Stereo Scan 440 - DCU

The total electron yield can also be increased by tilting the specimen. A tilt in
the region of 20 to 40 will greatly reduce charging.
The other most important factor affecting charging is electron "dose rate". This
can be defined as the total number of primary electrons per unit area of the
specimen as a function of time. In other words, the scan speed of the beam is
critically important. It can be seen that on some beam sensitive materials a fast
scan speed gives a good screen image with good contrast and topography (see
Figure 3.8(a» whilst a slow scan speed, ie for live photography, (see Figure
3.8(b» causes the image to display the defects mentioned previously. The
following diagrams illustrate this effect.
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FIgUre 3.8(a) Taken at a fast scan speed
The above shows a sample of Ceramic
In this case, the image store can be used to acquire the image, with noise
reduction if necessary, at a fast scan speed. The stored image can then be
photographed or stored to disk.
Stereoscan 440 Operator Manual
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