SKMnOXDI ( IONS 



339 



quires a systematic drift, riu'refore it also can contribute to the current; 

 in other words, current can llow as well by virtue of a deficit of electrons as 

 by an excess of them. 



In an illuminated and bombarded diamond crystal the electrons and holes, 

 produced in pairs by the excitation, will of course drift in opposite directions 

 under the intkience of a held; the electron, being negative, drifts in the op- 



+ 4 IN CORE OF 

 CARBON ATOM~-- 



m 



VALENCE 



ELECTRONS 



EACH ATOM, WITH THE 

 CHARGE OF ITS SHARE OF 

 VALENCE-BOND ELECTRONS, 

 IS ELECTRICALLY NEUTRAL. 



(b) 



(a) ELECTRON PAIR BONDS 



(C) PLANE DIAGRAM OF DIAMOND 

 LATTICE WITH BONDS REPRESENTED 

 BY LINES 



Fig. 3. 



FOUR 



VALENCE BONDS 



posite direction from the applied held, but its current is in the direction of 

 the lield. In the case of the hole, the recij)rocal electron motions are once more 

 opposite to the direction of the held (on the average). As a consequence, the 

 net result is that the hole drifts in a direction to increase the current repre- 

 sented by the electrons. If the source of bombardment or illumination is 

 removed, the conductivity dies away and the crystal will return to its nor- 

 mal state. This can occur by the recombination of holes and electrons. 

 Whenever an electron drops into a hole, both the hole and the electron dis- 



