I am currently a Ph.D. candidate in materials science and engineering at The University of Texas at Dallas studying under the supervision of Prof. Yves J. Chabal.
Since 2008 at UT Dallas, our research focuses on engineering and chemistry of the carbon materials to understand the surfaces and interfaces with their design and implementation for electronic devices and for energy storage applications. More specifically, our current research interests include chemistry of graphene, graphene oxide (GO) and oxidized carbon nanotubes (graphene nanoribbons), mainly their synthesis and characterization using in-situ infrared transmission or reflection spectroscopy. We are mostly focusing on oxygen interactions during thermal annealing process to understand the role of oxygen both on the surface and at the edges of graphene sheets. The main goal is to explore a better control of the chemistry with a good understanding of the edges which leads to achieve the best exfoliated graphite material with proper modifications for various applications for its use in the near future.
Our research brings up several interesting routes and collaborations to understand chemical interactions on the surfaces or in the presence of intercalants; such as, ionic liquids in the interlayers for ultracapacitors in energy storage applications, or via functionalization with N-containing organic molecules for electronic device applications and sensors. In another parallel project, graphene nanoribbons and their characterization was also studied using polarization studies coupled with the infrared spectroscopy. I am now specialized in advance spectroscopic data analysis involving in-situ Fourier Transform Infrared Spectroscopy (FTIR) in both transmission and reflection modes and X-Ray Photoelectron Spectroscopy (XPS) as well as crystallography with X-Ray Diffraction (XRD) in addition to my electrochemistry and microscopy background in the past.
In the light of all the work described above, I was involved in several large research projects. Two undergraduate students (Rodolfo Guzman and Juan Juarez) also contributed to our research projects. I led several collaborative work with different university research teams involving Prof. Manish Chhowalla’s group with two post-docs working on graphene oxide at Rutgers University and at Imperial College, Prof. Vivek Shenoy at Brown University, Prof. Chris Bielawski and Prof. Ruoff at the University of Texas at Austin, also at UTDallas (Prof. Ray Baughman and Prof. Dennis Smith). As a result, my Ph.D. work has been recently highlighted in several high impact journals. Couple of these publications is given below:
Nature Chemistry: http://www.nature.com/nchem/journal/v2/n7/abs/nchem.686.html
During my Ph.D. education, our GO projects were funded by SWAN-NRI program and DOE. In 2009-2010, I was awarded by Texas Instruments (TI) for a TI-CMOS Diversity Fellowship and for a graduate TI Co-op internship in Non-Volatile Memory Group in summer 2011.
I am studying the role nitric acid peptization has on the band gap of titanium dioxide synthesized by a sol gel method. This work is supervised by Dr. Padmakumar Nair, and some of the experiments were conducted in collaboration with Som Thomas. My research has shown that peptization reduces the band gap by a small but beneficial amount. The ultimate goal is to develop an inexpensive and durable solar cell coating that could be applied to a window, for example.I received a BS in materials science and engineering from Georgia Tech in 2008. Aside from my undergraduate years, I have lived entirely here in Richardson. I am an avid gardener, specializing in native plants, and a bird watcher.
Currently, I am a third year graduate student working under the supervision of Dr. Yves Chabal. My work focuses on the atomic layer deposition (ALD) of higher-κ dielectrics, particularly Al2O3 and HfO2, on III-V materials. Using various characterization techniques, such as FTIR, XPS, LEIS, AFM, and ellipsometry, we can look at the different properties of the materials being deposited. At the moment, I am looking at the effects that surface preparations have on the growth mechanisms of Al2O3 on InP by using a home-built ALD chamber equipped with FTIR. It was found that annealing an InP(100) surface with a native oxide (previously degreased) transforms a phosphite to a phosphate. A similar trend is observed for a HF and ammonia sulfide [(NH4)2S]-treated (minimal oxide). After several deposition cycles, HF and sulfur-treated surface shows a better defined Al2O3 LO phonon mode as compared to the degreased sample, which gives an indication of the quality of oxide. After these preliminary studies, I will continue to look at the effects different chemical treatments have on the surface prior to ALD, temperature dependence on the ALD growth of higher-κ, effects of various oxidizing agents on the growth mechanisms, and post ALD growth treatments. On a side note, I obtained my bachelor’s degree from the University of Nebraska at Kearney, where I worked on temperature-concentration dependence range of nematic phase transformation of IR-806 under the supervision of Dr. Liubov Kreminska. When I am not spending my time at the lab, I am taking part in various sports and trying to refine my skills on the guitar.
Nice to meet you, my name is Louis Caillard and I recently joined Yves Chabal’s lab as a PhD student. I am part of a common program between the university of Texas at Dallas (UTD) and “université Pierre et Marie curie” (UPMC) in Paris. I am working on the controlled deposition of gold nanoparticles on self assembled monolayer (SAM) in the perspective of performing the observation of the coulomb staircase phenomena. To do so, we are using a scanning tunneling microscope (STM). The main long term application for this project is to make single electron transistors by self assembly. I am also currently working on the microfabrication of nanopillars in the framework of photovoltaic cells manufacture, which involves the use of many techniques (Nanosphere lithography, Scanning electron microscopy, Reactive Ion Etching, E-beam evaporator, Atomic force Microscopy, …) mainly in cleanroom. I graduated from the Master Nanotech, joint program between “Grenoble INP” in France, “Politecnico di Torino” in Italy and “EPF Lausanne” in Switzerland. My background is based on physics for nanoscience and micro and nano electronics. I also performed an internship in Korea University in Seoul and in the Massachusetts institute of Technology (MIT) where I worked on the self assembly of gold particle on patterned surface.
Irinder S. Chopra
There has forever been an increasing demand for energy. With the natural resources running out fast steps are being taken to find alternative sources of energy. A very promising alternative energy source is hydrogen. Research is underway to enhance hydrogen storage to be used as an effective fuel. Different systems are being studied for that purpose.
We are concentrating on the mechanism of hydrogen storage in complex metal hydrides. The complex metal hydrides are prepared in-situ in an UHV chamber. In situ characterizations include LEED, AUGER, FTIR, TPD. We believe that by studying the basic mechanism of the nature of interaction and formation of the hydrides under different conditions we will be able to better understand the basic principles and can look forward to tuning the conditions for enhancing the storage.
I am working towards getting my PhD in Materials Physics. Currently I am working on Atomically precise ALE growth; which will lead to 3D control of semiconductor growth. I will also start working with Irinder on hydrogen storage via complex metal hydrides.
I have tried working with other research groups such as particle physics and condensed matter theory, but they didn’t have the working environment I was looking for. I enjoy working hands on; which I’ve found to mean, working with small experiments.
I represent the more indigenous side of the group; I was born and raised in the Houston/Galveston area of Texas. I am an avidly mediocre guitarist.
08/2010 -- Present Ph.D. in Materials Science and Engineering,
The University of Texas at Dallas
08/2008 -- 08/2010 M.S. in Materials Science and Engineering,
The University of Texas at Dallas
09/2004 -- 06/2008 B.S. in Electronic Science and Technology,
Huazhong University of Science and Technology, P. R. China
Cheng is involved in a broad range of research topics related to graphene, such as graphene interaction with gases, graphene oxide interaction with intercalated molecules, metal-graphene contacts, catalytic growth of graphene, etc. The main experimental characterization techniques are FTIR, Raman, XPS, AFM, XRD, and relative electrical measurements. The main theoretical simulation techniques are first-principles density functional theory (DFT) for the study of electronic structure, classical and ab inito molecular dynamics (MD) for the study of structural evolution and chemical reactions, and non-equilibrium Green’s function (NEGF) for the study of electronic transport.
My main research of interest focuses on hydrogen storage and gas separation in nanoporous materials, particularly Metal-organic Frameworks (MOFs). Their high surface area and porosity, in addition to the structures tuneabilty makes them attractive for many applications including hydrogen storage and gas separation. My work focuses on the characterization of guest-host interactions in MOFs using IR and Raman Spectroscopy techniques. These techniques are powerful to get information about molecular interactions at the atomic level. The common method used to characterize the adsorption of guests into nanoporous materials relies mainly on isotherm measurements. IR and Raman spectroscopic techniques are not widely employed, making our work unique in this area. This work is a result of a strong collaboration between three groups, Prof. Jing Li’s group (Rutgers University) synthesis of MOFs, Prof. David C.Langreth’s group (Rutgers University) van der Waals DFT calculations and Prof. Yves J. Chabal’s group spectroscopic characterization. This collaboration provides therefore the basic ingredients to study these interactions.
Our most recent studies in the area have centered on the characterization of molecular hydrogen interactions in a variety of MOFs, including MOFs with saturated and unsaturated metal centers.1-4 We have provided spectroscopic evidence combined with theoretical calculations for H2-H2 interactions in MOFs with unsaturated metal centers, in particular MOF-74 with Zn, Mg and Co metal centers.1,3 These interactions occur between H2 adsorbed next to the “metal center” (most stable) and H2 close to the nearest “oxygen site” and next nearest neighboring “benzene site”. The effect of populating these other sites on H2 at the metal site results in dramatic changes in the IR shifts and the dynamic dipole moment of adsorbed hydrogen on the metal site. Evidence for long range interactions extending to lower binding energy sites (benzene sites) in MOF-74-Co are observed.5 These results provide evidence for the importance of lower binding energy sites when a material is considered for hydrogen storage application.
We currently extended the work to study CO2 interaction and the MOFs selectivity in flexible systems using Raman and IR spectroscopy.6 Using these techniques in addition to vDW-DFT calculations we are able to understand the reasons for the MOFs remarkable flexibility and its CO2 selectivity.
(1) Nijem, N.; Veyan, J.-F. o.; Kong, L.; Wu, H.; Zhao, Y.; Li, J.; Langreth, D. C.; Chabal, Y. J. Journal of the American Chemical Society 2010, 132, 14834-14848.
(2) Nijem, N.; Veyan, J.-F.; Kong, L.; Li, K.; Pramanik, S.; Zhao, Y.; Li, J.; Langreth, D.; Chabal, Y. J. Journal of the American Chemical Society 2010, 132, 1654-1664.
(3) Nijem, N.; Kong, L.; Zhao, Y.; Wu, H.; Li, J.; Langreth, D. C.; Chabal, Y. J. Journal of the American Chemical Society 2011, 133, 4782-4784.
(4) Kong, L.; Cooper, V. R.; Nijem, N.; Li, K.; Li, J.; Chabal, Y. J.; Langreth, D. C. Physical Review B 2009, 79, 081407.
(5) Nijem, N.; Kong, L.; Zhao, Y.; Wu, H.; Li, J.; Langreth, D. C.; Chabal, Y. J. Journal of the American Chemical Society 2011, 133, 4782-4784.
(6) Nijem, N.; Thissen, P.; Yao, Y.; Longo, R. C.; Roodenko, K.; Wu, H.; Zhao, Y.; Cho, K.; Li, J.; Langreth, D. C.; Chabal, Y. J. Journal of the American Chemical Society 2011, DOI: 10.1021/ja2051149.
As a second year graduate student working in Dr. Chabal’s lab, I am focusing more and more on what I enjoy doing… research! I earned my bachelor degrees in Chemistry and Mathematics in 2010 and soon after moved to Dallas to start researching with Dr. Chabal. I have worked on quantum dot deposition on surfaces, nanoparticle deposition of gold and silver on amine-terminated SAMs, and functionalization of surfaces with phosphonic acids and anhydrous solvents on Si(111) substrates with different terminations. I have a passion for chemistry, discovering new reactions, and brainstorming with my peers to better understand unexpected experimental results. I am originally from Brazil but I have been in Texas most of my life now, so it is safe to say I am an honorary Texan.
Karla Bernal Ramos
I received my degree in Chemical Engineering in 2008 from the Universidad Autonoma de Coahuila (Mexico). I joined Prof. Chabal's group in 2009 as a PhD student in the Material science engineering program. My research is focused on the growth of metal oxides (TiO2, Al2O3, SnO2) on different silicon surfaces by using in-situ Fourier transform infrared (FTIR) spectroscopy during atomic layer deposition (ALD) processes, in order to understand the reactions taking place in the surface and initial film growth mechanisms. I love sports and watching movies.
My name is Saeedeh Ravandi and I am from Iran, I joined Prof.Chabal's lab on June 2010 as a Graduate student (research associate). I am working on the effect of plasma gases on semiconductors. I got my masters in material science (superconductors) at University PutraMalysia (UPM) in 2009. Since I have been here, I start to learn how to build chambers and using lot of equipments. I like politics and watching movies. Science changes people’s life, I am trying to help as a small part of this huge world.
09/2004-07/2008 B.S. in Materials Chemistry, College of Chemistry, Nankai University, China
08/2008-till now First year
Ph.D. Candidate in Materials Science and Engineering, The University of Texas at Dallas
Prof. Peng Cheng’s lab Design and synthesis of metal-organic frameworks based on the triazole and their derivates for hydrogen storage and further investigate their crystal structures, properties.
My name is Abraham Vega and I am currently a Graduate Student. I am a Research Assistant in Professor Chabal’s group and have a Bachelor in Mechatronic Engineering from the Instituto Tecnológico de Saltillo in Mexico. My research focuses on chemical functionalization of semiconductor surfaces to enhance its properties. My project consists in the chemical deposition and characterization of Phosphonic Acid SAMs (Self Assembled Monolayers) on oxidized silicon surfaces, which have proven to be a useful option for the development of integrated electronic-based devices. Among their advantages are the relative straightforward and low-cost process to make them, the good interaction between themselves and the stability that they provide by avoiding the reaction to external factors such as humidity.
In order to get the necessary information I use a variety of characterization tools, such as FTIR, AFM, XPS, Contact angle, among others, and work on a custom quartz chamber that can be used to anneal samples, bring gas phase molecules, all of this by getting In-situ FTIR, both under vacuum or Nitrogen purge.