Ritesh Agarwal, Ph.D. - US grants

0609083
Agarwal
This project will develop a new type of nano-scale device called a nanowire spectrometer for chemical analysis. The work will involve four steps: (1) synthesis and characterization of CdS, CdSe and ZnS nanowires with energy band gaps in the UV-Visible region; (2) fluidic assembly of single nanowires and 2-D nanowire rafts onto insulator substrates; (3) fabrication and optical testing of self-aligned gaps within nanowires and nanowire rafts; and (4) fabrication of spectrometers (single and multiple wavelength) by integrating the nanowire light source and detector with microfluidics. The broader impacts of the project include closely coupled research and education plans. Successful completion of the project could lead the development of low-cost, portable, miniature optical spectrometers with potential applications in environmental monitoring, biomedicine and many other fields.

0644737

Intellectual Merit: The objective of this CAREER proposal is to synthesize and study the optical properties of self-assembled nanowire heterostructure materials ranging from molecular to microscopic length scales. Fundamental understanding and exploitation of quantum effects in optical devices holds great promise to revolutionize nanophotonic systems. The research will focus on the synthesis and characterization of nanowire heterostructures and devices in different geometries with accurate control over composition and dimension for investigating fundamental optical properties of systems in confined geometries. The following approach will be undertaken: 1) Develop the atomic-layer deposition technique to synthesize nanowire heterostructures. 2) Characterization of nanowire heterostructures using electron microscopy, optical, electrical, and optoelectronic measurements. 3) Fabrication of quantum-confined nanowire photonic devices such as diodes, lasers, and single-photon sources. The proposed research extends across several frontiers of science and engineering, with the main focus on studying optical properties of chemically grown nanowire heterostructures where finite size, surface and quantum effects become predominant. It will lead to the development of new sub-lithographic nanophotonic devices, which are difficult to assemble using conventional techniques including integration of photonic components with Si-based electronics.

Broader Impact: The proposed research will greatly impact the field of nanophotonics, which represents a major driver ushering the era of nanotechnology. Bottom up approach to self assemble nanostructures will create highly efficient nanosystems with functionalities not possible with any conventional technology. Integrated nanophotonics/electronics will allow development of new, cheaper and efficient devices that will impact areas such as telecommunications, computing, diagnostics, and sensors. The main focus of the educational plan of this proposal is to develop innovative teaching tools to enable students at all levels to acquire high-quality scientific education. The PI will integrate research activities and educational goals by: 1) Developing a new curriculum in nanosciences in the Materials Science department at Penn. 2) Involvement of undergraduates, underrepresented groups and minorities in the research program. 3) Develop Science Van project to take scientific equipment and experiments to under-equipped high schools in West Philadelphia.

DESCRIPTION (Provided by the applicant) Abstract: We propose to assemble nanowire devices with optoelectronic and electrical functionalities to probe intra- and inter-cellular dynamics with unprecedented spatial and temporal resolution. Arrays of electrically pumped nanowire waveguides, lasers, light emitting diodes, and photodetectors combined along with their ability to function as nanoelectrodes will be utilized to probe organelles and other subcellular targets with nanoscale resolution and measure in real-time chemical reaction kinetics, signal propagation, and reactions due to a locally delivered drug, amongst other complex phenomena occurring over any relevant length scales. The arrays of nanowire probes will be functionalized with fluorophores, quantum dots, plasmonic nanocrystals, either at their tips or on their surfaces to enable almost any type of biological imaging technique. Using a general nanowire probe platform will lead to the development of a very broad set of tools with novel functionalities, to enable imaging and electrical probing with label-free techniques with the unique capability of probing any desired spatial domain within living cells. These nanowire-probe substrates can be easily integrated with AFM cantilevers or the tips of conventional fibers, which can then be combined with standard 3-D nanopositioning systems, external electrical circuitry, and optical microscopes to probe specific domains of intracellular organelles/components. As an example, these nanowire devices will be used to create novel nanoscale interfaces with neurons and neuronal networks in the hippocampus to study neuronal signal integration and network functioning and then utilized to investigate the pathophysiology of diseases such as epilepsy. The integration of optoelectronic and electrical functionalities of nanowires on a common platform would lead to a new generation of nanosystems with unprecedented sensitivity and selectivity in probing subcompartments of living cells at the molecular level, which could revolutionize our knowledge of these biological systems and tremendously aid in future drug discoveries. Public Health Relevance: The ability to visualize in vitro intra- and inter- cellular processes in real time with multiplexed and nanoscale resolution detection with the proposed combined optoelectronic and electrical nanowire probes will elucidate new chemical and electrochemical processes and signaling pathways. Detailed knowledge of suband inter- cellular processes using nanowire probes will lead to a much better understanding of overall cellular processes and will aid the design of new drugs for a large number of diseases thereby impacting public health.

TECHNICAL SUMMARY
The objective of this Materials World Network project is to investigate comprehensively the material properties of phase change materials in mixed optical-electrical phase transitions. The underlying principle of memory storage in Ge-Sb-Te alloys is reversible crystalline to amorphous phase transitions that are associated with significant changes in optical reflectivity and electrical resistivity. Although the optical and electrical mechanisms have been independently investigated, there is no work done on the mixed-mode operation, i.e. switching the material optically while probing it electrically and vice-versa. This is however extremely important for a host of potentially game-changing applications ranging from optically gated ultra-fast transistors to non-von-Neumann arithmetic processing. This collaboration between PIs in US, UK and Germany will focus on investigating fundamental phase switching properties in mixed-mode, elucidating phase change mechanisms via dynamic optical probing of electrical phase transitions, and exploring the materials best suited for unconventional future arithmetic processors. The work will involve growth and characterization of new compositions of phase change nanowires, optical pulse induced switching which will be probed electrically, and detailed size- and composition-dependent studies of mixed mode operation in nanowires.

NON-TECHNICAL SUMMARY
The von Neumann model of computing, which is currently used in computer architecture, utilizes designs with separate divisions for processing, logic and memory. Although this design has been highly successful for today's computers, there is clearly a need to go beyond von Neumann's model to keep up with the ever-increasing demand for faster computers with unprecedented capabilities. Combining arithmetic processing capabilities via optical excitation with electronic memory on a common platform is one possible solution to go beyond the conventional computer architecture and phase change materials are very promising in this regard. This Materials World Network project plans to study for the first time the optical-electrical mixed mode behaviour of phase change materials. Although the remarkable properties of these materials have made them commercially successful in memory devices, the fundamental material properties that govern their phase transitions between crystalline and amorphous states are still quite unknown. The project will provide fundamental and novel insights into how the electrical behaviour of these materials is influenced by optical excitation and vice versa. The research seeks to transfer best practises between PIs in three participating countries. The results of this work will greatly impact the development of non-von Neumann computing using arithmetic processing techniques that can revolutionize computing as we know it. Research and educational activities will be integrated by the involvement of undergraduates in the research program; incorporating new research results in the teaching module, and training high school teachers from the local school districts in three countries. In addition, international collaborative opportunities will give students opportunities to spend time in another laboratory and will provide a unique opportunity to pursue cutting edge research across national boundaries.

This project is supported by the Electronic and Photonic Materials program and Office of Special Programs, Division of Materials Research.

EFMA - 1542879
PI: Johnson, Alan T.

This project will develop new chemical sensors composed of biological molecules coupled to two-dimensional atomic crystals. The biological molecules will act as sensors by binding chemical targets in liquid and air samples. The atomic crystal layers will act as readouts by changing their optical or electronic properties when chemical targets are bound by the coupled biological molecules. The team will explore several biological molecules capable of binding specific targets coupled to various atomic crystals composed of compounds called transition metal dichalcogenides. The project will involve fabrication of the crystal layers, measurements of their electronic and optical properties, attachment of the biological molecules, and analysis of the resulting sensor capabilities. Experiments will be conducted in tandem with computational modeling to understand the response of the atomic crystals and predict sensor performance. Results of the project will lead to improved chemical sensors with unprecedented sensitivity and specificity for a variety of applications, including diagnosis of disease, environmental monitoring and law enforcement. The team will use the project to increase awareness of local communities about research at the frontier of nano-biotechnology and to involve student researchers, especially members of groups traditionally underrepresented in science and engineering.

The goal of the project is to develop the basic scientific and engineering knowledge needed to advance nano-biosensor research towards implementation of transition metal dichalcogenides-based biosensors with optical and/or electronic readout. The team will develop scalable chemical vapor deposition approaches to large-area synthesis of MoS2, WS2, SnS2, and other materials identified through materials exploration. The material properties of these systems will be rigorously benchmarked using a combination of advanced structural, chemical, optical, electronic, and scanned probe measurements. A comprehensive set of chemical functionalization techniques will be developed suitable for fabrication of protein-functionalized biosensors with plasmonic, nanophotonic, and/or electronic readout. The impact of chemical functionalization on the electrical and optical properties will be systematically investigated. The measurements will be correlated with multi-scale computational models appropriate for simulating the response of the biosensors, with the goal of developing simulation methodologies suitable for predicting biosensor performance and guiding sensor design.

Non-technical description:
Quantum information science, which utilizes the inherent principles of quantum mechanics, is leading the next revolution of electronic and photonic technologies with application in computing, communication, and sensing. Integrated quantum communication systems that go beyond the individual devices and components, are crucial to continue pushing the frontier of quantum information science. Novel approaches towards effective device integration into quantum technologies become necessary. In this project, the investigators will leverage the state-of-the-art integrated photonics technology to develop a disruptive integrated quantum photonic platform. The developed higher-dimensional control of photons will deliver high-density information capacity and a higher level of security against quantum hacking, as needed for quantum communication. This research is closely integrated with the existing educational activities, providing both undergraduate and graduate students with the opportunity to participate in cutting-edge science and technology in an innovative way. The investigators also provide educational outreach activities to promote the interests and participations of K-12 students and broaden the participations from underrepresented groups.

Technical description:
With funding from the Electrical, Communications and Cyber Systems Division, the investigators from the University of Pennsylvania and Stevens Institute of Technology are developing a disruptive integrated higher-dimensional quantum photonic platform based upon twisted single photons, ranging from deterministic twisted single-photon emission, to transmission and high-fidelity detection. The elusive symmetry and topology of twisted single photons will be explored, together with their interplay with quantum materials and device geometry, to produce efficient signal generation and high-fidelity detection of quantum qudits. To engineer the media-links between qudits' emitter and receiver enabling the fully integrated quantum system, novel optical fiber configurations will be investigated to support simultaneous transmission of multiple twisted photons. The investigators have highly complementary expertise on deterministic quantum emitters, integrated lasing and photo-detection, which will be actively synergized to perform high-density quantum key distribution with twisted single-photons, featuring the increased information capacity and enhanced robustness against eavesdropping and quantum cloning.

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.