NDnano Undergraduate Research Fellowships (NURF)
NDnano is pleased to announce that the Center has awarded NDnano Undergraduate Research Fellowships to 28 students for summer 2013. Each student will work with a faculty-led research team, earning $5,250 over the course of their 10-week project in nanoscience or nanoengineering.
The fellowship recipients are currently students at Notre Dame, Saint Mary's College, Ivy Tech Community College, and Purdue College of Technology. The NURF program also welcomes students from three schools in India: Amrita University, Indian Institute of Technology-Kanpur, and Indian Institute of Technology-Banaras Hindu University. In addition, the participation of students from Trinity College Dublin, University College Cork, and Dublin City University, all in Ireland, is made possible through the support of the Naughton Fellowship Exchange Program, which is also funding summer research in Ireland for several Notre Dame students.
Following is a list of project descriptions for this summer's NURF program, including the name of each fellowship recipient and their NDnano faculty mentor(s).
Check back in the fall to read a recap of each student's research experience!
Questions? Feel free to contact Heidi Deethardt at email@example.com.
Thank you for your interest in NDnano!
Project: Fabrication of polymer nanofibers with anomalous thermal conductivity
Amorphous polymers are known as thermal insulators with a thermal conductivity of ~0.1-0.3 W/mK. However, they can be more thermally conductive than many metals if we can reform them into highly aligned nanofibers (thermal conductivity > 50 W/mK). This suggests that polymers can be used to replace metals in many heat transfer devices and equipment, such as in electronic packaging and heat exchangers, with the additional advantages of reduced weight, chemical resistance, and lower cost. In this project, undergraduate researchers will fabricate polymer fibers with nanometer diameters by ultra-drawing fibers from polymer melt. They will also characterize the nanofibers using electron microscopes, X-ray scattering, and measure thermal transport properties using scanning thermal microscopy.
Project: Multi-array tip-nanocolloid plasmonic molecular sensing
We design plasmonic resonant grids and sharp nanostructures for exciting broadbanded plasmonic spectra but with a sensitive monochromatic scattering reporter. The resonant grids are fabricated by anodization of titania, and the nanostructures involve optical fibers etched into submicron tips. We also employ a peculiar effect of surface molecules on metal nanocolloid aggregation to detect DNA molecules captured by plasmonic nanocolloid probes. This combination of broadband tip plasmonic focusing and resonant grid coupling with metal nanocolloid high-Q plasmonic resonance allows us to use white-light illumination but sensitive detection and quantification of the scattered light. We also use photochemistry to functionalize separate probes onto each fiber tip. The objective is to design a multi-fiber array that can detect a large library of target molecules with simple optical sensors.
Project: Home-use nanosensors for screening chronic diseases
Professor Hsueh-Chia Chang's group is integrating microfluidics, plasmonic optical nanosensors and aptamer molecular probes into biochips for the first generation of home-use, turn-key medical devices that can monitor cardiovascular, diabetic and cancer miRNA biomarkers. The device is enabled by recently engineered hairpin aptamer probes that can dramatically change its conformation and the end-substrate distance upon molecular capture, such that the fluorophore at the end of the aptamer would not be quenched by the gold substrate via Forster electron-tunneling (FRET). The group has developed several metal and semiconductor nanopore and nanocone fabrication technologies to complement these FRET apatamer sensors by using photoconductive and plasmonic effects. These nanotechnologies are integrated with his earlier micro/nanofluidic technologies to lyse cells and concentrate protein/nucleic acid micro/nanofluidic technologies to yield the turn-key devices. His group works with a startup (FCubed, LLC: See Chicago Sunday Times coverage and has an outstanding record of placing alumni at top industrial and academic positions (www.nd.edu/~changlab).
Project: DNA origami
Take the genome of m13mp18, a small virus. Add 226 short synthetic strands of DNA, the "staple" strands, and you can fold it into a flat rectangle as shown in the picture (left). This is an example of the DNA origami technique. We are conducting research on DNA origami as structural templates for nanoelectronic and nanomagnetic devices by binding non-DNA components to specific staple strands. In this project, the NURF student will work with a researcher to chemically modify a DNA oligonucleotide with a functional group that can bind to metals. The project involves a little organic synthesis, followed by biomolecule derivatization and purification of the oligonucleotide by HPLC and/or gel electrophoresis. If pure oligos are obtained, the student will assemble the DNA origami in the presence and absence of metal ions and characterize them by atomic force microscopy. Two semesters of organic lab are required, and some experience working with biomolecules (DNA or proteins) would be a plus.
Project: Nanoelectronic material characterization using single-electron transistors
With the shrinking of electronics towards the nanometer scale, just a few misplaced dopants can cause significant variability in the performance of electronic devices. Therefore, developing the ability to accurately map vacancies, defects, dopant atoms, and interface structures becomes a critical technology for enabling future generations of electronic devices. To achieve these goals, this project is developing methods for the detection and characterization of charged defects in electronics-relevant materials. The approach is to integrate novel electronic materials with single-electron transistor structures so that the native imperfections in the materials and fabrication-induced defects are directly detectable through evaluation of the single-electron transistor's characteristics. Both low-frequency testing methods (e.g., conductance mapping) and high- frequency techniques (e.g., microwave reflectometry) will be used to provide detailed characterization of charged defects in the barrier materials over a broad frequency range. Students involved in this project will work in the low-temperature measurement facility characterizing single-electron transistors and the defects that their characteristics reveal, as well as working in the cleanroom to fabricate devices for evaluation.
Project: High-speed transistor characterization
GaN-based devices are emerging not only for power applications but also for high-speed, high-performance applications. In this project, aggressively-scaled GaN-based devices will be characterized (DC, CV, RF/millimeter-wave) and models developed to describe the observed performance. Physical insights into the internal operation of the devices (e.g., dispersive phenomena) are of particular interest, and the use of the characterization to more fully understand these effects will be a key focus of the project. In addition, equivalent circuit models suitable for circuit design will be extracted, and implemented in CAD software. Work will include on-wafer testing of devices (DC measurements, low- and high-frequency CV, and on-wafer RF-millimeterwave (10 MHz-220 GHz) network analysis).
Project: Design of nanomagnet logic devices
In nanomagnet logic (NML), magnetic signals are substituting electricity in performing computation. The building blocks of this magnetic computer are tiny (sub 100 nm size) magnetic dots. This is a fundamentally new computing paradigm, which was pioneered at Notre Dame. The Notre Dame Nanomagnetics group is now leading a large, international collaboration, where the goal is to build a prototype of a magnetic computing device. The student will use micromagnetic simulations to design and simulate logic gates. The gates will be built and tested in the ND Nanofabrication Facility. You will compare the experimental findings with simulation results. For more info on NML, see http://spectrum.ieee.org/semiconductors/design/magnetic-logic-attracts-money.
Project: Synthesis of nanocatalysts
Heterogeneous catalysis is performed on the surface of particles of metal or oxide or composited metal and oxide at the nanoscale. Size is critical as coordination of the environment and electronic structure of atoms on the surface of nanoparticles with different size depends on the size and shape of the catalyst particles. One specific type of nanoparticle catalyst is alloy nanocatalyst. The second metal typically modifies the electronic state of the atoms of the first metal and, therefore, their catalytic performances. In this project, we focus on new synthesis, which can produce new bimetallic nanocatalysts with controllable size and shape. We also measure their catalytic performance (conversion rate and selectivity), therefore building a correlation of structural factors at the nanoscale with catalytic behavior. This correlation is critical for design of new catalysts. More information can be found at http://www.franklin-tao.com/.
Project: Development of laser transmission spectroscopy as a bio-molecular detection system
Nanoparticles are common in nature as well as in many industrial applications. Engineering at the nanoscale is now becoming a part of a wide range of activities including the design of electronics and new materials. Although we may not realize it, we are already surrounded by manmade and natural occurring nanoparticles present in our air, water, food, and medicines. Nanoparticles have a huge impact, both good (i.e., pharmaceuticals) and bad (i.e., toxic materials, viruses, bacteria), on human, animal, and environmental health. Using presently available commercial technology, there is no good solution to the problem of rapidly (in real time) identifying and characterizing the size, shape, and number of nanoparticles present in a fluid sample. Our new platform technology, Laser Transmission Spectroscopy (LTS), has the ability to identify and accurately measure in real time the size, shape, and number of nanoparticles suspended in fluid. This technology has 1,000,000 times the sensitivity and 5 times the size resolution of competing technologies. This general tool for nanoparticle analysis has shown considerable promise for DNA identification and quantification based on successful species-specific measurements. A fully portable LTS prototype has been constructed and this summer project will include testing the instrument's ability to identify DNA without polymerase chain reaction (PCR) amplification--an important goal for many biological applications. The implications are profound and include streamlined invasive-species detection, the rapid genetic identification of specific strains of pathogens, the rapid diagnosis of genetic defects leading to disease, and the field survey of pathogens. If fully successful, LTS would represent the only non-PRC based DNA analysis technique in existence and as such would represent a true game-changer in medical diagnostics, medical research, and the general advance of human health.
Project: Ultra-low energy computation
Anyone who owns a laptop knows that power dissipation and the associated heat are a problem for the microelectronics industry. As electronic devices scale down in size, they use less power (and hence energy), but is there a lower limit to the energy that must be dissipated by each device? Recent experimental measurements have demonstrated our ability to measure energy dissipation in the range of a ~50 yJ (1 yJ is 10-24 J), and we are building complementary metal-oxide-semiconductor (CMOS) circuits to operate in this range. Projects in the group of Professor Gregory Snider will explore the limits of ultra-low power computing, and designing, building and measuring circuits that test these limits. The projects will include building circuits and amplifiers for energy measurements of the CMOS circuits as well as the actual measurements. A student involved in these projects will gain experience in programming, fabrication, CMOS design, and device measurement techniques.
Project: Single protein detection using nanostructure probes
Nanoparticles have become widely used as imaging probes. They have many advantages that make them useful over other imaging probes such as fluorescent dyes. In particular, when excited by a laser at their plasmon frequency, gold and silver nanoparticles exhibit large electromagnetic fields on their surfaces. Molecules in the presence of these fields give rise to increased Raman scattering. By measuring the Raman scattering, one can determine the molecules in close proximity to the nanoparticle. The goal of this project is to use Raman scattering obtained from proteins in contact with nanoparticles to determine the amino acid residues responsible for the protein binding to the nanoparticle. To accomplish this, Raman spectra will be obtained from pure amino acids and short amino acid sequences, and compared to the Raman spectra obtained from nanoparticles in contact with intact proteins. The long-term goal of this project is to use nanoparticle probes to detect specific proteins and protein binding interactions in cells. This project is appropriate for students with an interest in spectroscopy and biochemistry.
Project: Incorporating nanostructures into biocompatible flow detectors
The combination of fabricated nanostructures with materials amenable to cell culture provide new routes to detecting biomolecules associated with normal celluar function and that are also diagnostic of disease. In this project, students will work to embed nano structures into biocompatible polymer substrates that are incorporated into devices capable of high sensitivity detection. The goal is to develop existing technology in the lab to build a prototype in which cells remain viable while undergoing chemical monitoring. This project is appropriate for students with an interest in bioengineering, materials science, and analytical chemistry.
Project: Nanoparticle contrast agents for detecting pre-rupture tendon damage
Incidence of tendon and ligament ruptures is high among both athletes and the general population. Such ruptures are painful and debilitating, and frequently require surgical intervention to restore full function. Soft tissue ruptures are often associated with pre-rupture degeneration of the tissue. The detection of changes associated with this degeneration could allow clinicians to apply preventive treatments to avoid ruptures and the subsequent need for surgical treatments. Unfortunately, this is not currently possible due to a lack of suitable in vivo diagnostic imaging techniques. To address this issue, we are currently developing gold nanoparticle contrast agents functionalized to target biomolecules associated with soft tissue degeneration. These contrast agents will enable X-ray imaging of pre-rupture damage in tendons and ligaments. Students working on this project will use animal ex vivo models to investigate important practical elements associated with the use of these contrast agents in clinical settings. Students will also gain experience in nanoparticle synthesis and characterization, as well as biological sample collection, preparation and characterization. Experience with synthetic chemistry or materials characterization techniques would be desirable but all candidates with an interest in biomedical engineering will be considered.
Project: Hazard characterization and life cycle-based green redesign of a nanotechnology-enabled product
The US National Nanotechnology Initiative has emphasized ethical, legal, and social implications (ELSI) and environmental, health, and safety issues (EHS) as nanotechnology development proceeds. Nanotechnology-enabled products with considerable benefits to humanity are in early research and development stages in the laboratories of NDnano investigators. However, consideration of entire "cradle-to-grave" product life cycles may reveal potential for harmful unintended consequences associated with some product prototypes in addition to their intended benefits. Responsible development in these instances requires scientific characterization of potential harm and steps toward hazard elimination or reduction according to green design principles, the focus of this undergraduate research project. Project methods will include both empirical (conducted at the Center for Environmental Science and Technology) and literature-based research, requiring a versatile intellect, interest in advanced reading, and strong written and oral presentation skills. A rising senior is preferred.
Project: On-chip optical diagnosis using capillary electrophoresis
On-chip medical diagnostics provides researchers and clinicians ways of quickly identifying biomarkers that indicate disease and biological stress. In such devices biomarkers (e.g., proteins, lipids, DNA) typically interact with a functionalized electrode to "read-out" a positive presence. However, optical detection methods (e.g., measuring the amount of light that interacts with a biomarker) can additionally provide a high level of sensitivity and specificity. Recently at Notre Dame, groups from the Department of Electrical Engineering have begun looking at ways of efficiently coupling semiconductor laser light onto optical biosensors on a chip. This project will continue the work and explore light interaction with biomarkers in on-chip capillary arrays. Work will involve cleanroom fabrication, device characterization, and computer modeling/simulation. This project is best suited for rising juniors and seniors.
Project: Plasma jets for nanomaterials synthesis
Plasma jets are an emerging technology that have a wide variety of applications--from killing tumors and healing wounds to cleaning tumors and synthesizing new nanomaterials. This project targets using plasma jets for plasma electrochemistry to synthesize nanoparticles, focusing on how to control the interaction between the plasma jet and a liquid. A NURF student will conduct experiments that look at novel plasma configurations for plasma/liquid interactions and use simple simulations to predict the interaction thermodynamics. The student will work with a team of graduate students studying plasma science, but will have the opportunity to work independently and use their own creativity and imagination. Those who intend to continue the research for credit in the fall semester and have a high interest in going to graduate school will be given preference.
Project: Dynamically tunable THz devices based on magnetic carbon nano fibers (CNF)
Electromagnetic waves in the frequency range 0.1-10 THz have remained the least explored and developed in the entire spectrum, creating what is widely known as the Terahertz Gap. Recently, THz waves have attracted much attention and continuous interest owning to their prospective applications in many important fields, such as astronomy, chemical analysis, biological sensing, imaging, security screening, etc. Among many THz quasi-optical components now under development, THz shielding devices, attenuators, polarizers and filters, especially those with dynamically tunable properties, are in high demand. Conventional methods for realizing the above components usually require complex (i.e., costly) microfabrication processes, such as photolithography or chemical etching. In addition, THz wave modulation/manipulation mechanisms and devices studied so far (e.g., those based on electrical tuning, optical control, or thermal driving) generally exhibit compromised performance due to issues with structure complexity and manufacturing cost. We propose to explore an alternative approach for cost-effective manufacturing of dynamically tunable THz quasi-optical devices and components relying on magnetic tuning of nanoparticle-filled CNF composite coatings.
Our collaborator at the University of Illinois at Chicago has synthesized magnetic CNF powders consisting of CNFs filled with 10nm-dia. Fe3O4 superparamagnetic nanoparticles. On the basis of the novel composite materials, we will manufacture and demonstrate dynamically tunable THz polarizers controlled by an external magnetic field. We also plan to study and demonstrate tunable THz filters using the so-called frequency-selective-surface (FSS) approach based on the same composite coatings. This approach may provide an unprecedented method for extraordinary tunability (both transmission and center frequency) and modulation depth (as high as 60 dB based on our initial results). This project offers the student a unique opportunity to gain hands-on skills in terahertz measurement, spectroscopy, and instrumentation. The student will be expected to be a rising junior or senior with electrical engineering course work, but qualified applicants at other levels will also be considered. Furthermore, we expect that the completion of this work will lead to journal publications (Results from our NURF 2011 project have been published in Applied Physics Letters).
Project: Electrical characterization of silicon-on-insulator substrates
Recently, the demand for high resistivity SOI (HR-SOI) wafers dramatically increases due to the fast growing wireless telecommunication market. For example, RFICs built on HR-SOI wafers have already been seen on cellular handset front-end, which is traditionally dominated exclusively by GaAs-based technology. Compared to GaAs technology, high integration and low cost is always the biggest advantage for Si. While using HR-SOI wafers, the substrate RF loss can be minimized compared to using bulk Si or low resistivity SOI wafers. However, it is known that the effective resistance of the HR-SOI wafer can be significantly reduced due to a low resistivity layer of free carriers formed near the buried oxide (BOX) and handle Si interface. It is also known that intentionally forming a high density trap layer at the BOX/Si interface can effectively reduce the free carrier concentration. In this project, commercial SOI wafers processed with different trap formation techniques will be characterized from dc to microwave frequencies to understand the origin of the substrate RF losses and explore ways to eliminate them.
Project: Drug delivery using nanomedicine in cancers
Multiple myeloma (MM), a B-cell malignancy characterized by proliferation of monoclonal plasma cells in the bone marrow, is the second most common type of blood cancer in the U.S. Despite the recent advances in treatment strategies and the emergence of novel therapies, it still remains incurable. A major factor that contributes to the development of drug resistance in MM is the interaction of MM cells with the bone marrow microenvironment. It has been demonstrated that the adhesion of MM cells to the bone marrow stroma via α4β1 integrins leads to cell adhesion mediated drug resistance (CAM-DR), which enables MM cells to gain resistance to drugs such as doxorubicin (Dox)–a 1st line chemotherapeutic in the treatment of MM. The overall objective of this proposed project is to engineer "smart" nanoparticles that will deliver and exert the cytotoxic effects of the chemotherapeutic agents on MM cells, and at the same time do it in such a manner to overcome drug resistance for improved patient outcome. To enable this, we engineer nanoparticles that will be (i) functionalized with α4β1-antagonist peptides for targeting, (ii) loaded with chemotherapeutic agents, and (iii) designed to show the adhesion inhibitory and the cytotoxic effects in a temporal sequence. When the nanoparticles are delivered to the MM cells, as a first step they will interact with the cell surface α4β1 integrins and inhibit MM cell adhesion to the stroma, thereby preventing development of drug resistance (figure above). In the second step, chemotherapeutic agents will exert cytotoxic effects after cellular uptake, as the nanoparticles will be designed to require a low pH environment such as the endocytic vesicles, to release active drugs. This way, the "smart" nanoparticles will act on the MM cells in a temporal fashion and prevent development of CAM-DR for improved patient outcome.
Project: Photo-induced reconfigurable THz circuits and devices
Tunable and reconfigurable THz circuits and components such as filters, planar antennas, modulators and beam steering arrays are in high demand in THz imaging, sensing, spectroscopy, and communication. Demonstrations of the above active THz circuits have been reported using metamaterial and liquid crystal based devices. However, the tunability and versatility of the above approaches are still limited. We propose to optically produce circuit patterns on semiconductor substrates to implement tunable/reconfigurable quasi-optical THz components. The computer-generated photo-patterns are projected on substrates to induce spatially controllable free-carrier absorption of THz radiation, thus creating unlimited possibilities of quasi-optical THz circuits. In this NURF project, modulating and gating of THz waves under pattern-free light projection will be first demonstrated as a proof of concept (initial verification using photoconductive polymer materials has been performed). Photo-patterning of tunable/reconfigurable THz polarizers and mesh filters (frequency-tunable) will then be fully explored. We will further seek to demonstrate reconfigurable antenna arrays for THz beam manipulation and steering. If successful, this hybrid optical-THz approach will lead to extremely low-cost and versatile quasi-optical THz components. The NURF student selected for this project will be involved in the development of reconfigurable terahertz modulators and other circuits (e.g., polarizers, filters, arrays) using a computer generated photo pattern. The student will design and construct optical setup, and perform computer control and data acquisition. This project provides the student a unique opportunity to gain knowledge and hands-on skills in optics, THz circuits, and instrumentation. A rising junior or senior with electromagnetic waves or optics course work is preferred, but qualified applicants at other levels will also be considered.
Project: Low voltage memory using 2D materials
As electronic systems become smaller, the need for low-voltage components increases. For example, the development of low-voltage logic devices will necessitate the development of low-voltage memory devices. In this project, we will explore the idea of using novel two-dimensional (2D) materials, such as graphene and molybdenum disulphide, to create low-voltage nanoionic memories. By using materials that are one atom thick, such as graphene, we can approach the limits of scaling. The NURF student will prepare and characterize samples in an inert environment provided by a glovebox, where the oxygen and water concentrations are limited to a few ppm. We will characterize the morphology of the resulting samples using atomic force microscopy and scanning tunneling microscopy (AFM/STM). After a suitable sample preparation procedure is identified, the student will make electrical characterization measurements in vacuum. The student working on this project will gain experience working with 2D materials, learning about the limits of scaling in electronic devices, working within a glovebox, and making electronic measurements on 2D materials.
Project: On-chip lasers
CPU speeds are currently limited by their power density, and multicore processors need supremely fast buses to each other and to memory. Both of these could be solved by using optical interconnects. But Si doesn't emit light, so we can't make lasers with silicon. On the other hand, germanium is already used in CPUs, and strained Ge will emit light. In this project, the student will implement a straightforward technique for creating tensile strain in Ge films in order to study the maximum strain available using the stress liner technique and identify future improvements. The optical properties of the strained films will be measured using photoluminescence (PL) and other techniques. The student will be expected to produce research suitable for publication, with assistance from Prof. Wistey and other members of the research group.
Project: Quantum dot solar cell
In recent years, nanomaterials have emerged as the new building blocks to construct light energy harvesting assemblies.1,2 Efforts are being made to design organic and inorganic hybrid structures that exhibit improved selectivity and efficiency towards light energy conversion. This project will evaluate the performance of solid state quantum dot solar cells. The summer research involves synthesis semiconductor quantum dots, assembling them in a solar cell and evaluation of their photovoltaic properties. Quantum dots (CdSe, Sb2S3, CIS, etc.) are deposited on mesoscopic TiO2 or ZnO film serve as the photoanode. A hole scavenger such as CuSCN, PEDOT, or 2,2´,7,7´-tetrakis-(N,Ndi-p-methoxyphenylamine) 9,9´-spirobifluorene (spiro-OMeTAD) is then deposited onto these photoactive films. A thin layer of metal (e.g., Au or Ag) is deposited on top of the hole transport layer to make the electrical contact. Upon photoexcitation of the semiconductor QDs, the electrons are driven towards the oxide layer and the holes are driven towards the metal contact and thus generate photocurrent. The overall goal is to extend the photorespone into the infrared and overcome the electron recombination at the grain boundaries.
Project: Brightness scaling of mid-infrared sources
Quantum cascade lasers are relatively new mid-infrared sources that have matured greatly in the past decade. These compact, semiconductor sources have enabled myriad applications in health, homeland security, and environmental monitoring. Applications with long optical path lengths—such as mid-infrared countermeasures, remote sensing, and optical communications—however are limited by the brightness of the lasers. In this project, students will work to improve the brightness of mid-infrared quantum cascade lasers using an array of monolithically-integrated power amplifiers. Students involved in this project will have the opportunity to work on numerical simulations, device design and fabrication, and device characterization.
Project: 2-dimensional semiconductors: New toys for the next nano(opto) electronics era
Two dimensional (2D) materials such as graphene, MoS2, WS2, BN etc. are attracting enormous interests due to their excellent electrical and optical properties. Nanoscale devices based on these 2D materials potentially offer high-performance, large-area and low-cost electronics and optoelectronics. Researchers have recently proposed a variety of applications including low-voltage memory, solar cell, high-speed photodetectors, integrated circuits etc. One representative example of 2D material is graphene, consisting of one layer of carbon atoms. Its unique linear dispersion relation at low energies leads to a broadband optical transparency of ~97% for white light. Initially, the atomically thin 2D materials were obtained by mechanical exfoliation, which, however, can only produce micron-size flakes. To produce large-area films for practical applications, chemical vapor deposition (CVD) growth on metal (Cu or Ni) is well developed in recent years. As one of leading research teams in the field of 2D materials and devices, our group has developed capabilities of CVD-growth, transfer, device fabrication, characterizations of both material properties and device performance for 2D materials. Applications such as THz modulators, transparent electrodes, and tunneling field-effect transistors based on these 2D materials have been actively pursued by our group, with some prototypes being demonstrated recently. For more updated information on the group, please refer to http://www.nd.edu/~hxing and http://www.nd.edu/~djena.An example project on IPE is described in the figure above (click image for larger view), and an appropriate project will be decided based on the student’s interests and background upon joining the group. In the IPE project, we will target for using various 2D materials, not only graphene, but also MoS2, WS2 etc as transparent electrode to enable the observation of hole transitions and the complete determination of band alignment in semiconductor interface. Due to the atomically thin nature of these materials, their optical absorption to the light is significantly lower than the bulk materials. In addition, their excellent conductivities can guarantee that the photo-carriers injected from the emitter material is completely collected. These properties make them as ideal transparent electrodes in internal photoemission (IPE) measurements. A proof of concept trail has been demonstrated in graphene/SiO2/Si and graphene/Al2O3/Si structures by our group. Students that involve in this project will have the opportunities to gain hands-on experience and cutting-edge knowledge of 2D crystal growth, device fabrications, and building optical set-ups; more importantly, why researchers are interested in particular materials for particular applications.
Project: Plasmons in semiconductors and what they can do for us
Plasmons, or collective waves of electrons, can be excited in semiconductor materials at THz/IR frequencies. These electron waves can propagate at speeds much larger than those achievable by single electrons thus promise applications in very important areas such as high speed electronics, communications, security, and so on. By dynamically controlling the properties of the semiconductor material (plasmonic media) one can harness the plasmon properties thus develop reconfigurable devices for routing, modulating, or even performing logic. Moreover, higher frequency plasmons that can be excited in other types of materials such as metals can interact with semiconductors to boost the performance of traditional optoelectronic devices such as solar cells and LEDs. In this project the student will: i) learn the physical mechanisms behind these waves of electrons, ii) perform numerical simulations and design of plasmonic devices employing various semiconductor materials, and iii) be involved in the fabrication and characterization activities currently being carried out in Dr. Xing's group. This project will require the use of electromagnetic simulation software and hands-on work on optical setups. Students should preferably have prior knowledge of electromagnetic waves and semiconductor devices. For more updated information of the group, please refer to http://www.nd.edu/~hxing.