Chemisorption in organic semiconductor systems: Investigation of organic semiconductor-organic semiconductor and organic semiconductor-metal interfaces.
AuthorSchuerlein, Thomas John
Committee ChairArmstrong, Neal R.
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThe production of ordered thin films of organic monolayers is of general interest to the surface science community and of specific interest to our laboratory where the understanding of small molecule adsorption has been a long term goal. The production of ordered thin films may simplify the study of the interactions of adsorbate molecules on organic films. The production of ordered layers of aromatic hydrocarbons and dye molecules were performed under a variety of deposition conditions in an ultrahigh vacuum (UHV) environment. These films were studied with several UHV analytical techniques including low energy electron diffraction, photoelectron spectroscopies, thermal program desorption mass spectrometry and visible spectroscopy. The study of several aromatic hydrocarbons revealed that these molecules possess significant mobility on the Cu(100) surface, while adsorbing with their molecular plane parallel to the copper surface. A majority of phthalocyanine (Pc) molecules studied were observed to adsorb in a single packing structure at similar substrate temperatures for divalent metal centers and a slightly higher temperature for trivalent metal centers. Chloroaluminum phthalocyanine was determined to pack in a unique structure at 150°C and adopt the previously observed phthalocyanine structure at 175°C. It was determined that the perylene derivatives 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and N, N-dimethyl-3,4,9,10-perylene-bis(carboxylimide) (DMPI) dissociatively interact with a Cu(100) surface while forming an epitaxial overlayer. These two structurally similar molecules were determined to possess different growth modes at the initial stages of growth, which was attributed to their different bulk packing structures. The electronic properties of a Pc-PTCDA heterostructure were investigated via ultraviolet photoelectron spectroscopy. The investigation correctly anticipated the diode behavior of this isotype heterostructure. This study also proved the validity of the electron affinity rule, developed for inorganic structures, for organic systems.