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Etching
All as-polished surfaces contain mechanically induced defects ("scratches") caused by the polishing particles. These defects affect the electronic properties of the device to be fabricated on this crystal. Prior to
any device fabrication process, the polished surface is sometimes etched in order to remove the damaged/ defective layer produced during polishing process. Chemical etchant are commonly used for this purpose and
different crystals have different etchants. Other than removing the damaged layer, etchants are also useful for revealing bulk defects present in the crystals. Some etchants attack preferentially defect sites on the
crystal, revealing dislocations and other atomic arrangement faults. Some etchants are also used for determining the orientation of the crystal surface. Thus etching is a very powerful technique for removing the
damaged layer, determining defect density of the crystal and also the orientation of the crystal surface.
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