James Curtis Hone - US grants

Abstract
0428716
James Hone
Columbia University

Single-walled carbon nanotubes (SWNTs), tubes of carbon as small as 1 nm in diameter, are ideal candidates for sensing because every atom of a nanotube is at the surface. The use of SWNTs as high dynamic range fluid flow sensors will be investigated in this project. This work is based on the recent discovery [Ghosh et al., Science 299, 1042 (2003)] that flow of an ionic fluid across a collection of nanotubes produces a voltage in the flow direction. This phenomenon will be verified and the initial work extend in the following ways:

1. Fabrication of sensors based on thin films of nanotubes. Thin films of nanotubes with well-controlled geometry will be used for testing. This geometry will allow for better control and modeling of flow conditions
2. Systematic variation of relevant parameters, such as flow velocity and shear, sample geometry, and external variables such as temperature.
3. Fabrication of sensors based on single nanotubes. Ultra-long nanotubes will be grown using chemical vapor deposition, and integrated with microfluidics to make flow devices. The flow-induced voltage will be studied for different types of nanotubes, as well as for varying electrochemical potentials.

Potential applications of the technology explored in this work include integration of flow sensors into lab-on-a-chip devices, in-vivo biological fluid flow sensors, and low-cost, dispersed atmospheric and oceanographic flow sensing.

This is a project supported under the Sensors Initiative NSF 04-522.

This proposal was received in response to Nanoscale Science and Engineering initiative, NSF 04-043, category NIRT.

This Nanoscale Interdisciplinary Research Team (NIRT) project will create nanofabricated, biofunctionalized arrays to study the fundamental relationship between spatial order and function in biochemical systems. These 'nanoscale bioarrays' will be fabricated using leading edge nanofabrication technology to allow investigation of structure-function relationships on the molecular scale, i.e. a few to tens of nanometers. The arrays will be organized hierarchically, with unit cells (comprising one or more biofunctionalized 2-10 nm metal dots) organized into micron-sized domains, and patterned in mm-size areas. Each domain will comprise identical unit cells, and the unit cell geometry will be systematically varied from domain to domain, in order to allow for straightforward assay techniques on the micron scale. The nanoscale bioarray technique will be applied to three biological investigations: 1, the study of the dependence of binding of large cytoskeletal proteins on the spatial arrangement of ligands; 2, the study of the effect of ordering cytoplasmic dynein molecules on microtubule-dependent motility; 3, the seeding of protein crystals.

Intellectual Merit:
This project attempts to push the limits of nanofabrication technology in order to interface with biological systems. It will employ a "top-down" approach to study and control "bottom-up" assembly, function and synthesis of these systems. Each sub-project will use nanofabrication technology to extend a biological question or problem beyond where currently available techniques will allow. The project is organized around a central theme and fabrication technique, which will allow for rapid technology development. The project addresses the research and education theme "Biosystems at the Nanoscale."

Broader Impacts:
This project will have many broader impacts. The advances in the use of solid-state nanofabrication to address biological and chemical problems will enhance research infrastructure in ways that will impact areas of biological science beyond just cytoskeleton-based motility or protein crystallization. The participation of young scientists-in-training in this interdisciplinary environment will foster development of a cadre of future scientists with the necessary knowledge and cultural and technical skills to successfully pursue novel multidisciplinary science and technology. Undergraduate students will also participate in the research, including students drawn from institutions in the New York City area with significant minority enrollment. The Principal Investigator will draw on his experience as a New York City public high school teacher to extend outreach to the K-12 level.

0507111
Heinz

Single-wall carbon nanotubes constitute a family of one-dimensional materials exhibiting many remarkable properties. The goal of this research program is to provide comprehensive measurements of the electronic, optoelectronic, mechanical, and thermal properties of individual single-walled carbon nanotubes of fully defined structure. The experimental approach relies on the growth of freely suspended nanotubes across a slit in a silicon substrate. Optical characterization by Rayleigh and Raman spectroscopy will probe the electronic and vibrational properties, and the results will be correlated with direct structural characterization of the nanotubes. Evaporation of metallic pads onto the substrates will enable optoelectronic, thermal, and mechanical studies. The investigations will be carried out by a multidisciplinary team with researchers in Mechanical Engineering, Materials Science, Electrical Engineering, Chemistry, and Physics; the team will be complemented by strong interactions with researchers at government laboratories and in industry.

The proposed work will generate advances in the basic knowledge of the properties of carbon nanotubes. Studies of this model system enhance the scientific understanding of materials of reduced dimensionality. The results are also importance for a wide range of potential applications, in the areas including electronics, optoelectronics, sensors, and structural materials. The educational impact of the program extends to interdisciplinary training of graduate students and postdocs, as well as to significant participation of undergraduates in the research program. The educational impact is further enhanced by the integrated involvement of students and faculty at the City College of the City University of New York and Rowan University.

Proposal no: 508319
Title: NER/SNB: High-frequency, three-dimensional integrated CNFET/CMOS technology
Inst: Columbia University
PI: Ken Shepard


Carbon nano-tube field-effect transistors (CNFET) have emerged as a potential alternative field-effect technology to conventional deep-submicron silicon transistors. While operating under physical principles similar to complementary metal-oxide semiconductor (CMOS) silicon field-effect transistors, these devices offer several possible advantages in circuits including reduced short-channel effects, potential molecular-level control to reduce variability, and a hybrid three-dimensional integration in which active devices (CMOS on the bottom and CNFET on the top) will sandwich the metal interconnect layers. For any of these potential advantages to be realized, these devices must coexist with silicon CMOS FETs and must be able to leverage the existing investment in CMOS process technology. By combining CMOS-compatible CNFET fabrication with comprehensive circuit-focused device characterization, the PIs seek to further explore the potential advantage of CNFETs for real microelectronics applications while pursuing the development of viable circuits that combine CNFET transistors with conventional deep submicron CMOS technology.

This proposal describes a plan for combined experimental and theoretical efforts to expand the understanding of mechanical properties and electronic structure of graphene and other two-dimensional materials under ultrahigh strain. This proposal builds upon recent work published in Science by two of the PIs, in which unprecedentedly large elastic strains of approximately 25% were obtained prior to failure. The proposed work includes three experimental thrusts that build on these results. First, the directionally-dependent nonlinear mechanical properties of graphene will be measured up to ultrahigh strains by performing nanoindentation tests of graphene nanoribbons with known lattice orientation. Second, these techniques will be carried over to other two-dimensional materials. Third, the electronic properties of these materials will be studied under ultrahigh strain. A crosscutting theoretical thrust will explore the ability of ab-initio theory to predict these results, and the ab-initio results will be used to parameterize a continuum model.

Ultrahigh strain strain states are both a scientific and technological frontier. Given the many potential applications for which graphene is being studied, ranging from space elevators to electronic circuits, the results from this study will likely have widespread applications. Furthermore, the simplicity of these two-dimensional materials makes them a prime testbed for multi-scale modeling, ranging from the atomic level to the continuum. This work will sponsor two graduate students, who will learn a broad range of skills, including nanofabrication, nanomaterials synthesis, nanomechanical testing, and theory. In addition, the work is highly accessible to undergraduate and high school students: the PIs will support two undergraduates during the period of the grant, and at least one high school student. Finally, the PIs will develop simulations and animations to build a teaching module on the NanoEd resource portal maintained by the National Center for Learning and Teaching in Nanoscale Science and Engineering.

Technical abstract:

Fundamental advances of condensed matter physics require a comprehensive understanding of the impact of interactions and disorder on non-interacting electrons in a perfect lattice. One-dimensional (1D) electron systems provide a fertile ground for physicists as interactions and disorder can completely alter their physical behavior. This project will determine the fundamental origin of resistance in single-wall carbon nanotube, an ideal 1D material, and explore the localization phenomena and the consequences of electron-electron interaction in nanotubes of well-defined chiral structure as a function of disorder and interaction strength. The results will have a broad, long-term impact on carbon nanotube technology. Nanotubes are currently being evaluated and developed for a number of transformative applications, including high-speed electronics; transparent, conducting films for solar photovoltaic cells; and conducting supports for battery electrodes. Understanding the impact of phonons and impurities is essential for optimizing carbon nanotube performance in these applications. Beyond training graduate students at UCF and Columbia, this project will support educational outreach activities involving K-12 educators and students, and our respective communities, with emphasis on underrepresented minorities in the New York metropolitan area and the Greater Orlando.

Non-technical abstract:

Single-wall carbon nanotubes possess extraordinary electronic properties, which are important for both fundamental and applied nanoscale materials science. In addition to providing a fertile ground for exploring unusual physics in one-dimensional systems, nanotubes are currently being evaluated and developed for a number of transformative applications, including high-speed electronics; transparent, conducting films for solar photovoltaic cells; and conducting supports for battery electrodes. This project will study transport properties of carbon nanotubes of well-defined atomic structure while controlling the experimental environment down to atomic scale, eliminating any unwanted experimental variability. Such unprecedented approach enables this collaborative team to systematically investigate the intrinsic transport properties of carbon nanotubes, which remain poorly understood after years of intensive research. As such, the results will have a broad impact on carbon nanotube science and technology. Finally, this project will support training of graduate students at UCF and Columbia, as well as educational outreach activities involving K-12 educators and students, and our respective communities, with emphasis on underrepresented minorities in the New York metropolitan area and the Greater Orlando.

The goal of this NUE in Engineering program entitled, "NUE: Transforming Nanoscale Science and Engineering Undergraduate Education", at Columbia University, under the direction of Dr. Chee Wei Wong, is to create an institutionalized cross-disciplinary nanotechnology undergraduate program, reaching across multiple departments to serve a targeted ~90 (25% of cohort) undergraduates. Seven laboratory modules on nanoscale science and engineering will be developed, based on scientific advances by the project team such as in graphene, nanomechanics, nanostructured solar photovoltaics, and nanoelectronics. These hands-on modules
will be taught in conjunction with a theoretical numerical simulations class on the foundations of nanotechnology.

The classes will reach out across Columbia University and Barnard College (an undergraduate women's college), and the laboratory modules can further serve as stand-alone experiments in other nanoscale related curricula. In addition, research experiences for undergraduates will be provided under this program, as well as summer internships at GE Global Research and the Center for Functional Nanomaterials at Brookhaven National Laboratory. All course materials will be made freely available online for broad dissemination. Lectures in the theoretical foundations class will be recorded and made available for asynchronous download.

This Materials Interdisciplinary Research Team (MIRT) proposal examines the assembly and physical properties of new composite materials created by 'nano-laminating' atomic sheets of different van der Waals (vdW) materials. These vdW building blocks are materials in which the atomic bonds are strong in two directions, but weak in the third. This gives them a layered structure, like a stack of paper, and makes it easy to separate ('exfoliate') the layers. Common vdW materials include graphite, which can be exfoliated to form single sheets (graphene); many high-T superconductors; and layered chalcogenides such as MoS2. Many of these systems already display interesting behavior due to the low dimensionality of their electronic structure. The team pioneered a technique for re-stacking dissimilar vdW materials in a controlled fashion ('nano-lamination'). Using this technique, it is possible to create heterostructures that are essentially designer materials, with control at the level of the individual atomic layer. The aim of the MIRT is to create materials that provide unique functionality that is of interest to fundamental science and engineering applications.

The MIRT proposal includes a central synthesis effort that seeks to broaden the set of materials under study from the first examples (graphene and hexagonal boron nitride) to include layered chalcogenides, 2D oxides, topological insulators, and low-dimensional organic systems. The synthesis effort combines nano-lamination with single-crystal growth, molecular beam epitaxy, templated materials growth, and intercalation. Fundamental issues to be addressed include the nature of interfaces between dissimilar layers, how interlayer alignment changes properties, and 'design rules' for growth on vdW surfaces. The MIRT includes extensive characterization of the new materials by multiple techniques. These techniques include structural characterization, electronic transport, optical and Raman spectroscopy, scanned probe microscopy, and chemical methods.

Using the techniques and materials developed under the MIRT program, the team seeks to address a number of fundamental issues regarding behavior of materials in low dimensions. For instance, it will be possible to study the 3D-to-2D evolution of correlated electronic behavior such as superconductivity and charge density wave states as the host materials approach the limit of single atomic sheets. Likewise, nano-lamination will allow materials such as topological insulators and superconductors to be brought into proximity in order to probe exotic phases predicted to exist at these interfaces.

The MIRT team seeks to broaden the impact of its activities through REU and RET programs, as well as a school visitation program. In addition, a central goal of the MIRT is to strengthen interaction between Columbia and CCNY through better coordination of research and use of shared facilities, as well as joint student advising and recruiting.

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.

TECHNICAL: The search for high-performance electronic switches operating at low power dissipation has generated many concepts that go beyond the control of charge flow in traditional semiconductor device structures. These novel devices are based on the use of alternative state variables, including the characteristics of single-particle quantum systems, such as spin, pseudospin, and carrier wave-function phase, and the characteristics of correlated many-body quantum systems, such as excitons and exciton condensates. The goal of this project is to develop the basis for transformative technology that would be made possible by the availability of high-performance electronic devices employing such quantum state variables, rather than traditional semi-classical transport of charge. To this end, a team of investigators at Columbia University and University of Florida is devoted to the fabrication, characterization, and theoretical analysis of such quantum switches. The research exploits recent technological advances in the synthesis of atomically thin layers of van der Waals solids and heterostructures formed from combinations of such layered materials. The potential of this approach is exemplified by the excellent electrical characteristics exhibited by heterostructures of atomically thin layers of graphene and hexagonal boron nitride. In this project, devices are built from such well-developed material systems, where the primary fabrication challenges involve precise control over geometry and interface cleanliness. The key research components of the project are as follows: (i) The assembly and fabrication of atomically thin heterostructure devices based on the co-lamination of van der Waals materials, atomic-layer deposition processes, and advanced patterning techniques; (ii) the analysis of distinctive quantum coherent transport processes in weakly coupled layered heterojunction device structures by electrical and optical measurements; (iii) the establishment of new state variables based on quantum coherence; and (iv) the demonstration, characterization, and theoretical modeling of switching devices based on novel state variables. Devices resulting from this research effort promise performance with respect to switching speed and energy dissipation that significantly exceeds the limits imposed by conventional semiconductor device technology.

NON-TECHNICAL: The development of the new electronic devices based on low-dimensional functional material platforms opens important directions in both fundamental and applied research. The availability of practical high-performance, low-energy switching devices is of great significance for the continued advancement of electronics and the associated information technology industry. Thus, the demonstration of devices based on new switching principles has the potential for broad technological impact. The diverse capabilities of the team also significantly enhance the educational opportunities for students and postdocs at Columbia and at collaborating institutions. The highly interdisciplinary research carried out in this project provides cutting-edge training for graduate students and postdocs, as well as for undergraduate students. The team integrates research activities with educational efforts by offering new lecture and laboratory courses, as well as modifying existing ones. The team also undertakes broader educational outreach through sponsorship of summer research projects for high school students. Significant efforts are made toward K-12 outreach by training of highly motivated high school students, and by enhancing interactions with local K-12 educators to introduce front-line research to students.

Directional dry etching constitutes a fundamental fabrication technique in the research and manufacturing of micro- and nanoscale devices. The proposal seeks funding to allow Columbia University to acquire an advanced etching system that allows for a diverse set of uses and will expand the range of a variety of current projects at Columbia, including projects related to nano-electronics, nanobiology and nano-neuro-biology, optoelectronics, photovoltaics and medical research. The equipment will also enable a range of future projects that are currently not possible, including lasers at the nanoscale level and a class of semiconductors known as III/V semiconductors. As a major upgrade to the shared Columbia Cleanroom -- currently the only shared cleanroom facility in the New York City metropolitan area --the etching system to be acquired will directly impact the educational and research activities of over 250 researchers (faculty, staff, and students) at Columbia and neighboring institutions. The group of co-Principal Investigators includes all the researchers who serve on the Cleanroom Board of Directors, representing an accumulation of experience in the successful installation and support of such equipment for a varied and evolving set of users. The facility also hosts graduate and undergraduate lecture and laboratory courses taught by the co-PIs, REUs and RETs, and independent study projects advised by faculty from many departments. Since nanopatterning is a central component of these courses, the requested etcher will directly impact the educational program of several departments, providing students with important skills for future careers in science and engineering.

The ICP RIE (inductively-coupled plasma, reactive ion etching) system described in this proposal will employ chlorine-based etch chemistries for vertical etching of compound semiconductors, metals, and organic materials. The new patterning capability and system will enable a range of future projects including nanoscale lasers and sensors based on III/V semiconductors. During operation of the etcher, recipes will be systematically developed to provide optimal results to all researchers. The Columbia University clean room is currently the only shared-access micro- and nano-fabrication facility in the metropolitan New York City area and serves a diverse population of academic users and small businesses. The facility has permanent technical and administrative support, and the proposed ICP RIE system will constitute a crucial facility of the available infrastructure for research training in nanoscale science and engineering. The tool will be used directly by students and post-doctoral researchers as part of their research activities, providing training in advanced nanopatterning techniques.

Graphene--a single atomic layer of carbon atoms--is a two-dimensional material with many exceptional properties. For example, pristine defect-free graphene has the highest electrical conductivity as well as the greatest mechanical strength of any known material. To harness these unique properties, scientists and engineers have fabricated many different electrical, optical and magnetic devices from graphene using nanofabrication methods. Many of these devices are much superior to their microscale counterparts in terms of performance and/or energy usage. Thus graphene has tremendous potential to impact society positively. However pristine defect-free graphene is extremely expensive because manual methods must be used to isolate and manipulate it. To address this, several methods to grow graphene in an industrially scalable manner have been demonstrated recently. Graphene grown by such methods would benefit from an economy of scale that could translate to the mass production of nanofabricated devices that take advantage of graphene's unique set of properties. However graphene grown by these methods contains defects that degrade the properties, especially the mechanical properties. Our project addresses the fundamental challenge of quantifying the strength and reliability of graphene grown by industrially scalable methods. The outcome of the project is expected to be: (1) an experimental method to quantify the strength and reliability of as-grown graphene; (2) an understanding of how the growth process can be optimized to maximize the strength and reliability of as-grown graphene; (3) an experimentally validated multiscale theoretical and computational tool to predict the strength and reliability of graphene; and, (4) demonstration that as-grown graphene can be used as the backbone for ultrahigh strength laminate composites. The availability of large area CVD graphene with well-understood properties will make possible the mass production of graphene-based devices such as ever smaller and faster electronic devices and ultra high strength composite materials. In addition, the PIs and supported student will interact with high school teachers in the public New York City school system to host student visits and to develop laboratory experiments to measure the mechanical response of materials fitting high school science projects.

The objective is to quantify CVD graphene's probability of failure at a given stress as well as its mean strength. The Weibull probability distribution for a heterogeneous stress state will be employed. The experimental methodology will be via nanoindentation and pressure loading of free-standing circular films of CVD graphene. In order to rationalize the experimental results, a multiple length constitutive model of grain boundaries in graphene will be developed. Molecular dynamics simulations will predict the strength of individual grain boundaries that were previously characterized at the atomic length scale using Transmission Electron Microscopy (TEM). This information will be transferred to continuum cohesive zone models that will be incorporated into detailed finite element computational models. Thereby, the model will also account rigorously for the non-linear and anisotropic properties of the individual grains in the polycrystalline CVD graphene. The experimentally validated physics-based predictive capability of the model will serve as a tool to optimize the CVD growth of graphene and other two-dimensional materials.

****Nontechnical abstract****

New materials are typically created using the most basic building blocks of matter - atoms of the different elements in the periodic table. The Center for Precision Assembly of Superstratic and Superatomic Solids -- led by Columbia University in partnership with City College of New York, Harvard University, Barnard College, and the University of the Virgin Islands -- seeks to create novel materials from two new types of building blocks: atomically thin sheets stacked into layered structures; and precisely defined clusters of atoms linked together into bulk solids. The Center research will provide better understanding of low-dimensional materials and their interactions. This understanding will aid in the design and discovery of new materials with better applications in electronic/magnetic devices, optoelectronic systems, and thermoelectrics. The Center provides interdisciplinary graduate research training and opportunities for undergraduate research; includes research partners in industry, national laboratories, and internationally; and will build new shared instrumentation facilities available to the research community. The Center includes a comprehensive program to improve and support science education through partnerships with three local K-12 schools, and a new pilot program at the Columbia School of Journalism.

****Technical abstract****
This Center seeks to utilize atomically precise building blocks to create new materials and structures. The first research thrust will utilize two-dimensional sheets such as conducting graphene, insulating boron nitride, semiconducting transition metal dichalcogenides, and a large family of other materials with a wide variety of properties. New techniques developed by the research team will be used to combine these materials into layered heterostructures with unprecedented size, perfection, and complexity. These will be used to understand properties in a protected, ultralow-disorder environment, and to achieve emergent electronic phenomena at interfaces. The second research thrust will assemble atomically defined clusters into new classes of functional materials with new forms of inter-cluster chemical bonding. This approach will enable independent tuning of cluster properties and interaction to achieve designer materials with unprecedented levels of complexity and functionality. Three areas of focus are: independent control over magnetism and conductivity; independent control over thermal and electrical transport properties for thermoelectrics; and superatom assemblies that can have electronic phase transitions that may be induced by optical, mechanical, thermal, and other stimuli. The Center provides interdisciplinary graduate research training and opportunities for undergraduate research; includes research partners in industry, national laboratories, and internationally; and will build new shared instrumentation facilities available to the research community. The Center includes a comprehensive program to improve and support science education through partnerships with three local K-12 schools, and a new pilot program at the Columbia School of Journalism.

Non-technical Abstract
The aim of this project is to experimentally study the interactions between electrons in two coupled two-dimensional (2D) sheets. When the 2D layers are sufficiently close, interlayer Coulomb interactions result in momentum transfer so that electrons moving in one layer cause those in the second sheet to move in response, a phenomenon known as Coulomb drag. This work will study layered heterostructures of atomically thin materials -- including graphene and insulating boron nitride --to achieve atomic control over the spacing between the conducting layers. This will allow the exploration of Coulomb drag in the strong-coupling limit, and in high-mobility devices where electrical transport is ballistic. These structures are made possible by techniques developed by the Principle Investigators to fabricate ultraclean multi-layered heterostructures by mechanical layering of 2D materials. The primary effort will be a systematic characterization of the drag response in monolayer graphene versus temperature, density, layer separation, and magnetic field. Drag resistance together with inter-layer tunneling will additionally be used to pursue signatures of a theoretically-predicted exciton condensate phase in which spatially indirect excitons consisting of paired electrons and holes confined to separate layers condensed into a superfluid ground state. Careful studies of the Coulomb drag response provides a unique tool in which to study electron-electron interactions in mesoscopic systems, which is expected to have significant impact beyond the study of 2D systems, since electron-electron interactions underlie the rich and complex physics of correlated materials. If successful, this research could also enable revolutionary new low power electronic devices. The collaborative interdisciplinary work will provide training to a postdoctoral researcher as well as providing research experience to high school and junior level undergraduate students. Outreach efforts will focus on expanding long-term relationships with teachers at two affiliated public schools.

Technical Abstract:
The aim of this project is to experimentally study Coulomb drag in high mobility double layer quantum wells fabricated from 2D materials, such as graphene and related van der Waals materials, in the strongly interacting limit of small interlayer separation. The primary goal will be a systematic characterization of the drag response in monolayer graphene heterostructures versus temperature, density and interlayer separation, under both zero and finite magnetic field, through transport measurements. Several outstanding questions will be addressed such as the anomalous density and temperature dependences reported previously, origin of the anomalous drag response at the double neutrality point, and the nature of the Hall response in the finite magnetic field regime. Drag resistance together with inter-layer tunneling will additionally be used to pursue signatures of the exciton condensate phase in two regimes (i) electron-hole graphene layers at zero magnetic field, and (ii) electron-electron graphene layers at half filled Landau levels in the quantum Hall regime. The experimental effort will include studies of heterostructures fabricated from bilayer graphene, and mono and few-layer transition metal dichalcogenides where the effect of a bandgap on the exciton binding has so far received no experimental attention. The Coulomb drag response in graphene is not well understood at the most basic level. Theoretical efforts to model this system have yielded conflicting results, none of which well match the few experimental studies that have been reported so far. In this regard the systematic study proposed here promises to lay important groundwork for future understanding of this system, and more generally to provide quantitative boundaries on key physical parameters necessary to accurately model electron transport in graphene such as the strength of electron screening versus density and the specific role of the dielectric environment.

Nontechnical Description: This collaborative project between Stevens Institute of Technology and Columbia University seeks to understand and control the interaction of light with crystalline matter in nanoscale photonic structures. The research includes material growth of crystalline wires that are only one nanometer in diameter and several micrometers long. These so-called nanowires are then integrated with photonic nanostructures that strongly enhance their light emission. A particular focus is on the fundamental understanding of how electric charges interact with heat and light in these nanoscale structures. Ultimately, this research project enables an efficiency and performance boost for chip-scale light sources and detectors, in particular quantum-light sources that are needed to realize quantum-communication technologies to support, for example, national security. The principal investigators collaborate to introduce new research-based educational materials into the graduate curricula on both campuses by team-teaching these subjects via video link. This project offers research experience to graduate and undergraduate students. Outreach activities at Stevens leverage institutional programs such as the Women in Engineering Program. At Columbia, the co-principal investigator develops an outreach model that builds a close partnership with teachers at the Columbia Secondary School for Math, Science, and Engineering, a public, 6-12 school with a large population of under-represented students.

Technical Description: Carbon nanotubes have recently gained tremendous interest as a nanomaterial for the next-generation optoelectronics and quantum photonic devices. To date, the majority of experiments revealed, however, low quantum efficiencies due to extrinsic interactions with the environment that lower the prospects for applications. The collaborative project takes advantage of an ultra-narrow spectral linewidth regime featuring intrinsic spontaneous light emission rates and prolonged exciton dephasing in ultraclean carbon nanotubes, and integrates them with optical cavities. Specifically, the research objectives are (1) to dramatically enhance the light collection as well as the optical emission rate of carbon nanotubes in order to demonstrate efficient on-chip quantum light sources and (2) to uncover the intrinsic exciton dephasing mechanism and acoustic-phonon localization effects. The technical approach explores methods to integrate carbon nanotubes with metallo-dielectric antennas and plasmonic nanocavities, and to further engineer the exciton dephasing via manipulation of the acoustic-phonon density of states. The project advances the understanding of fundamental light-matter interaction in carbon nanotubes, in particular in the presence of localized excitons and phonons along the nanotubes and contributes to advances in on-chip quantum photonics and cavity-optomechanics.

1. Proposal Title: Collaborative Research: A Contact Lens-Based Glucose Nanosensor Using Affinity Polymer-Functionalized Graphene
2. Project Goals: The project goals are to create a mechanically flexible, contact lens-based, affinity nanosensor to continuously monitor glucose concentrations in tears

3. Abstract:

3a. Nontechnical Abstract: Approximately 25.8 million people in the U.S. have diabetes, which is the seventh leading cause of death. Continuous glucose monitoring (CGM) involves repetitive measurements of physiological glucose concentration to allow close monitoring and timely correction of problematic blood sugar patterns of diabetes patients. CGM can significantly reduce the risk of diabetes-related complications, but existing CGM devices are not yet adequate because of limited stability, insufficient accuracy, slow responses, and invasiveness. This project aims to create a mechanically flexible, contact lens-based nanosensor to overcome these limitations. The nanosensor will exploit the nanomaterial graphene and measure glucose concentrations in tears via physical interactions of a synthetic polymer with glucose, thereby enabling stable and accurate CGM in a noninvasive, nonobstructive and convenient manner. With these capabilities, the nanosensor will potentially lead to improved care of patients with diabetes and other related disorders, and can be extended to the monitoring or detection of additional tear-borne analytes in healthcare. The nanosensor can also broadly impact other applications. For instance, in military applications, the device can potentially be used to enable health monitoring as well as drug and nutritional supplement delivery, thereby improving the protection of soldiers and enhancing their performance in the battlefield. In addition, the principal investigators will extend their current educational efforts in training graduate students and educating undergraduate students, including those from underrepresented groups, in an interdisciplinary research environment. The research team will also actively participate in strong educational outreach activities in the New York City and Columbia, SC, areas.

3b. Technical Abstract: The affinity nanosensor will use polymer-functionalized graphene to enable continuous monitoring of glucose in tears in the eye. The device will be constructed by an interdisciplinary approach, which, as a primary intellectual merit of the proposed research, combines graphene nanotechnology, synthetic polymer chemistry, and flexible micro-electro-mechanical systems. Graphene, a single, tightly packed layer of carbon atoms bonded together in a hexagonal honeycomb lattice, is emerging as a highly promising functional nanomaterial in chemical and biological sensors. Such sensors at present most commonly operate in solid- or gas-phase environments, and their use in liquid media is relatively limited. In particular, graphene has not yet been explored to enable affinity glucose sensing in physiological fluids. This research exploits the high surface-charge sensitivity, mechanical flexibility and optical transparency of graphene for glucose measurement in tears. The graphene will be functionalized with a synthetic, boronic acid-derivatized polymer and bonded on a mechanically flexible, contact lens-shaped substrate. By differential measurement of changes in the electric conductance of graphene due to specific affinity binding between the boronic acid moieties and glucose molecules, the device will allow specific, sensitive and rapid measurement of glucose concentration. In this design, the device will possess optimal miniaturization to attain a rapid time response, high sensitivity to effect improved glucose measurement accuracy, and mechanical flexibility to reduce adverse tissue-device interactions. With future integration of wireless telemetry, the nanosensor can enable stable and accurate continuous glucose monitoring in a noninvasive, nonobstructive and convenient manner.

Nontechnical Description: Transition metal dichalcogenide (TMD) monolayers are the thinnest semiconductor materials, with thickness on the order of one to three atoms (i.e., a fraction of a nanometer) and are often called two-dimensional semiconductors. These materials may serve as a material platform for future electronics and optoelectronics applications as the conventional semiconductor technologies are reaching dimensional limits. The main goal of this project is to understand how charges move across the interface between two-dimensional semiconductors, a process central to the operation of many electronic and optoelectronic devices. The research combines advanced growth and processing technologies with various spectroscopic characterization methods. In addition, the project offers training opportunities for students, ranging from K-12, community college, and undergraduates to graduate students.

Technical Description: Optical and optoelectronic processes at two-dimensional semiconductor interfaces must satisfy the conservation of both energy and momentum; the later includes both spin and crystal momentum. The hexagonal structure of a transition metal dichalcogenide (TMD) monolayer leads to six valleys in momentum space, K and -K, with opposite spin-orbital splitting. The K or -K valleys in one monolayer are usually not aligned with those of the other. Thus, charge transfer across the interface is accompanied by change in parallel momentum. However, little is known about the mechanism for momentum conservation, due in a large part to the lack of momentum resolution in experimental techniques applied to date to the TMDs. This research experimentally tackles this problem by directly measuring the energy and momentum of the electron in the time domain, as it is excited in the K (or -K) valley of a TMD monolayer, transferred to the second monolayer as a free electron or to form an inter-layer exciton, and or recombine with the hole across the interface. This is enabled by a state-of-the-art experimental techniques, time-resolved two-photon photoemission spectroscopy with near-IR to visible excitation of the TMD monolayers or heterojunctions and an extreme ultraviolet laser to ionize the excited electron. The ionized electron is detected in both energy and momentum spaces with femtosecond time resolution. Such a direct experimental approach advances the understanding of interlayer excitons at TMD heterojunctions and guides the development of future optoelectronic technologies based on two-dimensional semiconductors.

Nontechnical description: A new class of atomically thin materials, so called two dimensional semiconductors, has gained considerable interest as a viable material for optoelectronic devices such as lasers and light emitting diodes. Previous research reports that these new materials suffer from detrimental environmental interactions and material defects that result in low light emission efficiencies, thereby impeding practical applications. This project ultimately enables an efficiency and performance boost for nanoscale light sources such as nanolasers as well as novel quantum light sources that are required in upcoming technologies that use light instead of electrons to realize densely integrated information processing directly on a semiconductor chip. The research approach utilizes a promising crystal growth technique that leads to very low defect densities in two dimensional materials. The research also integrates these materials with optical devices that can focus the light into extremely small spots, leading to drastically enhanced light emission efficiency from these semiconductors. The educational activities include reaching out to underrepresented groups as well as training the next generation of scientists and engineers in materials growth, clean-room fabrication and optical characterization, and through introducing new research-based educational materials into the graduate curriculum.

Technical description: Monolayer transition metal dichalcogenides are semiconductor materials that have gained considerable interest for optoelectronic and valleytronic applications but are often found to suffer from environment interactions and material defects that lead to low quantum efficiencies. This project integrates two-dimensional heterostructures featuring ultralow-disorder environments with low-group-velocity plasmonic band-edge modes in order to investigate lasing and quantum coherence signatures of on-chip nanolasers with highly-directional output. This project furthermore explores gate-tunable exciton and trion gain and realizes deterministic positioned quantum emitters coupled to plasmonic gap modes deeply in the Purcell regime. The research approach combines material growth, 2D assembly, and nanofabrication to enable transformative advances for the field of on-chip photonics and quantum information science that aims to facilitate the outstanding optical properties of "intrinsically-clean" 2D semiconductors. The integration with plasmonic nanocavities offers exciting new inroads to directly tailor the light-matter interaction in the Purcell and strong-coupling regime. Ultimately, this project enables an efficiency and performance boost for on-chip nanolasers for the integration in optical circuits, as well as for single-photon sources required for quantum information science; these are all affected by the exciton photophysics and significantly benefit by low-disorder environments, reduced material defects in flux-grown material, and plasmonic coupling to directly increase the quantum yield. The project also puts forth an outreach model that focusses on building long-term relationships with the Columbia Secondary School for Math, Science, and Engineering, a public, 6-12 school with a predominant Hispanic and African-American student population. Outreach activities to under-represented groups will leverage Stevens' institutional affiliations with organizations such as the Women in Engineering Program and the National Action Council for Minorities in Engineering (NACME).

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.

Nontechnical Description: The Columbia Materials Science and Engineering Center (MRSEC) - Center for Precision-Assembled Quantum Materials P(AQM) partners with faculty at Minority Serving Institutions and explores new materials systems that will enable future quantum technologies, and educates a diverse new generation of scientists and engineers who reach across disciplines to advance the frontiers of knowledge and technology. The PAQM research program comprises two interdisciplinary research groups (IRGs), both of which study materials assembled from lower-dimensional building blocks: the first group creates layered structures by stacking atomically thin sheets, and the second group uses chemically synthesized molecular clusters to create bulk materials. In both systems, the emergent properties can be controlled both by choosing different building blocks and controlling how they are assembled. PAQM seeks to harness this design freedom to create a next generation of quantum materials which provide new ways to manipulate the flow of charge, spin, and energy, and host quantum states such as superconductivity. These new properties will in turn enable future quantum technologies in computing, sensing, and communications like digital memory, switchable absorbers, and new photodetectors. PAQM trains researchers at the high school, community college, undergraduate, and graduate levels in an environment that brings together researchers from multiple science and engineering disciplines. The center engages students and teachers at the elementary and middle school levels to build interest in science. The educational and research activities of the Columbia MRSEC are designed to increase diversity at all levels, particularly in fields related to Materials Science and Engineering.

Technical Description: The Columbia MRSEC - PAQM consists of two IRGs focused on materials created by precise assembly of low-dimensional building blocks. IRG1 combines two-dimensional materials into van der Waals heterostructures (vdWH) hosting emergent quantum phenomena. Three classes of quantum phenomena ? tunable superfluids, non-equilibrium states, and topological quantum states ? motivate this work. IRG1 focuses on foundational materials issues by synthesizing high-purity crystals, creating ultraclean heterostructures, and performing detailed characterization to fully understand structure/property relationships in vdWH. These advances will propel the field and enable harnessing of quantum phenomena underpinning future quantum information, sensing and computing technologies. IRG2 designs and synthesizes atomically precise, functional materials from chemically synthesized molecular clusters (superatoms). Using a closed-loop approach that combines synthesis, theory, and characterization, the IRG2 team develops methods to control the coupling between superatoms. Tuning the superatoms? electronic, magnetic, vibrational, and symmetry characteristics allows the team to design reconfigurable phase change materials; control directional transport of energy, charge and spin; and achieve emergent quantum phenomena, properties that underpin future technologies including electronics, digital memory, switchable absorbers, and new photodetectors. Investments in new research tools and shared facilities supports this work. These research goals are propelled by collaborations, with major partners including Brookhaven National Laboratory, the Flatiron Institute, and the Max Planck Society. Industrial partnerships and an entrepreneurial seed program support translational efforts toward applications. PAQM education and outreach activities support STEM and materials education at all levels and train the next generation of interdisciplinary materials researchers in the cutting-edge area of quantum materials. Reflecting the diversity of the Columbia MRSEC faculty and its urban location, research and education are integrated with a diversity strategic plan aimed at increasing participation of underrepresented groups in materials science and related 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.