By means of full-potential all-electron density-functional theory and many-body perturbation theory, we compute the band alignment at a prototypical hybrid inorganic/organic interface. The electronic properties of a model system built of poly(para-phenylene) and rs-ZnO are studied in two different geometries, employing several approaches of increasing sophistication. To this extent, we explore models for predicting the level alignment, which are based on the knowledge of the electronic structure of the individual constituents and are commonly used for semiconductor interfaces. For their evaluation in the context of hybrid materials, we perform an ab initio study of the entire system, including a quasiparticle description of the electronic structure within the G0W0 approximation. Based on this, we quantify the impact of structure, charge redistribution, orbital hybridization, and molecular polarization on the band offsets and the alignment type. We highlight not only known limitations of predicting the level alignment at a hybrid inorganic/organic interface by simple models but also demonstrate how structural details of the interface components impact the results.

The In2O3(001)-Si(001) heterojunction is studied by means of the ab initio density functional theory, quasiparticle corrections, and the supercell method. We construct a model interface based on the idea of a coincidence lattice, only Si-O interface bonds and biaxially strained In2O3. The properties of the interface and their consequences for the junction are mainly described in terms of electronic band levels and charge redistribution. The results indicate a type II heterostructure caused by interface dipole alteration due to electron rearrangements.

The geometry and energetics of the unreconstructed tin-and oxygen-terminated (100), (010), and (110) surfaces, the tin-terminated (111) surface, and the stoichiometric (001) surface of rutile-SnO2 are investigated. Total energies and relaxed atomic geometries are calculated within density functional theory using the local density approximation (LDA). We conclude from these results that the (110) and (100) surfaces are most stable. Their termination depends on the experimental situation: While under oxygen-rich preparation conditions the oxygen termination is preferred, reduced surfaces are more likely to occur in the oxygen-poor limit. In addition, electronic band structures and densities of states are calculated using a recently developed approximate quasiparticle approach, the LDA-1/2 method. Except for the SnO-terminated (110) surface, all other faces are found to be insulating and O- or Sn-derived surface states appear in the projected bulk fundamental gap. While the surface barrier heights vary by more than 2 eV with orientation and termination, the ionization energies tend to the smallest values for the energetically favored surfaces.

We study the adsorption of the amino acid cysteine on the Au(110) surface by means of density functional theory. Different adsorbate-substrate geometries are investigated regarding geometry, adsorption energy, and changes in the density of states.In particular we compare flat versus upright adsorption configurations in which the molecule registers to the surface via a deprotonized thiolate head group and eventually the amino side group. Sulfur-gold and amino-gold bonding geometries are discussed with their implications for electronic properties. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim