• پارسی (Persian)

Titles

Surface and Thin Film Analysis
The interaction  particles& thin layer

The interaction  X Ray with thin layer

The interaction   Light with thin layer

SEM:  Scanning Electron Microscopy

TEM:Transmission Electron Microscopy
SPM :  Scanning   probe   Microscopy

AFM :  Atomic   Force      Microscopy

STM :  Scanning  Tunneling Microscopy

Sims: Secondary  ion  mass  Spectroscopy

RBS: Rutherford Backscattering Spectroscopy

 XRD:      X_Ray Diffraction

XPS:   X_Ray Photoelectron
 
Spectrophotometer

Ellipsometry

Thin film Structure

  Electron_Beam  Gun
Vacuum          About

Rotary               Pump

Turbomolecular   Pump

  Cryojenic           Pump

  Diffusion            Pump

The barometer History

  Low vacuum range gauge

  
Thickness Monitoring




 

Scanning tunnelling microscope

Scanning Tunneling Microscope (STM)
In 1981, Gred binnig and Heinrich Rohrer built one microscope in IBM specialized laboratories in Switzerland, using electron tunneling phenomenon, which can be seen with it the atomic dimensions. So called it STM microscope. They received the Nobel Prize for this effort in 1986.
Like atomic force microscopy, STM also makes use of a metal needle tip to scan. Sure, the needle tip can't touch the surface of the sample, but when the distance to the surface reaching almost to the atomic dimension (about 10 Å), as shown in Figure 8, by applying a voltage between the tip and the sample, electrons flow based on the tunneling phenomenon, from the sample towards atoms of the tip or vice versa, and at this time the computer receives an electrical signal that generated by the tunneling phenomenon, and scanning can be done in two different ways:
1. When the flow rate is fixed, needle tip is stimulated for going up and down.
2. When the height is fixed, the scan is done to forward and back and according to the ups and downs, as well as the surface electrical nature tunneling current has changed, and sends the required signals to the computer for reconstruction of image.
Due to the electrical nature of the surface, the tunneling current changes and sends a signal to reconstruct the image to the computer.
In Figure 8, some of the STM images for the silver layer, which is deposited in different temperature conditions by magnetic sputtering method and done heat process on it.
                                          

Figure 8: schematic representation of the scanning tunneling microscope.
                   

                   
Figure 9. The obtained images from STM, related to silver layer surface ,Right: deposited sample in substrate temperature, 100, 200 and 300 ° C. Left: annealed sample at 100, 200 and 300 ° C.


An important limitation of the scanning tunneling microscope is it that should both the sample surface and the needle tip be conductors or semiconductors to happen the tunneling phenomenon, though, can be used of AFM for semiconductor materials, semiconductor, and insulation.

Movie

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