arXiv subjects

Fritz Henneberger

Publications and source records attributed to Fritz Henneberger.

3 recordsLinked to original sources

arXiv2015

Nanoscale Transport of Surface Excitons at the Interface between ZnO and a Molecular Monolayer

Excitons play a key role for the optoelectronic properties of hybrid systems. We apply near-field scanning optical microscopy (NSOM) with a $100\,\text{-nm}$ spatial resolution to study the photoluminescence of surface excitons (SX) in a $20\,\text{nm}$ thick ZnO film capped with a monolayer of stearic acid molecules. Emission from SX, donor-bound (DX), and - at sample temperatures $T>20\,\text{K}$ - free (FX) excitons is separated in steady-state and time-resolved photoluminescence spectra. The $4\,\text{meV}$ broad smooth envelope of SX emission at $T<10\,\text{K}$ points to an inhomogeneous distribution of SX transition energies and spectral diffusion caused by diffusive SX transport on a $50\,\text{nm}$ scale with a SX diffusion coefficient of $D(T<10 K)=0.30\,\text{cm$^2$/s}$.

cond-mat.mes-hall↗

arXiv2014

Calculating optical absorption spectra of thin polycrystalline films: Structural disorder and site-dependent van der Waals interaction

We propose a new approach for calculating the change of the absorption spectrum of a molecule when moved from the gas phase to a crystalline morphology. The so-called gas-to-crystal shift $Δ{\cal E}_m$ is mainly caused by dispersion effects and depends sensitively on the molecule's specific position in the nanoscopic setting. Using an extended dipole approximation, we are able to divide $Δ{\cal E}_m= -Q W_{m}$ in two factors where $Q$ depends only on the molecular species and accounts for all non-resonant electronic transitions contributing to the dispersion, while $W_m$ is a sum running over the position of all molecules expressing the site-dependence of the shift in a given molecular structure. The ability of our approach to predict absorption spectra is demonstrated using the example of polycrystalline films of 3,4,9,10-perylene-tetracarboxylic-diimide (PTCDI).

cond-mat.mtrl-sci↗

arXiv2013

Space Charge Transfer in Hybrid Inorganic/Organic Systems

We discuss density functional theory calculations of hybrid inorganic/organic systems (HIOS) that explicitly include the global effects of doping (i.e. position of the Fermi level) and the formation of a space-charge layer. For the example of tetrafluoro-tetracyanoquinodimethane (F4TCNQ) on the ZnO(000$\bar{1}$) surface we show that the adsorption energy and electron transfer depend strongly on the ZnO doping. The associated work function changes are large, for which the formation of space-charge layers is the main driving force. The prominent doping effects are expected to be quite general for charge-transfer interfaces in HIOS and important for device design.

cond-mat.mtrl-sci↗