Download (4Mb) - Etheses - Saurashtra University

Chapter VII Reactivity at Dislocation….
7.2 Etching Methods
Etching is a process that has been used extensively in a variety of trades.
They range from the ancient craft of the jeweler to the application of
photolithography in the production of printed electrical circuits. With recent
advances in crystal growth and purification, more rigorous demands are put
forwarded on crystal perfection, orientation and special surface treatments.
Etching plays an important role in the perfection and characterization of the
crystals. Reasons for performing etching are grouped as follows [10].
1. Cleaning
Any surface for its macroscopic or microscopic study requires to be cleaned up
because cutting and other mechanical treatments leave a damaged layer that
must be removed before certain surface studies can be made.
2. Revealing Dislocations
Dislocations and other lattice imperfections affect the strength, surface potential,
electrical properties and other properties of crystals. Etchants that reveal
imperfections give direct measure of crystal perfection.
3. Orientation of crystals
Many studies such as dissolution, oxidation and electrical effects require single
crystals whose faces are of a specific crystallographic orientation.
The main etching techniques are listed as under with their brief outlines [11].
(a) Chemical Etching
When a crystal is etched in a proper etchant, its surface atoms undergo a
chemical reaction. The reactions at defect sites form products and is removed
247