Thin Solid Films, Vol.284-285, 234-237, 1996
NEXAFS Investigations of Highly-Ordered Ultrathin Films of DME-DCNQI on Ag(111)
Ultrathin layers of 2,5-dimethyl-N,N’-dicyanoquinonediimine (DMe-DCNQI) have been grown on a Ag (111) surface by vapour deposition in ultrahigh vacuum. The films have been characterized by near-edge X-ray absorption fine structure (NEXAFS), low-energy electron diffraction (LEED), Thermal desorption measurements and X-ray photoelectron spectroscopy to study orientation, lateral order, interface bonding, and electronic structure. On the clean Ag(111)-surface the DMe-DCNQI molecules adsorb in parellel orientation in the monolayer regime as well as for thicker layers up to thicknesses of more than 10 nm as proved by NEXAFS. For the first two layers a LEED pattern is observed indicating high lateral order in the interface. In addition, films of two radical ion salts, Cu(DMe-DCNQI)(2) and Na(DMe-DCNQI)(2), were prepared by subsequent evaporation of DMe-DCNQI and metal counterions and by annealing, The redox reaction strongly affects the fine structure in the NEXAFS spectra of DMe-DCNQI which correlates with a strong admixture of metal orbitals.