Characteristics of PZT thin films as ultra-high density recording media

Abstract

Ferroelectric thin films as the recording media of scanning probe microscope-based storage devices were investigated using an atomic force microscope(AFM) technique. Polarization domains were formed in the PbZrxTi1-xO3(PZT) thin films epitaxialy grown on the epitaxial SrRuO3(SRO) thin films on SrTiO3 substrate by applying a pulse voltage between the conductive tip of AFM and SRO as a bottom electrode. The polarized domains were observed by detecting the inverse-piezoelectricity-induced surface vibration of the PZT thin film caused by applying an ac modulation voltage to the conductive tip. The recording density of polarized domains, domain switching speed and preliminary retention characteristics of polarized domains were studied. The polarized domains as small as 30 nm are formed in the PZT thin film with the thickness of 45 nm. The small domains can be formed by applying a 100 ns pulse of 10 V to the conductive tip. As for the retention characteristics of polarized domains with a size of 90–110 nm, the temperature dependence of dømain retention time was found to be in accordance with the Arrhenius model. Extrapolation of the Arrhenius plot leads to an estimation that the time for 50% of polarized domains to become smaller than half initial size at 50 °C is 34 years for 90–110 nm polarized domains in the 45 nm PZT thin film.