Tellurite And Fluorotellurite Glasses For Active And Passive

7. Surface properties; MDO 261
detector counts the number of low energy secondary electrons (SE), and other radiation
from each point. Simultaneously, the spot of a cathode ray tube (CRT) is scanned across
the microscope screen, and its brightness modulated by the amplified current from the
detector. The electron beam and CRT spot are scanned in a similar way to a television, in
a rectangular array of straight lines known as a raster [5]. The magnification of the
microscope is the ratio of the CRT screen dimensions, to the area being scanned on the
sample; e.g. if the beam scans an area 50 × 50 µm, displayed on a screen 10 × 10 cm,
magnification = 10×10 -2 / 50×10 -6 = 2000.
Beam interaction with sample
As the electron beam interacts with the sample, the energy of the incident electrons is
reduced, resulting in a number of secondary, backscattered and other emissions. Fig.
(7.2) summarises the radiation emitted from a sample surface exposed to the electron
beam in an SEM.
X-rays
Cathodoluminescence
Incident
beam
Sample
Backscattered
electrons
Secondary
electrons
Fig. (7.2): Radiation emitted from a surface exposed to the electron beam in an SEM [5].