Adsorption state of diethyldisulfide on Au(111) studied with a combined system of HREELS and STM

The adsorption behavior of diethyldisulfide (DEDS), CH3CH2S2CH2CH3, on Au(1 11) was investigated using a combined system of high-resolution electron en ergy-loss spectroscopy (HREELS) and scanning tunneling microscopy (STM). At low exposure (0.5 L), all vibration modes of ethylthiolate on Au(lll) were observed by HREELS, and linear chains were recognized in STM images. At 10 0 L, some loss peaks decreased drastically in intensity and bright spots ap peared in STM images. At low exposure, the ethylthiolate moiety reads to fo rm a chain structure on Au(lll) with the terminal sulfur bonded to gold. Th e ethyl group is randomly oriented. At an exposure of 100 L, the orientatio n of the molecules is fixed, with the C-C bond of the ethyl group parallel to the surface due to the interaction between neighboring molecules. (C) 19 99 Elsevier Science B.V. All rights reserved.