ABSTRACT
The atoms around any vacancy tend to alter their positions slightly, so in general, there will be some distortion of the crystal structure near Schottky defects. There are two major classes of defect: point defects and dislocations. Point defects such as vacancies and interstitials can be found in crystalline areas of polymers, while the boundaries between different crystalline regions within a polymer can also be thought of as defects. Amorphous materials can either be naturally occurring—like the volcanic mineral obsidian—or artificially created from crystalline solids. Impurity atoms can also be found in amorphous materials and can even be deliberately added to amorphous semiconductors—just like they can be added to crystalline semiconductors—to alter their electrical properties. One of the most commonly used amorphous materials is glass. Amorphous polymers, for instance, tend to be transparent, whereas polymers with a mainly crystalline structure are generally opaque or translucent.
