S. Li et al., In situ XPS studies of thermally deposited potassium on poly (p-phenylene vinylene) and its ring-substituted derivatives, APPL SURF S, 181(3-4), 2001, pp. 201-210
The interactions of thermally evaporated potassium atoms with poly(p-phenyl
ene vinylene) (PPV) and its soluble derivative, poly(2-methoxy-5-(2'-ethyl-
hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) was studied in situ by angle-re
solved X-ray photoelectron spectroscopy (XPS). The changes in the C ls core
-level line shape of the polymers, the evolution of the K 2p core-level spe
ctra, and the changes in chemical compositions at the interface with progre
ssive deposition of the metal atoms were carefully monitored, The interacti
ons of the K atoms with the conjugated polymer surfaces were compared with
those involving metals of other work functions. Diffusion of the K atoms in
to the polymers and distinct charge transfer interactions were observed at
the interface. The migration of bulk adsorbed oxygen to the surfaces of bot
h polymers during the K deposition process resulted in an increase in oxyge
n concentration at the K/polymer interfaces. The diffusion of the adsorbed
oxygen from the bulk of the conjugated polymer film played a dominant role
in the interfacial reactions. The interfacial layer contains mainly oxidize
d metal and metal-polymer charge transfer species. (C) 2001 Elsevier Scienc
e B.V. All rights reserved.