AVS 50th International Symposium
    Applied Surface Science Thursday Sessions
       Session AS-ThM

Paper AS-ThM6
Charge Referencing in XPS Analysis of Self-assembled Nano-phase Particle (SNAP) Surface Treatments

Thursday, November 6, 2003, 10:00 am, Room 324/325

Session: Electron Spectroscopy
Presenter: L.S. Kasten, University of Dayton Research Institute
Authors: L.S. Kasten, University of Dayton Research Institute
V.N. Balbyshev, Universal Technology Corporation
M.S. Donley, Air Force Research Laboratory (AFRL/MLBT)
Correspondent: Click to Email
To investigate the surface chemistry of Self-assembled NAno-phase Particle (SNAP) SNAP films, X-ray photoelectron spectroscopy (XPS) was utilized to obtain detailed chemical state information on the coating constituents. SNAP coatings were created by forming nanosized siloxane structures comprised of hydrolyzed tetramethoxysilane (TMOS) and glycidoxypropyltrimethoxysilane (GPTMS) in aqueous solution and then crosslinking them upon application to form thin, dense protective organic surface treatment coatings on Al aerospace alloys. A charge referencing method from which accurate and reliable photoelectron peak binding energies could be determined was developed. In order to gain further insight into the chemical composition of the SNAP coatings, data from three related research efforts involving TOF-SIMS analysis of SNAP coatings, studies of the SNAP solution chemistry, and studies involving modeling of the SNAP oligomer formation process enabled some key assumptions to be made about the structure of the SNAP coatings. Based on these studies, an internal standard was chosen which enabled the spectra to be charge referenced, and the referenced data allowed accurate identification of chemical bonding states in the SNAP coatings. Results show that the Si bonds present in the SNAP film are a combination of the bonds in the individual precursors TMOS and GPTMS. The SNAP coatings retain the siloxane character of the of the GPTMS and TMOS precursors. These data support the concept that the nanosized siloxane macromolecules are retained through the coating application process and comprise the film. This was further verified by the use of a silicon chemical state plot, including the use of the modified Auger parameter. The SNAP film's Auger parameter value fell between the precursors' Auger parameter values. These surface analytical data are both self-consistent and consistent with the observations and assumptions of the model.