Applied Physics

APPENDIX B

Surface Defects

Two-dimensional crystal imperfections are known as surface defects or plane defects. In surface defects, the imperfections should lie about a surface having few atomic dimensions thick. Surface defects are of two types (a) external surface defects and (b) internal surface defects.

(a) External surface imperfections: Every atom present inside the crystal has a large number of surrounding atoms, whereas the atoms present on the surface of the crystal has no neighbouring atoms on one side of the surface. Hence atomic bonds do not extend beyond the surface of the crystal. Because of this, the surface atoms possess larger energy than the interior atoms. This larger energy at the surface causes imperfection at the external ...