Nanotribology and nanomechanics of AFM probe-based data recording technology

With the advent of scanning probe microscopes, probe-based data recording technologies are being developed for ultrahigh areal density recording, where the probe tip is expected to be scanned at velocities up to 100 mm s(-1). In one technique, a conductive atomic force microscope (AFM) tip is scanned over a phase change chalcogenide medium and phase change is accomplished by applying either a high or low magnitude of current which heats the interface. Another technique is ferroelectric data storage, where a conducting AFM tip is scanned over a lead zirconate titanate (PZT) film, 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. Tip wear is a serious concern in both data storage methods. The understanding and improvement of tip wear, particularly at the high velocities needed and at high interface temperatures for high data rate recording, is critical to the commercialization of these data storage technologies. This paper presents a review of nanotribological and nanomechanical studies on the materials used in phase change and ferroelectric probe-based recording. Although this work is aimed at probe-based data recording, it is also relevant to the development of robust AFM probes and to the study of nanocontacts in general.