Undergraduate Poster Abstracts
Annual Meeting
October 13-14, 2016
Undergraduate Intern Poster Abstracts
1. Odunayo Ayebajeje
Undergraduate, Howard University
Transport Properties of Chiral Carbon Nanotube Thin Films
Odunayo Ayegbajeje, Linda Ye, Takehito Suzuki, Thomas Searles, Joseph Checkelsky
2. Pawan Gaire
Undergraduate, Howard University
Faster Computer with Diamond - Fabrication and Characterization of Diamond Field Effect Transistors
Pawan Kumar Gaire, Dr Aaron Jackson, Amirhassan Shams Ansari
As the number of transistor on microprocessor increases, output power density increases as well, which has been going up exponentially last 2 decades. So, we are trying to find alternative material to silicon, which is material current processors are made up of. Diamond is one of the candidate. Taking advantage of its low dielectric constant, high thermal and heat conductivity and high carrier mobility, we fabricated field effect transistors in diamond.
3. Maria Gianello
Undergraduate, Wellesley College
Vacancy Centers Emissions Optimization, Simulations of Photonic Crystals' Heating Methods
Victoria Gianello, David Bracher, Xingyu Zhang, Evelyn Hu
Defects in SiC have various applications due to their quantum properties. Those applications rely on the emission of light from the defects. The light is enhanced by using photonic crystals cavities, but the enhancement produced by the cavities can change when they are heated. For that reason, for my summer project, I looked for the best method of heating the photonic crystal cavities to later conduct experiments on them.
4. Christa Harper
Undergraduate, Bunker Hill Community College
Optical Characteristics for Thin TaS2 Flakes
Christa L. Harper, Hiroshi Idzuchi, Kwabena Bedaiko, Philip Kim
Graphene, a conductor, and hexagonal Boron Nitride (hBN), an insulator, are well-studied by researchers. Transition Metal Dichalcogenides (TMDs) are quickly gaining popularity. This resarch helps show more specific data on the reliable relationship between flake thickness and optical contrast, similar to what has already been found for graphene and similar to findings of other TaS2 researchers, hopefully leading to a clear formula that shows the thickness of a TaS2 crystal using measurements made on an optical microscope, without having to use AFM or Raman Spectroscopy.
5. Mary Keenan
Undergraduate, Wellesley College
Device Fabrication for Electronic Exploration in Graphene
Robert Westervelt, Sagar Bhandari, Mary Keenan
This summer the conductance of a mechanically exfoliated graphene flake was measured through a homemade four-point contact device constructed on a silicon wafer. Graphene was identified via Raman spectroscopy and connected to gold leads by the processes of photolithography and thermal evaporation. Armed with these techniques, research is now underway to fabricate a stack consisting of graphene sandwiched between two flakes of boron nitride which will be used to measure conductance in graphene as a function of applied voltage. A cooled scanning probe microscope with a charged AFM tip will be used for conductance measurements.
6. Christopher Mbochwa
Undergraduate, Gallaudet University
The Effect Of Reaction Time And Solvent System On MoS2 Exfoliation
Paul Sabila, Henry Snyder, Tito Huber
Our research is interested in developing a process for a large scale synthesis of Molybdenum disulfide (MoS2) nanomaterials. The objective of the current research is to study the effect of reaction time and solvent systems on exfoliation and deposition of MoS2 films. Samples were prepared on a silicon wafer then analyzed by Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and Raman spectroscopy.
7. Breyonna Pinkney
Undergraduate, Howard University
Imaging Electron Motion In Atomic Layer Material
Sagar Bhandari, Delroy Green, Breyonna Pinkney, Gary Harris
Diamonds are widely admired by scientist all over the world. Diamond is one of the hardest material known to man, it has rare optical properties, highest thermal conductivity and heat resistance. Increasing the doping concentration and exploring doping techniques; Diamonds could possibly move from a semiconductor to an insulator. Imaging our samples with a cooling scanning probe microscope allowed us to calculate the electronic motion of our samples. Calculations and comparisons are done to determine which method of doping is most effective.
8. Prakash Regmi
Undergraduate, Howard University
Theoretical and Computational Study of Adsorption of Nitrogen Dioxide on Graphene
Prakash Regmi, Silvina Gatica.
9. Erin Strickland
Undergraduate, Howard University
Tunable Terahertz Metamaterials
Erin Strickland, Mehdi Rezaee, Dr. Thomas Searles
Metamaterials are artificial structures with engineered electromagnetic properties derived from the arrangement of metallic unit cells (“meta-atoms”) and not the material’s composition [1]. The feature size of the unit cell is directly proportional to the wavelength of interest. Therefore, large gains in research and development of metamaterials have been made in longer wavelengths (µm to mm) due to well-established microfabrication techniques. Traditionally, these devices are designed as static systems with very little space to adapt in spatial dimensions or in response to external stimuli. Graphene metastructures have several advantages over traditional metallic structures including high carrier mobility, flexibility and tunability through application of a gate voltage or external field. A diverse set of graphene metamaterials structures have been proposed such as single-ring resonators, plasmonic hybrid structures and cut wires [2-3]. Therefore, the objective of this research is to fabricate the theoretically proposed tunable graphene metamaterial devices with high amplitude modulation (up to ~80%) and tunablity (up to 400 GHz).
10. Bekuechukwu Uzondu
Undergraduate, Howard University
HFCVD Growth of Graphene on Silicon Carbide
Bekuechukwu Uzondu, Tina Brower Thomas
Graphene is a 2D crystalline structure of sp2 hybridized carbon which exhibits fascinating electrical and mechanical properties. There is a high demand for high quality large area graphene due to its properties. There are three ways researchers obtain graphene: by exfoliation, sublimation and by chemical vapor deposition (CVD). The exfoliation method yields high quality graphene but the process for obtaining sample sizes suitable for study is tedious. The CVD growth process is restricted to catalytic surfaces which means the grown graphene requires transfer to a device ready substrate. This process is also tedious and often provides samples with various imperfections. By sublimation however, graphene can be grown directly on SiC, a device ready substrate. Sublimation is typically done in a sublimation furnace with the capability to reach temperatures as high as 2000C. A promising way to grow large-area high quality graphene is by growing on semi-insulating silicon carbide using Hot Filament CVD. This method uses heat dissipated from Tungsten filaments at 2300°C. The HFCVD design allows for non-confinement controlled growth and therefore if successful, large samples can be produced. A rotating stage ensures even heating across the sample for uniform growth. Our challenge is finding the right condition for growth of graphene using HFCVD.
11. Bedhatu Wake
Undergraduate, Prince George’s Community College
The Study of Grapene Photo-response on top of Bi2Te3 Nanowires
Bedhatu Wake, Tito Huber, Scott Johnson
We focused on fabricating of Bi2Te3 nanowire arrays and extraction of a single nanowire. for different purposes such as the study of photo-response and AFM tips.
12. Haimei Zhang
Undergraduate, Wellesley
Measuring Magnetic Fields with Light: Optically Detected Magnetic Resonance of NV Centers in Diamond
Haimei Zhang, Robbie Berg
The Nitrogen-vacancy center (NV center) is a point defect in the structure of diamond with two adjacent carbon atoms replaced by a nitrogen atom and a vacancy. Not only is this defect a promising candidate to host a quantum bit, it can also serve as a magnetometer with high sensitivity and spatial resolution. This summer, we developed a technique to use optically detected magnetic of NV centers to measure small external magnetic fields with a spatial resolution of a few microns. Our setup is simpler than what are commonly used in related researches, so that this technique would be both more affordable and easier to apply. This experiment can also be used introduce undergraduate students to the NV center as a lab experiment. The NV center has a ground state with a spin of one unit of angular momentum. When there is no external magnetic field, the ms=±1 states are nearly degenerate and have a energy greater than the ms=0 state. When excited by green laser light, the red fluorescence of the NV center is brighter if the system originates from the ms=0 state rather than from ms=±1 states. A 2.87 GHz microwave matches the energy difference between ms=0 and ms=±1 states, so that the fluorescence intensity drops at the resonance frequency. Moreover, according to Zeeman Effect, a static magnetic field would split the ms=±1 into two slightly different energy sublevels, their energy difference given by ∆=2γ*B|| with γ=2.8 MHz/Gauss. We used two kinds of NV center diamond samples: a nanocrystal sample and a single crystal sample. With an applied magnetic field, we measured the fluorescence intensity while continuously changing the microwave frequency to observe the magnetic spin resonance. Comparing the data to computer simulation, we were able to determine the strength of the magnetic field near the laser focus. Specifically, with the nanocrystal sample, magnetic field strength is detected with a spatial resolution of a few microns, and the field strength sensitivity is on the order of 0.1 mT. Since each nanocrystal diamond containing NV centers has a diameter of only a few hundred nanometers, our result shows that nanocrystals can potentially be used as magnetometer to probe inside biological cells with a relatively simple experimental setup.
October 13-14, 2016
Undergraduate Intern Poster Abstracts
1. Odunayo Ayebajeje
Undergraduate, Howard University
Transport Properties of Chiral Carbon Nanotube Thin Films
Odunayo Ayegbajeje, Linda Ye, Takehito Suzuki, Thomas Searles, Joseph Checkelsky
2. Pawan Gaire
Undergraduate, Howard University
Faster Computer with Diamond - Fabrication and Characterization of Diamond Field Effect Transistors
Pawan Kumar Gaire, Dr Aaron Jackson, Amirhassan Shams Ansari
As the number of transistor on microprocessor increases, output power density increases as well, which has been going up exponentially last 2 decades. So, we are trying to find alternative material to silicon, which is material current processors are made up of. Diamond is one of the candidate. Taking advantage of its low dielectric constant, high thermal and heat conductivity and high carrier mobility, we fabricated field effect transistors in diamond.
3. Maria Gianello
Undergraduate, Wellesley College
Vacancy Centers Emissions Optimization, Simulations of Photonic Crystals' Heating Methods
Victoria Gianello, David Bracher, Xingyu Zhang, Evelyn Hu
Defects in SiC have various applications due to their quantum properties. Those applications rely on the emission of light from the defects. The light is enhanced by using photonic crystals cavities, but the enhancement produced by the cavities can change when they are heated. For that reason, for my summer project, I looked for the best method of heating the photonic crystal cavities to later conduct experiments on them.
4. Christa Harper
Undergraduate, Bunker Hill Community College
Optical Characteristics for Thin TaS2 Flakes
Christa L. Harper, Hiroshi Idzuchi, Kwabena Bedaiko, Philip Kim
Graphene, a conductor, and hexagonal Boron Nitride (hBN), an insulator, are well-studied by researchers. Transition Metal Dichalcogenides (TMDs) are quickly gaining popularity. This resarch helps show more specific data on the reliable relationship between flake thickness and optical contrast, similar to what has already been found for graphene and similar to findings of other TaS2 researchers, hopefully leading to a clear formula that shows the thickness of a TaS2 crystal using measurements made on an optical microscope, without having to use AFM or Raman Spectroscopy.
5. Mary Keenan
Undergraduate, Wellesley College
Device Fabrication for Electronic Exploration in Graphene
Robert Westervelt, Sagar Bhandari, Mary Keenan
This summer the conductance of a mechanically exfoliated graphene flake was measured through a homemade four-point contact device constructed on a silicon wafer. Graphene was identified via Raman spectroscopy and connected to gold leads by the processes of photolithography and thermal evaporation. Armed with these techniques, research is now underway to fabricate a stack consisting of graphene sandwiched between two flakes of boron nitride which will be used to measure conductance in graphene as a function of applied voltage. A cooled scanning probe microscope with a charged AFM tip will be used for conductance measurements.
6. Christopher Mbochwa
Undergraduate, Gallaudet University
The Effect Of Reaction Time And Solvent System On MoS2 Exfoliation
Paul Sabila, Henry Snyder, Tito Huber
Our research is interested in developing a process for a large scale synthesis of Molybdenum disulfide (MoS2) nanomaterials. The objective of the current research is to study the effect of reaction time and solvent systems on exfoliation and deposition of MoS2 films. Samples were prepared on a silicon wafer then analyzed by Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and Raman spectroscopy.
7. Breyonna Pinkney
Undergraduate, Howard University
Imaging Electron Motion In Atomic Layer Material
Sagar Bhandari, Delroy Green, Breyonna Pinkney, Gary Harris
Diamonds are widely admired by scientist all over the world. Diamond is one of the hardest material known to man, it has rare optical properties, highest thermal conductivity and heat resistance. Increasing the doping concentration and exploring doping techniques; Diamonds could possibly move from a semiconductor to an insulator. Imaging our samples with a cooling scanning probe microscope allowed us to calculate the electronic motion of our samples. Calculations and comparisons are done to determine which method of doping is most effective.
8. Prakash Regmi
Undergraduate, Howard University
Theoretical and Computational Study of Adsorption of Nitrogen Dioxide on Graphene
Prakash Regmi, Silvina Gatica.
9. Erin Strickland
Undergraduate, Howard University
Tunable Terahertz Metamaterials
Erin Strickland, Mehdi Rezaee, Dr. Thomas Searles
Metamaterials are artificial structures with engineered electromagnetic properties derived from the arrangement of metallic unit cells (“meta-atoms”) and not the material’s composition [1]. The feature size of the unit cell is directly proportional to the wavelength of interest. Therefore, large gains in research and development of metamaterials have been made in longer wavelengths (µm to mm) due to well-established microfabrication techniques. Traditionally, these devices are designed as static systems with very little space to adapt in spatial dimensions or in response to external stimuli. Graphene metastructures have several advantages over traditional metallic structures including high carrier mobility, flexibility and tunability through application of a gate voltage or external field. A diverse set of graphene metamaterials structures have been proposed such as single-ring resonators, plasmonic hybrid structures and cut wires [2-3]. Therefore, the objective of this research is to fabricate the theoretically proposed tunable graphene metamaterial devices with high amplitude modulation (up to ~80%) and tunablity (up to 400 GHz).
10. Bekuechukwu Uzondu
Undergraduate, Howard University
HFCVD Growth of Graphene on Silicon Carbide
Bekuechukwu Uzondu, Tina Brower Thomas
Graphene is a 2D crystalline structure of sp2 hybridized carbon which exhibits fascinating electrical and mechanical properties. There is a high demand for high quality large area graphene due to its properties. There are three ways researchers obtain graphene: by exfoliation, sublimation and by chemical vapor deposition (CVD). The exfoliation method yields high quality graphene but the process for obtaining sample sizes suitable for study is tedious. The CVD growth process is restricted to catalytic surfaces which means the grown graphene requires transfer to a device ready substrate. This process is also tedious and often provides samples with various imperfections. By sublimation however, graphene can be grown directly on SiC, a device ready substrate. Sublimation is typically done in a sublimation furnace with the capability to reach temperatures as high as 2000C. A promising way to grow large-area high quality graphene is by growing on semi-insulating silicon carbide using Hot Filament CVD. This method uses heat dissipated from Tungsten filaments at 2300°C. The HFCVD design allows for non-confinement controlled growth and therefore if successful, large samples can be produced. A rotating stage ensures even heating across the sample for uniform growth. Our challenge is finding the right condition for growth of graphene using HFCVD.
11. Bedhatu Wake
Undergraduate, Prince George’s Community College
The Study of Grapene Photo-response on top of Bi2Te3 Nanowires
Bedhatu Wake, Tito Huber, Scott Johnson
We focused on fabricating of Bi2Te3 nanowire arrays and extraction of a single nanowire. for different purposes such as the study of photo-response and AFM tips.
12. Haimei Zhang
Undergraduate, Wellesley
Measuring Magnetic Fields with Light: Optically Detected Magnetic Resonance of NV Centers in Diamond
Haimei Zhang, Robbie Berg
The Nitrogen-vacancy center (NV center) is a point defect in the structure of diamond with two adjacent carbon atoms replaced by a nitrogen atom and a vacancy. Not only is this defect a promising candidate to host a quantum bit, it can also serve as a magnetometer with high sensitivity and spatial resolution. This summer, we developed a technique to use optically detected magnetic of NV centers to measure small external magnetic fields with a spatial resolution of a few microns. Our setup is simpler than what are commonly used in related researches, so that this technique would be both more affordable and easier to apply. This experiment can also be used introduce undergraduate students to the NV center as a lab experiment. The NV center has a ground state with a spin of one unit of angular momentum. When there is no external magnetic field, the ms=±1 states are nearly degenerate and have a energy greater than the ms=0 state. When excited by green laser light, the red fluorescence of the NV center is brighter if the system originates from the ms=0 state rather than from ms=±1 states. A 2.87 GHz microwave matches the energy difference between ms=0 and ms=±1 states, so that the fluorescence intensity drops at the resonance frequency. Moreover, according to Zeeman Effect, a static magnetic field would split the ms=±1 into two slightly different energy sublevels, their energy difference given by ∆=2γ*B|| with γ=2.8 MHz/Gauss. We used two kinds of NV center diamond samples: a nanocrystal sample and a single crystal sample. With an applied magnetic field, we measured the fluorescence intensity while continuously changing the microwave frequency to observe the magnetic spin resonance. Comparing the data to computer simulation, we were able to determine the strength of the magnetic field near the laser focus. Specifically, with the nanocrystal sample, magnetic field strength is detected with a spatial resolution of a few microns, and the field strength sensitivity is on the order of 0.1 mT. Since each nanocrystal diamond containing NV centers has a diameter of only a few hundred nanometers, our result shows that nanocrystals can potentially be used as magnetometer to probe inside biological cells with a relatively simple experimental setup.