THERMAL ANNEALING BEHAVIOR OF AMORPHOUS NICKEL-NIOBIUM (METALS, THIN FILM REACTIONS, STRUCTURAL RELAXATION, STABILITY, OVERLAYERS)

The structural relaxation of sputter deposited and melt quenched amorphous Ni-Nb (a-(Ni-Nb)) in the 40-60 at. % Nb range has been investigated. Through resistivity change measurements, three relaxation regimes have been identified: (1) relatively rapid processes during heating at 3C/min. between (DBLTURN)300 and 450C; (2) a transition in resistance change behavior at (DBLTURN)450C; (3) a steady continuous decrease in resistance with further heating above 450C until the onset of crystallization. With high depth resolution Rutherford Backscattering, it was possible to observe the effects of structural relaxation on the penetration rate of Au from an overlayer and the early stages of nucleation and growth of the Au-Ni-Nb ternary compound. Extremely high depth resolution, (DBLTURN)15A, was obtained through a grazing angle incident scattering geometry, aligned with a laser, and calibration with a suitable standard. Interdiffusion between the a-(Ni-Nb) and the Au overlayer produced two layers: a Au-Nb layer, and a Au-Ni-Nb ternary compound. Preannealing, prior to the deposition of the Au overlayer, was found to reduce the Au diffusivity, at 450C, from 1.31 x 10('-17)cm('2)/sec to 1.44 x 10('-18)cm('2)/sec. The most significant regime of relaxation in terms of the effect on Au transport in a-(Ni-Nb) is the low temperature region below about 450C which appears to include irreversible processes. Metallic overlayer films influence the thermal stability of amorphous films. The extent of the influence for a-(Ni-Nb) ranges from dramatic in the case of Ni (T(,x) reduced by 200C) to essentially inert in the case of Nb (T(,x) unchanged). It appears possible to interpret the influence of a given overlayer metal in terms of the metastable phase equilibria that can be established between the overlayer and the glass. The metastable phase diagram can serve as a guide to the selection of overlayers that will minimize the reduction in thermal stability and perhaps enhance the intrinsic stability. The results show several controlling parameters and indicate some of the operating atomic mechanisms which govern the behavior of a-(Ni-Nb) in a high temperature environment.