932 



THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



at 800°K. To get the redistribution effect it is necessary to have both a 

 high T and a high V. 



It is fascinating and instructive to watch this redistribution progress 

 slowly. To do this we start with a pattern Hke that in photo e with T = 

 300°K and V = 7370 volts. The clusters are steady everywhere. T is then 

 raised to 800°K and the pattern observed for three to ten minutes. At first 

 the clusters in the 110, 211, and 111 regions are in violent agitation while 



Approximate <p in volts 



Size in A for T = 2400°K 



Size in A for T = 1200''K 



Size for large T and F 



''K for W^ migration, F = 0. . . . 

 °K for W migration V = 9000. 



4.2 

 <20 

 <20 

 <20 



Baon W:0 <1 



Size of clusters in A 



°K for cluster formation 



°K for cluster disappearance 



°K for Ba migration 



°K for evaporation: depends on 



300 

 —600 



Baon W;0 >1 



Size of crystallites in A 



°K for crystal formation .... 

 °K for crystal disappearance. 



300 

 800 



the few clusters in the 100 region are stationary. In ten seconds a few more 

 clusters appear in the 100 region. When a new cluster appears it seems to do 

 so suddenly. One gets the impression that one cluster pushed a neighboring 

 one closer to the 100 plane or that one cluster grew at the expense of material 

 from a neighboring one. Gradually as the concentration of clusters in the 

 100 region increases, the brightness of this region increases while the bright- 

 ness in the 110, 211, and HI regions decreases. A steady state is reached in 

 three to five minutes. 



References 



1. E. W. MUller, Pliys. Zs. 37, 838, 1836. 



2. E. W. Muller, Zs.f. P/iysik 106, 541, 1937; 126, (Al, 1949; Naturwissenschajten, July 



1950. 



3. R. O. Jenkins, Reports on Progress in Physics 9, 177, 1942-43. 



4. F. Ashworth, Advances in Electronics, 3, Feb. 1951. 



5. M. H. Nichols, Phys. Rev., 57, 1940 p. 297. 



6. Nordheim, Proc. Roy. Soc. 121, 1928 p. 638. 



7. R. Haefer, ZeUs. f. Physik 116, 604, (1940). 



