Noble metal-coated probes sliding at up to100 mm s−1 against PZT films for AFM probe-based ferroelectric recording technology

Abstract

With the advent of scanning probe microscopes, probe-based data recording technologiesare being developed for ultra-high areal density. In the ferroelectric data storage beingexplored, a conductive atomic force microscope (AFM) tip is scanned over a lead zirconatetitanate (PZT) film, which is a ferroelectric material. Ferroelectric domains can bepolarized by applying short voltage pulses between the AFM tip and the bottom electrodelayer that exceed the coercive field of the PZT film, resulting in nonvolatile changes in theelectronic properties. A crucial reliability concern is the wear of the AFM tip and PZTfilm. The understanding and improvement of tip wear, particularly at the highvelocities needed for high-data-rate recording, is critical to the commercialization offerroelectric data storage. To this end, wear experiments are performed usingvarious noble metal-coated tips sliding against a PZT film at velocities of 10 and100 mm s−1. The noble metals that were used were Pt, Au–Ni, Pt–Ir and Pt–Ni. High sliding velocitiesare achieved by using a custom calibrated piezo stage in a commercial AFM. The Au–Niand Pt–Ir tips are shown to exhibit the lowest wear. The tip wear mechanism isfound to be primarily adhesive and abrasive wear, with some evidence of impactwear. The coefficient of friction increases during wear. This study advances theunderstanding of the physics of friction and wear of noble metal-coated AFMprobes.