Kathryn A. Moler - US grants

9802719 Moler This award provides partial support for the construction of a low-temperature scanning system, designed for using miniature susceptometers to study the magnetization of individual electronic and magnetic nanostructures. The susceptometers are based on Superconducting QUantum Interference Devices (SQUIDs). Miniature SQUIDs with micron-scale spatial resolution can detect magnetic moments as small as a thousand electron spins, nine orders of magnitude smaller than can be detected by commercially available bulk magnetometers. Such sensitive magnetic measurements hold great promise for the study of qunatum chaos, macroscopic quantum coherence, superconductivity, and magnetism. At present, however, the promise of this technique is limited by the slow process of integrating each sample with its own SQUID. A scanning susceptometer would have several advantages. First, many samples could be studied in each cooldown, by placing well-separated individual mesoscopic, objects on the same substrate. Secondly, background discrimination could be much easier, since the SQUID could be moved away from the sample. Thirdly, a scanning susceptometer would not be limited to samples which can be integrated onto the same chip as the SQUID. In addtion to being an ideal tool to study mesoscopic magnetization, this apparatus could be used to make precise, quantitative, local magnetic susceptibility measurements of a wide range of materials. %%% This award will provide unique capability to study mesoscopic materials systems; is important for magnetism studies. Potential for broad impact on field. Will increase diversity in field and offer new educational opportunities.
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9875193
Moler
This CAREER project will focus on improved measurements of magnetic field distributions on small length scales. It will lead to advances in superconducting and magnetic materials, which have naturally occurring magnetic structure, and in artificially structured mesoscopic materials. The major goal of this project is the development of sensors with sufficient sensitivity to image mesoscopic electronic phenomena by detecting the magnetic fields produced by persistent currents. Magnetic Force Microscopes (MFMs), Hall probes, and Superconducting QUantum Interference Devices (SQUIDs) each have particular advantages and disadvantages. Fabrication, testing, and subsequent experimentation with these sensors will provide training for graduate and undergraduate students in materials physics and nanofabrication techniques. This award will also partially support the development of a microfabrication-based research experience course, which will provide undergraduates with a solid grounding in the scientific principles and practice of microfabrication, and with the opportunity to conceive, design, fabricate, and characterize their own microfabricated device. This course will be offered as part of a new applied physics minor, intended for undergraduate engineering and science majors, which is being offered by the historically graduate Stanford Applied Physics Department.
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This project focuses on research in the area of nanofabricated magnetic sensors related to the study of electronic structure on small length scales. In addition, the project will partially support the development of a new microfabrication-based research course to provide undergraduates with a solid grounding in the scientific principles and practice of microfabrication, and with the opportunity to conceive, design, fabricate, and characterize their own microfabricated device. This course will be part of a new undergraduate minor in applied physics being introduced by the Stanford Applied Physics Department which has historically been solely a graduate department. The work supported under this proposal will provide training for both graduate and undergraduate students in materials research and nanofabrication techniques at the Stanford Nanofabrication Facility and at the newly constructed Laboratory for Advanced Materials.
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Magnetic Force Microscopy (MFM) is one of the most promising and best-known techniques for probing magnetic phenomena on length scales approaching 10 nanometers, but the spatial resolution of MFM is presently limited to about 30 nanometers. Factors limiting the spatial resolution include both the the force sensitivity of the cantilevers used for MFM and the ability to create controlled magnetic nanostructures on the cantilevers. The PIs propose that MFM sensors based on the integration of nanomagnets, carbon nanotubes, and optimized silicon microstructures can push these limits to allow sub-10-nm spatial resolution. The PIs individually have experience in atomic force microscopy, novel magnetic microscopies, the growth of single-walled and multi-walled carbon nanotubes, the integration of carbon nanotubes with silicon microstructures, the growth and characterization of cobalt nanomagnets and nanorods, and the fabrication of high-bandwidth ultra-sensitive force cantilevers with integrated displacement sensors. This research requires the participation of an interdisciplinary research team, populated by a collection of graduate and undergraduate students from many departments in science and engineering. The fabrication of these sensors will require the integration of advanced nanomaterials and modern fabrication processes, benefiting researchers and industrial developers. The processes that are developed during the course of this research will be published in the NNUN's on-line process library, as well as in research journals. Undergraduate and graduate students whose research includes the development of these techniques and their application to materials science will be well suited to make ongoing contributions to nanoscience and technology.
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Research on "nanomaterials" such as bucky-balls, nanotubes, nanomagnets, molecular manufacturing, and many other examples has led to excited speculation regarding the technological promise of nanoscience. However, these nanotechnologies do not easily merge with conventional technologies, including microfabrication. Stanford has recently demonstrated methods for localizing the growth of carbon nanotubes on specific locations within a conventional microfabrication process, a breakthrough that could allow nanotechnology to approach important technological applications. The propsed work would use this breakthrough to integrate nanotubes and nanomagnets into MicroElectroMechanical Systems (MEMS) fabrication, producing a useful new family of ultrasensitive physical probes and developing realistic processes for the integration of nanomaterials and silicon microstructures.

This proposal was submitted in response to the solicitation "Nanoscale Science and Engineering" (NSF 00-119). The award is jointly supported through two directorates at NSF: (i) Mathematical and Physical Sciences and (ii) Biological Sciences. Additional support comes from the National Facilities and Instrumentation program of the Division of Materials Research (DMR).

The Nanoscale Science and Engineering Center at Stanford University on Probing the Nanoscale (CPN) addresses the development of novel nanoprobes and application of these probes to answer fundamental questions in science and technology. The Center, which is a partnership between Stanford and IBM, has 13 participants from 5 departments, including 3 participants from IBM.

Examples of novel probes with revolutionary capabilities that will be developed include:
a scanning tunneling potentiometer which can make electrical transport measurements on 10-nm length scales; a scanning Hall probe microscope with 30-nm spatial resolution; a near-field scanning optical microscopes with a thousand fold improvement in throughput; SQUIDs with sub-micron spatial resolution and sensitivity approaching the quantum limit with the ability to detect the spin of a single electron; a scanning tunneling microscope which can conduct electron spin resonance experiments at cryogenic temperatures; a magnetic resonance force microscope that can detect the spin of a single electron, specify the location of the electron, and measure the quantum mechanical state of the spin. These probes will be applied to answer many fundamental questions such as these: What is the length scale over which quantum mechanical behavior crosses over to become classical diffusive transport? How does the spin state of an electron vary over time and distance? How do the spins of electrons behave when the electrons cross a planar interface? What are the mechanisms of pinning in high-temperature superconductors? The Center also supports high risk, potentially high pay-off projects through a seed program.

The center is expected to have broader impact through its industrial and education outreach programs and its study of societal and ethical issues of nanoscale science and engineering. The Center expects to enhance the capabilities of the nanotechnology community to measure, image, and control nanoscale phenomena. Specific connections to users and manufacturers of nanoprobe instrumentation will be utilized to rapidly transfer technological advances. The Center is committed to educating the next generation of scientists and engineers regarding the theory, practice, and implications of novel nanoprobes. The Center has an active undergraduate research program, including undergraduate research opportunities at IBM. The CPN Fellows Program will support graduate students, postdocs, and visitors engaged in nanoprobe research and education. A Summer Institute for Middle School Teachers is anticipated to touch thousands of middle school students each year.

*******Technical Abstract*******
This individual investigator award will support the use of a dilution-refrigerator-based scanning Superconducting QUantum Interference Device (SQUID) to make direct magnetic measurements of mesoscopic normal metal rings. Persistent currents in normal metal rings should exist as a result of quantum-mechanical phase coherence around the ring and have been extensively studied theoretically. However, only one study measured single diffusive rings, presumably because of the difficulty of measuring the small signal from a single mesoscopic sample. The PI and her students propose to study these systems with a scanning SQUID, which will enable measurement of the properties of many mesoscopic samples, one sample at a time, in each cooldown, providing much-needed experimental input on some of the profound theoretical results of mesoscopics theory. These highly demanding experiments will provide the direct educational benefit of training some of the nation's top young scientists in an intellectually rich research environment. Undergraduate and graduate research students will learn nanotechnology and precision measurement techniques as well as fundamental physics.

*******Nontechnical abstract*******
Mesoscopic physics is the study of materials and devices that are sufficiently small for quantum-mechanical effects to be important. Direct magnetic measurements on single samples are important, but rare, because the magnetic signal is weak. Superconducting QUantum Interference Devices (SQUIDs) are arguably the world's most sensitive magnetic detectors. This award will support the use of an unusual low-temperature SQUID to make direct magnetic measurements of some of the most striking predictions of the quantum-mechanical theory of metals. The scanning approach employed in this work will provide experimental input on some of the profound theoretical results of mesoscopics theory. Beyond its own intellectual merit, this work will support and enhance the nation's scientific infrastructure through the maintenance of a very unusual scanning SQUID microscope which is also used collaboratively with other investigators of novel materials. These highly demanding experiments will provide the direct educational benefit of training some of the nation's top young scientists in an intellectually rich research environment. Undergraduate and graduate research students will learn nanotechnology and precision measurement techniques as well as fundamental physics.

MRI: Acquisition of a NanoSIMS

Stanford researchers in over 10 departments recognize a shared need to identify composition with nanoscale spatial resolution and have joined together to establish a NanoSIMS user facility for research and education. NanoSIMS combines the high mass resolution, isotopic identification, and sub-parts-per-million sensitivity of conventional SIMS with spatial resolution down to 50 nm. The NSF will maintain oversight through the Stanford Nanofabrication Facility (SNF), a node of the National Nanotechnology Infrastructure Network (NNIN). Internal and external users will carry out distinctive and high-quality science and develop methodologies that exploit the NanoSIMS? distinctive capabilities. The majority of the research will be carried out by students and postdoctoral scholars, providing excellent training for our Nation?s new scientists and engineers.

Stanford has a variety of programs designed to increase participation of women and minorities, and the PI and co-PI?s have a history of training diverse researchers and educators. The NanoSIMS will be available for a range of formal courses at Stanford and at partner schools. Industry research and development personnel rely on the Stanford facilities and research environment, and we are committed to building up a remote access capability to allow more widespread access for both research and classes. In addition, we will continue to place a high priority on the publication of technique papers, anticipating an explosion of interest in the unique capabilities of the NanoSIMS for many exciting research areas.

This award from the Division of Materials Research supports Stanford University with the conceptual engineering design and development of a prototype scanning sampling Superconducting Quantum Interference Device (SQUID) microscope. High spatial resolution sampling scanning SQUID microscopes are among the world?s most sensitive magnetic detectors. The project will provide scientist and engineers with a new imaging capability of time-independent magnetic fields with nanoscale spatial resolution and single electron spin sensitivity. It will enable imaging of time-dependent magnetic fields with 10 picoseconds time resolution. Such measurements of nanomagnetic phenomena are of interest in information technology, biotechnology, and energy technology, as well as fundamental science. The microscope is designed to become a general user tool at two co-located shared user facilities, the Stanford Nanofabrication Facility (SNF), a member of the National Nanofabrication Infrastructure Network, and the Center for Probing the Nanoscale (CPN). The microscope would be a transformative tool in the hands of the users, scientists and engineers, needing to characterize such widely varying materials as superconductors, magnetic nanoparticles, magnetic semiconductors, and multiferroics. The project is based on collaboration between IBM and Stanford. This university-industry collaboration will allow mentoring and hands-on experience for a diverse group of students and postdocs in an industrial environment.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

The project is to renovate the Stanford Nanofabrication Facility (SNF), which is an open-use, shared facility and a participating site in the NSF-funded National Nanotechnology Infrastructure Network (NNIN). Since the nanofabrication facility opened in 1987, the SNF's Class 100 clean room (10,500 sq ft) has operated around the clock for 50 weeks per year. With the exception of the annual two-week shutdown, the clean room facility has been used for research and research training 100% of the time. With its heavy usage and the rapidly changing toolbox for nanofabrication, the SNF needs to be renovated and updated to provide the flexibility, reliability, and capacity in nanofabrication that is needed by such a large set of internal and external users conducting research in nanoscience and nanoengineering.

The project plan calls for a series of renovation tasks including updating the wet chemical handling capability, renovating the process gas handling and exhaust ventilation systems, updating the electrical distribution, updating the process cooling water, and modernizing the temperature and humidity controls. The research facility space will be updated to include two specialized processing areas, a flexible micromachining room and a nanosynthesis facility. These areas will be used to expand the nanofabrication capability of the SNF and better support interdisciplinary research programs. Examples of nanofabrication activities supporting research goals include fabricating nanostructured electrodes for fundamental studies of electron transfer rates in molecules, production of silicon nanowires for biological sensing, growth of nanowire electrodes for higher performance batteries and fuel cells, and creation of novel nanoelectronics based on carbon nanotubes and graphene.

The renovated facility will attract an increasingly broader base of academic and industrial researchers from the physical sciences and the life sciences to SNF, enabling them to address new scientific questions and adopt new approaches to technology development. In 2008 alone, 581 researchers came to the SNF to fabricate nanostructures for their research in electronics, optics, MEMS, NEMS, biology, and chemistry. In a typical month, the SNF serves about 240 researchers, including about 50 from industry and about 20 from other universities. The cross-fertilization of research cultures and pursuit of interdisciplinary science will continue to ignite creativity and innovation in the renovated SNF and enhance the quality of graduate and undergraduate education for student users.

This award to Stanford University is for the acquisition of a Helios NanoLab 600i dual-beam Focused Ion Beam / Scanning Electron microscope manufactured by the FEI Company. The Helios offers unprecedented capabilities for fabricating and characterizing two- and three-dimensional nanoscale objects. It will enable more than thirty Stanford research groups to address grand challenges in nanoscience and nanotechnology. For example, the Helios will support research efforts to: create plasmonic optical tweezers that can trap single atoms; detect cancer in its earliest stages; create the first integrated circuit that can serve as an efficient source of terahertz radiation; develop organic solar cells with higher efficiency and organic transistors with higher mobility; determine how neurons communicate with each other in the brain; and, elucidate the quantum mechanical phenomena that determine the behavior of topological insulators. The Helios will also enable a broad range of scientists to prepare higher-quality samples for transmission electron microscopy because it prepares lamellae with a low-energy (500 eV) ion beam. As a result, researchers will be able to take full advantage of state-of-the-art aberration-corrected transmission electron microscopes that can image samples with sub-Ångstrom resolution.

The Helios will reside within the Stanford Nano Center (SNC), a shared user facility, where external users from corporations, national laboratories, and other academic institutions will have access. In addition, it will be part of the National Nanotechnology Infrastructure Network(NNIN). No open laboratory in northern California contains a Focused Ion Beam instrument as advanced as the Helios. Researchers at Stanford will collaborate with the FEI Company to implement full remote control by domestic and international users of the Helios. The Helios will be featured in public outreach events such as Stanford Days and Nanodays, and its capabilities will be shared with minority-serving institutions in an effort to catalyze future collaborations.

X-ray computed tomography (CT) is an approach to nondestructive examination of objects based on reconstructing three-dimensional (3D) images of the external and internal features of an object from a series of two-dimensional X-ray images taken at a large number of viewing angles. Medical CT imaging is commonly used as a diagnostic tool, and similar approaches using higher X-ray intensities can allow very detailed imaging of non-living samples for a wide range of research applications across many fields of science and engineering. This Major Research Instrumentation (MRI) award supports the acquisition of a high-resolution, 3D X-ray microscope capable of producing images with three-dimensional resolution smaller than 1µm (about 100 times smaller than the width of a human hair). This system will be located in the Stanford Nano Shared Facilities, a core facility providing researchers across Stanford University and from nearby institutions with state-of-the-art instruments for specimen characterization and analysis. This instrument will advance innovative research by investigators from multiple disciplines across Stanford's Schools of Earth Energy & Environmental Sciences, Engineering, Humanities & Sciences, and Medicine, as well as investigators from San Jose State University and the California Academy of Sciences, a museum, educational center and research facility in San Francisco.

The high-resolution X-ray microscope will improve Stanford's ability to conduct leading-edge research in materials science, earth science, and life science by filling the gap in length scale (0.4 to 40 µm) within which no equipment currently at Stanford can generate non-destructive 3D tomography images. It will support leading-edge basic research in materials science, earth science, and life science. Researchers will use the instrument to analyze the microstructure of shale rock, which contains pores and other features at a range of sizes, enabling studies on more efficient extraction of petroleum and sequestration of anthropogenic carbon dioxide. The ability to image large samples with high resolution at a long working distance will be exploited to study silicon microparticle anodes coated with self-healing polymers for optimal design of longer-lasting batteries. The instrument will be used for high-resolution imaging of inner-ear bones and the tympanic membrane of mammals ranging from mice to humans to aid in more detailed modeling of the mechanics of hearing and development of novel devices for correcting hearing abnormalities. Researchers on improved fabrication of micro-electro-mechanical systems (MEMS) devices will use the microscope to nondestructively examine the internal structure of devices designed to minimize or eliminate fatigue (repeated loading) failure, dramatically extending the useful life of devices and sensors for a wide range of applications. The dual-energy imaging capacity will allow simultaneous collection of high-resolution images of cartilage, bone and vasculature in a single scan, providing new insights into the processes of skeletal development and healing. Researchers at the California Academy of Sciences will take advantage of the instrument's high-resolution, phase contrast imaging capabilities for detailed examination of tissue interfaces as part of studies on the anatomical and physiological effects of evolutionary miniaturization. Through these and many other projects, this instrument will become a key part of Stanford University's research infrastructure and enhance the scope and impact of research across a wide range of science and engineering disciplines.

The Stanford Site of the National Nanotechnology Coordinated Infrastructure (NNCI) at Stanford University will provide open, cost-effective access to state-of-the-art nanofabrication and nanocharacterization facilities for scientists and engineers from academia, small and large companies, and government laboratories. Stanford will open the Stanford Nano Shared Facilities (SNSF), the Stanford Nanofabrication Facility (SNF), the Mineral Analysis Facility (MAF), and the Environmental Measurement Facility (EMF) more fully to external users. Open access to these facilities will not only promote the progress of science but also accelerate the commercialization of nanotechnologies that can solve a broad array of societal problems related to energy, communication, water resources, agriculture, computing, clinical medicine, and environmental remediation. Stanford will create and assemble a comprehensive online library of just-in-time educational materials that will enable users of shared nanofacilities at Stanford and elsewhere to acquire foundational knowledge independently and expeditiously before they receive personalized training from an expert staff member. Stanford staff members will also collaborate with two minority-serving institutions (California State University Los Angeles and California State University East Bay) to provide coursework, hands-on training, and nanofacility access to their students.

The Stanford Site's shared nanofacilities will offer a comprehensive array of advanced nanofabrication and nanocharacterization tools, including resources that are not routinely available, such as an MOCVD laboratory that can deposit films of GaAs or GaN, a JEOL e-beam lithography tool that can inscribe 8-nm features on 200-mm wafers, a NanoSIMS, and a unique scanning SQUID microscope that detects magnetic fields with greater sensitivity than any other instrument. The facilities occupy ~30,000 ft2 of space, including 16,000 ft2 of cleanrooms, 6,000 ft2 of which meet stringent specifications on the control of vibration, acoustics, light, cleanliness, and electromagnetic interference. The staff members who will support external users have acquired specialized expertise in fabricating photonic crystals, lasers, photodetectors, optical MEMS, inertial sensors, optical biosensors, electronic biosensors, cantilever probles, nano-FETs, new memories, batteries, and photovoltaics. Stanford will endeavor to increase the number of users from non-traditional fields of nanoscience (e.g., life science, medicine, and earth and environmental science) by creating a targeted formal curriculum, fabricating experimental nanostructures as a service, providing seed grants, and leading seminars and webinars.

Non-technical abstract:
Quantum devices have exceptional promise for computation, communication, and sensing. To realize this potential, scientists and engineers must find the right physical system in which to implement quantum bits, called qubits, with sufficiently low error rates. Small superconducting devices are one of the most promising candidates for building physical devices that function as qubits. This research seeks to address fundamental questions about the nature of small superconducting devices. The researchers make sensitive magnetic measurements to detect the current flowing through a superconducting device to determine whether it has a conventional superconducting state or an unconventional, "topological" superconducting state. Topological superconducting state are states that host special modes at their boundaries, called Majoranas modes. Qubits based on these Majorana modes could greatly reduce errors compared to other types of qubits.

Technical abstract:
The proposed operation of topological qubits is based on a special zero-energy modes known as Majorana modes. The objective of this research is to experimentally demonstrate the existence of Majorana modes using a new generation of fast, highly sensitive Superconducting Quantum Interference Device (SQUID) sensors. The two most important properties are the current-phase relation, a fundamental relation that will have conclusive signatures of Majoranas if they are present and stable, and the parity lifetime, which determines how long the Majorana states are stable. The experiments address longstanding questions in conventional (non-topological) mesoscopic superconductivity, such as the behavior of tunable few-mode junctions with perfect transmission. They also address newer, more urgent questions in topological devices, such as in which systems Majorana fermions exist and for how long their properties are stable. The realization and control of Majoranas would have great foundational significance as an experimental instance of engineered particles with non-Abelian statistics and could also enable certain quantum information technologies. The activities additionally foster the development of fast, ultrasensitive magnetic measurement techniques that are relatively noninvasive. The researchers engage actively in community and outreach activities designed to provide role models and experiential learning to science students at all levels. Student and postdoctoral researchers involved in the research are well-trained in nanotechnology, cryogenics, quantum science, and precision measurements, and are prepared for a lifetime of contributions both as educators and as scientists.