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XPS investigation of electrode/polymer interfaces of relevance to the phenylene vinylene polymer‐based LEDs
Author(s) -
Li S.,
Kang E. T.,
Ma Z. H.,
Tan K. L.
Publication year - 2000
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/(sici)1096-9918(200002)29:2<95::aid-sia699>3.0.co;2-g
Subject(s) - x ray photoelectron spectroscopy , materials science , polymer , indium tin oxide , phenylene , chemical engineering , indium , electrode , polymer chemistry , layer (electronics) , nanotechnology , chemistry , composite material , metallurgy , engineering
X‐ray photoelectron spectroscopy (XPS) was employed for the study of the physicochemical interactions at electrode/polymer interfaces involving metals of high and low work functions and thin films of poly( p ‐phenylene vinylene) (PPV) and poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylene vinylene] (MEH‐PPV). The changes in the C 1s core‐level line shape of the polymers, the evolution of the metal core‐level spectra and the changes in chemical compositions at the interfaces involving polymer coated on indium–tin oxide (ITO), sputtered ITO on polymer, and in situ evaporated magnesium (Mg) on polymer were carefully monitored. Indium of the ITO in both the ITO/polymer and polymer/ITO assemblies was found to diffuse towards the polymer at the interface. Oxygen migration was also observed at the ITO/polymer interfaces. The results obtained from in situ analysis by angle‐resolved XPS of the interactions between thermally evaporated Mg and PPV and Mg and MEH‐PPV indicated the formation of an interfacial layer in each case. The surface diffusion of adsorbed oxygen from the bulk of the conjugated polymer film played a dominant role in the interfacial reactions. The interfacial layer consisted of Mg oxides, Mg clusters, Mg metal and Mg–polymer complexes. Copyright © 2000 John Wiley & Sons, Ltd.