PROPERTIES OF IONIC BOMBARDED SILICON 



119 



tlie data for self-bias are tlie result of a direct measurement while those 

 for forward and reverse voltage are transcribed from a cathode-ray 

 plot, they are perhaps the most significant. Samples 1 to 3 represent 

 specimens of increasing degrees of purity. 



These alpha-particle bombardment experiments indicate rather defi- 

 nitely that results may be obtained similar to those obtained from 

 bombardment with gaseous ions and, like the ion bombardment, they 

 tend to produce high resistance surfaces. 



Table II 



MECHANICAL EFFECTS OF BOMBARDMENT 



The marked changes in the electrical properties of silicon imposed by 

 bombardment stronglj^ suggest that bombardment may also impose a 

 corresponding change in the lattice structure and that this might be 

 detected by suitable optical methods. Attempts were made at an early 

 date to detect such changes. To this end a mask of nichrome ribbon 5 

 mils wide and 1 mil thick was laid over a sample of silicon during bom- 

 l)ardment. An optical examination of the surface showed that after 

 bombardment in the case of helium the surface on either side of the 

 mask was elevated whereas in the case of argon it was depressed. This 

 result has since been confirmed by one of the authors's colleagues, 

 Dr. F. W. Reynolds, who has found that in cases of prolonged bom- 

 bardment by helium the adjacent surfaces may be elevated by as much 

 as 225 Angstroms'^ while in the cases of prolonged bombardment by 



^ One Angstrom is 10~* cm. 



