The initial growth structure of Ni1-xFex (x=0.6-0.8) films dc-biased plasma-sputter-deposited on Ni/MgO(001), and on Fe/MgO(001)

Cross sectional and plane-view transmission electron microscopy (X- and PV- TEM) were used to investigate the initial growth phase of 5, 10, 20 and 40 nm thick Ni1-xFex (x = 0.6-0.8) films, prepared on MgO(001) covered with a buffer layer of Fe or Ni as well as on naked MgO(0001). The 100 nm thick bu ffer layers of Fe and Ni were pre-grown on MgO(001). All of Ni0.20Fe0.80, N io(0.40)Fe(0.60), Fe and Ni films could be epitaxially grown at 250 degrees C by de-biased plasma sputtering at 2.9 kV in pure Ar gas. The films of Ni0.20Fe0.80 and Ni0.40Fe0.60 were grown in their own stable p hase, bce and fee on MgO(001), respectively. However, Ni0.20Fe0.80 film cou ld be grown in fee phase pseudomorphic with Ni(001) up to 20 nm thick on Ni /MgO(001), while Ni0.40Fe0.60 film in bce phase pseudomorphic with Fe(001) up to 10 nm thick on Fe/MgO(001). With increasing thickness, their growth p hases transformed into their own stable phases. Whether or not the pseudomo rphic phase may be induced and what its critical thickness may be should de pend primarily on the lattice misfit between the crystal planes in contact. The growth mode of Ni0.40Fe0.60 film was investigated more in details to b e compared with the simulations of the average strain energy versus thickne ss and with those of the critical thickness of the pseudomorphic films vers us the lattice misfit between the contacted crystal planes. (C) 2001 Elsevi er Science B.V. All rights reserved.