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Volume 10, Issue 1 Spring 2008
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INTERFACES
The Newsletter of the Nebraska Center for Materials and Nanoscience |
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Facility Focus: Nano-Fabrication Facility Recent Achievements of Center Researchers Magnetic Nanoclusters Put in Order – Insights with Scanning Tunneling Microscopy NCMN Welcomes Eva Franke Schubert Research Spotlight: Barry Cheung UNL Hosts 54th Annual Midwest Solid State Conference Engineers Part of $9 Million Project Studying Cell Context of Genes |
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It is a pleasure to have this opportunity to describe some of the new research achievements and developments in the Nebraska Center for Materials and Nanoscience. Our faculty and their research groups are amazingly productive and especially active in promoting interdisciplinary work involving people from different departments and colleges. |
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The NSF will house NCMN administrative offices and seven Central or Core Facilities some of which will be in the basement of the PSB. In addition space is allocated in the NSF for Nanofiber and Biomaterials Facilities. The NCMN Central Facilities include Nanofabrication, Materials Preparation, Electron Microscopy, X-Ray Materials Characterization, Scanning Probe Microscopy, Mechanical Characterization, and Crystallography. The Nanofabrication Facility will be housed in a Clean Room in NSF and will provide new and transformative capabilities for NCMN research. In addition the centralization of these Facilities will provide a huge boost to collaborative research of groups associated with many science and engineering departments. David J. Sellmyer
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Facility Focus: Nano-Fabrication Facility
by Ned Ianno
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The Nano-Fabrication Facility is housed temporarily in Ferguson Hall, but is being designed to allow faculty and students to work together in a state-of-the-art environment to create novel nanostructures from a variety of materials. The Facility in the new NanoScience Facility will contain 4 separate areas (bays). Each bay will be a laminar flow area equivalent to a class 1000-5000 clean room, with all non-clean room compatible equipment, such as mechanical vacuum pumps contained in access corridors placed between or behind the bays. Each bay will be on the order of 400 square feet, plus the area of the equipment corridors. The bays are roughly defined as lithography, etching, deposition and analysis/characterization.
Focused-Ion Beam Workstation at its current location 16 Ferguson Hall.
The lithography bay will contain both direct write electron beam lithography as well as back side alignment capable optical lithography. The electron beam lithography system is the primary choice of Nano Research Centers for ultra-high-resolution patterning in the nanometer range. A 20-MHz pattern generator using optimized pattern filling modes shortens exposure times. Stability is improved by newly designed shielding with independent temperature control. |
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Awards, Honors
Christian Binek received the Sigma Xi Outstanding Young Scientist Award in 2007 for “setting a first-class laboratory to fabricate magnetic thin films and novel magnetic heterostructures with an emphasis on finding new and clever ways of controlling the exchange bias phenomenon in magnetic structures.” Outstanding PapersThe article “Structural Nancomposites” by Yuris Dzenis (Eng. Mech.) was published in the January 25, 2008 issue of Science. Student Awards and Honors
Andrew Baruth (Physics, S. Adenwalla), John D. Burton and Karolina Janicka (Physics, E. Tsymbal), and Lu Yuan (Physics, S.-H. Liou) received the 2007 Sigma Xi Outstanding Poster Award.
The following NCMN-affiliated students have earned their PhDs during the last year:
New jobs: |
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Magnetic Nanoclusters Put in Order – Insights with Scanning Tunneling Microscopyby Axel Enders
The impact of nanomagnetism on information technology has been critical in recent years and will remain so in the coming years. Magnetic thin films have been used for data storage in computer hard-disks for decades, and continuous advancements of their properties have led to an amazing increase of the areal storage capacity by many orders of magnitude. The future of magnetic data storage might depend on the development of devices based on patterned layers with ultrahigh densities of discrete magnetic elements and without any moving parts. The ideal magnetic storage device would consist of smallest monodisperse magnetic clusters, densely packed into an ordered monolayer, with stable remanent magnetization at room temperature, accessible switching fields, and negligible interactions. The key to success will be to fabricate hard-magnetic particles of approximately 3 nm diameter, as they still exhibit a stable magnetization direction at room temperature. The magnetization of smaller particles is thermally unstable, whereas big particles lead to a waste of areal density. However, the positioning of nanostructures at surfaces and engineering their properties is a key challenge in nanotechnology.
Figure 1. Fabrication of nanometer size clusters with a noble gas buffer layer. (1) Adsorption of Xe on the metal substrate at T = 30 K. (2) Deposition of metal onto the Xe. (3) Thermal desorption of Xe; clusters make contact with the surface. (4) STM image of Fe clusters on Pt(111) (Image size 100 x 100 nm2).
Figure 2. Fabrication of ordered cluster layers with template surfaces, imaged with scanning tunneling microscopy. (a) Boron nitride nanomesh monolayer, imaged with atomic resolution (inset). The distance between the centers of neighboring pockets in the BN layer is 3.2 nanometer. (b) STM image of Cobalt clusters (yellow) on the BN layer (purple) after one deposition cycle. (c) Repeated deposition cycles result in higher cluster coverage; here: 3 deposition cycles. (d) Schematic drawing of an ideal nanocluster layer with potential for application in magnetic data storage.
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Dr. Eva Franke Schubert has joined the University of Nebraska in Lincoln in 2007 as an Assistant Professor in the Department of Electrical Engineering and as a new member of the Nebraska Center for Materials and Nanoscience. Eva Franke Schubert received her Ph.D. degree in 1998 and her diploma degree in 1994, both from the University of Leipzig in Germany. She spent her Postdoc time in the Department of Electrical Engineering at the University of Nebraska in Lincoln from 1999 to 2000. After returning to Germany, Eva Franke Schubert worked at the Leibniz-Institute for Surface Modification in Leipzig and served in various positions. |
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The geometric constellation supports columnar growth with a structure inclination towards the direction of the upcoming particle beam. An instant change of the substrate position relative to the particle beam alters the columnar growth direction yielding to nanoscale building blocks with manifold structure varieties such as post, screws, spirals, zig-zags or combinations thereof. A tremendous opportunity is given by the fact that sculptured thin films can be grown from basically all groups of materials, which are accessible to physical or chemical vapor deposition.
Dr. Franke Schubert’s research is committed to fabricate and investigate new hybrid materials whose physical performance will be designed by a useful combination of intrinsic physical and chemical material properties with the material’s shape and dimension. Exemplary, chiral sculptured thin films may be composed of spiral-like nanoscale building blocks. Each of the spirals can be envisioned as a mechanical spring with a spring constant being mainly dependent on the wire material and its diameter. If the spring is made from a piezoelectric material, e.g. zinc oxide, the compression and expansion can be tuned by a small external electrical voltage applied to the nanosprings. Materials like this are foreseen for next generation electromechanically operated nanoactuators for highly precise positioning of small objects. More applications expected from nanoscale sculptured thin films are envisioned for new types of frequency-tunable long wavelength electromagnetic materials, or materials in photonic or magnetic device applications. Dr. Franke Schubert’s recent contributions to the field include the description of the growth and modification of sculptured thin films upon thermal annealing and an evaluation of their properties in three-dimensional optical nanogratings or for sub-wavelength anti-reflection coatings in the DUV spectral range. Dr. Eva Franke Schubert is currently developing a new deposition tool, which allows the fabrication of sculptured thin films by means of both, electron beam evaporation or ion beam assisted deposition, respectively.
Dr. Eva Franke-Schubert has published her research results in one book chapter, over 70 scientific publications and 11 invited conference presentations. She is a member of the German Physical Society, Materials Research Society and American Vacuum Society. So far, Dr. Franke Schubert gained a total of $ 500,000 external research funding from the German Science Foundation and National Science Foundation and received the Young Faculty Award from the University of Leipzig in 2001. Eva Franke Schubert teaches at the undergraduate and graduate level in the Department of Electrical Engineering and has developed new courses on “Fundamentals of Ion-Solid Interactions” and “Electronic Materials for Electrical Engineers,” respectively.
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The research team of Barry Cheung focuses on the nanostructure-induced phenomena in metallic boride material systems synthesized by chemical vapor deposition (CVD). The family of metallic boride materials typically has refractory properties including high melting points, high chemical stability and high hardness. Its members exhibit a wide range of other unique physical properties such as low work function, superconducting behavior and high coercivity. Applications of metallic boride materials range from strong permanent magnets (e.g. Nd2Fe14B), superconductors (e.g. MgB2), electron emission materials (e.g. LaB6) and to even colorful decoration coatings. Judicious choice of chemical reaction schemes is the most important key for successful growth of nanostructured crystalline materials with designed functionalities by CVD. Precise control of chemical reactant flux, reaction temperatures, and appropriate catalyst systems allow the controlled growth of materials with various shapes down to a few nanometers. Such control also allows the creation of multi-layered artificial nanostructures. These quasi one-dimensional nanostructures are expected to exhibit novel physical properties deviated from those of the bulk materials. |
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Controlled growth of high-aspect ratio nanomaterials enables the fabrication of efficient field electron emitters. An important part of Cheung’s present research involves the investigation of the electron emission characteristics of low work function metallic boride nanomaterials in the field emission and ballistic regimes. Recently, low work function metallic boride materials with shapes ranging from nanoobelisks to nanowires of tip diameters down to a few nanometers have been synthesized by Cheung’s team. Presently, they are studying the relationship between geometric shapes and the field emission behavior of these materials.
The major component in Dr. Cheung’s research and training involve the creation of novel nanomaterials and tools for studying these nanoscopic systems. Dr. Cheung was born and raised in Hong Kong SAR of China. He earned his Ph.D. degree at Harvard University, where his research focused on the synthesis and the use of carbon nanotubes for scanning probe microscopy. He joined UNL after his post doctoral training on the study of virus assembly model systems at Lawrence Livermore National Laboratory.
Dr. Cheung’s team of graduate students Joseph R. Brewer, Gonghua Wang, and Wanwan Huang worked together with post doctoral researcher Nirmalendu Deo. Their research focus is the development of refractory metallic boride and boron systems of nanomaterials for efficient high current emitters functioning in the ballistic emission regimes. This research may possibly lead to the next generation of high power nanoelectronics ranging from compact tetra Hertz klystron, parallel electron beam writers to field emission displays.
Trans-disciplinary research in Dr. Cheung’s group is achieved through collaborations with other NCMN members and national laboratories. Recent collaborative work on the design of medical bioceramic films is carried out with Dr. Namavar, Dr. Zeng, Dr. Mei and Dr. Sabirianov. Potential applications of these materials include implant coating and substrate platform for cell growth study. Besides studying the fundamentals for the growth of metallic boride systems, Cheung’s team also investigates the growth kinetics of CVD boron thin films. Through exploiting the conformal boron coating method developed in Cheung’s laboratory, Dr. Cheung’s team collaborates with Lawrence Livermore National Laboratory in the development of pillar-structure-based thermal neutron detectors.
Dr. Cheung’s group applies scanning probe microscopy, electron microscopy, DC and AC electrical characterization under high vacuum, and optical spectroscopic methods to characterize nanostructured metallic boride systems. As a member of the Nebraska Center for Materials and Nanoscience (NCMN), Dr. Cheung’s team conduct the structural and chemical characterization facilities at NCMN and the microscopy facilities at the Center for Biotechnology.
The fifty-fourth annual Midwest Solid State Conference, held in Lincoln on October 6-7, 2007, was organized by Sitaram Jaswal (Chair), Sy-Hwang Liou, Ralph Skomski, and Verona Skomski. Over 110 people from fifteen universities in California, Illinois, Iowa, Kansas, Missouri, Nebraska, Ohio, Oklahoma, South Dakota, and Wisconsin attended the conference.
The conference was sponsored by the Nebraska Center for Materials and Nanoscience (NCMN), the Department of Physics and Astronomy, the College of Arts and Sciences, and the Office of the UNL Vice Chancellor for Research. The first Midwest Solid State Conference was held in 1952 at Purdue University. The most recent conference marks the sixth time that the Physics and Astronomy Department at UNL has hosted the conference.
The distinguished speaker was Prof. Lu Sham from the University of California, San Diego, who presented a lecture on “Quantum Engineering of Individual Electron Spins.” Prof. Sham is internationally well-known for his pioneering contributions to the quantum theory of molecules and solids, especially the Kohn-Sham density functional theory.
Additional invited speakers:
- Steve Smith, South Dakota School of Mines and Technology
- Owen Vajk, University of Missouri-Columbia
- Hongxing Jiang, Kansas State University
- Walter Lambrecht, Case Western Reserve Univ.
- Axel Enders, University of Nebraska-Lincoln
- Andre G. Petukhov, South Dakota School of Mines and Technology
- Viatcheslav V. Dobrovitski, Iowa State Univ.
- Anupam Garg, Northwestern University
- Hui Zhao, University of Kansas
- Michael E. Flatté, University of Iowa
- Wai-Yim Ching, Univ. of Missouri-Kansas City
- Maikel Rheinstädter, Univ. of Missouri-Columbia
The following students (all NCMN!) received the best student poster awards:
- “The Origins of Tunneling Anisotropic Magnetoresistance in Nanoscale Ferromagnetic Metal Break Junctions” by J. D. Burton (Physics, E. Tsymbal)
- “Locally Probed Ferroelectricity of Ferroelectric Nanomesas by Piezoresponse Force Microscopy” by Jihee Kim (Physics, S. Ducharme)
- “Magnetization Precession and Damping in Ni/Pt Bilayers” by Steven Michalski (Physics, R. Kirby)
- “Temperature Dependent Dielectric Function of AL0.52IN0.48P and GA0.52IN0.48P” by Eric Montgomery (Electr. Eng., M. Schubert)
- “Scaling Behavior of the Exchange Bias Training Effect” by Srinivas Polisetty (Physics, Ch. Binek)
- “Thermodynamics of Itinerant Magnets: A Simple Classical Model with Longitudinal Spin Fluctuations” by Alexsander Wysocki (Physics, K. Belashchenko).
The participants were entertained after the banquet on Saturday by an excellent performance by the “Kokyo Taiko Drummers.” The group specializes in Wadaiko, a Japanese style choreographed drumming.
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“Special Issue Dedicated to Professor Vitaly L. Ginzburg, Nobel Laureate, in Celebration of his 90th Birthday,” V. M. Fridkin, S. Ducharme, W. Kleemann, Y. Ishibashi, eds., Ferroelectrics, Vol. 354 (Taylor and Francis, Princeton, NJ, 2007), 281 pages. “Biomedical Applications of Nanotechnology” edited by Vinod Labhasetwar and Diandra L. Leslie-Pelecky, Physics (Wiley-Interscience 2007). “The Physics of NASCAR: How to Make Steel + Gas + Rubber = Speed” by Diandra Leslie-Pelecky, Physics (Reed Elsevier Inc. 2008). “Simple Models of Magnetism” by Ralph Skomski, Physics (Oxford University Press 2008). |
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Engineers Part of $9 Million Project Studying Cell Context of Genes
- Office of University Communications, UNL -
Nebraska’s Experimental Program to Stimulate Competitive Research has received a three-year, $9 million grant from the National Science Foundation to conduct research to better understand gene expression and regulation.
Engineer Joseph A. Turner, chair and professor of Engineering Mechanics and plant scientist Sally Mackenzie, professor in Horticulture and Agronomy, will head teams of 15 other biological and biomedical scientists and engineers who will collaborate to create a research niche for Nebraska in epigenetics research, which is the study of changes in inherited gene functions not associated with changes in DNA sequences.
Nebraska Center for Materials and Nanoscience
University of Nebraska - Lincoln
P.O. Box 880113
Lincoln, NE 68588-0113