Noble metal-coated probes sliding at up to 100 mm s(-1) against PZT films for AFM probe-based ferroelectric recording technology

摘要

With the advent of scanning probe microscopes, probe-based data recording technologies are being developed for ultra-high areal density. In the ferroelectric data storage being explored, a conductive atomic force microscope (AFM) tip is scanned over a lead zirconate titanate (PZT) film, which is a ferroelectric material. Ferroelectric domains can be polarized by applying short voltage pulses between the AFM tip and the bottom electrode layer that exceed the coercive field of the PZT film, resulting in nonvolatile changes in the electronic properties. A crucial reliability concern is the wear of the AFM tip and PZT film. The understanding and improvement of tip wear, particularly at the high velocities needed for high-data-rate recording, is critical to the commercialization of ferroelectric data storage. To this end, wear experiments are performed using various noble metal-coated tips sliding against a PZT film at velocities of 10 and 100 mm s(-1). The noble metals that were used were Pt, Au-Ni, Pt-Ir and Pt-Ni. High sliding velocities are achieved by using a custom calibrated piezo stage in a commercial AFM. The Au-Ni and Pt-Ir tips are shown to exhibit the lowest wear. The tip wear mechanism is found to be primarily adhesive and abrasive wear, with some evidence of impact wear. The coefficient of friction increases during wear. This study advances the understanding of the physics of friction and wear of noble metal-coated AFM probes.