PHASE-FORMATION IN COEVAPORATED NI-CR THIN-FILMS

Ni-Cr thin films with chromium concentrations spanning the 0-100% rang e were coevaporated onto NaCl substrates held at room temperature, 200 and 300 degrees C. Analytical transmission electron microscopy provid ed complete identification of the phases present in the films and char acterization of their microstructures. Films of 0-40% Cr contained gra ins of the f.c.c. solid solution of chromium in nickel which, when for med at 200 or 300 degrees C, exhibited {111}[11 $$($) over bar 2] twin ning. Films of 50-70% Cr deposited onto room temperature substrates co ntained nanocrystalline sigma phase, while larger grains of sigma phas e were found for elevated substrate temperature depositions. Films of 80% Cr, deposited onto 300 degrees C substrates, contained delta phase with the A15 structure in addition to the b.c.c. solid solution of ni ckel in chromium observed in films deposited onto lower temperature su bstrates. These observations are discussed in terms of thermodynamic c alculations and electron phase considerations as they apply to the Ni- Cr alloy system.