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

Paper EM1-ThA6
Characterization of Device Grade ITO/Conductive Polymer Interfaces Using Low Intensity Photoemission Spectroscopy and Electrospray In-Vacuum Deposition

Thursday, November 16, 2006, 3:40 pm, Room 2001

Session: Contacts to Organic and Molecular Devices
Presenter: Y. Yi, University of South Florida
Authors: Y. Yi, University of South Florida
J.E. Lyon, University of South Florida
M.M. Beerbom, University of South Florida
R. Schlaf, University of South Florida
Correspondent: Click to Email
Photoemission spectroscopic (PES) characterization of indium tin oxide (ITO) surfaces, that were exposed to the ambient prior to insertion into the vacuum results in a work function reduction of more than 0.5 eV within a short period of time (seconds to minutes, depending on x-ray or ultraviolet photon flux during measurement). This artifact impairs the characterization of charge injection barriers at ITO interfaces using the typical PES measurement protocol, consisting of a multi-step deposition sequence with PES characterization in between deposition steps. Particularly, the investigation of device grade ITO interfaces is affected by this phenomenon, since in most device fabrication protocols the ITO electrode is usually exposed to the ambient before the polymer is deposited. The presented experimental results focus on the quantification of the artifact, and the determination of the maximum "photon budget" that can be used for characterization, before a significant work function reduction is observed. Based on these data, a technique for ITO interface characterization based on low intensity x-ray photoemission spectroscopy (LIXPS) was developed. The technique was demonstrated on polythiophene/ITO interfaces, yielding injection barriers similar to those determined by others using current based methods. The results also demonstrate that exposure to UV flux immediately results in a change of the orbital line-up due to the work function lowering of the substrate.