Summer 2011 REU Participants
Research Experience for Undergraduates (REU) for non-Tech Students:
The Research Experience for Undergraduates program provides a ten-week paid summer research experience for six students enrolled in undergraduate science and engineering programs at U.S. institutions. Students work on exciting ongoing Center research projects with the MRSEC faculty mentors and graduate students. They are housed on campus, and in addition to a $600 travel allowance, are provided with a meal plan and a $5,000 stipend. Seminars, GRE preparation courses, professional development and graduate school application workshops are organized to maximize the learning experience outside of laboratories. The REU students are being admitted through the Summer Undergraduate Research in Engineering/Science (SURE) program. More information and an online application is available at, www.sure.gatech.edu.
| GT MRSEC REU 2011 PROJECTS | |||
|---|---|---|---|
Participant Name & Affiliation | Project Title | Project Abstract | Faculty Mentor |
| Sara Farooq, University of New Orleans | CVD Growth of Graphene on Copper and its Conductivity | Graphene is grown on copper by chemical vapor deposition (CVD). The system is first pumped down to a low pressure ~100 mTorr, and then flushed with H2/Ar gas mixture with a flow rate of 18 sccm, while the temperature is increased to 1000 C. After reaching 1000 C, the temperature remains constant for 20 minutes for annealing. Afterwards CH4 at 0.8 sccm is allowed in the system for 2.5 minutes. The next step is to get graphene on a desired substrate. The transfer process is a step by step process beginning with PMMA coating, followed by etching graphene on the bottom side of copper, then etching the copper, and finally fishing out graphene, coated with polymer, on desired substrate. The PMMA is removed by adding more polymer and leaving in a bath of acetone at 35 C. We use Raman spectroscopy and Atomic Force Microscope for characterization purposes. The sample is then tested for temperature dependent conductivity using the four contact method. | Zhigang Jiang |
| Nicholas Hines, Morehouse College | Optimizing the Accuracy and Functionality of Experimentation Targeting the Bio-Sensing Capabilities of Graphene | Simply stated, graphene is a single atomic plane of graphite, which and this is essential is sufficiently isolated from its environment to be considered freestanding. Although atomic planes are commonly recognized and acknowledged as constituents of bulk crystals, natural growth of materials such as graphene remains unknown. Though natural growth of 2D crystal structures has been deemed theoretically impossible, artificial growth has proven quite promising. There are two principle methods for making 2D crystals: mechanical splitting and epitaxial growth on top of other crystals. The samples used in our experiments are grown on Silicon Carbide (SiC). Graphene grown on SiC has been considered as the champion route for electronic applications primarily because SiC automatically provides an insulating substrate. With its atomic layer crystal structure, in theory, graphene has excellent electrical and thermal conductive properties, is nearly 98% transparent, and has extremely high tensile strength. The perfect structure of graphene also makes it suitable for the production of extremely sensitive sensors. Even a single molecule absorbed to the graphene surface would be discovered. With intentions of exploring this exciting theory, my lab mentor Mauricio Bedoya and I are exploring the functionality of graphene based sensors how well graphene could practically be used as a biological sensor with clinical applications. My project objectives were to: A) reduce electrical noise in voltage and resistance measurements across the graphene sample, B) determine whether or not fluctuation of laboratory air temperature affects our measurements, and C) troubleshoot and apply alternative technique of making contacts onto graphene samples. To help minimize electrical noise in our measurements, the output resistance stemming from our SR830 Lock-in Amplifier was varied to increase the current through the circuit. The magnitude of the noise decreased by at least an order of magnitude from these adjustments alone. Several control experiments that attempt to isolate the experiment from its surroundings were conducted to determine fluctuating temperature’s impact on our electrical measurements. To improve the quality of electrical contacts, we conducted experiments to critique and perfect a protocol for depositing metal electrodes onto the corners of our samples. From all of these experiments, we hope to improve the quality and consistency of our electrical experiments with our graphene samples. | Jennifer Curtis |
| Lauren Keiser, Colorado School of Mines | Characterization of pNIPAM-PEG-AAc Microgels Through Utilization of Light Scattering Techniques | The word microgel is used to describe a vast number of particles; each being unique in their preparation, chemical properties, structure, and tailorability. Fundamentally, a microgel suspension is a colloidal suspension of small, sponge-like particles consisting of a polymer and a cross-linker. In this paper, a variation of the widely studied poly-N-isopropylacrilamide (pNIPAM) microgel is characterized. These pNIPAM microgels were prepared using a polyethylene glycol (PEG) cross-linker in addition to an acrylic acid (AAc) copolymer giving them unique temperature and pH dependence. At lower temperatures (below T ≈32 C), these particles will swell until the elastic forces of the cross-linker are equal to the osmotic forces induced by the solvent. As temperature increases, the amount of water-monomer hydrogen bonding decreases causing the particle to collapse upon itself (1). The swelling due to changes in pH is similarly a result of the presence of ions within the microgel particles. As pH rises above the pKa of the acrylic acid, the hydrogen atoms dissociate, the now negative acrylic acid molecules attract counterions and thus increase the osmotic pressure resulting in swelling. Below the pKa the acrylic acid is neutral, having no effect on the microgel (2). To elucidate this particle size dependency on temperature and pH, light scattering measurements were analyzed. We have observed that that these particles, with pH values ranging from about three to eleven, do display the aforementioned deswelling with an increase in solution temperature. The particles exhibited an average decrease in size of two orders of magnitude from 60 C to 14 C at a constant pH. Additionally, these microgel particles display the predicted pH dependence; increasing in size with an increase in pH. With an average particle size at 27.8 C of 490 nm at a pH of 3.8 and a particle size of 850 nm at a pH of 7.8, the results are quite evident. Furthermore, the effect of atmospheric CO2 on the samples was also analyzed. At basic pH, absorption of CO2 results in an increase in the osmotic pressure outside of the particles causing a decrease in size over time. | Alberto Nieves |
| Holly Tinkey, Georgia Institute of Technology | Determination of the Mean Free Path of Electrons in Graphene | Graphene, a two-dimensional sheet of carbon atoms arranged in a hexagon lattice, exhibits incredible electronic properties such as ballistic transport and the quantum Hall effect and has promising applications for high-frequency electronics. Multi-layered graphene films can be grown epitaxially from a silicon carbide (0001) substrate, but the silicon back pressure in radio-frequency induction furnaces leads to silicon re-condensing on the graphene films at high temperatures. Several multi-layered graphene samples were placed into a silicon deposition chamber with heating capabilities to recreate the furnace environment, and the surfaces were analyzed with Low Energy Electron Diffraction (LEED) and X-ray Photoemission Spectroscopy (XPS) to investigate the behavior of heated silicon evaporated on the film. LEED and XPS data indicates that the silicon did not etch the graphene film but rather was buried in the interface between the film and substrate. Comparing XPS spectra allowed us to calculate both the mean free path of electrons in graphene, which we determined to be 3.30+-0.15A, and an estimate for the amount of silicon that will saturate at the interface. | Edward Conrad |
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