temperature and oxygen pressure resulted in thin films that have higher resistivity values.Deposition of Pb(Zr0.52 Ti0.48)O3 films using targets doped with 10 and 20% excess PbO with LNO as the electrode and underlayer were investigated. Single oriented Lead zirconate titanate (PZT) thin films with (001) out of plane orientation were successfully deposited. The remnant polarization and coercive field obtained using a target with 20% excess PbO was 34.88mC/cm2 and 78.98 kV/cm respectively at applied voltage of +5 V. This makes it suitable for applications in DRAM and FERAM. The LNO underlayer is found to play an important role in orienting the PZT film. The substrate temperature was found to be within narrow temperature range for perovskite PZT formation without any pyrochlore phase. Oxygen pressure also plays a role in orientation of the PZT layer. PZT films deposited using PZT targets with 10wt% excess PbO and high laser fluence all display poorer ferroelectric properties.