ANGLE-RESOLVED ULTRAVIOLET PHOTOELECTRON-SPECTROSCOPY OF THIN-FILMS OF BIS(1,2,5-THIADIAZOLO)-P-QUINOBIS (1,3-DITHIOLE) ON THE MOS2 SURFACE

In this paper we report on the angle-resolved ultraviolet photoelectro n spectroscopy on ultrathin films of bis(1,2,5-thiadiazolo)-p-quinobis (1,3-dithiole) (BTQBT) deposited on a MoS2 surface with synchrotron r adiation, and describe the quantitative analysis of the angular distri bution of photoelectron from the highest occupied state. The observed angular distributions were better explained by those calculated with t he single-scattering approximation combined with molecular orbital cal culation considering intramolecularly scattered waves than the previou sly used independent-atomic-center approximation combined with molecul ar orbital calculation. Further, the low-energy-electron diffraction m easurements were performed on the film. From the low-energy-electron d iffraction, the two-dimensional lattice of the ultrathin films on the MoS2 was found to be MoS2(0001)-(root 13 x root 13, R = +/- 13.9 degre es)-BTQBT, and from the analysis of the photoelectron angular distribu tions, it was found that at the lattice points the molecules lie flat with azimuthal orientations of 19 degrees and 47 degrees with respect to each surface crystal axis of MoS2. On the basis of these results, t he full structure of the thin film, the two-dimensional lattice, and f ull molecular orientations at the lattice points, is proposed. (C) 199 7 American Institute of Physics.