The objective of this Nanoscale exploratory research is to design a deconvolution-optimized probe tip (DOPT) whose nano-dimension resolving abilities drastically exceed that of current probe tips. The efforts of this design will enable measurement, analysis and understanding at levels capable of markedly improving the current state of realizable nanoscale processes and structures. In the probe tip design, we focus on the scanning probe microscopy (SPM) mode of magnetic force microscopy (MFM) because of (1) the inherently poor spatial resolution afforded by MFM (currently 20 nm) relative to other SPM modes and (2) the immediate implications to manufacturing the next generation of magnetic recording media at densities at 1 TeraBit/in2 and beyond (currently at 100 GigaBit/in2 commercially). The interdisciplinary effort required to achieve this resolution-increase necessitates the marriage of nanoscale magnetic physics and digital signal processing since the only way to overcome the physically imposed and resolution-limiting long range magnetostatic interactions between the magnetic media and the probe tip is through deconvolution processing. Tips will be manufactured for both perpendicular and longitudinal magnetic recording media. This effort will be supported by a close collaboration with Seagate Technology.
The research consists of designing and manufacturing a probe tip whose sensitivity response is optimally designed for magnetostatic interaction removal by digital deconvolution processing. The design process will iterate between (1) designing a digital filter from which a sensitivity response can be extracted that meets manufacturing constraints and (2) establishing tip geometries that exhibit the desired sensitivity responses. Of all the manufacturable tips, the best ones will satisfy the favorable design and digital deconvolution processing filter properties of invertibility, compact support size, separability and symmetry. The designs will have accounted for the physical manufacturing restrictions of minimum tolerable sensitivity main lobe width, maximum tolerable sensitivity response extent and sampling period allowable by the MFM machine. The manufacturing consists of focused ion beam (FIB) trimming of conventional MFM tips along with additional treating so that the tip's response is most sensitive to the longitudinal or perpendicular media under study. To assess the resolution increase achieved, atomic force microscopy measurements (known to achieve Angstrom level resolution) and others will serve as the comparative basis. Preliminary results by the PIs in tip fabrication and deconvolution processing are indicative of the resolution promise that the proposed tip design methodology holds.
The integrated research and education effort will allow a host of undergraduate and graduate students alike to contribute to the design process since much of the underlying concepts in the design are obtained in senior undergraduate or first semester graduate courses. Three existing courses in our curriculum will serve as the avenue for presenting and reinforcing research-based concepts through carefully planned class projects that benefit different phases of the research. Project and research results will also be incorporated into a web-based applet for DOPT design enabling other students and researchers to experiment with various configurations and trade-offs. Because FIU has one of the largest minority student (B.S. and M.S.) engineering concentrations on the U.S. mainland, and responding to the minority PI's leadership in this work, minority students will be positively impacted.
The intellectual merit lies in the proposed research being a substantial, unique and innovative departure from the current process of designing nanoscale probe tips. The most fundamental and important accomplishment of this work will be to demonstrate that sensors that are inhererently physically limited by convolutionally-based phenomena can be designed in conjuction with deconvolution processing such that these believed "limitations" are significantly overcome. The 10-fold resolution-increase expected to be achieved results from signal processing corrections to the physically imposed sensor degradations. Because of this, the proposed deconvolution-optimized probe tip promises to allow for rapid technological developments in nanoscale magnetic devices due to the Angstrom level resolution it is expected to achieve.
The broader impacts resulting from this research are that (1) it is believed that this marriage of tip manufacturing and deconvolution processing can be extended to other types of nonmagnetic interactions, such as Van-der-Waals, with analogous benefits and (2) it will act as a catalyst for the commercial magnetic hard disk storage industry to reach the 1 TeraBit/in2 frontier sooner than what might be considered achievable. The broad societal benefits to increasing bit densities to the levels listed are in the production of smaller, lighter weight hard disks and other magnetic memory devices of improved information capacity that would prove useful in portable devices, such as laptop and tablet computers and personal digital assistants (PDAs), and further fuel the push towards ubiquitous use of wireless devices and wireless infrastructure development.
This NER proposal addresses two of the high-risk/high-reward research and education themes that have been identified by NSF: Manufacturing Processes at the Nanoscale and Multi-scale, Multi-phenomena Theory, Modeling and Simulation at the Nanoscale.
