John A. Woollam, George Holmes Distinguished Professor
John A. Woollam
George Holmes Distinguished Professor
Electrical & Computer Engineering
University of Nebraska–Lincoln
240N Scott Engineering Center
Lincoln, Nebraska 68588-0511
We have focused our research in recent years on thin films. This involves film preparation, and characterization by numerous experimental techniques. These include atomic force microscopy, spectrophotometry, optical interference microscopy. Our specialty however is spectroscopic ellipsometry. We cover the spectral range with existing ellipsometers from 0.023eV to 6.6eV. Ellipsometers measure optical constants, thin film layer thickness, alloy concentrations, surface roughness, sample temperature, and can be used on multilayered condensed matter samples with nanometer scale dimensions.
Our most recent research is on biomaterials at interfaces, especially protein attachment to various surfaces. For these studies we use in situ and ex situ spectroscopic ellipsometry (including both visible and infrared spectral ranges), contact wetting angle measurements, atomic force microscopy, interference microscopy and visible and infrared spectrophotometry. Studied are the kinetics of attachment, and surface orientations of various molecules and combinations of molecules at molecular surfaces and in interfaces of individual molecular layers. Molecular layers as thin as a single molecule with dimensional scales of a few nanometers are studied and characterized
Under National Aeronautics and Space Administration (NASA) support we worked on thin films for spacecraft chemical, mechanical, and thermal protection from the space environment of atomic oxygen, ultraviolet radiation, and particulate and chemical contamination from other activities in space. Students in our laboratories have worked on degrees in Electrical Engineering (MS and PhD), Physics (PhD), and Chemical and Materials Engineering (PhD), and Biomedical Engineering (PhD).
- J. Sun, J. Hilfiker, M. Saenger, M. Schubert, J. Woollam, R. Synowicki, “Characterizing Antireflection Coatings on Textured Mono-Crystalline Si with Spectroscopic Ellipsometry”, Proceedings of the 34th IEEE Photovoltaics Specialists, June 8-12, Philadelphia, PA, (2009).
- T. Hofmann, C.M. Herzinger, T.E. Tiwald, J.A. Woollam, M. Schubert, “Hole diffusion profile in a p-p+ silicon homojunction determined by terahertz and midinfrared spectroscopic ellipsometry”, Applied Physics Letters, 95, No. 3, 032102-1 – 032102-3, (2009).
- M.F. Saenger, M. Schadel, T. Hofmann, J. Hilfiker, J. Sun, T. Tiwald, M. Schubert, J. A. Woollam, “Infrared ellipsometric characterization of silicon nitride films on textured Si photovoltaic cells”, MRS, Fall, 2009, Volume 1123, pages 1-6. (2009).
- A. Sarkar, T. Viitala, T. Hofmann, T. Tiwald, J. Woollam, A. Kjerstad, B. Laderian, M. Schubert, “Monitoring Organic Thin Film Growth in Aqueous Solution In-Situ with a Combined Quartz Crystal Microbalance and Ellipsometry”, MRS, Fall 2008, pages 1-7, (2009).
- D. K. Goyal, G. K. Pribil, J. A. Woollam, A. Subramanian, “Detection of Ultrathin Biological Films Using Vacuum Ultraviolet Spectroscopic Ellipsometry”, Materials Science and Engineering B 149, 26-33 (2008).
- T. Berlind, G.K. Pribil, D.W. Thompson, J.A. Woollam and H. Arwin, “Effects of ion concentration on refractive indices of fluids measured by the minimum deviation technique”, Physica Status Solidi, Proceedings of ICSE4 (c) 5, No. 5, 1249-1252, (March 2008).
- H. Arwin, A. Askendahl, P. Tengvall, D.W. Thompson, J.A. Woollam, “Infrared ellipsometry studies of thermal stability of protein monolayers and multilayers” Physica Status Solidi, (c) 5, No. 5, 1438-1441, (2008).
- L. G. Castro, D.W. Thompson, T.W. Tiwald, E. M. Berberov and J.A. Woollam, “Repeatability of Ellipsometric Data in Cholera Toxin GM1-ELISA Structures”, Surface Science Vol. 601, No. 8, 1795-1803 (2007).
- W.H. Nosal, D.W. Thompson, T. E. Tiwald, S. Sarkar, A. Subramanian, J.A. Woollam, “Vacuum Ultraviolet Optical Analysis of Spin-Cast Chitosan Films modified by Succinic Anhydride and Glycidyl Phenyl Ether”, Surface and Interface Analysis, Vol. 39, 747-751 (July, 2007).
- S.M. Aouadi, A. Bohnhoff, T. Amriou, M. Williams, J. N. Hilfiker, N. Singh, J.A. Woollam, “Vacuum ultra-violet spectroscopic ellipsometry study of single-and multi-phase nitride protective films”, J. Phys.: Condens. Matter 18, No. 32, S1691-S1701, (2006).
- S. Aouadi, Y. Zhang, P. Basnyat, S. Stadler, P. Filip, M. Williams, J.N. Hilfiker, N. Singh, J.A. Woollam, “Physical and Chemical Properties of Sputter-Deposited TaCxNy Films”, J. Phys.: Condens. Matter 18, No. 6, 1977-1986, (February 2006).
- B.W. Woods, D.W. Thompson, J.A. Woollam, “Cermet Thermal Conversion Coatings for Space Applications”, Protection of Materials and Structures from the Space Environment, Space Technology Proceedings, Vol. 6, ICPMSE-7, 265-276, (2006).
- W.H. Nosal, D.W. Thompson, L. Yan, S. Sarkar, A. Subramanian, J.A. Woollam, “UV-vis-Infrared Optical and AFM Study of Spin-cast Chitosan Films”, Colloids Surfaces B: Biointerfaces 43, 131-137 (July 2005).
- J. N. Hilfiker, J.A. Woollam, “Encyclopedia of Modern Optics”, Elsevier Ltd., 297-307 (2005).
- H. Arwin, L.M. Karlsson, A. Kozarcanin, D.W. Thompson, T.W. Tiwald, J.A. Woollam, “Carbonic Anhydrase Adsorption in Porous Silicon Studied with Infrared Ellipsometry”, 4th Int. Conf. on Porous Semiconductors - Science and Technology (PSST04), Cullera-Valencia, 14-19 March 2004, phys. stat. sol. (a), 202, No. 8, 1688-1692, (June 2005).
- W.H. Nosal, D.W. Thompson, L. Yan, S. Sarkar, A. Subramanian, J.A. Woollam, “Infrared Optical Properties and AFM of Spin-Cast Chitosan Films Chemically Modified with 1,2 Epoxy-3-Phenoxy-Propane”, Colloids Surfaces B: Biointerfaces 46, No. 1, 26-31, (November 2005).
- D.W. Thompson and J.A. Woollam “Enhancing infrared response of adsorbed biomaterials using ellipsometry and textured surfaces," Spectroscopy-an International Journal 19, 147-164, (2005).
PhD students advised since 1990 (graduates prior to 1990 are not listed)
- He, Ping Ph.D, March, 1993 in Physics “Microstructure and Magneto-Optical Properties of Cobalt-based Magnetic Multilayered films”
- McGahan, W.A. Ph.D, January, 1994 in Electrical Engineering “Optical and Thermal Properties of Amorphous Hydrogenated Carbon Thin Films”
- Zhang, Ying Bo Ph.D, December, 1995 in Physics “Magnetic and Magneto-Optical Properties of Co/Ni Multilayer Thin Films”
- Tiwald, Thomas Ph.D, 1999 in Electrical Engineering "Measurement of Free Carriers in Silicon and Silicon Carbide Using Infrared Ellipsometry"
- Gao, Xiang Ph.D, May, 1999 in Electrical Engineering “Magneto-Optic and Dielectric Properties of MO Materials”
- Yan, Li, PhD, December, 2003 in Chemical and Materials Engineering “Materials Under The Adverse Environment in Space”
- Thompson, Daniel W, PhD, December, 2004 in Electrical Engineering "Enhanced Infrared Ellipsometry for Adsorbed Proteins"
- Nosal, William, PhD, 2006 in Chemical and Materials Engineering “Ellipsometric Studies of Chemically Modified Surfaces for Biocompatability”
- Sabyasachi Sarkar, PhD, May, 2008 in Chemical and Materials Engineering “Ellipsometric Studies of Synthetic Albumin-binding Chitosan-derivatives and Selected Blood Plasma Proteins”
M.S. students advised
- Hassanayn Macklab, August, 1991 “Thermal Diffusivity Measurements by Photothermal Laser Beam Deflection”
- Ronald A. Synowicki, July, 1993 “Low Earth Orbit Degradation of Spacecraft Materials: Plasma Asher Simulation with Comparison to Spaceflight Exposure”
- Joel D. Lamb, January, 1995 “Electrical and Interfacial Properties of Amorphous Carbon Films”
- Blaine R. Spady, May, 1995 “Spacecraft Materials Degradation in Low Earth Orbit and Laboratory Simulation”
- James N. Hilfiker, August, 1995 “Ellipsometric Investigation of the Electrodeposition of Magneto-Optic Materials”
- Scott Heckens, December, 1995 “An In-Situ Ellipsometric Investigation of Sputtered TbFeCo Magneto-Optic Thin Films”
- Darin Glenn, November, 1996 “Modeling and Analysis of Magneto-Optic Thin Films”
- Jeff Hale, May, 1997 “Electrochromic Materials and Devices for Thermal Emissivity Modulation”
- Michael J. DeVries, May, 1999 “Ellipsometric Investigation of Electrochromic Materials”
- Corey L. Bungay, October, 2000 “Study of Modifications to Polymers in the LEO Enviroment Using Spectroscopic Ellipsometry”
- Leon Castro, December, 2008 “Kinetic Modeling and Spectral Analysis of Protein Adsorption”. Co-advised w/Dr. D.W. Thompson.