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).S.R., C.R., and R.B. acknowledge support from the Department of Energy under Grant No. FG02-01ER15256. C.R. acknowledges support from the Peter Lindenfeld Graduate Fellowship. J.I.M. acknowledges funding from the ERC-Synergy Program (Grant ERC-2013-SYG-610256 NANOCOSMOS). F.F. and J.O. acknowledge support from the Spanish Ministerio de Economía y Competitividad (MINECO) under project MAT2014-59966-R and through the “María de Maeztu” Program for Units of Excellence in R&D (MDM-2014-0377)”