Scanning Electron Microscopy and X-Ray Microanalysis

178

12

Skirt intensity

Elastic

scattering

event with

gas atom

Unscattered

beam intensity

Limit for 99 % of

beam electrons

Intensity

Position

. Fig. 12.5 Schematic diagram
showing gas scattering leading to
development of the skirt
surrounding the unscattered
beam at the specimen surface

0

20

40

60

80

100

0246810

1 Pa

10 Pa

100 Pa

1000 Pa

2500 Pa

Sk

irt R

adius (micrometers)

Gas Path Length (mm)

Development of Beam “Skirt”

Gas Scattering Skirt (Oxygen; beam energy 20 keV)

30

. Fig. 12.6 Development of
beam skirt for 20-keV electrons
passing through oxygen at
various pressures as calculated
with Eq. 12.1

Chapter 12 · Variable Pressure Scanning Electron Microscopy (VPSEM)