Recording more data in smaller areas is an important goal in the electronics industry. The majority of approaches for reducing the recording space rely on modifying a material’s phase using a probe tip to create patterns that record the data. Usually, however, the probe is heated to induce the phase change, which consumes relatively large amounts of energy because of the inefficiency of heat transfer between the probe and material.

Now, Jin Kon Kim from the Pohang University of Science and Technology and colleagues in Korea1 have demonstrated an alternative way of making patterns using pressure instead of heat. Their approach still involves a phase change to record data, but without heating, meaning much less power is consumed to write the patterns. They were also able to read and erase patterns one point at a time or all points at once.

Fig. 1: Nanometer-scale indentations on the polymer film record data at ultrahigh density.

Kim and colleagues used a polymer exhibiting baroplasticity — phase change upon applying pressure. In this case, the polymer is normally in an ordered state at room temperature. When pressure is applied, the polymer becomes disordered, and as a consequence, dents can be made by simply pressing with an atomic force microscopy (AFM) probe tip (Fig. 1).

The researchers created patterns that could record over one terabit of information per square inch, and they say that using a smaller probe tip would allow even higher recording density. The data in the pattern were read using a piezoelectric sensor that monitored the depth profile of the film. The whole pattern was quickly erased by heating on a hotplate to about 120 °C. Individual sections of the pattern could also be erased using the probe, at room temperature and without heating.

“IBM introduced the Millipede for the fabrication of nano-sized patterns on a polymer surface using an AFM tip a decade ago, but the AFM tip must be heated to at least 350 °C in their system,” says Kim. “Since we do not use a heated AFM tip, we can fabricate nanoscopic indentations without power consumption during the processing, and the possibility of degradation of the polymer film is minimized.”