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STM / AFM Images Explanations from Scanning Tunneling Microscopy

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stm afm images

STM / AFMImages

Explanations from

scanning tunneling microscopy
Scanning Tunneling Microscopy
  • In 1981, the Scanning Tunneling microscope was developed by Gerd Binnig and Heinrich Rohrer – IBM Zurich Research Laboratories in Switzerland (Nobel prize in physics in 1986).
  • This instrument works by scanning a very sharp metal wire tip over a sample very close to the surface. By applying an electric current to the tip or sample, we can image the surface at an extremely small scale – down to resolving individual atoms.

Quantum mechanics tells us that electrons have both wave and particle like properties.

Tunneling is an effect of the wavelike nature. The top image shows us that when an electron (the wave) hits a barrier, the wave doesn't abruptly end, but tapers off very quickly. For a thick barrier, the wave doesn't get past.

The bottom image shows the scenario if the barrier is quite thin (about a nanometer). Part of the wave does get through, and therefore some electrons may appear on the other side of the barrier.

The number of electrons that will actually tunnel is very dependent upon the thickness of the barrier. The actual current through the barrier drops off exponentially with the barrier thickness.
  • To extend this description to the STM: The barrier is the gap (air, vacuum, liquid) between the sample and the tip. By monitoring the current through the gap, we have very good control of the tip-sample distance.
scan image demonstrate analysis use images from science express laptop
SCAN IMAGEDEMONSTRATE ANALYSISUse images from Science Express laptop.

Actual Demonstration...

purdue university physics department

Purdue UniversityPhysics Department

Visit Purdue and other image alleries online !

atomic force microscopy
Atomic Force Microscopy
  • In principle, the AFM works like the stylus on an old record player.
  • There is actual contact between the probe tip and the sample.

The following explanation taken from

atomic force microscopy26
Atomic Force Microscopy

1. Laser

2. Mirror

3. Photodetector

4. Amplifier

5. Register

6. Sample

7. Probe

8. Cantilever

atomic force microscopy27
Atomic Force Microscopy

afm images





DIC (Differential Interference Contrast) image of human lymphocyte

metaphase chromosomes on microscopy slidedimensions 83 µm * 83 µm  


height image (left, 3D plot) and corresponding optical microscope image (above, bright field) of a moth wing scaleintermittent contact mode

scan field 10 µm * 10 µmz-range 0 - 1.7 µm


Height image (left, 3D plot) and corresponding optical microscope image (above, phase contrast) of a moth's eye - region of three adjacent facets. intermittent contact mode

scan field 10 µm * 10 µmz-range 0 - 6.0 µm


Atomic force microscope topographical scan of a glass surface. The micro and nano-scale features of the glass can be observed, portraying the roughness of the material.

Constructed at the Nanorobotics Laboratory at Carnegie Mellon University (