Scattering&Spectroscopy
Universität Wien

Scanning Probe Microscopy and Spectroscopy



H. Rohrer, K.G. Binnig, Nobel prize for physics 1986

Wave function mapping for 48 Fe atoms on a Cu (111) surface, Crommie et al., Science 1993

Scanning probe analysis with local atomic resolution

AFM: Atomic force microscopy: for nonconducting materials, attractive or repulsive forces induce a bending of the cantilever on approaching the sample surface
STM: Scanning tunneling microscopy: for conducting materials, the tunneling current between tip and surface is recorded on approaching the surface
STS: Scanning tunneling spectroscopy: The local density of states is probed by recording the I-V characteristic of the tunneling process and evaluating its derivative

In all cases feedback between detected signal and tip approach is the fundamental principle for this type of microscopy.

Some related techniques:

NFSPM/NFSPS: near field scanning probe microscopy/spectroscopy: Immediately at the orifix of a light pipe (near field wave zone) light can be localized to a much smaller area as given by diffraction theory. This allows highly localized microscopy/spectroscopy.
MFM: magnetic force microscopy: for magnetic material; The interaction between tip and sample is of magnetic origin

Recent Developments

Wave function mapping in quantum dots or quantum wires
Inelastic tunneling spectroscopy for phonons
Spinpolarized electron tunneling
Surface reconstruction for metals
Manipulation of single molecules on surfaces

I-V characteristic and first derivative for a quantum dot Schmidt, Nanoparticles 2004

Equipment Available

AFM/STM system from Topometrix: operates in air
Variable temperature UHV scanning probe system from Omicron: operates in UHV at temperatures between 25 and 1500 K (for direc heating)
Easy PLL excitation and detection system from Schäfer GmbH: for high stability AFM detection

Surface reconstruction on Si (111)

Monoatomic step edges on a graphite surface

Omicron microscope head