Maissarath Nassirou

Charge-based scanning probe readback of nanometer-scale ferroelectric domain patterns at megahertz rates

We present a method for data storage in continuous ferroelectric (FE) media, applicable to storage systems based on one or more scanning probes. Written FE domains are read back in a destructive fashion by applying a constant voltage of magnitude greater than the coercive voltage, as is done in FE random access memory (FeRAM). The resulting flow of screening charges through the readback amplifier provides sufficient signal to allow readback of domains of minimum dimension of the order of 10 nm at MHz rates, orders of magnitude faster than previously demonstrated techniques for readback of domains in continuous FE media.

Comparison of depth-sensing indentation at ultramicroscopic contacts by single- and multiple-partial-unload cycles

Abstract Thin films typically exhibit variations in modulus and hardness with increasing indentation depth during depth-sensing indentation experiments at ultramicroscopic contacts (“nanoindentation”) because the measured stiffness response is affected by the substrate. There are three techniques commonly used to sample this variation in properties with depth: multiple indentations with increasing peak load, a single indentation with multiple-partial-unload cycles, and continuous stiffness measurement during a single indentation event. Experiments using the first two options were performed on a series of thin film systems and the method of multiple-partial-unloading found to have significant drawbacks when used at the sub-micron length scale that lead to erroneous conclusions.