Department of Chemistry

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

Dr. Rodriguez's Webpage

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) Plasma Enhanced Chemical Vapor Deposition of Thin Films of Semiconductors

It is apparent at this point in time that we have reached a junction in the path we will take to power the world of the future. If we intend to have sufficient non polluting energy for the growing and maturing word it is apparent that 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 beyond that of silicon. We have been depositing thin films of chalcopyrite-like material, CuInS2 from metal-organic precursor materials.

We are also developing PECVD methodology to deposit amorphous chalcogenide materials, like GexSy, GexSey, as possible phase memory or ion-conductive memory materials. Germanium sulfide is also known to have a large difference in conductivity between it amorphous phase and its crystalline phase. This is essential for phase memory devices. It is also known to have a high ionic conductivity toward Ag and lithium ions. This property is essential for ion conductive or bridge-conductive memory (also known as resistive RAM) and in Li battery applications. GexSey is likely to have higher ion conductivity and we are investigating the ion-conductivity as a function of the relative ratio of the Ge to Se in the PECVD films. This work is being performed in conjunction with Prof. Kris Campbell at Boise State University.

Figure 1

The plasma reactions are monitored in-situ by CARS and mass spectrometry, and the resulting films are analyzed with a scanning electron microscope with energy dispersive scattering (SEM/EDS), a Raman microscope, and an IR microscope to get information about morphology, thickness, atomic composition, molecular composition, and crystal structure 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.

Figure 2

2) 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.

3) Construction and Characterization of Dye Sensitized Solar Cells (DSSCs) and Nanocomposite Solar Cells

We are working in conjuction with Profs. Pak and Holland (Chemistry), Prof. Hunt (Physics), and Dr. Robert Fox (INL) on the construction and characterization of dye sensitized photocells constructed from ligand modifications of ruthenium(II) compounds and Bacteriorhodopsin based dyes and on nanocomposite solar cells made with CuInS2 nanoparticles and TiO2.

Students in Prof. Pak's research group are synthesizing the Ru-based dye compounds, and our group is constructing the cells characterizing the dyes by their UV-Vis, fluorescence, and lifetime characteristics. The group under the guidance of Prof. Hunt is characterizing the electrical characteristics of the DSSCs made with these new dye materials. The dyes are being varied in a systematic way to determine the affects of electronic structure and electron withdrawing potential of the substituents on the efficiencies the solar cells constructed from these materials.

Our group is also working on ways to incorporate nanomaterials into TiO2 to make nanocomposite solar cells. Efficiencies of these types of solar cells have been reported to be as high as 7% using a spray process to deliver the absorbing nanomaterial into the TiO2 matrix. Students in Prof. Pak's and Holland's groups are making the nanomaterial and our group is characterizing the materials and looking at ways to make nanocomposite solar cells from them.

Selected Journal Publications

"A Large Scale Synthesis and Characterization of Quaternary CuInxGa1-xS2 Chalcopyrite Nanoparticles via Microwave Batch Reactions," Chivin Sun, Richard Westover, Gary Long, Cyril Bajracharya, Jerry Harris, Alex Punnoose, René G. Rodriguez and Joshua J. Pak Int. J. Chem. Eng, Article ID 545234, 2011.

"Thin Film Growth of Germanium Selenides from PECVD of GeCl4 and Dimethyl Selenide," Patrick J. Whitham, Dennis P. Strommen, Lisa D. Lau, and René G. Rodriguez Plasma Chem. Plasma Proc., 31(2), 251, 2011.

"Controlled Stoichiometry for Quaternary CuInxG1-xS2 Chalopyrite Nanoparticles from Single Source Precursors via Microwave Irradiation," Chivin Sun, Joseph S. Gardner, Gary Long, Cyril Bajracharya, Aaron Thurber, Alex Punnoose, René G. Rodriguez, and Joshua J. Pak, Chem. Mat., 2699-2701, 2010.

"A High Yield Synthesis of Chalcopyrite CuInS2 Nanoparticles with Exceptional Size Control," Chivin Sun, J. Gardner, E. Shurdha, K. Marguleieux, R. Westover, L. Lau, G. Long, C. Bajracharya, C. Wang, A. Thurber, A. Punnoose, R. Rodriguez, and J. Pak., J. Nanomaterials, 748567, 2009.

"Rapid and Size Controlled Synthesis of CuInS2 Nanopartilces via Microwave Irradiation", J. Gardner, E. Shrudha, L. Lau, C. Wang, R. Rodriguez, and J. Pak, J. Nanoparticle Research, 10, 633-641, (2008).

"Thermal Lensing in a Supercritical Water Medium," R. Rodriguez, S. Mezyk, C. Stewart, H. Rollins, B. Mincher, R. Fox, BJ. Phillips and R. Brey, J Phys. Chem A, 113(3), 468-471, 2007.

"Rapid and Size Controlled Synthesis of CuInS2 Nanopartilces via Microwave Irradiation", J. Gardner, E. Shrudha, L. Lau, C. Wang, R. Rodriguez, and J. Pak, J. Nanoparticle Research, 10, 633-641, (2008).

"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.


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