Electrically driven fluorescence of single-molecule junctions
CIC nanoGUNE Seminars
- Speaker
-
Michael Chong (Univ. Strasbourg)
- When
-
2017/01/13
13:00 - Place
- Donostia International Physics Center
- Add to calendar
-
iCal
A
study of the optoelectronic properties of molecular junctions
performed by
scanning tunneling
microscopy (STM) is
presented. First, the
molecular
structures are synthesized on a Au(111) surface : an emitting
unit
(fused-porphyrin) is embedded in a molecular wire
(oligothiophene) by means of
on-surface polymerization. Then, by manipulation we lift and
suspend the
emitter between the tip of the STM and the gold surface,
creating a single
molecule junction. The molecular
wire
acts as an organic linker that allows the flow of electrons
and decouples the
fused-porphyrin from the metallic leads.
By
applying a voltage bias between the tip and the
sample, a current is generated, which leads to the excitation
of the molecule.
This process is mediated by the localized surface plasmon
modes of the tip.
Eventually, the molecule de-excites in a radiative way,
generating a
fluorescence signal. This type of junction generates a
narrow-line emission of
light whose color is controlled by selecting the chemical
structure of the
emitting unit. Moreover, control over the linewidth is
obtained by
progressively detaching the emitting unit from the surface.
Also, we observe
red-shifted vibronic features that provide a chemical
fingerprint of the
emitter, and blue-shifted vibronic features that are a sign of
hot-luminescence.
(host: Nacho Pascual at nanoGUNE)