Hitachi S-4800 manual Accelerating Voltage and Image Quality

3.10Image Quality

The followings are references for getting better image quality.

3.10.1Accelerating Voltage and Image Quality

There is a multitude of accelerating voltages to choose from. Resolution, image quality, charging and other effects are greatly determined by the selected accelerating voltage. Below is a guideline for selecting an accelerating voltage in which to image various specimens.

(1) Resolution

Higher spatial resolution can be obtained at higher accelerating voltages.

(2) Charging

For uncoated insulator specimens, accelerating voltages lower than 1kV are recommended for minimizing charging. In some cases, high accelerating voltages (20kV or higher) may produce a better image.

(3) Contamination

Influence of contamination appears more at low accelerating voltages.

(4) Magnetic field disturbance

Disturbance by leakage magnetic field (wobbling or distortion of the image) is greater at low accelerating voltages.

(5) Contrast

Generally a soft-tone image is obtained at low accelerating voltages, because more secondary electrons are detected than backscattered electrons at low accelerating voltages.

(6) X-ray analysis

X-ray analysis generally requires accelerating voltages higher than 10kV. The required accelerating voltage depends on the exciting energy of elements for x-ray detection.

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