Interface Formation Between Aluminum and Polythiophene

BINDING ENERGY (eV) BINDING ENERGY (eV) BINDING ENERGY (eV) 

the combined experimental and theoretical results indicate that the chemical shift observed for the S(2p) core level, of about 1.6 eV, should be due to a secondary effect from the attachment of Al atoms to the adjacent carbon atoms. Indeed, this is fully consistent with ab initio Hartree-Fock ASCF calculations of the chemical shifts in aliuninum-oligothiophene complexes [87]. From calculations on a Al2/a-3T complex, where the two Al atoms are attached to the a-carbons on the central thiophene unit, the chemical shift of the S(2p) level for the central sulfur atom is found to be 1.65 eV, which is in close agreement with the experimental value of about 1.6 eV [84]. It should be pointed out that although several different Al-thiophene complexes were tested in the ASCF calculations, no stable structure, where an Al atom binds directly to a S atom, was found [87]. 

The UPS spectra (not shown here) recorded upon Al deposition onto the conjugated thiophene systems shows only small visible changes in the positions of the peaks in the spectra [84]. The main effect is a rapid decrease in intensity, which indicates that a metallic overlayer is formed since the cross-sections for the Al(3p) or Al(3s) are much lower than for the C(2p) or S(3p) orbitals. This is consistent with the Al(2p) XPS spectra discussed above. 

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