Assistant Professor
Physical (Analytical) Chemistry/Chemical Physics
Vordiplom, 1991, Freie Universität, Berlin, Germany
Diploma Thesis, 1995, Fritz-Haber-Institute of the
Max-Planck-Society, Berlin, Germany
Doctor Rerum Naturum, 1997, Freie Universität, Berlin, Germany
Postdoctoral Fellow, 1997-1998, Paul-Drude-Institute for Solid State
Electronics, Berlin, Germany
Postdoctoral Fellow, 1998-2000, Columbia University, New York, USA
1998 Ramsauer Award
Research Interests:
Scanning Tunneling Microscopy (STM)
STM allows imaging of individual atoms and molecules on metal and
semiconductor surfaces. The spatial expansion of specific electronic states
of surfaces can be visualized directly. On the right a couple of STM images
are shown. Scanning Tunneling Microscopy is based on scanning a sharp tip
less than a nanometer (10-9 m) above a surface while applying a small bias
of a few mV to a few V. Using the resultant tunneling current as a feedback
signal, a substrate profile is obtained at a resolution of a few picometer
(10-12 m). However, an STM cannot only be used to acquire images of atoms,
molecules and bare surfaces. The sharp tip can also position atoms and
molecules at desired surface locations.
Surface Reactions Studied by STM
Using the STM tip, extreme electric fields and currents can be applied to
adsorbed molecules. This permits investigation of molecular reactions. The
images on the right show the transfer of a CO molecule between the substrate
and the tip, as it can be induced by transiently attaching an electron from
the tunneling current to the molecule. Recently, our attention focused on
the addressal of intramolecular bonds such as the S-H bond of thiols and the
C-X (X=Cl, Br, I) in haloaromatic compounds.
Construction of Molecules Piece-by-Piece
We develop a variety of techniques able to modify individual molecules with
the aim of assembling more complex molecules step by step. An example is the
Ullmann reaction on the right, where we first abstracted Iodine from two
iodobenzenes and then assembled the phenyls to biphenyl.
Optical Excitation of Surface Reactions
Recently we were funded by the Department of Energy to develop nanosize
catalysts that can control the diffusive and energetic dynamics of
adsorbates. We use fs-optical excitation of surface reactions for initial
investigations.
THz Spectroscopy
THz electromagnetic radiation can probe the mobility of electrons in a
variety of mediat without the necessity of applying wires to the specimen
under investigation. We develop THz measurement schemes specifically
applicable to chemical reactions and information processesing.
WWW: Research
Email: ludwig.bartels@ucr.edu
Extension: 2041