Scanning tunneling microscopy and molecular orbital calculation of pentacene molecules adsorbed on the Si(100)2 x 1 surface

Adsorption of the organic molecule pentacene on Si(100)2 x 1 surfaces was imaged using scanning tunneling microscopy (STM). The molecular images exhibit distinct shapes corresponding to the expected shapes for adsorption configurations. Semi-empirical molecular orbital (MO) calculations reveal a local surface density of states for the adsorbed pentacene on the Si surface. In the cases where the pentacene molecule is adsorbed on an Si dimer row, the calculated MOs are in good agreement with the molecular images observed in STM. In the case of pentacene adsorbed on two or three Si-dimer rows, however, the MOs of the pentacene do not correlate directly with the observed STM images. it is thus considered that the STM images are produced by a combination of Si dimer states and MO. (C) 1998 Elsevier Science B.V.