OPTIMIZATION OF THIN-FOIL BASED PHOSPHOR SCREENS FOR CCD IMAGING IN TEM IN THE VOLTAGE RANGE OF 80-400 KV

The voltage dependence characteristics of thin-foil based phosphor scr eens in the thickness range of similar to 10-60 mu m are examined for CCD imaging in transmission electron microscopy (TEM) in the voltage r ange of 80-400 kV. The brightest screen is obtained with a P20 layer o f about 12 mu m at 80 kV, and a thicker screen lowers both the screen brightness and resolution. The thickness of the brightest screen is hi gher at higher voltages, but other considerations for a practical CCD imaging system suggest that the P20 layer should not be greater than s imilar to 18 mu m for the voltage range stated above.