Study of aniline on a Si(111)7X7 surface by scanning tunneling microscopy

The adsorption of aniline on a Si(111)7x7 surface was examined by scanning tunneling microscopy (STM). In the STM images at negative sample bias, anil ine molecules were observed as bright ring-like features. We have found tha t aniline molecules adsorb on the center adatom site, with its amino group oriented to the rest atom site. The differences in reactivity of the variou s sites on the Si(111)7x7 surface to aniline were observed. The center adat om site is more reactive than the corner adatom site. With increasing anili ne exposure, an aniline chain was observed. From the STM images obtained at various sample biases, this aniline chain is seen to have different electr onic structure from an aniline molecule singly adsorbed on the Si(111)7x7 s urface. This suggests that aniline molecules are associated with each other on the Si(111)7x7 surface. (C) 2000 American Vacuum Society. [S0734-211X(0 0)04105-6].