Demonstration of thermomechanical recording at 641 Gbit/in/sup 2/

Ultrahigh storage areal densities can be achieved by using thermomechanical local-probe techniques to write, read back, and erase data in the form of nanometer-scale indentations in thin polymer films. This paper presents single-probe experimental results in which large data sets were recorded at 641 Gbit/in/sup 2/ and read back with raw bit-error rates better than 10/sup -4/. (d,k) modulation coding is used to mitigate the effect of partial erasing, occurring when subsequent indentations are spaced too closely together, and to increase the effective areal density. The physical indentation profile, the sensitivity of the probe in readback mode, and noise sources that affect data detection are also discussed. Quantitative measurements of the partial erasing effect in both the on-track and cross-track directions are reported.