René Rodriguez
Professor of Chemistry
B.S. Chemical Engineering,
University of Colorado -- 1981
M.S. Physical Chemistry
University of Minnesota -- 1984
Ph.D. Physical Chemistry
University of Idaho -- 1987
| Research Area: | Plasma Enhanced Thin Film Deposition of Photovoltaic Materials, Spectroscopic, Chromatographic, and Spectrometric Analytical Instrumentation, Vibrational Spectroscopy |
| Student Experience required for research: | Chem 112 |
| Student Experience gained from research: | Instrumentation Design, electronics, spectroscopy, mass spectrometry, Thin film deposition techniques for Semiconductor Materials |
| Ideal Preparation for: | Chemical industry, computer chip manufacturing, analytical laboratory, preparation for graduate school in Physical/Analytical Chemistry or for Engineering School |
Research Description
1) Enhanced Chemical Vapor Deposition of Thin Films of Semiconductors
In the future, solar energy conversion will likely represent a large component of the total energy sources available for humankind. Thin films of silicon represent a relatively cheap and non-toxic material, but its conversion efficiency is much less than desired. Increasing conversion efficiency will likely come through two approaches. One approach is to alter the efficiency of the silicon by altering its absorptive and band-gap properties or by incorporation of quantum wells between the n and p doped portions of the photovoltaic sandwich. By making nanometer sized crystals of silicon, the absorptive and band-gap properties of silicon may be controlled. A relatively quick and easy method of producing uniform sizes of sub-micron sized Si crystals is needed. Plasma enhanced chemical vapor deposition (PECVD) is not known for its ability to give uniform size distributions, but with a template on the substrate, this may be possible.
In a second approach, newer photovoltaic materials are being developed that potentially have higher efficiencies and may be able to act as the quantum wells needed to enhance the conversion efficiency of Silicon. We have been depositing thin films of chalcopyrite-like material, CuInS2 from metal-organic precursor materials. One such single source precursor is (PPh3)2Cu(C2H5S)2In(C2H5S)2. A group at NASA Glenn led by Dr. Al Hepp has been making the precursors and using thermal decomposition at about 350°C. We are attempting to deposit the material at lower temperatures by plasma enhanced deposition.
The plasma reaction is monitored in-situ by CARS and mass spectrometry, and the resulting films are analyzed by scanning electron microscopy and energy dispersive scattering (SEM/EDS) to get information about morphology, thickness and atomic composition of the resulting films. Reactor operating conditions are varied to alter the stoichiometric composition of the films and the temperature of deposition. X-ray diffraction is used to determine the crystallinity of the resulting films.
2) Determination of Chemical Concentrations during Pulsed Radiolysis
Through a collaboration with the Physics Dept. and the Idaho Accelerator Center (IAC) at Idaho State University concentrations of molecular species such as PCB’s, hydrogen peroxide, hydroxyl radicals, hydrogen gas, and other molecules of interest are monitored using gas chromatography and laser spectroscopy during pulsed radiolysis of the material of interest. The radiolysis is performed using one of several linear accelerators available at the IAC. A 4MeV _ and others are used for the experiments described below.
Degradation of Polychlorinated Biphenyls
Polychlorinated biphenyls are known carcinogens and are typically destroyed by incineration. An alternative method that we
are investigating with Dr. Bruce Mincher of the INEL, is the destruction of PCB using electron or gamma radiation. Dr.
Mincher is also interested in the effect of the addition of alkaline isopropanol to speed up the rate of decomposition.
Instrumentation was developed to remotely monitor the concentration of PCB during radiolysis using a gas chromatography.
Determination of Hydroxl-Radical, Hydrogen Peroxide, and Hydrogen Gas during Pulsed Radiolysis of Supercritical
Water
The generation four nuclear reactors will also likely be an important source of energy during this century. A proposed
working-fluid in those reactors is supercritical water, however, the degradation of the supercritical water into potentially
harmful and hazardous materials due to the radiation present is not well documented. In these studies we are developing laser
induced fluorescence and CARS to monitor the concentrations of hydroxyl radical and hydrogen peroxide as a function of the
relaxation time after a 60 ps pulse of 20MeV radiation enters the supercritical water.
3) Development of an in-situ Mass Spectrometric Probe for rf-PECVD
Mass spectrometry is a very sensitive technique. It can be used as an identification tool to determine species present in a radiofrequency discharge. However unless the species are stable, detection by the typical method of residual gas analysis gives only information about stable species and not ions or radicals that may be present in the plasma.
An alternate way of sampling is to build a high vacuum chamber, intermediate between the plasma chamber and the mass spectrometer chamber. An electromagnetic lens system can then be used to extract ions through a small orifice in the lower electrode of the plasma and focus the beam of ions into the quadrupole mass spectrometer. Alternatively, radicals may be detected by allowing the molecules which effuse from the plasma region to move through the intermediate chamber with the lensing system powered down. This capability is currently being developed in our lab.
4) Construction and Characterization of Dye Sensitized Photocells (DSPs)
We are working in conjuction with Profs. Pak and Castle (Chemistry), Prof. Stout (Engineering), Prof. Hunt (Physics) and American Microsystems on the construction and characterization of dye sensitized photocells constucted from ligand modifications of ruthenium(II) compounds.
The organic lab groups of Profs. Pak and Castle are synthesizing the compounds, our group is constructing the cells characterizing the dyes by their UV-Vis, fluorescence, and lifetime characteristics. The groups under the guidance of Profs. Stout and Hunt are characterizing the electrical characteristics of the photocells.
Journal Publications
"Thermal Lensing in a Super Critical Water Medium," R. G. Rodriguez, C. Stewart, S. Mezyk, H. Rollins, B. Mincher, B. Fox, and R. Brey, J. Phys. Chem. A., submitted
"Pulsed-Spray Radiofrequency PECVD of CuInS2 Thin Films,", R.G. Rodriguez, D. Pulsipher, L. Lau, E. Shurdha, J.J. Pak, M. Jin, K. Banger, and A. Hepp, Plasma Chem. Plasma Proc., 26(2), 137, 2006.
"Continuous Flow PCB Radiolysis with RealTime Assessment by GC", A. Ruhter, R. G. Rodriguez, B. J. Mincher, and R. Brey, Appl. Radiat. Isot., 64(5) 532, 2006.
"PCB Radiolysis in a Continuous Flow Cell," B.J. Mincher, R.G. Rodriguez, R. Brey, and A. Ruhter, in Photocatalytic and Advanced Oxidation Technologies for Treatment of Air, Water, Soil and Surfaces. ISBN 9738746-0-0, David Ollis and Hussain Al-Ekabi, Editors, 2005.
"Effect of Reactant Gas Velocity and Geometry on CARS Monitored Pulsed rf-PPECVD of Silicon Nitride Thin Films," B.J. Phillips, R. Rodriguez, L. Lau, S. Steidley, Plasma Chem. Plasma Proc., Submitted for publication, 2004.
"Effect of Showerhead Pattern on rf-PPECVD of Silicon Nitride Thin Films," B.J. Phillips, L. Lau, R. Rodriguez, S. Steidley, Plasma Chem. Plasma Proc., 24, 307, 2004.
"Increasing PCB Radiolysis Rates in Transformer Oil," B. Mincher, R. Brey, R. Rodriguez, S. Pristupa, A. Ruhter, Rad. Phys. Chem., 65, 461, 2002.
"Coherent Raman Spectroscopic Monitoring of Pulsed Radio Frequency PECVD of Silicon Nitride," B.J. Phillips, S. Steidley, L. Lau, R. Rodriguez, Applied Spectroscopy, 55, 946, 2001.
"Investigation of Irradiated Soil Byproducts," R. Brey, R. Rodriguez, F. Harmon, P. Winston, Waste Management, 21, 581, 2001.
"Post Consumer Plastic Identification Using Raman Spectroscopy," V. Allen, J. Kalivas, R. Rodriguez, Applied Spectroscopy, 53, 672, 1999.
"Photoreduction of Mercuric Chloride Solutions Under High pH," L. Lau, R. Rodriguez, S. Henery, D. Manuel, L. Schwendimann, J. Envir. Sci. & Technology, 32, 670, 1998.
"A Simple Computer-controlled scanning for a Coherent Scattering Spectrometer," D. Warner, R. Rodriguez, F.V. Wells, S. Wood, Rev. Sci. Instr., 67, 3050, 1996.