Indentation of piezoelectric micro- and nanostructures

This study is focused on obtaining a comprehensive understanding of the influence of geometry - size and shape - on the indentation response of a large set of piezoelectric small-volume structures such as nanoislands, nanowires and thin films. Using three-dimensional finite element modeling, the complex interplay between the properties of the indented materials and the indentation response of piezoelectric micro- and nanostructures is analyzed. It is demonstrated that: (i) In general, the indentation response of thin film structures tends to be much stiffer than that of the piezoelectric nanoisland and nanowires, resulting in more charges being generated during the indentation of the thin-film structures. (ii) The indentation of the piezoelectric nanowire structures with a spherical indenter whose radius is substantially larger than the width of the nanowires, introduces a combination of deformation modes - structural bulging and indentation-induced compression. The combined effect of two deformation modes produces a maximum in the charges generated during the indentation process on a nanowire structure with a particular aspect ratio (i.e., wire width/wire height), which is greater than that produced in nanoisland and thin films structures with the same characteristic size.