Effects of dopant molecules on the electronic properties of organic thin films: Solid state conductivity measurements and surface electron spectroscopic techniques.

Persistent Link:
http://hdl.handle.net/10150/185399
Title:
Effects of dopant molecules on the electronic properties of organic thin films: Solid state conductivity measurements and surface electron spectroscopic techniques.
Author:
Pankow, Joel Walter
Issue Date:
1991
Publisher:
The University of Arizona.
Rights:
Copyright © 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.
Abstract:
Organic molecular electronic materials are used in many applications such as chemical sensors, p-n junction devices, photovoltaics and xerography. Chlorogallium phthalocyanine (GaPc-Cl), shown by previous research in this group to have exceptional photoelectrochemical properties and sensitivity to chemical dopants such as oxygen and hydrogen, is suspected to be influenced by growth conditions and subsequent exposure to ambient conditions. GaPc-Cl films were grown on interdigitated array microcircuits in an ultra high vacuum chamber and several solid state parameters (in vacuum) were measured. This yielded information concerning: structural trap concentration; chemical impurity concentration and energetic levels; trap depths; ohmic or space charge limited current behavior; quantum efficiencies; and, photocurrent sensitivity to changes in illumination intensity. Films with higher chemical impurity concentrations had larger rise and decay times; high dark currents and low dark activation energies; larger photoactivation energies; a poor contrast of photo-to-dark current; extended ohmic regions in dark current-voltage curves; enhanced absorbed light quantum efficiencies; and low sensitivity of photocurrent to changes in light intensity. Chemical dopants (O₂, NH₃, NO₂ and TCNQ) were then chemisorbed on the films and uptake curves were obtained by monitoring dark and/or photocurrent responses. Solid state measurements were repeated for comparison and contrast to the native state. O₂ and NH₃ cause irreversible dark and photocurrent decreases followed by reversible dark and photocurrent increases. TCNQ and NO₂ caused immediate reversible photo and dark current increases. Solid state parameters varied depending on whether the dopant was surface-bound (TCNQ), or could intercalate into the bulk (O₂, NH₃ and NO₂). XPS and UPS experiments were conducted on native GaPc-Cl or TCNQ films and bilayers of these two compounds. UPS established HOMO levels for GaPc-Cl and TCNQ and substantiated feasibility of GaPc-Cl oxidation; however, no useful XPS/UPS information was obtained for reactions between GaPc-Cl and TCNQ primarily because of overlapping spectral regions. XPS quantitation of TCNQ peak areas established identities of carbon atoms responsible for them. TCNQ deposition on various work function metals demonstrated the identity of TCNQ carbons susceptible to reduction.
Type:
text; Dissertation-Reproduction (electronic)
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Chemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Armstrong, Neal R.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleEffects of dopant molecules on the electronic properties of organic thin films: Solid state conductivity measurements and surface electron spectroscopic techniques.en_US
dc.creatorPankow, Joel Walteren_US
dc.contributor.authorPankow, Joel Walteren_US
dc.date.issued1991en_US
dc.publisherThe University of Arizona.en_US
dc.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.en_US
dc.description.abstractOrganic molecular electronic materials are used in many applications such as chemical sensors, p-n junction devices, photovoltaics and xerography. Chlorogallium phthalocyanine (GaPc-Cl), shown by previous research in this group to have exceptional photoelectrochemical properties and sensitivity to chemical dopants such as oxygen and hydrogen, is suspected to be influenced by growth conditions and subsequent exposure to ambient conditions. GaPc-Cl films were grown on interdigitated array microcircuits in an ultra high vacuum chamber and several solid state parameters (in vacuum) were measured. This yielded information concerning: structural trap concentration; chemical impurity concentration and energetic levels; trap depths; ohmic or space charge limited current behavior; quantum efficiencies; and, photocurrent sensitivity to changes in illumination intensity. Films with higher chemical impurity concentrations had larger rise and decay times; high dark currents and low dark activation energies; larger photoactivation energies; a poor contrast of photo-to-dark current; extended ohmic regions in dark current-voltage curves; enhanced absorbed light quantum efficiencies; and low sensitivity of photocurrent to changes in light intensity. Chemical dopants (O₂, NH₃, NO₂ and TCNQ) were then chemisorbed on the films and uptake curves were obtained by monitoring dark and/or photocurrent responses. Solid state measurements were repeated for comparison and contrast to the native state. O₂ and NH₃ cause irreversible dark and photocurrent decreases followed by reversible dark and photocurrent increases. TCNQ and NO₂ caused immediate reversible photo and dark current increases. Solid state parameters varied depending on whether the dopant was surface-bound (TCNQ), or could intercalate into the bulk (O₂, NH₃ and NO₂). XPS and UPS experiments were conducted on native GaPc-Cl or TCNQ films and bilayers of these two compounds. UPS established HOMO levels for GaPc-Cl and TCNQ and substantiated feasibility of GaPc-Cl oxidation; however, no useful XPS/UPS information was obtained for reactions between GaPc-Cl and TCNQ primarily because of overlapping spectral regions. XPS quantitation of TCNQ peak areas established identities of carbon atoms responsible for them. TCNQ deposition on various work function metals demonstrated the identity of TCNQ carbons susceptible to reduction.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorArmstrong, Neal R.en_US
dc.contributor.committeememberPemberton, Jeanne E.en_US
dc.contributor.committeememberBurke, Michael F.en_US
dc.contributor.committeememberSalzman, William R.en_US
dc.contributor.committeememberMiller, Walter B.en_US
dc.identifier.proquest9123453en_US
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