both halves is used (A-B) we obtain topographic contrast. Detector in this case is placed at high
take-off position that is not a good choice for detection of topographic contrast. Better topographic column 5
contrast can be obtained with a large scintllation detector placed at the side of the beam (7) (Fig le) y
but still it is not an optimum arrangement. The best topographic contrast can be obtained when a poz
low take-off BSE detector of large solid angle is used. Fig. 1f shows detector of such kind - the ir
sector-shaped ring detector optimized for detection of topographic contrast (8). AN
: S vo. ogc ,
= | - = 4 “ en
| 6 J Ry
101%. a 10 kV. ; DEER -100v
. “3007 “> 2 mm rd +300V 2
= 1
3 — he 7 / | x
i a B + A ]
“— + | X 3 | [=
Leva * +300V "2 nz
53
- i. 3 3 ku 1
. y Sn SL
i ]
ee E— ;
71 2, a
A! I
Fig. 1: Methods of detection of topographic contrast in the SEM. (a)- Detection of SE with the E-T
detector. ((b) and (c))- Indirect detection of BSE by their conversion to SE and detection of SE with
the E-T detector. (d)- Detection of BSE at high take-off angles by a semiconductor annular-split top
detector. (e)- Detection of BSE by a large scintillation side detector. (f)- Detection of BSE at low
take-off angles by the sector-shaped scintillation ring detector. Solid lines show trajectories of BSE,
dashed lines — trajectories of SE. 1- primary beam, 2- specimen, 3- scintillator, 4- light-guide, 5-
lens pole-piece, 6- grid. Arrows show direction to a photomultiplier.
Experimental.
Metallographic sections of different steel specimens were prepared and replicated in the AGAR
replication material (cellulose acetate). Negative and positive replicas of specimens were made. The SE
specimens and their replicas were observed in the Cambridge Stereoscan 180 and in the JEOL fig 2:
JSM5800LV SEM. Both microscopes were equipped with the E-T detectors of SE and BSE mene
detectors. The first SEM was equipped with the custom-made sector-shaped ring BSE detector, the dees 0
second microscope with the commercial annular-split semiconductor BSE detector. In the left Signed of:
mfg
On repfiea
(a) (b)
+100V
(c) (d)
fed ti
348
