Resistance of a Sputtered Film after Deposition. 145 



is never greater than one, but varies in a haphazard manner 

 from film to film. This is no doubt due to the impossibility 

 of ensuring a constant texture of film throughout a given 

 series. 











Table 



I. 











R > 



R 





R . 



R 





R . 



R 



Film 



ohms. 



R 

 091 



Film 



ohms. 



K 



Film 



ohms. 



Bo' 





243 



4000 



085 





14,140 



081 





278 



0'98 





4870 



092 





14,980 



064 



G. 



407 



090 





5550 



0-85 





15,110 



0-88 





1070 



072 





7500 



089 





15,930 



0-74 



B. 



1545 



0-98 



L. 



7600 



095 



M. 



16,270 



051 



D. 



1790 



0-80 



E. 



9200 



0-77 





20,500 



060 





1970 



0-87 



i 



11,800 



0-89 





29,000 



0-53 



A. 



3100 



100 



F. 



12,550 



0-95 





68,400 



0-84 



K. 



3400 



100 















The reason for the metastability of a newly deposited film 

 •cannot be definitely stated. The most feasible explanation 

 is that of Kohlschutter and Noll (loc. cit.), who suggest that 

 owing to surface-tension the finely divided particles in a 

 freshly deposited film undergo a process of coalescence, by 

 .means of which the gaps between the particles are lessened 

 in number, and so in general the resistance falls. Further 

 evidence that such a process occurs was obtained from an 

 -examination of the optical properties of films. Kohlschutter 

 and Noll point out that if the conditions are such that coa- 

 lescence can only go on with increase of distance between 

 the particles, the resistance will rise and may reach infinity. 

 As evidence of this they cite the rise in resistance that they 

 observed if silver films were deposited in hydrogen and left 

 to age in vacuo, when it was found that the resistance 

 decreased to a minimum and then rose to infinity. From a 

 number of different observations they conclude that the 

 metal is deposited in hydrogen in a coarse form, and hence 

 that less material is required for a film of given resistance than 

 if the deposition had occurred in nitrogen or argon ; this in- 

 creases the chance of a break in the film . In the author's expe- 

 riments on platinum and palladium films, despite the extreme 

 thinness of many of the films, this rise in resistance was never 

 observed — the resistance always decreased with time when 

 the film was left to age in vacuo, whether the deposition had 

 taken place in air or in hydrogen. 



The phenomenon may be viewed somewhat differently by 

 Phil Mag. S. 6. Vol. 32. No. 187. July 1916. L 



