Surface Analysis Applied to Thin Films of Molecular Solids
Davis, Robert Edgar
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https://hdl.handle.net/2142/67274
Description
Title
Surface Analysis Applied to Thin Films of Molecular Solids
Author(s)
Davis, Robert Edgar
Issue Date
1981
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Analytical
Language
eng
Abstract
Surface analysis techniques were examined with the goal of application to thin films of molecular solids. The compelling need for additional characterization techniques for molecular films was presented. Some of the techniques which are currently employed were highlighted, and their deficient aspects pinpointed. By modification of standard operating procedures, and particularly, careful attention to sample design and construction, the surface analysis techniques of Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS) were successfully applied to a study of molecular solids.
From this study of molecular solids, insight was gained into the degree of architectural control which can be achieved and maintained in the fabrication of assemblies which have been called organized chemical systems. Auger depth profiling was established as a reliable technique for determining the elemental composition in depth of phthalocyanine/phthalocyanine (Pc/Pc) and Pc/metal interfaces initially. Also examined were the mechanisms which can lead to physical and chemical degradation of these interfaces with time.
A variety of techniques were relied upon to study the chemical degradation of FePc which took place during annealing in air. A fairly detailed understanding was obtained of the phenomena which take place when FePc is annealed.
The question of a molecular sputtering mechanism was addressed from a unique perspective. The interest of this research group was in materials which were more complex than those which can be treated by molecular dynamics. Therefore, the approach taken here could not be quantitative or exact. However, by examining some basic parameters such as diffusivity, fragmentation, energy loss cross-section, and range for various charged particles, these results could be examined in greater detail than that usually employed for molecular sputtering.
Using the results obtained from these AES studies, the technique of SIMS was evaluated for the analysis in depth of molecular solids. Although SIMS data are perhaps more difficult to evaluate quantitatively, due to artifacts, the method did have advantages which allowed the identification of silver on the surface of unannealed Pc/Ag/glass assemblies. The presence of silver was not detectable by AES due to spectral overlap, and had not been anticipated by previous researchers.
Finally, some preliminary results with polymer film assemblies were presented. Although the major problems of charging and film rupture were avoided, the research was handicapped by a loss of the components of interest, which were low concentration of organic compounds dispersed in the polymer matrix.
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