HALL EFFECT AND SPECIFIC RESISTANCE IN EVAP- 
ORATED FILMS OF SILVER, COPPER AND IRON 
J. C. STEINBERG 
Previous investigators have found the specific resistance a con- 
stant for metallic films, until the thickness becomes comparable with 
particle dimensions, at which thickness the resistance becomes very 
great. Wait 1 found the resistivity of chemically deposited silver 
films, whose thicknesses were greater than the above mentioned criti- 
cal thickness, to be only slightly greater than that of the bulk metal. 
He found the Hall effect in these films, as well as in films whose 
thicknesses were less than the critical thickness, to be the same as 
that of bulk silver. On the conception that the substance in a film 
consists of granules not in the intimate contact obtaining in the 
bulk form, these results could be accounted for. Consequently it 
became desirable to investigate silver films obtained by an evap- 
oration method, in order to ascertain how they differ from chemi- 
cally deposited films, and how these differences affect their pro- 
perties. 
Evaporated films are obtained by carrying an electrically heated 
filament of the metal back and forth over a glass microscope slide 
in high vacuum. The filament when sufficiently hot ejects par- 
ticles of metal which adhere to the slide, giving a hard uniform 
film. The surfaces of these films reflect very well without the 
aid of artificial polishing. No trace of structure is visible under 
the microscope. Hull’s method of X-ray analysis shows lines simi- 
lar to those in the bulk metal, from which it is inferred that the 
films are crystalline, the elementary crystal being of the same 
type as that found by Hull for the respective bulk metals. It is 
thought that the films possess a very fine grain. 
The resistivity of evaporated films is much greater than that 
of the bulk metal, in the case of copper and silver about 1000 
per cent. Also the critical thickness for evaporated silver films is 
less than that for chemically deposited silver films. 
The Hall coefficient for evaporated silver and copper films is 
only slightly less than that for the bulk metal, whereas for evap- 
1 State University of Iowa, Physics Laboratory. 
