Recently, there have been many researchers for probe based data storage because of memory density limit of memory device. And many types of probe based data storage have been investigated. There are thermal-mechanical type, conductivity change type, charge change type of ferroelectrics, magnetic writing type and etc. In this study, charge change type of ferroelectrics among them was investigated. Because charge change type of ferroelectrics has low power cost, fast movement, rewritability, high density and etc. It was investigated suitable composition of $Pb(Zr,Ti)O_3$ thin films for the probe based data storage using charge change type of ferroelectrics.
In the top and bottom of ferroelectric films, electrodes were deposited for conventional ferroelectric memory device like FRAM. But in probe based data storage, there is no top electrode. In the charge change type of ferroelectrics, surface charge of ferroelectrics is used for identification of polarization states. Therefore in probe based data storage without top electrode, suitable composition of PZT thin films is different from conventional ferroelectric memory device.
To study suitable composition for probe based data storage, 100 nm thick PZT thin films as a function of Zr to Ti ratio were fabricated. The structural analysis of PZT thin films were investigated by SEM and XRD. And the electrical analysis of PZT thin films were investigated by P-V hysteresis loop, imprint measurements and Kelvin probe Force Microscope(KFM). And bit writing analysis of PZT thin films were investigated by Piezoelectric Force Microscope(PFM).
From these results, KFM contrast was large and bit signal transition width was small in 25/75 composition of PZT thin films. In probe based data storage, the larger bit signal intensity is, the easier identification of polarization states is. And when the bit signal transition width is small, the smaller bit can be formed. Therefore when Zr to Ti ratio is 25/75, it is most suitable for PZT media of probe based data storage. And in this study, it could be selected most suitable composition of PZT thin films using these analysis process for probe based data storage.
