AVS 50th International Symposium
    Contacts to Organic Materials Topical Conference Monday Sessions
       Session OM-MoM

Paper OM-MoM5
Adsorption of Sexithiophene on Clean and Potassium-Dosed Al(111)

Monday, November 3, 2003, 9:40 am, Room 318/319

Session: Contacts to Molecules and Molecular Films (I)
Presenter: J.E. Whitten, University of Massachusetts, Lowell
Authors: J.E. Whitten, University of Massachusetts, Lowell
H. Ahn, University of Massachusetts, Lowell
S.K. Sengupta, University of Massachusetts, Lowell
Correspondent: Click to Email
Oligo- and polythiophenes are finding important organic electronic device applications that include light-emitting diodes, photovoltaics, and field-effect transistors. Low work function vacuum-deposited metals, such as aluminum, are commonly used as electrode materials, and understanding the nature of the organic/metal interface may lead to improved device performance. In this study, we have taken the approach of adsorbing the organic layer on top of bulk metal in order to obtain complementary information to previous investigations of aluminium deposition on sexithiophene. X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) have been used to study the interfaces between sexithiophene sublimed in ultrahigh vacuum onto clean and potassium-doped Al(111) surfaces at 130 K. These investigations demonstrate that sexithiophene adsorbs very weakly on the clean surface, as suggested by minimal work function changes and a lack of shifts in the binding energies of the C1s and S2p core levels and in the frontier valence orbitals of the adsorbate. In contrast, even a small amount of deposited potassium leads to strong interaction between the surface and interfacial sexithiophene. The adsorption of this oligomer on the K-doped aluminum surface has been studied as a function of potassium dose. Even at low potassium coverage, strong interaction of sexithiophene with the surface is indicated by low binding energy components in the C1s and S2p peaks and the emergence of a potassium-induced peak near the Fermi level.