Influence of Vacuum Conditions on Epitaxially Grown Permalloy Films

Permalloy films (83 wt% Ni-17 wt% Fe) epitaxially grown on (100) NaCl were examined in the electron microscope before and after beam annealing. An ultra-high vacuum system with an ultimate vacuum of 10−10 Torr and a vacuum system with an ultimate vacuum of 10−6 Torr were used for the evaporation. Films at 10−5 Torr were prepared in both systems to rule out the influence of the vacuum system on the films. Evaporation rates were adjusted to either 30 Å/sec or 14 Å/min. Electron micrographs and electron diffraction patterns showed that the films ranged from polycrystalline for films evaporated at 30 Å/sec and 10−5 Torr to single crystalline with grains of several millimeters diameter for films evaporated at 30 Å/sec and 10−9 Torr. The crystallographic misorientation varied widely in films which were partially single crystalline and amounted to only a few degrees over areas up to ⅛-in. diameter for films which exhibited perfect single-crystal electron diffraction patterns.