Channel modeling and detector design for dynamic mode high density probe storage and nano-imaging applications

In this paper, we provide a consolidated summary of the work reported in [1], [2], [3], [4] which is based on probe based high density storage and nano-imaging using atomic force microscopy (AFM) setup. In probe based high density storage, we consider a data storage system that operates by encoding information as topographic profiles on a polymer medium. A cantilever probe with a sharp tip (few nm radius) is used to create and sense the presence of topographic profiles, resulting in a density of few Tb per in.2. The high quality factor dynamic mode operation, that is less harsh on the media and the probe, is analyzed. The read operation is modeled as a communication channel which incorporates system memory due to inter-symbol interference and the cantilever state. Next, the solutions to the maximum likelihood sequence detection problem and maximum a posterior (MAP) symbol detection problem based on the Viterbi algorithm and BCJR algorithm respectively are devised. Experimental results demonstrate that the performance of the Viterbi and BCJR detectors are several orders of magnitude better than the performance of other existing schemes. Nano-imaging has played a vital role in basic sciences as it enables interrogation of material with sub-nanometer resolution. In this paper, we also present a high speed one-bit imaging technique using dynamic mode AFM with a high quality factor cantilever. Experimental results demonstrate that our proposed algorithm provides significantly better image resolution compared to current nano-imaging techniques at high scanning speed.