Instruction manual

3-107
3.10 Image Quality
The followings are references for getting better image quality.
3.10.1 Accelerating 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.