Influence of Vacuum Conditions on Epitaxially Grown Permalloy Films

Abstract

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.