Ve. Choong et al., INVESTIGATION OF THE INTERFACE FORMATION BETWEEN CALCIUM AND TRIS-(8-HYDROXY QUINOLINE) ALUMINUM, Applied physics letters, 72(21), 1998, pp. 2689-2691
X-ray and ultraviolet photoemission spectroscopy investigations reveal
strong interactions between Ca and tris-(8-hydroxy quinoline) aluminu
m (Alq(3)) during the Ca/Alq(3) interface formation. The details of th
e interaction depend on the direction of the interface formation. For
the case of Ca deposited on Alq(3), a staged interface reaction is obs
erved. For low Ca coverages (Theta(Ca)less than or equal to 4 Angstrom
), negatively charged Alq3 radical anions are formed by electron trans
fer from the Ca, The emergence of new states in the energy gap is obse
rved in the UPS spectra. At higher coverages, the Ca reacts with the p
henoxide oxygen resulting in the decomposition of the Alq(3) molecule.
On the other hand, for the case of Alq(3) deposited on Ca, a strong c
hemical reaction takes place as soon as Alq(3) is deposited, and Ca at
tacks every constituent of Alq(3),. Finally,:no interaction occurs bet
ween Alq3 and the Ca substrate if the substrate has been passivated by
oxygen prior to the Alq3 deposition. (C) 1998 American Institute of P
hysics.