814 THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



was used, and ie is estimated to lie between 200 and 300 A. For that of Fig. 

 14, 1 mg at 8 cm with 6a = 35° was used and h, between 100 and 150 A, is 

 in the optimum thickness range. The micrograph has the appearance of a 

 correctly exposed photographic negative, whereas Fig. 13 resembles an 

 over-exposed negative. Since germanium films are amorphous unless heated 

 to temperatures higher than 300°C, the fine structure is perhaps due to 



Fig. 13 — Germanium replica (/,. ~ 3(X)A, da = 30°) of thermistor flake surface. Reso- 

 lution about 150A. Over-exposed appearance shows replica is thicker than optimum. 



plastic granularity, although some features are probably real in the ther- 

 mistor flake surface. Resolutions are perhaps 150 A (Fig. 13) and 75 A 

 (Fig. 14). A film clearly appears in the shadow in Fig. 14. Germanium shadow 

 films are relatively thinner than silica, indicating that a is greater than 0.5 

 (perhaps 0.7 to 0.8), but thicker than chromium or gold-manganin shadow 

 films. 



Germanium has many advantages as a replicating material. It is easily 



