Introduction
History
Principle
History of microscopes
From waterdrops to ...
Microscopy techniques
Medizine
Lightmicroscopy
Electronmicroscopy I
Electronmicroscopy II
Scanningtunnelingmicroscopy
Oddities
The Microscopes
STM
Construction
Measuring Principle
Tunneling current
Tip
Two methods
AFM
Construction
Measuring principle
Atomic forces
Contact Mode
Tapping Mode
Pieces
Piezos
Controller
Limits
Internal
External
Glossary
 

Measuring Principle

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To record the change in altitude by the sample a voltage is impressed between the tip and the sample. If the distance is short enough there will be a current. A topographical change in the sample therefore causes a change in the current. The microscope then adjusts its distance through adjusting the voltage in the z piezo. Thus the current and accordingly the distance between the tip and the sample is held constant to not risk a crash of the tip into the sample.
The whole process is recorded so there results a set of horizontal and vertical data of the sample. These can be visualized by a computer. To get a taste of what it could look like we link to our image gallery.

The film shows how the tip reacts to changes in the topography. A laser beam is reflected by a mirror on the cantilever to a light detector which records the changes.

Ideally one atom lies on the top of the tip out of which the current flows.

 
  Construction                  Tunneling current

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