Characterization Techniques in Nanotechnology …
47
of 0.323 nm) and grain growth in <110> direction (Asafa et al. 2014). The direction of the grain boundary (GB) further explains the growth direction. Figure 23c
is the HRTEM image of silver nanoparticle obtained via reconstruction of the crystalline structure using digital micrograph (Virgen-Ortiz et al. 2015). The interplanar
distances are in line with a crystalline structure of type 4H hexagonal (index Miller
of the electron diffraction is shown in the inset). High-resolution TEM (HRTEM)
images of Te precipitates along 112 M zone axis are shown in Fig. 23d (Zhou et al.
2018).
2.5 Scanning Transmission Electron Microscopy
Scanning transmission electron microscopy (STEM) uses the combination of the
principles for transmission electron microscopy and scanning electron microscopy
and can be conducted on either type of instrument. Some TEM equipment have
installed scan coils for scanning electron beam across the specimen (Keyso et al.
1998; Nellist 2011). Similar to the TEM, STEM can be performed on very thin
specimens and concentrates primarily at beam electrons transmitted by the specimen.
One of the primary advantages of STEM over TEM is that it utilizes other signals that
cannot be effectively utilized in TEM which include secondary electrons, scattered
beam electrons, characteristic X-rays, and electron energy loss. Unlike TEM, the
electron beam in STEM is focused on a small spot (having a spot size range of 0.05–
0.2 nm) which is then scanned over the specimen in a raster illumination system
constructed in such a way that the specimen is illuminated at each point with the
beam parallel to the optical axis. The raster pattern of the beam across the specimen
makes STEM suitable for the imaging of biological specimen in the high contrast of
annular dark-field images, which can allow imaging of biological specimens without
the need for staining. Advanced STEM equipment particularly those fitted with extra
lenses to correct spherical aberration in the electron beam (STEM probe correction)
coupled with ultra-stable scan electronics means that the electron beam spot can
be sequentially positioned with accuracy down to different atom columns (Nellist
2011).
An example of STEM image is that of nanostructured copper-supported mesoporous carbon FDU-15 shown in Fig. 24 (Sahin et al. 2018). The STEM images
(Fig. 24a, b) together with the bright-field STEM images (Fig. 24b, d) showed how Cu
nanoparticles were distributed in the FDU-15 support. Further analysis also showed
that some nanoparticles are crossed by holes (Sahin et al. 2018).
2.6 Atomic Force Microscopy
Atomic force microscopy (AFM) is a kind of scanning probe microscopy having
resolution on the order of fractions of a nanometer (Cappella and Dietler 1999).
47
of 0.323 nm) and grain growth in <110> direction (Asafa et al. 2014). The direction of the grain boundary (GB) further explains the growth direction. Figure 23c
is the HRTEM image of silver nanoparticle obtained via reconstruction of the crystalline structure using digital micrograph (Virgen-Ortiz et al. 2015). The interplanar
distances are in line with a crystalline structure of type 4H hexagonal (index Miller
of the electron diffraction is shown in the inset). High-resolution TEM (HRTEM)
images of Te precipitates along 112 M zone axis are shown in Fig. 23d (Zhou et al.
2018).
2.5 Scanning Transmission Electron Microscopy
Scanning transmission electron microscopy (STEM) uses the combination of the
principles for transmission electron microscopy and scanning electron microscopy
and can be conducted on either type of instrument. Some TEM equipment have
installed scan coils for scanning electron beam across the specimen (Keyso et al.
1998; Nellist 2011). Similar to the TEM, STEM can be performed on very thin
specimens and concentrates primarily at beam electrons transmitted by the specimen.
One of the primary advantages of STEM over TEM is that it utilizes other signals that
cannot be effectively utilized in TEM which include secondary electrons, scattered
beam electrons, characteristic X-rays, and electron energy loss. Unlike TEM, the
electron beam in STEM is focused on a small spot (having a spot size range of 0.05–
0.2 nm) which is then scanned over the specimen in a raster illumination system
constructed in such a way that the specimen is illuminated at each point with the
beam parallel to the optical axis. The raster pattern of the beam across the specimen
makes STEM suitable for the imaging of biological specimen in the high contrast of
annular dark-field images, which can allow imaging of biological specimens without
the need for staining. Advanced STEM equipment particularly those fitted with extra
lenses to correct spherical aberration in the electron beam (STEM probe correction)
coupled with ultra-stable scan electronics means that the electron beam spot can
be sequentially positioned with accuracy down to different atom columns (Nellist
2011).
An example of STEM image is that of nanostructured copper-supported mesoporous carbon FDU-15 shown in Fig. 24 (Sahin et al. 2018). The STEM images
(Fig. 24a, b) together with the bright-field STEM images (Fig. 24b, d) showed how Cu
nanoparticles were distributed in the FDU-15 support. Further analysis also showed
that some nanoparticles are crossed by holes (Sahin et al. 2018).
2.6 Atomic Force Microscopy
Atomic force microscopy (AFM) is a kind of scanning probe microscopy having
resolution on the order of fractions of a nanometer (Cappella and Dietler 1999).