REPLICA AND SHADOWING TECHNIQUES 



enables a high resolvmg power to be obtained; 

 the shadows cast are extremely sharp. 



A mixture of platinum and carbon in the 

 form of rods is evaporated by the passage of 

 a high current through the points of the rods 

 which are sprung together in a vacuum. 

 These points are situated a short distance 

 from a 2-mm aperture which is aligned with 

 the specimen to be shadowed. The aperture 

 reduces inherent background structure to a 

 very small size. 



Shadowing Direction 



The electron micrographs obtained appear 

 to have a resolving power better than that 

 obtained using platinum metal. Very fine 

 step structures can be seen in Figure 9, 

 which is a platinum/carbon replica of a 

 crystal of the mineral sodium faujasite. 



Many other devices, such as nozzle sys- 

 tems (23), have been employed in attempts 

 to improve the results obtainable by conven- 

 tional shadowcasting materials. 



/ 



=J 



parbon 



r ." ' I Shadowing 

 J^y^etol 



Shadowing Direction 



/Shadowing 

 Corbon 



Slide 



specimen 



(a) 



Slide 



J~L 



Metal Specimen 



Metal Specimen 



5hodow,ng^D,rection K^r'^^/l'SrCn 



/5nodowing 



Metal 



Carbon Replica 



Carbon Replica 

 © 



Direction of Carbon Evoponotion 



Corbon Film 



H 



1 



Slide.- 



/ 



Specimen 



Ce) 



Fig. 10. Diagrammatic representation of the various ways of shadowing a replica. (By courtesy of 

 the Journal of Applied Physics) 



237 



