Professor Jin Kon Kim (Department of Chemical Engineering) and his group have succeeded in developing macromolecule materials which use pressure to store terabit-scale ultrahigh-density data at room temperature, as well as the supporting technology to write, read, and erase the ultrahighdensity array of nanoscopic indentations.

The existing technology for fabricating nanopatterns, developed by IBM, was based on a thermomechanical recording system, using a heated atomic force microscope (AFM) tip at about 350°C. However, in addition to the difficulties in the fabrication of heated AFM tips, a relatively large power was consumed because of the very small percentage (<1%) of heat transmitted from the heated AFM tips to the polymer film.

Professor Kim’s group introduced a novel concept of using AFM, but without a heated tip. The nanopatterns are generated on the polymer film by the AFM tip at room temperature, and these nanopatterns retain their original shapes at room temperature. This process is only possible by using a specific block copolymer film exhibiting a baroplastic property that enables processing at a relatively low pressure and temperature by micro-phase transition.

The team found that polystyrene-block-poly(n-pentyl methacrylate) copolymer (PS-b-PnPMA) exhibits baroplasticity properties, and that because of its sensitive transitions to hydrostatic pressure, the microdomain PS-b-PnPMA disappears and becomes disordered at the relatively low pressure. By simple indentation with the AFM tip on the PS-b-PnPMA film at room temperature, a nanopattern was generated. An ultrahigh areal density of up to 1.03Tb in-2 was achieved, and this value could be increased further if a more sharpened AFM tip is available. The research group also demonstrated that the generated nanopatterns could be transformed into electric signals using a piezoelectric sensing method. Furthermore, local and bulk erasing of the nanopatterns was successfully carried out, and repeated erasing and rewriting processes up to 10 cycles were also demonstrated without any damage to the film.

This newly generated pressure-based phase-change memory at room temperature may expedite the development of a next-generation ultrahigh-density data storage medium. The technology is particularly expected to save energy consumption compared to the existing technology of IBM, whose operation requires a temperature of about 350°C. “Now, we can construct nanoscale patterns using only pressure at room temperature. Our achievement has prepared a technology basis for development of very high scale data storage materials, for which many global enterprises are scrambling,” commented Professor Kim.

The results of the study were published in the September 13, 2009, online issue of Nature Nanotechnology (2009, vol. 4, no. 11, 727-731) and introduced in News and Views of the same issue (703- 704). The work was also highlighted in NPG Asia Materials (2010, vol. 2, no. 1, 10).