Towards an optoelectronic characterization of molecules by nanoscale gold antennas

Molecular electronics and plasmonics are both very promising fields
in nanoscale sciences in which their combination is a big
challenge. This thesis is divided into two parts. First, we studied
the conductance of two differently capped benzodifuran derivatives
in a mechanically controllable break junction setup. Based on the
results of the electrical transport measurements, we discuss
possible binding sites of both molecules to the gold electrodes.
Secondly, we present photoluminescence measurements of gold
nanostructures. Lithographically fabricated gold antennas were
investigated by a confocal laser microscope. Gold nanostructures
are a candidate for optoelectronic devices where optically active
molecules such as benzodifuran-derived compounds can interact with
light to achieve further functionality. We studied the dependence
of single-photon photoluminescence on the size of the gold antenna.
Here, we applied successfully a plasmon-enhanced photoluminescence
model onto the measured spectra to explain the dependence in
detail. Interestingly, we observed an additional peak in the
spectra of long antennas which we assigned to a radiative decay at
the interband absorption edge. Our investigations provide
additional insight into this feature, which remains to date only
poorly studied. Furthermore, we investigated the coupling between
two closely located monopole antennas and described the shift of
the dipole resonance energy by plasmon ruler equations.