Adsorption Geometry and Energy Level Alignment at the PTCDA/TiO2(110) Interface.

The adsorption geometry and energy alignment at the PTCDA/TiO2(110) interface are investigated using a combination of experimental and theoretical approaches. The energy alignment is determined experimentally from the occupied and unoccupied states electronic structure measured using X-ray and UV photoemission and inverse photoemission, respectively. Two possible adsorption geometries compatible with previous studies, a flat geometry and a tilted geometry, were explored using DFT techniques, in order to obtain theoretical STM images and energy alignment at the interface. Both STM images simulation and resulting energy alignment point to a tilted geometry for PTCDA on TiO2(110).