Physical and Chemical Mechanisms of Preparation Techniques - Sample Preparation Topic for Transmission Electron Microscopy - page 117

The setup used is represented in Fig. 5.23. The anode is composed of a graphite
pencil that has been hollowed out at one end. A disk of the metal to be evaporated
(platinum, chrome, etc.) is then placed in this hollow. This electrode is placed within
an electrical field created by a tungsten filament, corresponding to the cathode. The
system of shutters makes it possible to channel the flow of particles to the specimen
to obtain a better output. The setup is in the upper part of the chamber, which is
placed under a high vacuum of 10 -4 -10 -5 Pa. The specimen is placed on a specimen
holder stage that can sometimes be tilted and rotated some tens of rotations per
minute. It is then placed under the gun at a short distance (5-10 cm). This system
makes it possible to evaporate the metal with a weaker current and much less heating
than previously, which allows much smaller particles to be obtained.

Focal Diaphram

High
Voltage

Anode

Carbon Cathode

Heating Filament

Front Diaphragm

Ion Sink Plates

High Vacuum

Removable Shutter

Thickness
Measurement

Air Release Valve

Secondary Vacuum

Fig. 5.23 Electron-gun evaporator

Pulverization Using an Ion Gun

In this device, an ion gun is added to the evaporation source, so that the coating is
made under the ion beam, in what is called ion beam-assisted deposition (IBAD).
This system is relatively recent and designed to overcome the often poor quality
of coatings made by simple evaporation (bad aging, poor density, poor adherence,
etc.). The setup used is represented in Fig. 5.24 and shows a classic evaporator
equipped with an ion gun. Coatings are made in a chamber under a vacuum of
10 -5 -10 -6 Pa. The deposition technique consists of evaporating the material present
within a crucible while simultaneously bombarding the film during its growth, using
a beam of energetic ions coming from a plasma source. The energy provided by the
ions is transferred to the atoms derived from the evaporation, which are adsorbed
onto the surface of the substrate. Depending on the type of atoms evaporated and
the plasma-bombardment ions, chemical reactions may occur, giving rise to defined