Properties of Thin Metal Films. 



669 



A few films were made and their thickness and resistance 

 measured. They were then heated in vacuo for ninety hours 

 to a temperature of 90° C, and their resistance again measured. 

 The results obtained are given in Table VIII. 



Table VIII. — Resistance of Silver Films. 



No. of 

 film. 



Dimensions of film in cm. 



Resistance 



- - -j 



Length. 



1-38 

 189 

 1-45 

 1-96 



Breac ; th. 



107 

 1-04 

 106 

 1-1 



Thick- 

 ness. 



Before 

 heating. 



After j 

 heating j per em. 

 90 hours i square. 



to 90° 0. 



per cm. 

 cube 

 Xl0 c . 



85 



88 

 86 

 84 



5-7210-6 

 5-7510-6 

 8-92 10-6 



2-339 



3080 

 2-588 

 1-852 



1-561 1-210 

 2-538 1 1-397 

 1-892 1 1-383 

 1-410 j 0-791 



1 



6-9 



7-9 

 120 



The specific resistance of film No. 86 appears considerably 

 greater than that for the other films, but this was most pro- 

 bably due to the crystalline structure of the film which was 

 lacking in the others. 



It will be seen from Table VIII. that heating has a 

 considerable effect on the resistance of the films, although 

 probably not so much as in the case of platinum. Film No. 85 

 was heated in vacuo by the electric current for 4J hours 

 withOo ampere, and then for 2 hours with 0*75 ampere, when 

 the resistance became 2*068 ohms. In this case the electric 

 current increased the resistance instead of diminishing it. 

 These results are sufficient to show that in silver, as well as 

 in platinum and bismuth, the specific resistance is much 

 greater than for silver in bulk, and consequently these 

 experiments were not pursued further. 



Some thick silver films were also made by depositing 

 the silver from the solution known as Common's silvering 

 solution*. 



The films were thoroughly dried and their resistances 

 measured. They were then heated, one in vacuo by the 

 electric current, and the other in a hot-air bath, while the 

 third was left exposed to the air. Table IX. (p. 670) exhibits 

 the effect of heat on these films. 



The resistances were measured at the temperature of the 

 room, and a slight change in that would account for the small 

 difference obtained in the second case. It would seem from 



* Proc. R. I. vol. xiii. (1890-92). 



