Tungsten filament gun

On heavy materials (Au. Pt, etc.), the limiting resolution of the microscope can be reached. On a test sample of gold particles on a carbon substrate (conducting sample) a resolution of 7 nm at 35 kV is obtained with a tungsten filament gun and 1.2 nm at 15 kV (see Fig. 7.14) with a field emission gun. The resolution at a voltage of 1 kV is multiplied by a factor equal to the square root of Eq (the resolution reaches 40 nm on a traditional microscope, whilst it is about 5 nm on a field-effect microscope). 

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