Thermal writing and nanoimaging with a heated atomic force microscope cantilever

In thermal writing for surface modification or data storage, a heated atomic force microscope cantilever (AFM) tip is in contact with and scans over a thin polymer film, as shown in Fig. 1. Heat conduction along the cantilever tip induces thermomechanical formation of nanometer-sized indentations in the polymer. Erasing or modifying previously written structures is possible by writing such that heat from the tip and flow of the polymer influence nearby structures, also shown in Fig. 1. A thermal nanoimaging technique measures vertical feature sizes by monitoring changes in the thermal impedance across the cantilever-polymer gap as the cantilever tip follows the contours of the written structures, shown in Fig. 2. Indentations written with varying periodicity in Figure 3 show that heat transfer and polymer flow near the tip limit the packing density of indentations, corresponding to a data storage density limit of 0.9 Tbit in(-2). Figure 4 shows indentations written and then erased. Figures 3 and 4 are made with the thermal nanoimaging technique at 3 KHz and a lateral pixel spacing of 3 nm. The DeltaR/R reading sensitivity is 0.02 per vertical nanometer.