Research Summary

Surface science is now a very well established method for the examination of surfaces. Professor Sherwood's research group has been involved in primarily X-ray photoelectron spectroscopy (XPS) of inorganic solids and surfaces with particular interest in:

The aim of the research has been to develop the experimental techniques and the theoretical basis of the work, in order to tackle the complex but very important practical problems concerning material properties, corrosion, and surface oxidation and chemistry. The work is an example of how basic science can be applied to analyze and understand important practical problems, many of which have a direct relevance to industry. A number of these projects have and continue to involve direct contact with and funding from industry.

The interface between the solid electrode and the liquid electrolyte plays a substantial role in any electrochemical process. This process may be one corresponding to a system of known composition under careful electrochemical control, or it might be a general corrosion system (many corrosion systems are electrochemical in nature). The occurrence of a different surface nature is common in electrochemical situations. Our research group was one of the early groups to apply the combination of XPS and electrochemistry to the study of electrode surfaces, and we have examined many noble and non-noble metal systems. Current projects involve surface studies related to the understanding of corrosion and its prevention, and the chemistry of carbon fiber surfaces and the importance of this chemistry in the development of advanced materials. A recent U.S. patent25, illustrates how the results of corrosion studies conducted by the group can lead to novel metal surfaces which have enhanced corrosion resistance, adhesive properties and biocompatibility.

A number of projects related to material surface properties are in progress. These include carbon fiber surfaces, carbon-carbon composites, thin metal films, studies of oxide surfaces and corrosion, and studies of corrosion inhibitors. Carbon fibers provide a good example of a material whose surface properties have a marked effect on its applications. The properties of composites made from carbon fibers (such as those used in the construction of the space shuttle, the high speed civil transport, and many small aircraft) depend greatly on the surface chemistry of the fibers.

Surface science is now a very well established method for the examination of surfaces. Professor Sherwood's research group has been involved in primarily X-ray photoelectron spectroscopy (XPS) of inorganic solids and surfaces with particular interest in:

The aim of the research has been to develop the experimental techniques and the theoretical basis of the work, in order to tackle the complex but very important practical problems concerning material properties, corrosion, and surface oxidation and chemistry. The work is an example of how basic science can be applied to analyze and understand important practical problems, many of which have a direct relevance to industry. A number of these projects have and continue to involve direct contact with and funding from industry.

The interface between the solid electrode and the liquid electrolyte plays a substantial role in any electrochemical process. This process may be one corresponding to a system of known composition under careful electrochemical control, or it might be a general corrosion system (many corrosion systems are electrochemical in nature). The occurrence of a different surface nature is common in electrochemical situations. Our research group was one of the early groups to apply the combination of XPS and electrochemistry to the study of electrode surfaces, and we have examined many noble and non-noble metal systems. Current projects involve surface studies related to the understanding of corrosion and its prevention, and the chemistry of carbon fiber surfaces and the importance of this chemistry in the development of advanced materials. A recent U.S. patent25, illustrates how the results of corrosion studies conducted by the group can lead to novel metal surfaces which have enhanced corrosion resistance, adhesive properties and biocompatibility.

A number of projects related to material surface properties are in progress. These include carbon fiber surfaces, carbon-carbon composites, thin metal films, studies of oxide surfaces and corrosion, and studies of corrosion inhibitors. Carbon fibers provide a good example of a material whose surface properties have a marked effect on its applications. The properties of composites made from carbon fibers (such as those used in the construction of the space shuttle, the high speed civil transport, and many small aircraft) depend greatly on the surface chemistry of the fibers.

The group has four X-ray photoelectron spectrometers, one equipped with a special anaerobic electrochemical experimental chamber, and another a special chamber for high temperature studies. One of the spectrometers has a 35-quartz crystal monochromator and a 16 channel detector system. It also has scanning Auger and SIMS capabilities. A third X-ray photoelectron spectrometer is a highly automated instrument especially appropriate for the rapid study of real world samples. A fourth spectrometer has a monochromator and preparation chambers. We also have an electron microprobe with three wavelength dispersive and one energy dispersive X-ray spectrometers. The equipment is automated to provide high quality data. Extensive use is made of valence band XPS data, interpreted by X-alpha, ab initio and band structure calculations, to identify subtle chemical differences.2-14

Figure 1Figure 1. Calculated and experimental (monochromatic X-rays) valence band spectra of alpha-alumina and aluminum orthophosphate and aluminum metaphosphate. The calculated spectrum was obtained by convoluting the calculated density of states adjusted by the photoelectric cross section, with a Gaussian-Lorentzian product function to represent the experimental X-ray lineshape.11 The orthophosphate spectrum is significantly different from the metaphosphate spectrum, and both phosphate are significantly different from the oxide. The spectrum illustrates how valence band XPS can be used to identify a novel phosphate containing layer (U.S. patent 26) from the normal oxidized metal layer. These phosphate layers have significant potential for corrosion protection, adhesion enhancement and in situations where a biocompatible metal surface is needed.

Selected Publications

  1. T.P.Hoar,M.Talerman,and P.M.A.Sherwood,"Electron spectra of oxidefilms on pure iron and an iron-aluminium alloy",Nature Physical Science, 240, 116 to 117 (1972) (Editorial comment Nature, 240, 256, (1972).

  2. P.M.A. Sherwood, "Photoelectron spectroscopic studies of Electrode and Related Surfaces", Chem. Soc. Reviews, 14, 1 to 44 (1985).

  3. Y. Liang, D. Paul, Y. Xie and Peter M.A. Sherwood, "Core and valence band photoemission studies of nickel oxidation studied in an anaerobic cell", Anal. Chem., 65, 2276 to 2281 (1993).

  4. H. Hixson and P.M.A. Sherwood,"Electrochemical Oxidation of Molybdenum Metal in 0.5M H2SO4 Studied by X-Ray Photoelectron Spectroscopy", Chem. Mater. , 8, 2643 to 2653 (1996).

  5. H.Hixson and P.M.A. Sherwood, "Valence-band and Core Photoelectron Spectroscopic Studies of Molybdenum Aqueous Oxidation and the Influence of Argon Ion Etching", J. Chem. Soc., Faraday Trans., 91, 3593 to 3601, (1995).

  6. John A. Rotole and Peter M.A. Sherwood, "Valence Band X-ray Photoelectron Spectroscopic Studies to Distinguish between Oxidized Aluminum Species", J. Vac. Sci.Technol., A17, 1122 to 1129 (1999).

  7. J.A. Rotole and Peter M.A. Sherwood, "Oxide-free phosphate films on copper probed by core and valence band X-ray photoelectron spectroscopic studies in an anaerobic cell", J.Vac. Sci.Technol., A18, 1066 to1071 (2000).

  8. Holly H. Hixson and Peter M.A. Sherwood, "Study of the Corrosion Behavior of Electroplated Iron-Zinc Alloys Using X-ray Photoelectron Spectroscopy", J.Phys. Chem. B, 105, 3957 to 3964, (2001).

  9. John A. Rotole, Karen Gaskell, Alex Comte and Peter M.A. Sherwood, “Formation of potentially protective oxide-free phosphate films on titanium characterized by valence band X-ray photoelectron spectroscopy”, Journal of Vacuum Science and Technology A, 19, 1176 to 1181 (2001).

  10. Peter M.A. Sherwood, "Valency at Electrode Surfaces", in "Encyclopedia of Surface and Colloid Science", Edited by A. Hubbard, Marcel Dekker, Inc, ( ISBN 0-8247-0633-1) 10-29, (2002).

  11. John A. Rotole and Peter M.A. Sherwood, “Oxide-free Phosphate Surface Films on Metals studied by Core and Valence Band X-ray Photoelectron Spectroscopy”, Chemistry of Materials, 13, 3933 to 3942, (2001).

  12. Peter M.A. Sherwood, “Valence Band Photoelectron Spectroscopy as a Probe of the Surface Chemistry Associated with Corrosion and its Prevention, Proceedings of the Electrochemical Society, PV 2001-5 (State-of-the-Art Application of Surface and Interface Analysis Methods to Environmental Material Interactions: In Honor of James E. Castle’s 65th Year: Edited by D.R. Baer, C.R. Clayton, GP. Halada and G.D. Davis) 46 - 65, (2001).

  13. Ahmad Ali Audi and Peter M.A. Sherwood, “Valence Band X-ray Photoelectron Spectroscopic Studies of Manganese and its Oxides interpreted by Cluster and Band Structure Calculations”, Surface and Interface Analysis, 33, 274 to 282 (2002).

  14. Gregory D. Claycomb and Peter M. A. Sherwood, “Investigation of Surface Oxides on Aluminum Alloys by Valence Band Photoemission”, Journal Vacuum Science and Technology A, 20, 1230-1236 (2002).

  15. W. Temesghen and P.M.A. Sherwood, “Valence Band X-ray Photoelectron Spectroscopic Studies of Iron and its Oxides interpreted by Cluster and Band Structure Calculations”, Analytical and Bioanalytical Chemistry, 373, 601-608 (2002).

  16. Y. Xie and P.M.A. Sherwood, "X-ray Photoelectron Spectroscopic Study of Kevlar Fiber and the Valence Band Interpretation by Xa Calculations",Chem. Mater., 5, 1012 to 1017 (1993); T. Wang, Y. Xie and P.M.A. Sherwood, "X-Ray Photoelectron Spectroscopic Studies of Poly(ether ketone ketone): Core Level and Valence Band Studies and Valence Band Interpretation by Xa Calculations",Chem. Mater., 5, 1007 to 1011 (1993).

  17. P.M.A. Sherwood, "Surface Analysis of Carbon and Carbon Fibers for Composites", J. Electron Spectrosc. Rel. Phenom., 81, 319 to 342 (1996).

  18. T. Wang and P.M.A. Sherwood, "X-Ray Photoelectron Spectroscopic Studies of Carbon Fiber Surfaces. 20. Interfacial Interactions between Phenolic Resin and Electrochemically Oxidized Carbon Fibers using Titanium Alkoxide Coupling Agents and their Effect on Oxidation Behavior", Chem. Mater., 7, 1031 to 1040 (1995).

  19. M.A. Rooke and P.M.A. Sherwood, "Surface Studies of Potentially Oxidation Protective Si-B-N-C Films for Carbon Fibers", Chem. Mater., 9, 285 to 296 (1997).

  20. Y-Q. Wang, H.Viswanathan, A.A. Audi, and P.M.A. Sherwood, "X-ray Photoelectron Spectroscopic Studies of Carbon Fiber Surfaces. 22. Detreatment of Commercially Treated Fibers and its Effect on the Oxidation Behavior of Carbon Fibers", Chem.Mater., 12, 1100 to 1107 (2000).

  21. Y-Q. Wang, F-Q.Zhang and P.M.A. Sherwood, "X-ray Photoelectron Spectroscopic "Studies of Carbon Fiber Surfaces. 25. Interfacial Interactions between PEKK Polymer and Carbon Fibers Electrochemically Oxidized in Nitric Acid and Degradation in a Saline Solution", Chem. Mater., 13, 832 to 841 (2001).

  22. P.M.A. Sherwood, Data Analysis in X-ray Photoelectron Spectroscopy., Chapter 7, pp. 257-298, in Surface Characterization of Advanced Polymers, L. Sabbatini and P.G. Zambonin, Eds., VCH Weinheim (1993).

  23. P.M.A. Sherwood, "Curve fitting in surface analysis and the effect of background inclusion in the fitting process", J. Vac. Sci. Technol A., 14, 1424 to 1432 (1996).

  24. P.M.A. Sherwood, "Extracting more Chemical Information from X-Ray Photoelectron Spectroscopy by using Monochromatic X-rays", J. Vac. Sci. Technol. A., 15, 520 to 525 (1997).

  25. Peter M.A. Sherwood and John A. Rotole, United States Patent No.: 6,066,403 "Metals having Phosphate Protective Films" - Patent issued May 23, 2000.

Some Recent Publications

  1. P.M.A. Sherwood, “XPS Valence Bands”, chapter in “Surface Analysis by Auger and X-ray Photoelectron Spectroscopy” edited by D Briggs and J T Grant, SurfaceSpectra Ltd and IM Publications, Chapter 19, 531-555, 2003.

  2. Yu-Qing Wang and P.M.A. Sherwood, “Interfacial Interactions of Polymer Coatings onto Oxide-free Phosphate Films on Metal Surfaces”, Journal of Vacuum Science and Technology A, 21, 1124-1128, 2003.

  3. A. L. Asunskis, K.J. Gaskell, D.J. Asunskis and P.M.A. Sherwood, “Valence Band X-ray Photoelectron Spectroscopy Studies of Different Forms of Sodium Phosphate”, Journal of Vacuum Science and Technology A, 21, 1120-1125, 2003.

  4. D. J. Asunskis and P.M.A. Sherwood, “The Study of Vanadium Phosphates by Valence Band X-ray Photoelectron Spectroscopy”, Journal of Vacuum Science and Technology A, 21, 1133-1138, 2003.

  5. P.N. Deepa, M. Kanungo, Greg Claycomb, Peter M.A. Sherwood, and Maryanne M. Collinson. “Electrochemically Deposited Sol-Gel Derived Silicate Films as a Viable Alternative in Thin Film Design”, Analytical Chemistry, 75, 5399-5405, 2003.

  6. D. Rochefort, P. Dabo, D. Guay and P.M.A. Sherwood, “XPS investigations of thermally prepared RuO2 electrodes in reductive conditions”, Electrochimica Acta, 48, 4245-4253, 2003.

  7. Peter M.A. Sherwood, “Nanostructured Composites Using Carbon-Derived Fibers”, Dekker Encyclopedia of Nanoscience and Nanotechnology, Marcel Dekker Inc., New York, NY, 2551-2561, 2004.

  8. Karen Gaskell, Michelle M. Smith and Peter M.A. Sherwood, “Valence band X-ray photoelectron spectroscopy studies of phosphorus oxides and phosphates”, Journal of Vacuum Science and Technology, 22, 1331-1336, 2004.

  9. Yuqing Wang and Peter M.A. Sherwood, “Studies of Carbon Nanotubes and Fluorinated Nanotubes by X-Ray and Ultra-violet Photoelectron Spectroscopy”, Chemistry of Materials, 16, 5427-5436, 2004.

  10. Hyung J. Kim, David W. Graham, Alan A. DiSpirito, Michail A. Alterman, Nadezhda Galeva, Cynthia K. Larive, Dan Asunskis, and Peter M.A. Sherwood, “Methanobactin, a Copper-Acquisition Compound for Methane-Oxidizing Bacteria,” Science, 305, 1612-1615, 2004.

  11. Wei Chen, Jan-Olov Bovin, Shaepeng Weng, Alan G. Joly, Yuqing Wang and Peter M.A. Sherwood, “Fabrication and Luminescence of ZnS:Mn2+ Nanoflowers, Journal of Nanoscience and Nanotechnology, 5, 1309-1322, 2005.

  12. Peter M.A. Sherwood, “Exploiting Differential Sample Charging in X-ray Photoelectron Spectroscopy, Surface Science, 600, 771-772, 2006.

  13. D.J. Asunskis and P.M.A. Sherwood, “Thin Oxide-Free Phosphate Films of Novel Composition formed on the Surface of Vanadium Metal and Characterized by X-Ray Photoelectron Spectroscopy”, Journal of Vacuum Science and Technology A, 414, 1179-1184, 2006.

  14. Yuanfang Liu, Wei Chen, Alan G. Joly, Yuqing Wang,| Carey Pope, Yongbin Zhang, Jan-Olov Bovin, and Peter Sherwood “Comparison of Water-Soluble CdTe Nanoparticles Synthesized in Air and in Nitrogen, J. Phys. Chem. B, 110, 16992-17000, 2006.

  15. A.L. Asunskis and P.M.A. Sherwood, “Interfacial Interactions of PEKK Polymer Coatings onto Oxide-free Phosphate Films on an Aluminum Surface”, Journal of Vacuum Science and Technology A, 25, 872-877, 2007.

  16. P.M.A. Sherwood, "Composites" in "Handbook of Surface and Interface Analysis - Methods for Problem-Solving – Second Edition", Edited by J.C. Rivière and S. Myhra, Markel Dekker. Inc, New York, Chapter 14, in press, 2007.