Nikoleta Theodoropoulou, Ph.D. - US grants

0923509
Theodoropoulou
Texas State U. - San Marcos

Technical Summary: The ability to both pattern and image at the nanoscale is indispensable for present-day materials science. The acquisition of a FEI NOVA NanoSEM 230, Ultra High Resolution Scanning Electron Microscope (SEM) capable of electron beam (e-beam) lithography provides the capability and reliability necessary for interdisciplinary research in the new Materials Science and Engineering Ph.D. program at Texas State University. This instrument eliminates barriers to research productivity presented by the existing antiquated SEM capable only for larger scale imaging, and enables the platform for interdisciplinary research linking innovation and discovery between the physical, engineering, and biological sciences. This Field Emission (FE) SEM combines high- and low-voltage ultra-high resolution with an imaging resolution of 1.0 nm and a writing resolution of nominally <10 nm at 30 kV. Importantly, 20-nm patterning can be done routinely. The system features: a high stability ultra-high brightness FE electron source with high beam current capability; low pattern distortion and drift; high precision stage and pattern overlay; environmental SEM technologies; high speed electrostatic beam blanker; and gas injection systems for direct e-beam writing of nanostructures. The e-beam writing capability enables fabrication of structures applicable to multidisciplinary problems such as investigation of nanostructure based photonic or electronic biological sensors for molecular recognition, nano devices for more efficient energy conversion, and the spin physics of magnetic nanostructures. The SEM?s accessibility, ease of use, and consistency make the e-beam system ideal for integration into our educational and research programs benefitting undergraduate, graduate and post doctoral students. The core faculty involved in this project at Texas State, which anticipates achieving Hispanic Serving Institution status next year, will use the instrument to enhance outreach programs to assure the maximum opportunity for training and research by a diverse population of students.
Layman Summary: The ability to both pattern and image at the nanoscale is indispensable for present-day materials science. The acquisition of an Ultra High Resolution Scanning Electron Microscope (SEM) capable of electron beam lithography provides this necessary capability for interdisciplinary research in the new Materials Science and Engineering Ph.D. program at Texas State University. This instrument eliminates barriers to research productivity presented by the existing antiquated SEM capable only for larger scale imaging, and provides the platform for interdisciplinary research linking innovation and discovery between the physical, engineering, and biological sciences enabling advances in nanoscale materials research for health, energy and security applications. The electron-beam writing capability enables fabrication of structures at the nanoscale (10-7m - 10-9 m) applicable to multidisciplinary problems such as investigation of nanostructure based biological sensors for molecular recognition, nano devices for more efficient energy conversion, and the spin physics of magnetic nanostructures. The SEM?s accessibility, ease of use, and consistency make the electron-beam system ideal for integration into our educational programs benefitting undergraduate, graduate and post doctoral students. The core faculty involved in this project at Texas State, which anticipates achieving Hispanic Serving Institution status next year, will use the instrument to enhance outreach programs to assure the maximum opportunity for training and research by a diverse population of students.

Technical Description: The overarching research goal of this CAREER project is to explore new physical phenomena that emerge when interfaces between different oxides are created with atomic-scale precision as afforded by the Molecular Beam Epitaxy deposition technique, which enables better control of stoichiometry and termination of the interfaces than other deposition methods. Synthesis, in-situ and ex-situ characterization of heterostructures consisting of perovskite oxides with different valence and multiferroic properties are used to (a) tailor the electronic properties of the interfaces and to investigate the presence of a predicted 2-dimensional electron gas and the metal-insulator-transition at the interfaces; (b) study the epitaxial growth and stabilization of novel oxides; (c) investigate spin injection and the spin transport properties of the established 2-dimensional electron gas at oxide interfaces in magnetic nanostructures using integrated, epitaxially grown oxides as tunnel barriers and spin filters.

Non-technical Description: The project involves materials growth and characterization, and explores new interfacial phenomena. The successful implementation of the scientific findings could lay the foundation for a new technology platform based on the interfaces of hybrid materials. It can lead to a large-scale use of oxide technology and has the potential to usher in a new era of highly integrated oxide-based charge and spin electronics. The educational and outreach project activities impact and benefit the society by engaging high-school science teachers in materials science research through a "hands-on" summer workshop; attracting the attention of the local, largely Hispanic community and exposing them in scientific research through a "Science Open House" initiative; recruiting and engaging high-school and undergraduate students into research, fostering their understanding of scientific methodology and reasoning; training and retaining the next generation of physicists and materials scientists; leveraging the institutional pool of minority students to increase the level of diversity in scientific disciplines.

This Major Research Instrumentation grant provides funding for the acquisition of a vibrating sample magnetometer (VSM) used for the characterization of magnetic materials. A VSM is used to determine the magnetic hysteresis curve, i.e. the relation between the magnetic field and the magnetic moment. The hysteresis curve provides the magnetic response of the material under an applied field and is often referred to as the magnetic fingerprint. The VSM allows the measurements of the magnetic moment both parallel and perpendicular to the applied magnetic field. This unique instrumental feature is crucial to the understanding of magnetic properties as magnetic moment and field are vector quantities that have in addition to a magnitude also a direction. The instrument is used to study thin film and powder materials that are currently being investigated at Texas State University. The VSM acquisition enhances the research in at least 8 different academic groups across 5 different programs. Research projects impacted by the new VSM include studies of (1) new permanent magnetic materials to be applied in wind turbines and generators, (2) two-dimensional (2D) materials for electrochemical energy storage, (3) nanocomposite materials with superior mechanical properties, and (4) novel metal oxide thin films for applications in sensors, actuators, and new non-volatile memory devices. The VSM instrument will enhance education and research within Texas State which is a Minority-serving Institution with a significant population of 1st generation students and students from underrepresented groups. The VSM further enable development of a meaningful collaboration with a regional start-up company, Urban Mining

Texas State University proposes to acquire a high field vector vibrating sample magnetometer (VSM) for the characterization of magnetic materials including powders, thin films and bulk magnetic materials. This vector VSM allows the study of the magnetization and magnetic anisotropy over a wide temperature, field magnitude, and field direction range. The fast temperature and field control and the simplicity and robustness of tool enables the use of the new VSM as a work-horse magnetic characterization tool and effectively implement it in Texas State University undergraduate and graduate curriculum. The VSM acquisition enhances the research in at least 8 different academic groups across 5 different programs. Proposed research includes studies of the magnetic properties of: defect clusters in RRAM transition metal oxides, low dimensional systems, specifically hydroxides and oxyhydroxides that are being studied for applications in batteries, hard magnetic materials including NdFeB permanent magnets, novel spintronic devices and the role of oxygen vacancies, thin ferromagnetic films grown by MBE, RF sputtered BFO films for application in novel sensors and applications, and printed magnetic thin films for use in meta-materials.

Texas State University (TxState) is one of the largest Hispanic-Serving Institutions (HSIs) in the U.S., the fourth largest university campus in Texas, and the flagship of the TxState University System, with nearly 38,000 students (>33,000 undergraduates). The current representation of 39% Hispanic, 11% African American, and 46% first-generation students reflects the population of the state of Texas. As a Partnership for Research and Education in Materials (PREM), TxState is collaborating with The University of Texas at Austin (UT) Materials Research Science and Engineering Center (MRSEC), namely, the Center for Dynamics and Control of Materials (UT-CDCM). This ensuing TxState-UT partnership will create the PREM Center for Intelligent Materials Assembly (CIMA). The PREM CIMA will promote recruitment, retention, and degree attainment of a diverse student cohort with a pathway into advanced degrees and careers in materials science. The PREM CIMA will offer students high impact research experiences, mentorship by TxState and UT faculty and students, personnel exchanges including biannual joint research conferences, professional development opportunities and a supportive community. A key element of building a robust pipeline will be early recruitment of first- and second-year STEM majors to become ‘PREM Associates.’ Students will develop confidence and a materials science identity through effective mentorship, research engagement and community development. Retention will be augmented by the students’ transition to ‘PREM Researchers’ status where career development workshops, exposure to the R1 research environment at UT, and experience in presentation and publication of research results will prepare students for interdisciplinary materials careers following degree attainment as ‘PREM Graduates.’ Over 60 undergraduate students (20 Researchers and 40 Associates) and 15 graduate students (10 Researchers and 5 Associates) will participate annually, supported by the PREM CIMA. Research results will be disseminated through peer-reviewed publications, professional conferences, online presence, and community outreach.

The research goal of the PREM CIMA is to create new materials based on the assembly of organized molecular and nanoscale structures. The TxState-UT PREM CIMA will utilize a collaborative model in which “PREM Researchers” are the unifying link between the TxState and UT research teams. The geographic proximity of the partners will facilitate collaborative projects and exchange. The proposed research has been organized into two main thrusts. Thrust 1, entitled ‘Reconfigurable Soft Materials’ centers on the templated assembly of macromolecular and nanocomposite systems through reversible covalent bonding or non-covalent interactions to form materials whose equilibrium states can be modulated via photothermal effects, photoisomerization, redox processes, or nucleic acid-enabled remodeling. Thrust 1 aligns with one of UT-CDCM’s Interdisciplinary Research Groups (IRGs), specifically IRG 1, with focus on multifunctional, reconfigurable networks of nanoparticles, polymers and organic molecules that respond to external stimuli. Thrust 2, entitled ‘Control of Nanostructure for Energy and Electronics’ concentrates on the use of chemical synthesis, laser-based materials processing, and epitaxial growth to control solid-state nanostructures to develop materials for catalysis, energy storage, memory, electronics, and photonics. Synergy in Thrust 2 is derived from collaboration with UT-CDCM IRG 2 faculty with expertise in nanocrystal synthesis, molecular beam epitaxy of semiconductors, and solid-state device fabrication. The proposed research will create advanced materials for applications that include biomedicine, water purification, chemical fuel generation from renewable energy sources, and nanoelectronics.

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.