New molecular electronic materials: Gas phase chemical sensors and organic molecular beam epitaxy.
AuthorCollins, Gregory Earl
AdvisorArmstrong, Neal R.
MetadataShow full item record
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 trivalent metallophthalocyanines, GaPc-Cl and InPc-Cl, have been investigated with respect to: (1) their possible application as gas-phase chemical sensor coatings for the detection of O₂, NH₃ and NO₂; and (2) the development of a new class of molecular electronic materials based upon the epitaxial growth of these large organic molecules. UHV analyses of InPc-Cl coated interdigitated array transducers have indicated that impurity phthalocyanines (such as FePc, MnPc and CuPc) have a dramatic impact upon the electrical nature and responsivity of these devices toward various gas analytes. Each of the different gas analytes examined, O₂, NH₃ and NO₂, were found to possess at least two different types of chemisorption sites on the surface of these organic films. Chemical sensor devices prepared and characterized under vacuum (including quartz crystal microbalance, surface acoustic wave and interdigitated array transducer devices), were also examined within an atmospheric sensing chamber in order to assess their ultimate feasibility as chemical sensors. The simultaneous monitoring of both electrical and microgravimetric changes within these devices allowed for complimentary information to be obtained concerning the chemisorption events taking place on the surface of these materials. Photoelectrochemical metal modification of the surface of these phthalocyanines provided a means for further enhancing the response of the chemical sensors toward NH₃, while a modification of the phthalocyanine surface with reducing agents such as polyvinyl ferrocene and MnPc provided an analogous enhancement in sensitivity to NO₂. The epitaxial growth of InPc-Cl has been demonstrated on both bulk SnS₂(0001) and MBE grown SnS₂ on muscovite. The optical absorbance and photoaction spectra obtained from these highly ordered phthalocyanine films have, in some cases, been found to be as narrow as the solution absorption spectra for these materials (FWHM = 40-60 nm). The epitaxial growth of CuPc, perylene tetracarboxylic dianhydride, C₆₀ and coronene were demonstrated on the MoS₂(0001) surface, with specific models developed to explain the nature of these organic overgrowths on the metal dichalcogenide surface. The formation of highly ordered heterojunctions or bilayer films based upon various combinations of these organic semiconductor materials has also been investigated as a precursor to the development of organic superlattice structures.