Christian Binek - US grants

Professors Jody G. Redepenning and Bernard Doudin of the University of Nebraska-Lincoln are supported by the Analytical and Surface Chemistry Program in the Division of Chemistry to develop chemically modified nano-electrodes to be used in magnetoelectronic devices, such as permanent memories, reconfigurable logics, and fast electronic components. To accomplish this goal, the investigators plan to explore two types of barriers and to reduce the size of the junctions. One will be comprised of silicon oxide produced by repetitive hydrolysis/condensation of tetramethylorthosilicate on the surfaces of the electrodes. A second class of junctions will be produced by irreversible polymerization of appropriate metal complexes onto the surfaces in the junction. The idea is to passivate the surfaces of magnetoresistance tunnel junctions while introducing thin dielectric materials with controllable properties. The goal is to understand the elusive properties of barriers and how resonant tunneling effects occur.
The discovery of giant magneto-resistance led to commercial devices such as hard-disk read heads, magnetic field sensors and magnetic memory chips. Tunnel magneto-resistance devices are another example of development from laboratory proof of principle to industrial applications within a remarkably short time. Future generations of magnetic sensors and memory elements are likely to be be constructed in the nano-scale. Understanding magnetoresistance properties at the nanoscale will help build the knowledge base required for future device miniaturization. This research will involve graduate students, undergraduate students, and high-school teachers, giving them complementary and interdisciplinary education in nanotechnology. The interdisciplinary nature of this project will create new synergies between chemists and physicists.

Non-Technical Abstract:
Modern materials science permits manufacturing of layered magnetic thin film structures where growth conditions are controlled down to the atomic scale, which in turn enables fabrication of new and potentially useful artificially designed heterosystems. This Faculty Early Career Award funds education and research on nanoscale spintronic systems and magnetic heterostructures at the University of Nebraska-Lincoln. Special emphasis is laid on the fabrication of novel spintronics devices combining memory and logical functions. In general, spintronics takes advantage from the control of electric currents via the electron spin which adds a new degree of freedom to the conventional charge based current control. Here, new functionality is based on the electric control of the interface magnetization and the resulting electrically controlled interaction between magnetoelectric and ferromagnetic thin films in close contact. State of the art technology of thin film growth is used to produce these novel devices. In addition, fundamental aspects of thermodynamics in artificial magnetic superstructures are explored. This includes the control of interlayer interaction in novel superlattices by temperature, magnetic and electric fields. These studies have applications in magnetic refrigeration technology and provide access to hitherto unexplored magnetic phases. Research and education in spintronics and nanostructuring offers key qualifications in a field which presumably will revolutionize future information technology and will have a huge impact on US economy. The complexity of this field demands new educational methods. This award funds an E-learning approach using interactive online virtual experts ("knowledge Avatars") as a new key element. An Avatar is an interactive online character communicating face to face with the user, creating an intimate relation with a virtual platform. Web-based, Avatar-guided visualizations, hypertexts combining power point shows and animations, and virtual "hands-on" experiments will provide an interactive approach to learning and are a modern platform to attract public interest in research and education at the University of Nebraska-Lincoln.

Technical Abstract:
Modern materials science permits control of the composition and the morphology of layered structures on the nanoscale or even below, which in turn enables fabrication of new and potentially useful artificially designed heterosystems. This Faculty Early Career Award funds education and research on nanoscale spintronic systems and magnetic heterostructures at the University of Nebraska-Lincoln. Special emphasis is laid on the fabrication of novel spintronics devices combining memory and logical functions. Their functionality is based on the electric control of the interface magnetization in exchange bias heterosystems using molecular beam epitaxial growth of magnetoelectric/ferromagnetic exchange coupled thin films. In addition, fundamental aspects of thermodynamics in artificial magnetic superstructures are explored. This includes the control of interlayer exchange in antiferromagnetic superlattices by temperature, magnetic and electric fields. These studies aim on the creation of very large entropy changes in artificial magnetocaloric heterostructures and the control of staggered fields in artificial antiferromagnets providing access to hitherto unexplored magnetic phase transitions. Research and education in spintronics and nanostructuring offers key qualifications for the challenges involved in future technology. The complexity of this field demands new educational methods. This award funds an E-learning approach using interactive online virtual experts ("knowledge Avatars") as a new key element. An Avatar is an interactive online character communicating face to face with the user, creating an intimate relation with a virtual platform. Web-based, Avatar-guided visualizations, hypertexts combining power point shows and animations, and virtual "hands-on" experiments will provide an interactive approach to learning and are a modern platform to attract public interest in research and education at UNL.

0922937
Schubert
U. of Nebraska-Lincoln

Technical Summary: Measurement of free charge carrier properties in complex nanostructure materials and heterostructures is becoming increasingly indispensible for understanding of fundamental and new physical phenomena in such materials. Traditional electrical Hall effect instruments are limited in their ability to probe the free charge carrier properties, particularly in operation modes which are contactless, non-invasive, non-destructive and yet capable of spatially resolving the charge carrier behavior. This project aims to develop a low-operation-cost, feasible, easy-to-use, desk-top-style, and world-unique Optical Hall effect instrumentation for the 0.1 to 50 Terahertz (THz) spectral region for studying samples within magnetic fields up to 8 T, and in the temperature range between 4 K and 300 K. The new development measures the transverse and longitudinal optical birefringence at long wavelengths due to displacements of charge location in an external magnetic field, as a function of wavelength, magnetic field direction, and strength. The Optical Hall effect instrument allows understanding of charge and spin transport properties, and will greatly advance our understanding of multiferroic tunnel structures, magnetoelectric heterostructures, ferromagnetic, and ferroelectric polymer structures, magnetic, and piezoelectric hybrid nanostructures and novel solar cell materials and devices, for example. The instrumentation will be developed at the University of Nebraska-Lincoln (UNL), and will be used in collaboration between different Universities, National Laboratories and Companies working with electrical properties of nanostructure materials and devices. The proposal will integrate the education of graduate and undergraduate students with basic research and new instrumentation development, and will leverage with NSF-MRSEC QSPIN, 2 NSF-CAREER, and NSF-DMR program activities and inter-departmental and inter-collegiate collaborations within the University of Nebraska-Lincoln. The MRI development will promote productive partnerships for instrument development between UNL, and the J. A. Woollam Co., Inc. of Lincoln, Nebraska, the world-leading manufacturer of spectroscopic ellipsometry instrumentation.

Layman Summary: The motion of electrons and their positively charged counterparts - holes - in nanostructure materials is governed by new phenomena due to the confinement imposed by the nanostructure geometry and composition. Knowledge of the charge properties within such nanostructures will enable design of new materials and devices with capabilities far beyond current technology. Monitoring electron and hole motions within strong magnetic fields using polarized Terahertz and Far infrared light at frequencies up to ten thousand times faster than current desktop computer clock speed reveals their location and properties, and fundamental and new physical phenomena can be explored in such materials. Traditional methods require electrical contacts, which are difficult or simply impossible to attach to the nanostructures. The new and world-unique Optical Hall effect instrumentation employs frequencies which penetrate the nanostructures and screen their electron and hole properties without electrical contacts. Many innovations are expected from studying new multifunctional nanostructures for solar and energy restoring applications, for example. The instrumentation will be developed at the University of Nebraska-Lincoln (UNL), and will be used in collaboration between different Universities, National Laboratories and Companies working with electrical properties of nanostructure materials and devices. The proposal will integrate the education of graduate and undergraduate students with basic research and new instrumentation development, and promote productive partnerships between UNL, and the J. A. Woollam Co., Inc. of Lincoln, Nebraska, the world-leading manufacturer of spectroscopic ellipsometry instrumentation.

Non-technical abstract

Phase transitions refer to changes in a material's properties, often driven by temperature changes. The ubiquitous phase transition of water, which transforms from ice to liquid water to steam as the temperature increases, serves as an excellent example. Pressure significantly alters the temperature of water's transitions, as anyone who has baked a cake at high altitude well knows. The research component of this project will investigate the effects of rapidly changing pressure on phase transitions of technologically important magnetic materials by focusing a very fast (ultrasonic) sound wave on the material. By varying the pressure at rates of up to 10 billion times a second, the investigators will probe how the material's properties vary. The fundamental questions being probed are how quickly can the material respond, what will the response be and why does a particular material respond the way it does. The educational component is informed by the PIs' extensive experience in outreach and education at all levels ranging from preschool, K-12 and undergraduate education. New activities on phase transitions, tailored to the needs of a particular age group, will be developed to tie in with this research project.

Technical Abstract

The research activity will investigate the dynamics of strain driven phase transitions in materials that show intricate entanglement between structure and ordering, viz. the magnetoelectric antiferromagnet Cr2O3 and the antiferromagnetic Mott insulator NdNiO3. In both cases the antiferromagnetic ordering is coincident with the appearance of another transition, surface boundary magnetization for Cr2O3 and a metal-insulator transition for NdNiO3. Focused surface acoustic wave transducers will generate strains that are comparable in magnitude to fixed, epitaxial strains and allow for controlled variable strain on a single sample, as well as the ability to drive strain at high frequencies. This approach of precisely controlled lattice excitation is unique in its the ability to drive materials back and forth across the phase transition at GHz frequencies, resulting in large changes in the order parameter, rather than small perturbative changes. This approach can be extended to a wide variety of strain sensitive ordering in thin film materials and will answer two fundamental questions. First, it will quantify the effects of external strain on the phase transition temperature of a single thin film sample, eliminating the uncertainties associated with thin film growth. Second, it will measure the temporal scale over which these strain driven phase transitions occur. The educational objectives will extend the reach of this cutting edge science by expanding the PIs' portfolios to include topics that are relevant to this project. The PIs will share their knowledge, skills and excitement with the already extensive ongoing outreach and education projects that include K-12 students and teachers, science cafes, science clubs, and senior citizen groups.

The Nebraska Nanoscale Facility (NNF) at the University of Nebraska will provide a regional center of excellence for instrumentation and service in nanoscience and nanotechnology to the NNCI. It will contribute to the United States research and educational infrastructure for transformative advances in the fabrication, understanding and utilization of novel nanostructures, materials and devices. These structures and devices play an increasingly critical role in contemporary technologies including ultraminiaturization in information processing, digital communications, energy processing, sensors for threat detection, and biomedicine. Special attention will be given to serving the nanotechnology needs of educational institutions and industry in the western region of the United States Midwest. NNF will significantly enhance economic development through industrial collaborations, spin-offs, materials analyses, and tech-transfer to companies. National impact will result from interactions and collaborations with the newly developing Nebraska Innovation Campus and the National Security Research Institute at the University of Nebraska. A strong education-outreach program at NNF is focused on increasing diversity through summer research experiences for students and professor-student pairs, after school middle-school programs, community-college programs, minicourses, and others. In addition, education and outreach efforts will be pursued with Native Americans and tribal colleges in Nebraska associated with the Winnebago, Santee Dakota, and Omaha tribes.

NNF will build upon the established Central Facilities of the Nebraska Center for Materials and Nanoscience to strongly galvanize research and education in nanotechnology in Nebraska and the region. The Central and Shared Laboratory Facilities include: Nanofabrication Cleanroom, Nanomaterials and Thin-Film Preparation, Nanoengineered Materials and Structures, Electron Microscopy, X-ray Structural Characterization, Scanning Probe and Materials Characterization, Low-Dimensional Nanostructure Synthesis, and Laser Nanofabrication and Characterization. Most of these facilities are housed in the 32,000 sq. ft. Voelte-Keegan Nanoscience Research Center that was completed in 2012 and funded by major grants from the National Institute for Standards and Technology and the University of Nebraska Foundation. The research in NNF is bolstered by strong research groups in nanoscale electronics, magnetism, and materials and structures for energy. NNF in turn will reinforce several centers and focused research programs including the Nebraska NSF-MRSEC: Polarization and Spin Phenomena in Nanoferroic Structures, DOE-EERE Consortium on Magnetic Materials, SRC-NIST Center for Ferroic Devices, NSF-Center for Nanohybrid Materials, and others. These programs have many national and international collaborators that will add vitality to and provide a broad base of users for the NNF. Hundreds of graduate and undergraduate students, postdoctoral research associates, and visiting scientists and engineers from companies will benefit each year from the state-of-the-art facilities in NNF.

There is a critical need for new technologies as the semiconductor industry reaches the limits of how small a transistor can be made and how much power can be used in an increasingly small space. This project will meet this need through the development of novel memory and logic devices. Continual interaction between academia and the semiconductor industry will ensure in new semiconductor device concepts that lead to faster and better electronics that use significantly less energy than current approaches. These advances will exploit the unusual magnetic properties of magnetoelectrics, a special class of materials that tie together magnetism and voltage. An important aspect of the devices will be their nonvolatility, a feature that makes them prime candidates for use in the emerging Internet of Things. Nonvolatility refers to the property that once written, information can be recovered, even if electrical power has been absent for an extended period. An example of such a situation is the shutdown of a computer. A computer equipped with this type of "instant on" circuitry will restart to the exact state when power failed. Nonvolatility will also lead to energy savings by enabling electronics to operate longer on smaller batteries with less need for recharge. Reducing the energy cost of consumer electronics could also lead to some world-wide energy savings, as new less energy expensive electronics become available.

This project develops novel device concepts to greatly extend the practical limits of energy-efficient computation, focusing primarily on magnetoelectric materials, enabling interfacial magnetism to be reversibly switched by voltage. This approach to the writing of magnetic information via voltage will result in a significant reduction in energy consumption, while improving the computing speed of integrated circuit technologies. To enable electronic applications based on these devices to come to fruition, the new concepts must allow for miniaturization, inexpensive fabrication on a huge scale, and long working lifetimes. Just as for conventional electronic circuits, to ensure reliable operations, the new devices will be capable of operating repeatedly at well above room temperature. By exploiting more than just electrical charge in each device, these new devices will have more function than a simple transistor, which in turn, will present new opportunities for the development of circuit ideas that go beyond existing technologies ? ideas that will also be explored as this research program develops.

Non-Technical Description
One of the core elements of modern science is to acquire structural information from a broad range of length scales including the scale of atoms, molecules, and nanostructures to solar systems and galaxies. Imaging methods in real space play an ever-increasing role in structure analysis. From the acquired information, it is then possible to build theoretical models that can explain the underlying phenomena. In the case of nanoscience and materials research, imaging structures and properties has led to revolutionary progress in nanotechnology, information technology, and biotechnology, particularly after the invention of electron and scanning-probe microscopy, for which Nobel prizes were awarded in 1986. This grant allows purchase of a cutting-edge microscopy system with extreme sample environments to further advance the boundary of science in terms of elucidating the underlying mechanisms of complex material properties on the nanometer scale. The outcome of the research carried out using the microscopy system is expected to have important impacts on the applications of many mechanical, electrical, magnetic, and energy materials. The microscopy system also provides training opportunities on the state-of-the-art microscopy instrument for a large group of graduate and undergraduate students and postdoctoral researchers and help promote public awareness of the importance of nanoscience and nanotechnology.

Technical Description
This project acquires a state-of-the-art, multifunctional, low-temperature, high-magnetic-field scanning probe microscopy system at the University of Nebraska-Lincoln and enables broad usage of the system for nanoscale science and engineering research. The system is capable of characterizing spatially resolved conductivity, magnetic force, piezoresponse force, and topography down to the nanoscale. The system is equipped with an ultra-low-vibration sample environment that offers a wide range of temperature and magnetic fields. Building on the versatile capabilities of the system, this instrument enables research projects that explore: 1) the morphology, electric transport, magnetism, and ferroelectricity on nanoscale and low-dimensional materials; 2) the coupling between these properties; 3) material properties that emerge only at extreme conditions, as well as the related thermodynamic phase transitions; and 4) quantum phase transitions in electric and/or magnetic fields.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Materials science is in the midst of a second quantum revolution where quantum phenomena on a macroscopic scale enable new forms of quantum materials and quantum technologies with revolutionizing impact in medicine, banking, and defense due to quantum enabled advances in information technology, sensing, communication, computation, simulation and cryptography to name just a few examples. This Major Research Instrumentation award supports the University of Nebraska-Lincoln which hosts the Nebraska Center for Materials and Nanoscience (NCMN) and its NSF funded EPSCoR center on emerging quantum materials and technologies. With this MRI award, researchers will take full advantage of the existing cryogenic scanning probe microscope which enables atomic, magnetic and piezo force microscopy at temperatures between 4 and 300K and magnetic fields up to 9T, and utilize it to create a commercial high-resolution quantum sensing platform. This versatile characterization tool is a quantum sensing application which enables state-of-the-art characterization of novel quantum materials. The instrument puts Nebraska on the map as a pioneer in many areas of quantum materials science. Because the instrument is part of NCMN’s core facilities, it becomes accessible to internal and external users. Access to this instrumentation paves the way for Nebraska’s emerging quantum technology-based economy, which builds on the existing high-tech industry within the Silicon Prairie. Equally important is the fact that the access to this instrument allows educating students and training quantum engineers for the much-needed quantum workforce. <br/><br/><br/>This Track 1 Major Research Instrumentation award is for the acquisition of a Nitrogen Vacancy (NV)-Attocube (Atto) atomic force microscope (AFM) integrated with a confocal microscope (CFM), which allows magnetic, optical, and quantum measurements at the nanometer scale. The instrument will be located at the Surface and Materials Characterization division of the Nebraska Center for Materials and Nanoscience (NCMN) at the University of Nebraska-Lincoln (UNL). The acquisition of the module will transform the existing NSF-funded low-temperature high-magnetic-field multifunctional scanning probe microscope into a versatile platform for NV quantum sensing and fundamental research on quantum entanglement. The point defect atomic nature of the NV center and its spin millisecond quantum coherence lifetime allow measurements of a wide range of quantum materials with high sensitivity and spatial resolution (< 40 nm). Additionally, it operates at high magnetic fields and across a wide range of temperatures. The system can support various experiments, including magnetic imaging of solid-state materials and biomolecules as well as mapping optical and thermal properties of low-dimensional materials. Currently, there are five similar instruments in the U.S. with limitations in types of materials studied (e.g., only superconductors) or magnetic field range (only < 0.5 T). In acquiring the NV-AttoAFM/CFM, the goal is to position UNL at the forefront of quantum sensing capabilities ushering in the age of applied quantum technologies in Nebraska and U.S. Midwest. The infrastructure of NCMN, a user facility serving the Midwest research community and startup companies, includes the technical support of a PhD-trained expert in scanning probe microscopy, which ensures long-term maintenance, sustainability, and user support.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.