Research Depth Legacy




a. Nano Materials and Nanoelectronics in Space Extreme Environments

         My current research in Nano Materials and Nanoelectronics in Space Extreme Environments is supported by previous investigations that led through synthesis, characterization, architecture design and device fabrication with terrestrial testing. Collaborative work has underpinned each step and led to wider insertion beyond a single research community. My newer researches in quantum communications, nickel nanowires, and carbon onion lubricants are following similar paths to success. This research has been/is supported by 14 NASA grants, fellowships and internships, 1 NSF, and 3 materials or beam time award from NSF and FRIB. I know from my service as a NASA reviewer that larger awards are made in conjunction with industry and am using my new (2020) position as PI for the MSU Affiliate, NASA Michigan Space Grant consortium to initiate industrial contacts for myself and for others.



a.1. GaN Nanowires

         Gallium nitride (GaN) nanowires were known to self-assemble in two different morphologies as a function of growth temperature, with triangular versus hexagonal cross-sections. Ayres’ group was the first to demonstrate that both have internal structures that can affect device performance. Zinc-blende and wurtzite crystalline domains grow simultaneously along the entire length of triangular nanowires forming “nanowires within a nanowire”, energetically enabled through formation of 111/0001 coherent interfaces.



a.2.

         Cross section studies of hexagonal GaN nanowires revealed a different internal structure: hollow core screw dislocations, or nanopipes at or near the center of the nanowires and rods, along the axis of a screw dislocation. The formation of these hollow cores is consistent with relaxation of the giant Burgers vector screw dislocations predicted in “thin rods” from theoretical strain energy considerations seventy years ago.



a.3.

         This research was essentially enabled by collaboration with a group at Howard University, Washington DC that developed a very careful and unique nanowire synthesis procedure that eliminated much of the variability that plagued the field. Our mutual focus on fundamental understanding of the synthesis process as well as its results led to the determination that catalyst-free growth mechanism(s) were responsible. Our reporting credibility was high thanks to the resources of the Center for Advanced Microscopy at Michigan State University and at NASA Jet Propulsion Laboratory, Pasadena, CA, which enabled us to report cross-checked results obtained by cathodoluminescence, high-resolution transmission electron microscopy (HRTEM) in plan-view and cross-section, selected area electron diffraction (SAED), electron dispersive spectroscopy (EDS), electron energy loss spectroscopy (EELS), and fast Fourier transform (FFT) analysis.



a.4. GaN Nanocircuit Electronics

         We next fabricated nanowire based field effect transistors (nanoFETs) using the zinc-blende/wurtzite nanowires and investigated their electronic performance using a Zyvex KZ100 Nanomanipulator system in collaboration with the Zyvex corporate laboratory group in Richardson, TX. The electronic characterization with the KZ100 was performed in a LEO 1530 FESEM at room temperature (using a low-energy beam) that enabled real-time, visual inspection during the 2- and 4- point probe investigations. All experiments consistently indicated very high ~1-5 x 106 A cm−2 current densities. The SEM visualization uniquely enabled a new finding during the breakdown behavior investigations. During apparently normal I-V operation, a liquid protrusion formed at the probe contacted end. When breakdown did occur at ~50 μA, it was via sudden ductile pull-apart of the nanowire at a point approximately midway between the probes with evidence of interior nanowire melting that left an outer nanowire shell intact. The influence(s) of the zinc-blende/wurtzite internal structure on transport, scattering and phonon confinement are under investigation by our group. These results made it clear that electronic investigations alone may miss significant changes.



b. Nanoscale Cues for Regenerative Neural Cell Systems

         My current research in Nanoscale Cues for Regenerative Neural Cell Systems is uniquely supported by Scanning Probe Recognition Microscopy (SPRM). SPRM is a new investigative capability, developed by Profs. Ayres and Lalita Udpa during NSF GOALI CMMI-0400298 and NSF SGER BES-0225805. In SPRM, a scanning probe microscope system is given the ability to auto-track on regions of interest through incorporation of recognition-based tip control. The recognition capability is realized using algorithms and techniques from computer vision, pattern recognition and signal processing fields. Adaptive learning and prediction are also implemented to make the detection and recognition procedure quicker and more reliable. It is applicable to any scanning probe microscopy investigation and its first major use was to enable the first-time along-nanofiber tissue scaffold quantitation in NSF PHY 0957776, Collaborative Research: Nanoscale Cues for Regenerative Neural Cell Systems.

         This research has been/is supported by 3 NSF grants (+ 1REU) with 1 pending (change from 3-year to exploratory is pending). There are excellent opportunities to extend to NASA support as multiple calls for proposals for tissue scaffolds in space have been issued, with that my collaborative group and I are responding to.