5 OPERATION
5-38
EM210F-1
5.4 SPECIAL
OBSERVATION
5.4.1 Bright
Field
Image
When the incident electron beam passes through the specimen, it splits chiefly into
unscattered electron beam and scattered (diffracted) electron beam; the former forms a
bright field image.
1.
Obtain a selected area image (
F
Sect. 5.5.1).
2.
Insert an objective aperture into the electron beam path (
F
Sect. 5.2.9b).
3.
Adjust the objective aperture position using the aperture assembly knob 2
and 3 so that the direct spot paths through the aperture.
?
The center spot in the diffraction diagram is called as “direct spot” and other
spots are called as “Diffraction spots”.
4.
Depress the MAG1 switch (R1-
②
) to obtain the MAG mode.
5.
Select the desired magnification using the MAG/CAM L knob (R1-
⑤
).
A bright field image (Fig. 5.37-a) appears on the screen.
a: Bright field image
b: Diffraction pattern
(aper ture position)
c: Dark field image
Fig. 5.37 Bright/dark field images
5.4.2 Dark Field Image
When the incident electron beam passes through the specimen, it splits chiefly into
unscattered electron beam and scattered (diffracted) electron beam; the former forms a
bright field image, and the latter a dark field image. Though the dark field image does
not provide sufficient image brightness, it has an advantage that image contrast is much
greater than that of a bright field image.
1.
Obtain a selected area image (
F
Sect. 5.5.1).
2.
Insert an objective aperture into the electron beam path (
F
Sect. 5.2.9b).
3.
Adjust the objective aperture position using the aperture assembly knob 2
and 3 so that the direct spot paths through the aperture.
?
The center spot in the diffraction diagram is called as “direct spot” and other
spots are called as “Diffraction spots”.
4.
Depress the DARK TILT switch (L1-
⑤
).
5.
Adjust the objective aperture position using the DEF/STIG knobs (L1-
⑩
, R1-
④
) so that the desired diffraction spot paths through the aperture.
