Cleavage mechanoluminescence in elemental and III–V semiconductors

The present paper reports the theory of mechanoluminescence (ML) produced during cleavage of elemental and III–V semiconductors. It seems that the formation of crack-induced localized states is responsible for the ML excitation produced during the cleavage of elemental and III–V semiconductors. According to this mechanism, as the atoms are drawn away from each other in an advancing crack tip, the decreasing wave function overlap across the crack may result in localized states which is associated with increasing electron energy. If the energy of these localized states approach that of the conduction band, transition to the conduction band via tunnelling would be possible, creating minority carriers, and consequently the electron–hole recombination may give rise to mechanoluminescence. When an elemental or III–V semiconductor is cleaved, initially the ML intensity increases with time, attains a peak value Im at the time tm corresponding to completion of the cleavage of the semiconductor, and then it decreases following power law decay. Expressions are derived for the ML intensity Im corresponding to the peak of the ML intensity versus time curve and for the total ML intensity IT. It is shown that both Im and IT should increase directly with the area of the newly created surfaces of the crystals. From the measurements of the ML intensity, the velocity of crack propagation in material can be determined by using the relation v=H/tm.