A Study on the Time-Dependent Deformation Behaviors of PMMA in Nanoindentation Process for Hyperfine Pit Structure Fabrication

The nanoindenter and AFM have been used for nanofabrication, such as nanolithography, nanowriting, and nanopatterning, as well as measurement of mechanical properties and surface topology. Nanoscale indents can be used as cells for molecular electronics and drug delivery, slots for integration into nanodevices, and defects for tailoring the structure and properties. Therefore, it is very important to make indents of desired morphology (shape, size and depth). Indents of different shapes can be obtained by using indenters of different geometries such as a cube comer and conical and spherical tips. The depth and size of indents can be controlled by making indentations at different indentation loads. However, in case of viscoplastic viscoelastic materials such as polymethylmethacrylate (PMMA) the time dependent deformation (TDD) should also be considered. In this study, the effect of process parameters such as loading rate and hold-time at peak load on the indent morphology (maximum penetration depth, elastic recovery, transient creep recovery, residual depth pile-up height) of PMMA were studied for hyperfine pattern fabrication.