Nonequilibrium Structures in Codeposited Cr-Fe-Ni Films

摘要

Ternary libraries are prepared by codeposition of Cr, Fe, and Ni on single-crystal Si and AI2O3 (sapphire) substrates at ~100°C. The varying proximity to the three metal sources produces a spread of compositions in the films, which are analyzed both as-deposited and after annealing in vacuum for 2 h at 500°C. Structural maps are produced using synchrotron radiation and simultaneous detection of 2D diffraction patterns and x-ray fluorescence spectra. Four phases are identified in the as-deposited films. Three phases occur in equilibrium: bec (a), fee (y), and intermetallic (a). The fourth phase does not correspond to any equilibrium phase in the Cr-Fe-Ni system; it is tentatively identified as isomorphic to the a-Mn (A12) structure. After annealing, the nonequilibrium phase is no longer observed, but the occurrence of the three equilibrium phases is still far from the equilibrium phase boundaries. The particle size measured by x rays is small (9-15 nm), suggesting that higher annealing temperatures are required for the growth of equilibrium phases.