PYROLYTIC FILM RESISTORS.* CARBON AND BOROCARBON 



309 



conditions and of the nature of the parent hydrocarbon. The specific resist- 

 ance of borocarbon films, however, is a function of boron content, and it 

 can be varied over a wide range, as shown in Fig. 22. Associated with this 

 dependence of specific resistance on boron content there is a corresponding 

 dependence of a, the relationship between a and specific resistance being 

 shown in Fig. 23. 



1.0 

 0.8 



0.6 

 0.5 

 0.4 



0.3 

 0.2 



0.08 



I 0.06 

 O 0.05 



> 0.03 



H 0.02 

 IS) 



<n 



CL 



0.01 

 0.008 



0.006 

 0.005 

 0.004 

 0.003 





0.3 0.4 0.6 0.8 1.0 2 3 4 5 6 8 10 



BORON CONTENT OF FILM IN PER CENT 



Fig. 22 — Dependence of the specific resistivity of borocarbon films on boron content. 



As for pyrolytic carbon films, the value of a for pyrolytic borocarbon films 

 of constant composition depends on the film thickness. However, the nature 

 of this relationship is dependent on the boron content of the film, as illus- 

 trated by Fig. 24 for three different boron contents and hence three differ- 

 ent specific resistances. Film thickness is given in terms of fihn resistance 

 and hence to each of these curves there corresponds a separate scale of 

 geometrical film thickness. The greater is the specific resistance of the film, 

 the greater, of course, is the actual thickness at any given film resistance. 

 It will be noted that at, for example, a film resistance of 2000 ohms the value 



