PTCDA induced reconstruction on Sn/Si(111)-23×23

Abstract

The electronic structures of the Sn/Si(111)-$2\sqrt{3}\ifmmode\times\else\texttimes\fi{}2\sqrt{3}$ surface and deposited 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) have been studied by use of high-resolution photoelectron spectroscopy and scanning tunneling microscopy. On deposition, PTCDA molecules form a $4\sqrt{3}\ifmmode\times\else\texttimes\fi{}2\sqrt{3}$ periodicity superposed on the substrate. The new reconstruction is caused by a charge transfer between the Sn/Si(111)-$2\sqrt{3}\ifmmode\times\else\texttimes\fi{}2\sqrt{3}$ surface and the molecules, as indicated by a new component of the Sn 4$d$ core level that is shifted toward higher binding energy. In contrast to earlier reports, the charge provided by Sn is given to carbonyl C atoms instead of O atoms. This is evidenced by a new component in the C $1s$ core-level spectra, which is shifted toward lower binding energy. The charge transfer also induces a splitting in the highest occupied molecular orbital level of PTCDA seen in the valence band structure.