Page 329 - Book Hosokawa Nanoparticle Technology Handbook

FUNDAMENTALS CH. 5 CHARACTERIZATION METHODS FOR NANOSTRUCTURE OF MATERIALS

Incident electron beam

Characteristic X-rays
Cathodoluminescence

Specimen

Ineastically
scattered electron Elastically
scattered electron
Unscattered electron

Figure 5.5.3
Interaction between the incident electron beam and the
specimen, in the case of TEM.
the specimen normal to its surface. All electrons
that are scattered by the same atomic spacing
will be scattered by the same angle. These “the
same angle” scattered electrons are gathered by
lens and form a pattern of spots; each spot cor-
responding to a specific atomic spacing. This
diffracted pattern yields information about the
orientation, atomic arrangements and phases
present in the region of interest.
Figure 5.5.2 3. Inelastically scattered electrons are caused by
Spatial resolution for observing materials.
the incident electrons that interact with atoms in
specimen with loosing their energy. These
electrons, elastically scattered electrons and inelasti- inelastically scatted electrons provide two types
cally scattered electrons.
of information. One is the inelastic loss of
1. Unscattered electrons are caused by incident energy by the incident electrons, characteristic
electrons transmitted through the thin specimen of the elements. These energies are unique to
without any interaction occurring inside the each bonding state of each element and thus can
specimen. Since the amount of unscattered elec- be used to extract both compositional and chem-
trons is inversely proportional to the specimen ical bonding information of the specimen.
thickness, thicker areas of the specimen have Another one is the formation of bands with
fewer unscattered electrons and appear darker. alternating light and dark lines, known as
2. Elastically scattered electrons are caused by the Kikuchi bands. These bands are also formed by
incident electrons that are scattered by atoms in inelastic scattering interactions related to the
the specimen without losing energy. These elas- atomic spacing in the specimen.
tically scattered electrons are transmitted
through the remaining portions of the specimen, 5.5.1.1 Images and diffraction contrast
and follow the Bragg’s diffraction law. All inci- The bright-field imaging technique is the most com-
dent electrons have the same energy and enter mon method for the imaging method using TEM.

304