UTAH ACADEMY OF SCIENCES 177 
THE VARIATION OF THE ELECTRIC CONDUCTIVITY 
OF THIN METALLIC FILMS. 
By ORIN TUGMAN. 
(Abstract). 
It is known that the electrical conductivity of a very 
thin sheet of metal may change rapidly with time. Films 
of metal, made by chemical deposition and by a cathode 
discharge, show this change. Usually the conductivity 
increases with age so that in a few hours after the film is 
made its resistance has decreased to one half of its former 
value. 
This phenomenon has been explained by the emission 
of occluded gases which when escaping allow the particles 
of deposited metal to coalesce. 
The experiment described in this abstract was done to 
find the effect, if any, of violet light on the conductivity 
of thin metal films. Silver films were made by chemical 
deposition on glass. The Brashear formula using Rochelle 
Salts to precipitate the metallic silver, was used. 
In ordinary daylight the resistance of such films de- 
creased, from the beginning the thin film showing a more 
marked change than thick films. Under the light from 
a quartz mercury lamp the resistance increased with the 
first incidence of the illumination. If the film was taken 
out of this light the resistance again began to decrease. A 
film left in the light from the quartz lamp for several days 
showed an increase of resistance to infinity. An examina- 
tion of the film revealed a dark brown deposit on the glass 
which was soluble in ammonium hydroxide. It is evident 
that the silver becomes oxidized under the ultra violet light 
and that the increase of resistance is due to this chemical 
change. 
These thin films are more readily oxidized under ultra 
violet light than the surfaces of thick plates. A polished 
plate was under this illumination for thirty-six hours and 
showed no oxidation. 
More extended experiments of this nature are in 
progress. 
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