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XI. On the Chanye in the Resistance of a Sputtered Film 

 after Deposition. By Miss E. W. Hobbs, B.Sc. (Bristol)*. 



A CONSIDERABLE amount of work has been carried 

 . out by various investigators on the electrical resist- 

 ance of metallic films deposited by cathodic sputtering. In 

 the main, the films dealt with have been previously aged by 

 exposure to air and high temperature after their removal 

 from the discharge-vessel, but in some instances arrangements 

 have been made for measuring the resistance of a film in 

 position during and after deposition. Thus in 1912 f 

 Kohlschiitter and Noll published some results of experiments 

 on thin films of silver deposited in hydrogen, nitrogen, and 

 argon, in which measurements were made in situ of the 

 changes in resistance with time which occur when a film is 

 left in vacuo and in various gases after deposition. The 

 following is an account of experiments on thin films of 

 platinum and palladium carried out on somewhat similar 

 lines,, in which a fuller study of these changes was made. 

 In particular, the effect of admitting gas into the discharge- 

 vessel was investigated in detail; it is this that forms the 

 chief subject of the paper. 



Apparatus. 



The apparatus did not differ in essentials from that usually 

 employed for the deposition of films. The films, 1*2 cm., 

 long and 1 cm. wide, were deposited on polished strips of 

 fused silica, which rested on the anode. In order to measure- 

 their resistance, leads were introduced into the discharge- 

 vessel and contact was made with the film through thick 

 end deposits, in some cases by soldering wires to them and 

 in others by means of a mercury pellet. The latter method 

 was found to be by far the more convenient, and was almost 

 invariably employed. It was quite satisfactory if the mercury 

 were covered by mica disks in order to protect it from 

 electrical bombardment. An exploring point connected to 

 a Braun electrometer was introduced for measuring the 

 cathode fall of potential during deposition, and the current 

 was controlled by a cadmium-iodide amyl alcohol adjustable 

 resistance. While adjustments were being made, the silica 

 could be screened by a mica shield, rotated by a ground- 

 glass joint, but it was not necessary to use this in most of 

 the work. 



* Communicated by Dr. A. M. Tyndall. 



t Zeitschrift fur Electrochemie, vol. xviii. p. 419 (1912). 



