SURFACE PROPERTIES OF GERMANIUM 



0.8 



0.7 



0.6 



? 0.5 



_i 

 < 



Z 0.4 



0.3 



0.2 



\ 8 12 16 20 24 28 32 36 40 44 48 52 



TIME IN MINUTES 



Fig. 3 — Contact potential cycles for etched sample A. 



In Fig. 2 zero time is taken after the spark discharge was run in the O2 

 flow line for 2 minutes. This started the first cycle. After approximately 

 17 minutes the O2 was made to bubble through H2O. Fifteen minutes or 

 so later the O2 was changed back to dry. At this time, 32 minutes, the 

 flow rate was increased by a factor of three. The c.p. was followed for 

 about 17 minutes, then the process was repeated. The results and the 

 reason for the choice of time intervals, are all evident from a study of 

 Fig. 2. The spark discharge in O2 decreases the c.p. After this treatment 

 the c.p. increases with time, most of the change occurring in the first 

 15 minutes. The wet O2 then increases the c.p. to a maximum value 

 which is reached in about 15 minutes. Finafly the dry O2 reduces the 

 c.p. It is evident that there is a quasi-equflibrium value of c.p. in dry 

 O2, to which the c.p. returns after either extreme treatment. At first 

 there is quite a large shift from cycle to cycle but this shift gradually 

 disappears as the cycling is continued. In Fig. 2 cycles 2, 4, 6 and 10 

 are shoA\Ti. Very little change takes place after cycle 10. Such results 

 have been obtained many times over a period of two years. When al- 

 lowance is made for shifts in work function of the reference electrode 

 and for the fact that the experimental technique improved as the work 

 progressed it is found that all the results for a given sample of Ge are 

 very consistent. 



In Fig. 3 are sho^vn similar results for an n-type slice A. In this case 

 the surface was first ground or sandblasted to remove any films, and 



