Susanne Stemmer - US grants

0076501
Jacobson

This is an instrument acquisition award to upgrade a user facility and provide a new capability at the University of Houston and at Rice University. With this new capability, variations in the chemistry and the composition of materials can be detected, even if these changes occur within less than one nanometer within the material. The key to the new technique is the ability to form very small electron probe (less than 0.2 nanometer in diameter) and the ability to precisely position and control the probe. Electrons transmitted through the material contain information about the chemistry of the material at the location of the electron probe. This new capability allows researchers to analyze these electrons. These electrons can also be used to generate a "compositional" image of the material, in addition to the "structural" image. It is anticipated that the close collaboration between the users at the University of Houston and at Rice University initiated with this proposal will lead to transfer of knowledge in modern electron microscopy techniques benefiting the education of undergraduate and graduate students. Educational opportunities will be provided as formal courses in electron microscopy including a laboratory component and through multi-user materials characterization facility (MCF) research experience programs. MCF is also an important component in this educational outreach programs designed to increases K12 student interest and achievement in science and provide opportunities for the development of teachers.
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This is an instrument acquisition award to upgrade a user facility and provide a new capability at the University of Houston and at Rice University. With this new capability, variations in the chemistry and the composition of materials can be detected, even if these changes occur within less than one nanometer within the material. The key to the new technique is the ability to form very small electron probe (less than 0.2 nanometer in diameter) and the ability to precisely position and control the probe. Electrons transmitted through the material contain information about the chemistry of the material at the location of the electron probe. This new capability allows researchers to analyze these electrons. These electrons can also be used to generate a "compositional" image of the material, in addition to the "structural" image. It is anticipated that the close collaboration between the users at the University of Houston and at Rice University initiated with this proposal will lead to transfer of knowledge in modern electron microscopy techniques benefiting the education of undergraduate and graduate students. Educational opportunities will be provided as formal courses in electron microscopy including a laboratory component and through multi-user materials characterization facility (MCF) research experience programs. MCF is also an important component in this educational outreach programs designed to increases K12 student interest and achievement in science and provide opportunities for the development of teachers.
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9909963
Stemmer

This award supports Susanne Stemmer from Rice University in a collaboration with Christian Ruessel of the Department of Glass Chemistry at the University of Jena, Germany. The collaboration studies the titanate family of molecules, such as barium titanate, which have attracted attention recently for many important applications such as information storage devices or tunable microwave devices. Techniques that provide information about the distribution of defects within these microstructures are currently lacking. The cooperative work funded here will develop a method to quantify the point defect chemistry and dielectric properties of titanates almost down to the atomic level by means of electron energy-loss spectroscopy. The project benefits from synergy of expertise in defect-property relationships of multicomponent oxides and expertise in the synthesis of oxides from highly reduced melts. The research will also benefit from sharing characterization facilities and materials-synthesis facilities.

The objective of this CAREER project is a comprehensive education and research program aimed at the development of next-generation devices using functional perovskites by providing atomic-level understanding of interface properties relevant for practical applications. Materials science research will be pursued research toward: (a) mixed ionic-electronic conducting (MIEC) perovskite oxides for electrochemical devices, and (b) ferroelectric thin films for capacitors and microelectromechanical systems (MEMS). In these devices, interface structure and properties play a key role in determining materials and device properties. Providing a fundamental understanding of transport mechanisms across interfaces will enable more energy-efficient, cost-effective devices, and aid the design of thin film electrochemical devices. Ferroelectric perovskites have a host of properties that enable further development of technologies such as microelectromechanical systems (MEMS). The physical properties of ferroelectric perovskite thin films are drastically different from those of bulk materials, for reasons that are currently poorly understood. Establishing the role of interfaces in observed behavior is expected to allow development of optimized microstructures for applications in MEMS and electronic devices. The method developed in this project will concentrate on interfaces with known atomic arrangements and defect chemistry. These will be obtained by controlled thin film growth experiments and by utilizing unique capabilities of high-resolution transmission electron microscopy in combination with electron energy-loss spectroscopy. Macroscopic measurements of transport properties of oxide interfaces and of the physical behavior of ferroelectric thin films is being studied to establish fundamental limits of interfacial properties, relevant for all applications of functional perovskites. In addition, this research is intended to set the stage for atomic level calculations that will need the true atomic structure as input. Part of the research on thin film electrochemical devices will involve an established collaboration with industry, as well as interdisciplinary research with national and international university researchers in the areas of electrochemical transport and electrical characterization.
An important feature of the project is the training of students in interdisciplinary, industrial and international collaborative activities, in technologically important research areas. A main goal of the project is to thoroughly integrate research into educational activities. Emphasis will be placed on (a) participation of undergraduate students in research early in their studies (b) interdisciplinary and international training, and (c) mentoring of students of underrepresented groups with the goal to encourage them to pursue graduate studies in materials science and engineering. Course development plans include strengthening the core curriculum to emphasize conceptual understanding of the course material for a broad interdisciplinary audience, and to incorporate new technologies. Conceptual testing as a method to evaluate the success of the educational activities will also be developed.
%%% The project addresses fundamental research issues in a topical area of materials science having high technological relevance. The scope of the project will expose students to challenges in materials synthesis, processing, and characterization. An important feature of the project is the strong emphasis on education, and the integration of research and education.
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NIRT: Metal-Dielectric Interfaces at the Nanoscale for Quantum Information and Microwave Devices
Abstract
A multidisciplinary program will be developed to understand the metal-dielectric interface and improve the quality of insulating materials for use in quantum information and microwave devices. The project will use in-situ epitaxial metal/dielectric structures that will enable the growth of well-controlled, clean interfaces with a reduced defect density to allow for a fundamental understanding of the interface. Central to the approach are new tools based on superconductivity capable of analyzing even minute loss mechanisms in metal-dielectric structures and advanced transmission electron microscopy techniques. The combination of these methods will allow the establishment of a direct correlation between device performance and atomic structure, which will point to the most efficient method for the optimization of materials, interfaces and fabrication methods

This program will impact electronics in a number of ways, enabling the development of devices that are more complex, faster, and quieter. Understanding the basic science of materials at the nanoscale will open up for invention entirely new classes of devices, an example of which is the construction of a quantum computer that would be vastly more powerful than present day computers.

The objective of the research is to gain an experimental and theoretical understanding of dielectric losses in ferroelectric thin films. The effort is motivated by microwave devices and circuits that make use of high-permittivity thin films and the large electric field tunability of the dielectric constant of ferroelectric thin films. In parallel with the progress in device technology, a number of scientific questions have emerged. In particular, the origins of high dielectric losses in thin films used for tunable devices are not understood. While it is known that thin films often accommodate a high density of defects and large stresses, experimental studies are needed that address the relationship between specific defects and the dielectric loss. Furthermore, only limited theoretical understanding exists with respect to the nature of the coupling of specific defects to the dielectric properties. Understanding the origins of thin film losses would not only enable new applications by improving device performance but also advance our understanding of the materials physics of dielectric thin films at high-frequencies and the relationship between dielectric response and materials defects. The research addresses these questions by complementary experimental and theoretical studies aimed at elucidating the relative contributions of defects, strain and intrinsic mechanisms to the dielectric loss of high-permittivity oxide thin films. The project is carried out in collaboration with Dr. Tagantsev of the cole Polytechnique Fdrale de Lausanne (EPFL) in Switzerland. Thin films of tunable dielectrics, such as (Ba,Sr)TiO3 and SrTiO3, will be synthesized and characterized at UCSB, and the results from dielectric loss measurements will be compared with the predictions of the models developed at EPFL. The theoretical effort will provide guidelines for the interpretation of the experimental results, which will be used to test the validity of the theoretical models and to motivate further developments. The collaborative program will involve graduate students at UCSB and at EPFL. The interdisciplinary collaboration between students in experimental and theoretical materials science will allow the students to bridge the gap between applied and fundamental materials research. Exchange visits and collaboration meetings will train students in international collaboration, thus fostering an understanding of cultural nuances and research environments in another country.
This award is co-supported by the Europe and Eurasia Program of the Office of International Science and Engineering.

Technical Abstract

The University of California Santa Barbara will acquire a new molecular beam epitaxy (MBE) system for the growth of high-performance oxide thin films. Numerous research programs at UCSB require the growth of insulating or semiconducting oxide thin films. These include tunable dielectrics for microwave devices, oxide thin films for optoelectronics and sensing, gate dielectrics for the development of CMOS devices employing high-mobility semiconductor channels and for high-electron mobility transistors with reduced gate leakage and high charge densities. These applications require the deposition of structurally perfect oxide thin films with low impurity and point defect concentrations, control over interface atomic structures and compatibility with underlying active device layers. Oxide thin films grown by MBE will allow for the understanding of the basic physics and materials science of oxides that currently lags far behind that of other electronic materials. Experimental testing and realization of the theoretical predictions requires high-quality, pure materials and the atomic layer control afforded by MBE. We anticipate that the high-purity, structurally perfect oxide films synthesized by MBE will lead to new scientific insights that generate new device applications. Graduate students and post-doctoral researchers are the primary 'hands-on' users of MBE at UCSB. The proposed MBE system will be operated as a shared facility, impacting the education and training of a large number of students in a wide range of interdisciplinary research activities at UCSB and collaborating academic institutions - we will build on the strong culture for MBE of compound semiconductors at UCSB and house the tool in the same large shared facility. Formal training in MBE is offered in graduate courses and weekly MBE seminars in the Materials Department while hands-on-training is provided by two development engineers. The oxide MBE system will significantly extend the opportunities that have previously been offered to student and teacher research interns and education programs aimed at underrepresented groups.


Lay Abstract

Molecular beam epitaxy is unique among the techniques used for making new electronic materials that enable modern electronic and optical devices, such as transistors and lasers. The performance of these devices depends largely on the degree of materials perfection. In molecular beam epitaxy, layers that are a few atoms thick can be stacked and materials with different electronic properties can be combined. Molecular beam epitaxy allows for unprecedented purity of these layers - the impurity levels can be as low as a few ten parts per billion. The new molecular beam epitaxy system at the University of California Santa Barbara will be utilize these unique capabilities to develop new classes of electronic thin film materials, based on metal oxides. We anticipate that the high-purity, structurally perfect oxide films synthesized by molecular beam epitaxy will lead to new technologies, such as transistors with higher operating speeds and capacitors that enable new wireless communication devices. The oxide molecular beam epitaxy system will contribute greatly to the education and training of students at the University of California Santa Barbara, who will be the primary hands-on-users of the new system. The oxide MBE system will also significantly extend the opportunities that have previously been offered to student and science teacher interns and education programs aimed at underrepresented groups.

Technical: This project aims to gain a quantitative understanding of the chemical contrast in atomic resolution scanning transmission electron microscopy (STEM) with the ultimate objective of achieving a comprehensive knowledge of defects and interfaces in solids. High-angle annular dark-field (HAADF or Z-contrast) imaging in STEM has been recognized as a technique that provides atomic structure images with chemical sensitivity. A quantitative understanding of the atomic number contrast in these images would allow for analysis of impurity or dopant atoms near interfaces and defects with atomic-level spatial resolution. Despite the significant progress that has been made over the last decade in the theory of STEM Z-contrast imaging a significant mismatch exists between predictions of image contrast made by theory and that of experimental images. While this discrepancy does not affect the interpretation of images of perfect crystals, it precludes a quantitative, atomic-scale chemical analysis of defects and interfaces. In this project, the physical origins of the disagreement between theory and experiments will be investigated in a systematic series of experiments designed to distinguish between contributions from instrumental, environmental and sample effects and those related to the scattering physics of high-energy electrons. In particular, the influence of temperature (phonon scattering), sample thickness, acceleration voltage, convergence angle, inelastic scattering, sample surface layers, point defects, and atom displacements on the image contrast will be examined. The experimental findings will be compared with simulation results, in collaboration with scientists at the University of Melbourne.
Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance, and is expected to provide new scientific knowledge of structure and chemistry at the atomic scale, which is critical for advances in modern materials science and nanotechnology. The project will contribute to the interdisciplinary and international training of graduate students. Through collaboration with theorists in Australia, the students supported by the program will learn about the latest developments in theory, bridge the gap between applied and fundamental materials research, learn a broad range of scientific methods, and become trained in international collaboration. The project also offers two- to three-month-long, self-contained internships for undergraduate students. Results obtained in this project will be used to develop teaching modules for a web-based Electron Microscopy Database (EMdb) on the topic of quantitatively analyzing chemical contrast in atomic resolution imaging.

The proposed atom probe instrument will address and solve a wide range of fundamental and applied problems in ongoing and future research at the University of California, Santa Barbara. The atom probe instrument is capable of revealing the location and identifying most of the atoms in a material. The atom probe will be used to solve key problems in atomic scale structure and chemistry for ~15-25 research groups in Materials, Electrical Engineering, Chemical Engineering, Physics, Chemistry, and Geology. It will be used to analyze the three-dimensional structure and composition of materials for light emission and electronic devices, materials systems for advanced propulsion, energy generation, including gas turbines and nuclear reactors, and hypersonic flight. Dedicated space will be provided for the atom probe in UCSB?s Microscopy and Microanalysis Facility. The atom probe is an ideal tool for introducing future scientists to the wonders of the atomic scale structure of nature. We will offer a new course in our characterization course sequence. We will host a teachers and undergraduate students to work with atom probe techniques. We will take advantage of the new visualization capabilities of the UCSB Allosphere, which is a sphere, spanning three stories, which provides a fully immersive visual and audio environment. and is an integral component of UCSB?s California Nano Systems Institute.

The proposed atom probe instrument will address and solve a wide range of fundamental and applied materials problems in ongoing and future research at the University of California, Santa Barbara (UCSB). It will allow researchers at UCSB to perform three-dimensional, atomic resolution, compositional imaging and analysis with a local electron atom probe (LEAP). The LEAP will have laser pulsing capabilities for the analysis of low electrical conductivity materials including semiconductors, ceramics and geological materials. The atom probe will be used to solve key problems in atomic scale structure and chemistry for ~15-25 research groups in Materials, ECE, Chemical Engineering, Physics, Chemistry, and Geology and other departments at UCSB. In the area of electronic materials, the atom probe instrument will be used to solve key problems in interfacial chemistry and abruptness, alloy composition and homogeneity, and dopant and impurity distributions in wide bandgap semiconductors for light emission and electron devices, epitaxial materials for spintronics and materials for novel CMOS devices. In the area of nuclear materials, atom probe tomography will be used extensively to the study of nanoscale precipitates in nuclear steels. The structural materials group will benefit from a LEAP system for their work on high temperature materials systems for advanced propulsion, energy generation, including gas turbines and nuclear reactors, and hypersonic flight. Dedicated space will be provided for the atom probe in UCSB?s Microscopy and Microanalysis Facility. The atom probe is an ideal tool for introducing future scientists to the wonders of the atomic scale structure of nature. We will offer a new course in our characterization course sequence. We will host a secondary school teacher and an undergraduate student to work on atom probe techniques. We will take advantage of the new visualization capabilities of the UCSB Allosphere, which is an integral component of UCSB?s California Nano Systems Institute.

NON-TECHNICAL DESCRIPTION
The project focuses on oxide materials that exhibit unique functionalities not found in any other materials class, such as ferroelectricity, superconductivity or electric field tunable dielectric constants. These properties are of great interest for potential application in new devices for communication, computing or digital memories. A major objective of the project is the development of techniques to obtain thin films of these oxide materials with unprecedented perfection. Highly-perfect materials are needed, not only for improved properties, but also to gain fundamental insights into the physics of these materials. The understanding gained in this project will be used towards the development of atomic-scale engineered film structures that make use of the unique properties of oxide materials. The project will contribute to the interdisciplinary training of graduate and undergraduate students through collaboration with theorists and training in both formal (courses and weekly seminars) and informal (shared laboratory) settings. The project will provide opportunities for internships for undergraduate students and teachers.

TECHNICAL DETAILS
The goal of the proposed project is the development of highly perfect, epitaxial complex oxide thin films and heterostructures by molecular beam epitaxy (MBE). The project builds on novel oxide MBE approaches that overcome known challenges, such as oxygen deficiency, and that allow for the growth of stoichiometric films with high purity and low defect concentrations. The project focuses on technologically important perovskites, such as SrTiO3 and BaTiO3 and their solid solutions, which exhibit unique functionalities, such as ferroelectricity, superconductivity or tunable dielectric constants. The dielectric and electrical properties of insulating and conducting films are documented and, in conjunction with growth studies and physical measurements, used to establish the role of interfaces and defects in the properties of oxide films and heterostructures. The research is timely, because not only have high defect concentrations limited widespread application of these materials, but also because highly perfect films are needed for a fundamental understanding of the unique phenomena observed in oxide heterostructures. The project contributes to the interdisciplinary training of graduate and undergraduate students in advanced thin film growth and characterization of novel materials through collaborations and training in both formal (courses and seminars) and informal settings. The project provides opportunities for internships for undergraduate students and physical science teachers.

Technical Abstract

Research programs in oxides at the University of California, Santa Barbara (UCSB) span a wide range of applications, including as dielectrics, semiconductors, thermoelectrics and memristive devices. Many of these research activities are central to interdisciplinary programs and centers and all support graduate student education and training. These programs require oxide thin films with low defect densities, high purity, compatibility with active electronic device structures, low interface trap states and near-monolayer control over layer thicknesses. To address these needs, we propose to acquire a versatile, state-of-the-art oxide molecular beam epitaxy (MBE) system that will significantly expand capabilities for the synthesis of highly-perfect oxide thin films and structures, as needed to solve key problems in the development of new devices with oxides and in the materials physics of oxide structures. The project will contribute to advancing oxide MBE through the development of approaches to address issues such as stoichiometry control and poor volatility of constituents. In keeping with the tradition of UCSB's MBE Laboratory, the proposed oxide MBE system is designed to facilitate compatibility and accessibility and will be operated as a shared facility, impacting the training of a large number of students in interdisciplinary research programs at UCSB and at collaborating institutions. Graduate students and postdoctoral scholars are the primary users and oxide MBE will be the central focus of many Ph.D. dissertations. Two development engineers provide hands-on training in MBE while formal training is provided by a graduate course and weekly MBE seminars. The oxide MBE system will significantly expand research internship opportunities offered through education programs that target undergraduate and high-school students from underrepresented minority groups.


Non-Technical Abstract

Research programs in oxide materials at the University of California, Santa Barbara (UCSB) span a wide range of applications, such as new electronic devices and energy conversion. Many of these research activities are central to interdisciplinary programs and centers and all support graduate student education and training. These programs require the deposition of thin film oxides with exceptionally low defect densities and high purity, comparable to what is now standard for conventional semiconductor materials. To address these needs, we propose to acquire a versatile, state-of-the-art molecular beam epitaxy (MBE) system for the deposition of thin film oxides. In keeping with the tradition of UCSB's MBE Laboratory, the proposed oxide MBE system will be operated as a shared facility, impacting the education and training of a large number of students in a wide range of interdisciplinary research programs at UCSB and at collaborating institutions. Graduate students and postdoctoral scholars are the primary users. Two development engineers provide hands-on training in MBE while formal training is provided by a graduate course and weekly MBE seminars. The oxide MBE system will significantly expand research internship opportunities offered through education programs that target undergraduate and high-school students from underrepresented minority groups.

Intellectual merit: This project is awarded under the Nanoelectronics for 2020 and Beyond competition, with support by multiple Directorates and Divisions at the National Science Foundation as well as by the Nanoelectronics Research Initiative of the Semiconductor Research Corporation. Progress in transistor and integrated circuit (IC) scaling has slowed, in part because of physical limits of transistor operation at small dimensions, but primarily because power consumption and power density are becoming excessive as complexity and density are further increased. IC power density results from opposing constraints in transistor and circuit design; the electron thermal distribution sets a minimum transistor control voltage for low off-state dissipation, while the dissipated energy on interconnects increases as the square of voltage. Addressing these limitations, radical changes in transistor design are proposed. To increase the on-current, designs are proposed that will overcome the so-called density of states (DOS) bottleneck in III-V semiconductors, adding additional valleys to those used in transport, therefore increasing the amount of charge that can be transported through the device at a high velocity. To increase drive current in N-channel field effect transistors (FETs) and the IC speed at reduced voltages III-V transistors will be develop using for the first time transport in the L (satellite) valleys, i.e. L-valley electronics. These will use the light electron part of their dispersion in the transport direction for fast carriers and will use the heavy electron characteristics to pack multiple bands into the ?same? energy space. Similar density of states engineering will be applied to P-channel FETs, achieved using light- and heavy-hole states mixed by strain and quantum confinement. To reduce supply voltages, steep transistors will be developed, having I-V characteristics varying much more rapidly than a thermal distribution. In addition to established tunnel injection devices having only moderate on-current, high-current steep-FETs will be developed. These use transport in energy bands of tightly constrained energy range, produced using 1-D semiconductor superlattices. Combining these two classes transisto rs, state-density-engineered transistors designed for high drive currents at low voltage, and steep transistors designed for very low off-state leakage, the program will explore new logic gate designs providing low power and high speed.

Broader Impacts: The proposed work seeks to increase the speed and complexity, and reduce the power consumption of ICs. The industry is of enormous worldwide value. The participants interact regularly with the VLSI industry, communicating ongoing work and seeking guidance, and will continue with this model in the NSF program. Development of high-speed yet low-power logic devices will circumvent present power-consumption limits now constraining VLSI speed and complexity. This program will enable further large increases in the speed and power-limited computational performance of ICs, benefiting applications in industry, commerce, and personal use. Ph.D. students will be trained in semiconductor materials, device physics, and IC design. Their training will emphasize the interaction of system and circuit design with device design. Simulation tools will be developed and distributed by nanoHub to a worldwide user community. The program will operate a summer internship program, affiliated with that of the NNIN, providing laboratory experience exposure to a research environment for 8 undergraduate students.

This project is jointly funded by the Electronic and Photonic Materials (EPM) and Ceramic (CER) Programs in the Division of Materials Research.

NON-TECHNICAL DESCRIPTION:
The project focuses on the development of a new class of thin film oxide semiconductors that are of great interest for applications as energy materials and for novel electronic devices. The project addresses technical challenges through basic materials studies and the development of advanced thin film deposition methods. The highly perfect films synthesized in this project impact the theoretical understanding of oxide materials. The research activities in the project contribute to the interdisciplinary training of graduate and undergraduate students in advanced thin film deposition methods and materials characterization through training in both formal (courses and weekly seminars) and informal (laboratory) settings.

TECHNICAL DETAILS:
The project focuses on the development of molecular beam epitaxy methods for the growth of a new class of thin film oxide semiconductors, the perovskite stannates, with the goal of achieving a high degree of materials perfection and to determine the intrinsic properties of these materials. Materials such as SrSnO3 and BaSnO3 combine high charge carrier mobilities with wide band gaps, which makes them highly interesting for applications such as transparent conducting oxides, power semiconductors, or in novel heterostructures for the integration with functional perovskites. Conditions for stoichiometric thin film growth, structure-property relationships, and the role of materials defects will be established. The project provides opportunities for two- to three-month-long, self-contained internships for undergraduate students and for interdisciplinary collaborations with materials theorists and experts in electronic devices.

Measurements of the physical properties of materials at ultralow temperatures are key to discoveries in condensed matter physics, the science of new and emerging materials, and future technologies, such as quantum computing and new detectors. The Major Research Instrumentation program supports the acquisition of a versatile dilution refrigerator system with an integrated magnetic field capability for an interdisciplinary, multi-user facility at the University of California, Santa Barbara (UCSB). The system will be housed in the Low Temperature Facility at UCSB, which already serves a diverse and interdisciplinary user community. It will be available to all members of the University community, to researchers at other academic institutions, and to industry throughout Southern California and beyond. The instrument will greatly expand the training opportunities for graduate and undergraduate researchers, who are the primary hands-on users. Both formal (course work) and practical training will be provided, while the facility's staff will be responsible for student training, safety, day-to-day oversight, and routine maintenance. In addition to its central role in the training of the next generation of scientists and engineers, the dilution refrigerator will be ideally suited for undergraduate design and research projects, and serve to expose undergraduate researchers to low temperature science and measurement techniques.


The instrument addresses critical needs in materials characterization at ultra-low temperatures within a wide range of interdisciplinary research programs at UCSB that focus on low-dimensional materials, quantum computing, the realization and discovery of new quantum phenomena and phases, the development of new measurement techniques, and the characterization of the electronic structure of low-mobility materials. The Low Temperature Facility at UCSB already serves a diverse and interdisciplinary user community, who will have access to the dilution refrigerator system. The dilution system takes advantage of recent developments in technology that greatly facilitate its operation as a multiuser facility. These include recent advances in pulse-tube technology, allowing for cryogen-free and fully automated operation. The system is load-locked, which increases the number of samples that can be analyzed per instrument time. These features facilitate accessibility and ease of operation, dramatically reduce maintenance and operating costs, and allow for a high throughput of samples.

Non-technical Description: The world has seen an enormous increase in computing power, but the current path forward for the semiconductor industry is beset with roadblocks. A different strategy for a future generation of electronic devices is based on materials that exist in multiple electronic states. A new generation of electronic materials are required for this purpose, as are the means for switching between multiple electronic states. The fundamental science that is the focus of this project is centered on the sudden change in the electrical properties of certain materials when they are switched through a so-called metal-to-insulator transition by an external trigger. On one side of the transition, the material behaves like copper metal, while on the other side, it behaves like insulating wood. The project goal is to design and discover materials exhibiting such metal-to-insulator transitions that enable room-temperature operation and that display large changes in the key property of interest; the electrical resistivity. The strategy is to control properties by structural design at the atomic scale. The approach employs a tightly integrated combination of experiment, theory, and data-mining of the literature, that would enable new insights to emerge and aid in the design of desirable materials. This project will deliver a research workflow with a suite of tools to enable assessment and experimental validation of new concepts for the discovery of key materials. The project will articulate protocols for selecting high-performing materials, leading to an expanded palette of compounds that could impact future technologies. The teaching and training of students and the discovery capabilities of the project are interwoven, and aimed at broadening participation through the involvement of the investigators and their group members in public outreach events. The development of modules for undergraduate and graduate courses and the involvement of students in interdisciplinary team environments are intrinsic to project plan. The project will yield a plethora of new and mined data on a range of oxides and new computational materials approaches. These will be aggregated into open-access databases on public portals.

Technical description: This project will pursue discovery of the atomic-level genetic code of materials displaying metal-to-insulator transitions through approaches that establish links between unit cell level crystal structure and the macroscopic electronic response, profiting from a coupling of theory, data, and comprehensive experimentation. At the present time, the essential data and structure-electronic function relationships to decipher the genetic code (generic descriptors) of metal-to-insulator transitions do not exist in a format which permits predictive synthesis. The project?s significance is that it recasts the problem into one of atomic structure, focusing on the role of different kinds of structural distortions, notably, breathing modes, Jahn-Teller distortions, and Peierls-like instabilities across a broad range of structure types and chemistries. The project will generate and collect a range of data that will permit the mapping of electronic interactions into atomic features, applying informatics-based methods to enable supervised and unsupervised learning. The project will articulate predictive rules and protocols for selecting high-performing materials, leading to an expanded palette of compounds that could impact technologies beyond electronics. The teaching and training of students at multiple levels and the discovery capabilities of the project are interwoven and aimed at broadening participation by through public outreach events, through the development of modules for undergraduate and graduate courses; and finally, by involving students in interdisciplinary team environments. The project will yield a plethora of new data on a range of oxides and new computational materials approaches. These will be aggregated into databases on public web-portals using a new portable file format designed for materials data. New methods of data visualization will allow external users to interact, query, and analyze the data for aims beyond those proposed herein. Data-driven models and informatics workflows for generating quantitative models for metal-to-insulator performance will be hosted with the aforementioned data and visualization tools on the MIST: Metals and Insulators by Structural Tuning platform. The PIs also plan to release MIST as open source and build a user community around the platform by ensuring that interested researchers are able to contribute to the MIST codebase. This will allow a wider growth of the project. This aspect is of special interest to the software cluster in the Office of Advanced Cyberinfrastructure, which has provided co-funding for this award. Advances in synthesis, theory, and characterization will strengthen the scientific capabilities and workforce by allowing students and academic or industrial researchers to employ the formulated structure-property relationships for educational and research purposes.

The project focuses on new oxide materials that may enable a new generation of electronic devices for computing. The project will offer interdisciplinary training of graduate and undergraduate students in new electronic devices, materials, and circuits. Their training will be fostered by close collaboration and student exchanges between the investigators' groups at the University of California, Santa Barbara (UCSB) and Ohio State University (OSU). UCSB has a diverse undergraduate population and is a minority/Hispanic-serving institution. Regular phone conferences with industry stakeholders and related activities will ensure knowledge transfer to industry and expose the participating students to matters relevant to the transitioning of new materials and devices into emergent technologies.

Novel electronic devices will be realized that employ electric fields to control the unique electronic properties of oxide materials, in particular, their ability to change the electrical resistance by a large amount. These devices will be investigated for their potential as alternatives to current transistor devices used for computing, which are based on conventional semiconductor materials, such as silicon. The project is motivated by unique opportunities, including the potential for abrupt switching and a reduction in the energy that is required to switch. Close collaboration between materials scientists at UCSB and electrical engineers at OSU will focus on optimizing oxide materials, their scientific understanding, and their control using electric fields, and establishing the device characteristics relevant for applications. The results from this project will contribute to a solid-state electronics technology that has been underexplored.

Non-technical Description: Fundamental understanding and control of heat conduction processes in materials are important for energy infrastructure, electronic devices, and renewable energy generation systems. This project focuses on a novel property of phonons – vibrations of atoms that carry the heat in materials - called "topology". This property may allow new phenomena, such as heat conduction perpendicular to the temperature gradient direction and more efficient transport of heat waves on the material surfaces. To discover topological phonons, the research team will exploit a Materials Genome approach to search for materials hosting these special heat carriers. Once candidates are identified, the research team will synthesize and characterize them, and the results will be used to refine the search algorithm. The research team plans to establish a public database storing the heat conduction properties of a large number of materials. This research will not only advance the fundamental understanding of how topology affects heat conduction in real materials, but also provide new routes to realizing unusual functionalities such as heat conductors that can be switched on and off. This project also supports educational activities to teach basic materials physics concepts to K-12 and undergraduate students through hands-on class projects and short courses. To promote diversity in the materials science workforce, the team also provides research opportunities to high school and undergraduate students from underrepresented minority communities.

Technical Description: While the topology of electronic states has been a central theme in condensed matter physics for the past decade, topological phononic states have received much less attention. Unlike their fermionic counterparts, topological states in the entire phonon spectrum can contribute to observable material properties, making topological phononic materials ideal testbeds for emerging new physics in topological bosonic systems, including phonon thermal Hall effects, novel topological phonon-electron interactions and the resulting phenomena, such as unusual superconducting states. This project aims to systematically identify materials hosting intrinsic topological phonons in the thermal regime, where the topological phononic states explicitly modify intrinsic material properties, including thermal transport, electron-phonon interactions, and surface phonon modes. The research team will seek to accelerate material discovery by incorporating symmetry-guided machine learning based on Euclidean neural networks. Machine learning predictions will be verified using first-principles phonon simulation and topological invariance analysis. Promising candidate materials will be synthesized as thin films and bulk single crystals and characterized using inelastic neutron and x-ray scattering, thermal transport, and surface-sensitive spectroscopy and scanning probe measurements. This research will advance fundamental understanding of topological bosonic systems and examine new thermal functionalities enabled by topological phonons.

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.