Fig.1: Scanner tube with scanning tip
Fig.2: Complete Mini-STM
Fig.3: Phthalocyanin molecule on a carpet of carbon atoms
Fig.4: Surface of highly orientated pyrolytic graphite
Fig. 5: Atomic structures of a gold surface
Fig.6: Expanded view of the superlatice
Fig.7: Bit structure on a CD
Fig.8: Structure written into a high-temperature semiconductor with the
This is the world's smallest commercial scanning tunneling
microscope (STM). Its heart is formed by the Nanomotor. The sample lies
on top of three balls mounted on the scanner tube.
The complete Mini STM fits under a thimble and is
thus very insensitive to environmental vibrations. No additional vibration
damping systems are needed.
Figure 3 shows a phthalocyanin molecule lying on a
carpet of carbon atoms (Highly Oriented Pyrolytic Graphite, HOPG). The
distance between two visible atoms of this carpet is 0.25 nm. This picture
was taken without additional vibration damping.
The Mini STM can also be used to write structures
on surfaces. The Mini STM is available with complete control electronics
and Windows-based control program.
Below you see some results derived from different
applications of the Mini-STM:
At the University
Figure 4 shows a HOPG-surface (Highly-Orientated Pyrolytic Graphite),
featuring the individual atoms in their hexagonal lattice. The scanned
area is about 1.8 x 1.8 nm2.
This image was taken by a group of students doing a practical physics
laboratory course at the University of Aachen (RWTH) with the microscope
located on a regular office desk on the 3rd floor of the University building.
On the road
Figure 5 and 6 show the atomic superlattice of a gold surface. They were
taken by a customer (Institut für Experimentalphysik, FU Berlin)
at the Hannover fair 1998, the biggest industrial fair in Germany. The
Mini-STM without any vibration damping system sat on an exhibit table
placed on a wooden floor covering electrical cables. Visitors walked over
this floor, causing no visible effects in the scanned pictures of a gold
sample, not even during low speed scans of large sample areas. The insensitivity
of the Mini-STM to vibrations is made possible by the small size, and
this is only possible by using a Nanomotor.
Longer Tube Scanner
This picture of CD bits was taken with a Tube Scanner Head "Tall"
having the same diameter as that of the Mini-STM, but twice the length.
The stability decreases but with our high voltage amplifiers a scanning
range of up to 20 µm is possible. The same head is used for the
The STM can also be used to write structures:
The "Phi" in Fig. 8 was written directly into a High Temperature
Superconductor and visualized at the same time in the same device: an
STM (2. Physikal. Institut, RWTH Aachen). This structure can be treated
to form a superconductor, conductor or insulator. Since the structures
are extremely small they can form quantum mechanical devices, e.g. Josephson
Contacts, tunneling devices or Superconducting Quantum Interference Devices
(SQUID). Until now SQUID's have been made by several complex lithographic
steps in a process having a poor yield. This technique was patented in
co-operation with the RWTH-Aachen. The structures can be made and visualized
without expensive equipment "on a normal table".