Phase Composition and Structure of Nanocrystalline Films of NiCu, NiCo, and NiFe Alloys

Abstract

The work is devoted to the study of the crystal structure and phase composition of thin films of NiCu, NiCo, and NiFe alloys. Alloy films with thicknesses of 1-200 nm were obtained in vacuum at a residual gas pressure of ~10-4 Pa. The films were condensed at a rate of ω ≥ 1 nm/s. For electron microscopy studies, both NaCl chips and thin carbon layers were used as substrates. All films underwent stabilizing annealing in a vacuum to T = 700 K. In films based on NiCu and NiCo alloys with effective thicknesses of d < 10 nm, obtained on amorphous substrates at T = 300 K, an island structure was observed. In structurally continuous annealed films of NiCu and NiCo alloys at CCo < 70 wt.%, an fcc structure was formed. For NiCu alloy films, depending on the concentration of the components, the crystal lattice parameter was a = 0.353-0.362 nm. Films of the NiCo alloy at CCo ≥ 80 wt.% had a two-phase composition (fcc + hcp)-solid solution NiCo. Films of the Ni50Fe50 alloy had a fcc lattice with a = 0.359-0.361 nm. Unannealed films exhibited a fine-grained structure; annealing led to an increase in grain size to 50 nm.