Resistance of a Sputtered Film after Deposition, 151 



-expected from what is known of the relative sorption of 

 hydrogen and air in palladium. 



The latter stages in the examination of film P deserve 

 notice. After exposure to hydrogen for 48 minutes, the 

 film was placed in vacuo for 21 minutes and hydrogen was 

 again added. The results are shown as P' at a lower level. 

 The second dose of hydrogen, it will be seen, only caused a 

 small rise in resistance and no succeeding marked fall. It 

 may be assumed that at this stage the film has been trans- 

 formed into a state in which the sorption of hydrogen is 

 -only slight. The rate at which palladium takes up hydrogen 

 is known to vary not only with the form of palladium 

 employed, but also with different samples of the same 

 lind. 



The result of adding hydrogen to platinum films deposited 

 in hydrogen is similar to that with palladium, and needs 

 no further comment. The addition of hydrogen to platinum 

 films deposited in air gave changes in resistance which varied 

 in magnitude and in sign for different films. The following 

 examples may be cited of films, deposited in air, to which 

 hydrogen and air were added alternately, the pump being 

 applied between the additions. 



(1) Film K. (Resistance 3400 ohms.) The first addition 



of hydrogen gave a small rise of 0'8 per cent, in 



14 minutes ; subsequent additions gave small falls 



from 2 per cent, to 0*5 per cent, in 10 minutes. Air 



always gave a rise in resistance. 



{2) Film L. (Resistance 7660 ohms.) Small rises, from 



2 per cent, to 0*2 per cent, in 25 minutes, followed 



every addition of hydrogen. The rise given by the 



first addition of hydrogen is shown in curve L (fig. 2). 



It will be seen that the change of resistance-time curve 



is similar to those for the addition of air. As before, 



a rise in resistance always followed the admission 



of air. 



(3) Film M. (Resistance 4900 ohms after having been 



subjected to several treatments of air but none of 



hydrogen.) The resistance fell to 1900 ohms in 



80 minutes on the addition of hydrogen. Subsequent 



additions of hydrogen and air both gave slight rises, 



in the former case followed by a fall. 



If it be assumed, as seems probable, that the relative 



values of the direct effect of hydrogen on the resistance 



and the indirect effect due to evolution of heat in sorption 



