AVS 53rd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM1-ThA

Paper EM1-ThA5
Metallization of Organic Semiconductors: Interface Chemistry and Surface Morphology

Thursday, November 16, 2006, 3:20 pm, Room 2001

Session: Contacts to Organic and Molecular Devices
Presenter: K. Demirkan, University of Delaware
Authors: K. Demirkan, University of Delaware
C. Weiland, University of Delaware
A. Mathew, University of Delaware
J.J. Krajewski, University of Delaware
D. Allara, The Pennsylvania State University
R.L. Opila, University of Delaware
Correspondent: Click to Email
Aluminum was thermally evaporated onto the conjugated semiconducting polymer, poly(2-methoxy-5,2'-ethyl-hexyloxy-phenylene vinylene) (MEH-PPV) and polystyrene. The interface formation and chemical interactions between the polymers and Al were investigated using X-ray Photoelectron Spectroscopy (XPS) and synchrotron based Ultraviolet Photoelectron Spectroscopy (UPS). The C-O bonds in MEH-PPV decreased with increased Al evaporation. Reaction between Al and the carbon backbone of the polymer leading to the creation of carbon-metal bonds was also observed. Scanning electron microscopy (SEM) images of Al surface deposited on MEH-PPV showed agglomeration of the Al. The poor surface wetting and agglomeration of the Al causes a non uniform and porous metallic layer with a much higher surface area and a potential for greater oxidation and presumably elevated device degradation. UPS spectra (at photon energy =120 eV) of MEH-PPV and polystyrene at considerably high Al coverage (equivalent to 6 nm of uniform Al film) showed features from the organic layers, and supports the idea of a non-uniform Al film and the existence of poorly metallized regions on the polymer surface. Atomic Force Microscopy (AFM) studies of Lithium Fluoride (LiF) evaporated on MEH-PPV surfaces also show very rough surfaces compared to the MEH-PPV surface, indicating poor wetting of LiF on MEH-PPV.