Thermomechanical Formation of Nanoscale Polymer Indents With a Heated Silicon Tip

In thermomechanical data storage, a heated atomic force microscope cantilever tip is in contact with and scans over a polymer film. Heating in the cantilever and cantilever tip induces local deformation of the polymer near the tip, with indents as small as $22nm$⁠. This paper reports a simple modeling approach for predicting heat and mass transfer in the cantilever tip and polymer with the goal of predicting indent formation conditions. The model accounts for subcontinuum conduction in the cantilever tip and for the time- and temperature-dependent mechanical properties of the polymer. Simulations predict steady state and transient indent formation, and the results compare well with data. For loading forces $30–200nN$ and a tip radius of $20nm$⁠, a cantilever temperature of $200°C$ is required to form an indent at steady state. For heating pulses as short as $5μs$⁠, the cantilever temperature required for bit formation is as high as $500°C$⁠. By quantifying the conditions required for indent formation, this work may improve the operation of heated probes for thermomechanical data storage.