Structure-property relations characterizing the devitrification of Ni-Zr glassy alloy thin films

Abstract

The investigation of devitrification in thermally annealed nanodimensional glassy alloy thin films provides a comprehensive understanding of their thermal stability, which can be used to explore potential applications. The amorphous to crystalline polymorphous transformation of cosputtered Ni-Zr alloy (Ni78Zr22 at. %) films, with a thickness lower than the reported critical limit of devitrification, was studied through detailed structural characterization and molecular dynamics (MD) simulations. Devitrification to a nanocrystalline state (Ni 7 Zr 2 structure) was observed at 800°C, with an increase in density (∼3.6%) much higher than that achieved in bulk alloys. Variation in the magnetic property of the films and the overall physical structure including morphology and composition were examined before and after annealing. MD simulations were employed to effectively elucidate not only the high densification but also the increased magnetic moment after annealing, which was correlated with the simulated change in the coordination number around Ni atoms. The structural relaxation process accompanying devitrification was described as a disorder-to-order transformation while highlighting the crucial role played by chemical short range order prevalent in glassy materials.

Thermal stability of interfacial mixed layers in c-Ni/a-Zr multilayer during annealing: Structural and magnetic properties

“…Another aspect of the likely candidates for demixing in a binary system which was brought out by the same simulation studies was that, the attraction between dissimilar atoms exceeds that between like atoms. This is pertinent to the Ni-Zr system as well [36]. In the present study, the demixing of atoms in the Ni-on-Zr layer caused the enthalpy of the system to drop.…”

“…XRR and PNR techniques are non-destructive tools which are used in a complementary manner to probe chemical and magnetic profiles of layered structures and binary materials [36,37]. The average layer thickness and average surface roughness for the Ni, Ni-on-Zr, Zr and Zron-Ni layers of the as-deposited and annealed Ni/Zr multilayers obtained from reflectivity data analyses are plotted in Fig.…”

“…( 1) and ( 4) and following the methodology outlined in ref. [36]. The number of atoms/cc of Ni and Zr each in the mixed interface layers of the as-deposited and annealed multilayers derived from these analyses, are graphically represented in the stacked column Comparing these values for the interface layers it is seen that the Ni concentration in the Ni-on-Zr layer at R.T. was higher than that in the Zron-Ni layer, while the Zr concentration at R.T. showed a reverse trend.…”

Structural properties and surface oxidation states of sputter‐deposited TiO2−x thin films

“…Used in specular mode, XRR experiments probed the electronic densities, which were averaged in the sample plane but varied along the depth of the sample. The associated depth‐dependent electron scattering length density (ESLD) in units of Å −2 , which is a function of number of atomic components per unit volume for a binary system, is given as , where r e (=2.818 fm) is the classical electron radius and N i and Z i are the depth‐dependent number density per unit volume and charge number, respectively, of the i th component of the binary system under study 44 . The thicknesses of the films were measured between 515 and 672 Å with different sputter powers at both RT and T s .…”

“…where r e (=2.818 fm) is the classical electron radius and N i and Z i are the depth-dependent number density per unit volume and charge number, respectively, of the ith component of the binary system under study. 44 The thicknesses of the films were measured between 515 and 672 Å with different sputter powers at both RT and T s .…”