Latika Menon - US grants

This NIRT proposal focuses on the preparation of ordered arrays of nanodots and nanowires and incorporating them into device structures. This is a critical problem in nanometer-scale science of semiconductors. The NIRT research will build on our ability to grow quantum heterostructures with layer thickness down to a few atomic layers and to prepare ordered nanostructured templates. The two approaches will be combined to form structures and devices ordered on the nanometer scale in three dimensions. The research will include self-assembly of alumina masks, with pore sizes as small as 10 nm, on semiconductor substrates and deposition of semiconductor dots and nanowires into these pores using selective epitaxy. By either removing the alumina template or leaving it in place, we will have produced an array of identical semiconductor quantum dots. These will be compared with dots produced by epitaxial self-assembly. We will apply knowledge gained from these experiments to prepare ultraviolet light emitting devices based on the AlN/AlGaN heterostructures. These techniques will also be applied to the formation of nanowires of dilute magnetic semiconductors and to investigate spin transport and device applications of the (Ga, Mn)N and (In,Mn)N systems. Equally important, results of this research will be used to inject nanoscience into current courses, producing new laboratory based courses, and to educate science and engineering graduate students in this important area.
Intellectual Merit: This proposal addresses fundamental problems that need to be solved in order to produce useful ultraviolet optoelectronic and spin-based devices. Advanced growth methods will be developed to produce nanoarrays of technologically important semiconductors. Devices will be fabricated out of these nanoarrays and their properties explored. There are several reasons to study three-dimensional quantum structures based on GaN and related compounds: 1. Quantum dots have higher radiative efficiency than two-dimensional layers, thus providing better device performance. Superior spin transport is expected in nanowires of dilute semiconductors. 2. Ordered nanostructures - devices grown with vertical (heterostructure) and lateral (nanodot) control will allow us to engineer properties on a quantum level, resulting in new device functionalities. 3. Further miniaturization of device structures requires better understanding of the self-assembly processes and finer control over nanodot and nanowire quality.
Broader Impact: The assembly of nanostructured semiconductors into nanoscale devices will enable new applications in electronics, spintronics, and photonics. At the same time, preparation of such devices challenges our understanding of fundamental limits of size and scalability that determine electrical and optical properties of nanostructures. New approaches to research and education are needed to meet this challenge. Under this NIRT proposal the research plan will be closely integrated with educational activities. Specific steps that will be taken towards this goal include involvement of graduate and undergraduate students in advanced interdisciplinary research. Their participation will develop critical technical, team, and leadership abilities. New components of classroom and laboratory courses will be produced based on nanofabrication, attracting students from diverse backgrounds into research.

Current state of the art in nanotechnology is the study of advanced, high-performance nanoscale materials. In order to fabricate devices based on these materials, several fundamental issues need to be considered: novel nanofabrication techniques amenable to devices need to be invented, appropriate growth and processing techniques suitable to nanostructures need to be developed, novel methods must be devised to investigate properties of these materials and most importantly, device processing issues need to be considered for such small structures. In this proposal several of these critical issues will be addressed. Non-lithographic, nanofabrication methods based on porous alumina templates will be developed. Nitride semiconductor nanoarrays will be synthesized for UV-light emitters and spintronic device fabrication.
Nanotechnology is also concerned with developing new materials exhibiting exotic properties at the nanoscale level. In this work, new nanoscale materials, magnetic alloys (FePt) and energetic nanocomposites (Al-Fe2O3) will be fabricated

Intellectual Merit: This is a unique proposal covering research in many different aspects of nanotechnology. Success of this research proposal will lead to development of highly efficient nanofabrication methods, development of advanced growth and processing methods and demonstration of novel nanodevices based on nitrides. Fabrication of UV light emitters will not only impact the optoelectronics industry, it will also have applications in advanced chemical and biosensors, relevant to national security issues. Spintronic devices will allow easy integration into present-day micro-electronic systems. FePt alloys are important materials for data storage devices and high density recording media while novel Al-Fe2O3 nanocomposites will find applications in energy storage.

Broad Impact: The interdisciplinary nature of this research proposal will have a broad impact in many different areas of research including magnetic materials, energetic nanocomposites, materials science, device physics and advanced engineering. A major goal of this program will be the creation of excellent student education and training programs. This will be achieved through development of advanced laboratory facilities, involvement of students in all aspects of the research plan, introduction of nanotechnology into courses, active recruitment of students from underrepresented groups into my research program, and by fostering inter-disciplinary and industrial collaborations.

The objective of this research is to develop an ultra high vacuum materials deposition and characterization system. The system will provide combined deposition and analysis capabilities not currently available at TTU, significantly enhancing our materials research and educational efforts. Development of these capabilities will have an immediate impact on numerous projects funded by NSF.
Intellectual Merit: The system will be used to conduct basic and applied research in thin film deposition and surface analysis. In large bandgap materials, our recent work has demonstrated ultraviolet LEDs operating at wavelength 262 nm. New questions regard the influence of surface chemistry and metallization on contact formation. The development of microelectronic materials with high dielectric constant leads to questions on the importance of silicon gate-dielectric interface. Our nano-engineered energetic materials rely on interdiffusion reactions. To optimize structures for energy storage and release, improvements are needed in control over deposition and in situ characterization to study the reactions. MOEMS research involves micromirror development and basic studies of wear. Surface characterization will advance our efforts in stiction and friction remediation and extend our MOEMS research into of fatigue and failure. Broader Impact: This instrumentation impacts numerous ongoing research projects and enhances our interactions with industry and national laboratories. The scope of our studies is broad, and spans numerous areas in science and engineering. The TTU Nano Tech Center provides an interdisciplinary setting with excellent technical, team, and leadership building opportunities for postdoctoral researchers and students at all levels through research and courses conducted within Center facilities.

0608892
Menon
The goal of this NER application is to develop nano-biodevices for recording and stimulating nerves that are reliable and long lasting. This exploratory proposal addresses some of the critical issues entailed. These issues include gold nano-wire size, cell growth and motion artifacts, and cell viability at the electrode-cell interface. The research plan calls for fabrication of an array of nano-wires in three sizes ranging of 50, 100, and 200 nm. Measurements will be performed by culturing two types of neural (rat hippocampal and human neuroblastoma) cells onto the surface of Au and peptide conjugated Au nano-wires.

As the trend towards smaller electronic devices continues, current silicon technology consisting of metal-oxide semiconductor junctions and metal interconnect will face significant deficiencies such as a large leakage current, increase in film resistance and electromigration of atoms. In this regard, one-dimensional nanomaterials such as carbon nanotube and nanowire offer advantage as nanoscale alternatives to current silicon-based devices. The goal of this NER project is to fabricate and test hierarchically designed one-dimensional heterostructures based on carbon nanotubes and nanowires. The specific goals are to: (a) create precisely controlled (diameter, length, and geometry) nanotube/nanowire heterostructures in various configurations using anodize aluminum oxide nanochannels as templates followed by chemical vapor deposition and electrodeposition techniques, (b) characterize and study their structures, junctions, and transport property, and (c) perform computational investigations of structural and electronic properties of nanotube/nanowire heterostructures. The intellectual merit of the research lies in the first detailed study that will attempt to create and characterize novel heterostructured and hierarchical molecular scale junctions based on carbon nanotubes with nanowires. The research will demonstrate control over tailoring transport properties and building of one-dimensional nanomaterial based nanodevices. These heterostructured materials will open up new opportunities for both fundamental research and building of true nanoscale interconnection and architecture. Specifically, these nanotube-nanowire hybrid structures will enable advanced nanoelectronics for logic devices, multi-terminal nanoelectronic devices, switches, integrated diode circuits, and multifunctional nanosystems. The research emphasizes the participation, education, and training of undergraduates, and graduate students who will all benefit from exposure to nanoscience and nanotechnology research in three participating universities.

Latika Menon

The objective of this SGER is to develop an advanced nanodevice for recording electrical activity in neurons. The device will consist of an array of conducting nanowire arrays which will record electrical signals from neurons at the nanoscale level. This will provide a fundamental understanding of learning and memory processes in neurons and will lead to important clinical applications in neural implants and future brain machine interface devices.

Intellectual Merit:
This SGER has many features that will be very useful for learning about recording electrical activity in neurons. This will be the first demonstration of a nanowire-array based device which will allow recording of electrical activity from simultaneous locations in a single neuron thus leading to high spatial resolution. In addition, nanowires will cause minimal damage to the cell due to their small size with respect to the neuron (typically of the order of several microns). This research will provide an excellent integration of nano/microfabrication with biology, laying the groundwork for other novel devices in the future using similar principles. Use of nanowire-arrays for electrical recording from neurons is clearly a novel approach opening a number of possibilities for studying neuronal activity at the nanoscale level. The nanowire-neuron device proposed here will be a model system to study biophysical interactions between nanowires and cells. Nanowires provide the platform for functionalization with appropriate biorecognition molecules, ensuring cell immobilization and a more stable 'cell-attached' electrical recording.

Broad Impact: Due to the small size of the nanowires with respect to the neuron sizes our device will allow a fundamental understanding of neuronal functions which will impact our understanding of changes in neural circuits that underlie neurological disorders and stroke. A more direct impact of our work will be related to a fundamental understanding of cell interaction with nano-environment which will relate not only to neurons but also to other cells such as cancer cells, stem cells, etc. In the area of education, one graduate student will be involved in the work and the project will lead to development of new laboratory facilities, particularly those pertaining to cell culture and cell characterization.

NON-TECHNICAL DESCRIPTION: Technological breakthroughs to support societal needs, such as solar energy harvesters and improved data storage strategies, require disruptive advances in new materials with novel functionalities. To that end, this project employs the tools of nanotechnology to fabricate, characterize and tailor the response of titanium-iron-oxide-based nanotube arrays with simultaneous functionality employing electronic charge, magnetic spin and optical response. Properly engineered, these materials hold promise for potential application in devices to efficiently absorb and transfer solar energy and/or to process data with increased speed, precision and accuracy. The research is carried out by an interdisciplinary team of researchers from science and engineering and includes the involvement of students, teachers and junior scientists at all levels of experience. Unique features of the educational experience of this proposal are the opportunities to introduce students to research at large scientific facilities such as the National Synchrotron Light Source at Brookhaven National Laboratory and the fact that the proposal is led by a majority female PI team, providing diversity models to both students and colleagues.

TECHNICAL DETAILS: Iron-doped titania nanotubes are fabricated by electrochemical means and studied using a variety of probes (structural, magnetic and optical, including synchrotron-based spectroscopies) to obtain a fundamental understanding of their magnetic, spintronic, optical and magnetocatalytic properties as functions of composition and structural attributes. As pure titania is a large-bandgap semiconductor, Fe additions not only perturb the band structure but also serve as sensitive probes of the lattice modification by virtue of the large Fe magnetic moment. Further, nanostructured titania is anticipated to exhibit enhanced functional responses due to its large surface area. In this manner it is desired to develop novel multifunctional nanostructures for combined spintronic, optical and photocatalytic properties, at room temperature, in one material. Eventual device applications in sensing, catalysis and spintronics to enable advances in alternative energy and data processing technologies are envisioned.

The objective of this research is to develop epitaxial GaN and related alloy based nanowires and investigate their magnetic, optical and electrical properties for nanoelectronic device applications. The approach will utilize a controlled catalyst deposition followed by chemical vapor deposition methods.

Intellectual Merit: The new technology involves controlled deposition of Ni catalyst nanoparticles with small dimensions followed by chemical vapor deposition leading to the production of GaN epitaxial nanowire networks on the substrate. The crystal structure of the new kind of GaN nanowires is of the cubic zinc blende type, technologically more significant than typically grown wurtzite GaN. Growth procedure for such epitaxial GaN nanowire networks and the related alloys will be optimized in this project; magnetic properties of GaMnN nanowires will be studied by means of magnetization and magnetic force microscopy; optical properties such as photoluminescence, Raman spectra will be investigated; electrical properties: FET characteristics and LED characteristics will be investigated.

Broad Impact: The epitaxial configuration of the nanowires is perfectly suited for device fabrication - the technology is high-throughput, easily scalable to wafer-sizes and compatible with advanced micro and nanoengineering processes. The technique allows for complete control and flexibility over tailoring the structure, optical and transport properties. From a fundamental aspect, the project will enhance research and discovery in the technologically important field of GaN-based nanowire systems. The research will provide students (graduate, undergraduate and high school students) with interdisciplinary educational experience through an ongoing nanotechnology course, a newly proposed laboratory-based nanotechnology course and also through additional laboratory facilities. The project will contribute to the professional development of students through publications in refereed journals and conference presentations.

Technical. This project addresses new understanding and progress in fabricating novel nanodot and nanowire arrays of semiconductors and ferromagnets. The approach involves a multi-step process using porous alumina templates, and is being studied for precise control of nanopatterns and its use in fabrication of novel nanoarrays. Synthesis and processing phenomena associated with the fabrication of vertically heterostructured, ferromagnet/semiconductor nanodevices based on MBE-grown III-V semiconductors and Heusler alloys will be pursued. Nanowires of GaAs have been achieved via MBE using Au-catalyzed vapor-liquid-solid (VLS) growth and will be further studied on this project for growing arrays of hybrid nanowires composed of ferromagnetic (e.g., MnAs) and semiconducting materials. A wide range of experimental tools and expertise will be utilized for systematic investigations aimed at gaining greater fundamental understanding of electrical, magnetic, and optical properties of nanostructured materials and devices.
Non-Technical. The project addresses fundamental research issues in a topical area of electronic/photonic materials science having technological relevance. There is potential that the research could substantially impact the development of novel electronic devices such as nonvolatile memories and nanowire electronic circuits. Development of novel nanostructures could even open doors to new device designs never before contemplated. Educating and training young people in the areas of electronic, magnetic and optical nanostructures--areas which are crucial for future applications in information technology is of primary importance to this project. In addition to training students in diverse aspects of science and engineering, this project couples with existing educational outreach to K-12 students, women, and underrepresented groups through activities in programs already established at Northeastern University with active participation by these PIs. Four to eight undergraduates will contribute to the research through Northeastern's unique Co-op program, and high school students will be involved in summer research programs.

The project will investigate the commercial potentail of titania nanotubes for applications in solar cells, photocatalysis, catalysis, etc. Research in these areas by the PI over the last several years has identified several high-efficiency, low-cost technology-ready methodologies in (i) the development and characterization of titania nanotube anodes with ultra-high surface density produced via inexpensive and scalable electrochemical routes. (ii) synthesis of low-cost polymer hole-regenerators such as poly-ethylene-dioxy-thiophene (PEDOT) amenable to solar cell applications (iii) Titania nanotubes decorated with gold nanoparticles with extraordinarily high catalytic oxidation efficiencies thus demonstrating promise for applications in fuel cells, automobile catalysts, etc. Several advances in energy technology will emanate from this work: (i) tech-ready biocompatible nanomaterials; high-performance catalyst materials; photocatalyst and photovoltaic anodes with superior charge transport and solar absorptive properties will be developed (ii) the liquid electrolyte which is the main bottleneck in current PV cells/modules will be replaced by solid hole-conductors and (iii) an optimal integration of high-performance solar cell components will be achieved resulting in stable, low cost, high-efficiency solar cells which are amenable to large-volume manufacture.

If successful, this project may have commercial impacts with the establishment of several new contacts. The novel developments within this project will be patented and rapid tech-transfer measures will be taken. The research draws on a number scientific disciplines, combining materials science with photovoltaics, optoelectronics and chemistry, thus providing a unique educational experience for students including the participation of underrepresented groups, enhancement of infrastructure for research and education, and industrial outreach.