Scanning Probe Microscopy in the School of Physics
The School of Physics has established the Atomic Force Laboratory with the
acquisition of two Scanning Probe Microscopes (SPM), a JEOL 4200 and a
JEOL 4500. These instruments complement the existing Electron
Microscopes, Ion Beam Microprobes and Raman Spectroscopy facilities.
SPMs provide information by monitoring the interaction of a sharp tip with
the surface to be analyzed. The tip is scanned over the region of interest in a
raster pattern at very close distances, and an image of the interaction is
acquired. In the Scanning Tunneling Microscope (STM) mode, the tunneling
current between conductive tip and sample surface provides topographical
and electrical information with sub-Angstrom resolution.
In the Atomic Force Microscope (AFM) mode, the optically detected
deflection of a micro-cantilever, with a tip attached to it, generates
topographical information for conductive and non-conductive samples.
Cantilevers coated with conductive or ferromagnetic layers further enhance
the AFM usefulness in providing simultaneous topographical and
electromagnetic surface properties for immediate comparison. Operation is
possible in the attractive (Non-Contact) or the repulsive (Contact) region of
the van der Waals forces. Several modulation techniques are also available
to further enhance surface features resolution and allow the determination of
visco-elastic and electro-chemical parameters.
The JEOL 4200 is an “ambient” SPM with a complete range of accessories:
samples can be analyzed at ambient temperature and pressure with very little
preparation. The in-built turbo molecular pump and the attached cryogenic
cooler and heating stage allows monitoring of surface parameters under
controlled temperature (from 100oK to 1000oK) and pressure ( 10-6 Torr to
atmospheric).
The JEOL 4500 is a “state of the art” UHV based SPM system with
capabilities for sample preparation and observation under ultra clean
conditions ( 10-10 Torr). It has demonstrated capability of imaging reactive
surfaces at high temperature in AFM mode with atomic resolution.
The Atomic Force Laboratory is open to all Researchers in the School of
Physics and other Departments. External users are welcome to apply for
analysis and characterization of samples on a user-pay basis. We particularly
welcome users for collaborative research purposes.
Our strength lies in the provision of expert services to generate answers to
research problems. These include interpretation of the data and optimization
of experimental procedures. We can provide a unique synergistic approach
to problem solving.
Examples of current research activity in the Atomic Force Laboratory
 Topographical and current imaging of grain boundaries of Diamond films
and DLC.
 GaN
 Sapphire surface reconstruction
 Si-Si and Si-Ge characterization
 Dentine channels/filling
 DNA/proteins interactions
 Visco-elastic properties of PAMS Polymer films at variable temperature
 Temperature dependence of friction force of Polyethylene films
 AFM atomic resolution imaging of reconstructed 7x7 Silicon surface
 Nanostructures for Quantum Computer Technology development
 Reconstruction of 7x7 silicon surfaces
 Cleaved Si in UHV
A gallery of images using some of the SPM capabilities:
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Lithography on Si surface
7x7 Silicon surface
Diamond films
Paleo-biological samples (insect wing)
Diffraction Grating
Atomic imaging of cleaved HOPG film
Si implanted arrays
Magnetic imaging of Hard Disk surface
DNA fragments on Mica
Dentine channels