题目：Complete crystal-orientation control of FeCo nanowires for use in nanoscale magnetic resonance imaging
报告人：Ye Tao
时间：2017年12月29日上午10：00
地点：betway必威动力与机械学院报告厅
欢迎各位师生踊跃参加！
Abstract text:
The development of strong nanomagnetic gradient sources is important for of magnetic resonance force microscopy (MRFM) cite{1} cite{2} cite{3} and force-based detection of magnetic moments cite{4}. These techniques have the potential to significantly advance material science and structural biology research by providing direct 3D, atomic-resolution structural information on a single-copy of heterogeneous nanoscale matter. Access to highly magnetic tips with precise, nanometer-resolution controls of tip geometry and material composition would further advance the technique by enabling closer approach of the gradient source to the sample cite{5} cite{6}.
One approach to controllable tip geometries is the bottom-up growth of single-crystalline magnetic nanowires cite{7}. However, the production of nanowire materials, uniformly oriented along any arbitrarily chosen crystal orientation, is an important, yet unsolved, problem in material science cite{8}. A practical need for MRFM has thus led us to devise a generalizable solution to this material science problem, using FeCo as the demonstration material system.
We found a solution is based on the technique of glancing angle deposition cite{9} combined with a rapid switching of the deposition direction between crystal symmetry positions. We showcase the power and simplicity of the process in one-step fabrications of <1 0 0>, <1 1 0>, <1 1 1>, <2 1 0>, <3 1 0>, <3 2 0> and <3 2 1>-oriented nanowires, three-dimensional nanowire spirals, core-shell heterostructures and axial hybrids. The resulting nanowires are single-crystals, have high saturation magnetization of 2.0(2) Tesla, and passivated by a surface oxide below 3 nm in thickness after one year of storage in air. Our results provide a new capability for tailoring the shape and properties of nanowires, should be generalizable to any material that can be grown as a single-crystal biaxial film, and has already offered a new route towards next-generation tip-on-cantilever MRFM sensors.
References
[1] https: //doi:10.1038/nnano.2007.105
[2] https://doi.org/10.1063/1.2752536
[3] https://doi.org/10.1103/PhysRevB.85.054414
[4] https:// doi:10.1038/ncomms12714
[5] https://doi.org/10.1103/PhysRevLett.96.156103
[6] https://dx.doi.org/10.1063/1.4928929
[7] https://dx.doi.org/10.1021/nl103301x
[8] https://dx.doi.org/10.1002/adma.201305929
[9] https://doi.org/10.1116/1.2764082
About the lecturer:
- Ye Tao is a principal investigator at the Rowland Institute at Harvard. He currently spearheads nanoscale device engineering, materials synthesis, and instrumentation development to push magnetic resonance imaging (MRI) towards atomic resolutions.
- Tao received doctoral training in experimental solid-state physics at ETH Zurich and holds a Ph.D. degree in physical chemistry from MIT in 2015, supported by a MIT Presidential Fellowship. Prior to that, he had become well-versed in physical organic chemistry and structural molecular biology at Harvard University. His undergraduate research resulting in a publication in Science and a Hoops Prize Award for his thesis, which was praised by advisor Prof. Eric Jacobsen as ‘outstanding’ even among PhD theses from the group.
Research led by Dr. Tao has consistently set records relating to ultrasensitive force detection and extreme-geometric control in device fabrication. The multidisciplinary work have been recognized in journals including Advanced Materials, Applied Physics Letters, Chemical Communications, Nano Letters, Nanotechnology, Nature Communications, Small, and Science.
The Tao lab welcomes passionate researchers at all levels of training to bolster our efforts in developing atomic-resolution MRI. While self-funding for living expenses is necessary, general research funding for highly qualified collaborators may be available. We hope that you share our enthusiasm about the prospect of revolutionizing practices in material science metrology and structural biology!
