25 research outputs found
Imaging isodensity contours of molecular states with STM
We present an improved way for imaging the local density of states with a
scanning tunneling microscope, which consists in mapping the surface topography
while keeping the differential conductance (d/d) constant. When
archetypical C molecules on Cu(111) are imaged with this method, these
so-called iso-d/d maps are in excellent agreement with theoretical
simulations of the isodensity contours of the molecular orbitals. A direct
visualization and unambiguous identification of superatomic C orbitals
and their hybridization is then possible
Pulling and Stretching a Molecular Wire to Tune its Conductance
A scanning tunnelling microscope is used to pull a polythiophene wire from a
Au(111) surface while measuring the current traversing the junction. Abrupt
current increases measured during the lifting procedure are associated to the
detachment of molecular sub-units, in apparent contradiction with the expected
exponential decrease of the conductance with wire length. \textit{Ab initio}
simulations reproduce the experimental data and demonstrate that this
unexpected behavior is due to release of mechanical stress in the wire, paving
the way to mechanically gated single-molecule electronic devices