Processing and microstructural characterization of sputter-deposited Ni/Ni₃Al multilayered thin films

Abstract

The crystallographic texture, orientation relationships, coherency stress, and thermal stability of sputter-deposited Ni/Ni 3 Al multilayered thin films were studied as a function of bilayer period (⌳) as well as processing parameters such as substrate type, deposition temperature, and prebake conditions. Deposition onto oxidized Si or single-crystal Cu(001), NaCl(001), or KBr(001) substrates near room temperature produces multilayers with a [111] crystallographic texture along the Ni/Ni 3 Al interface normal and a disordered face-centered cubic structure for the Ni 3 Al phase. In contrast, deposition at 673 K onto NaCl(001) or KBr(001) substrates that are prebaked in vacuum at 693 K produces a chemically ordered L1 2 structure for the Ni 3 Al phase and (001) epitaxial growth. X-ray diffraction measurements of (001) multilayers with equal volume fraction of Ni and Ni 3 Al reveals a transition from a nearly incoherent state at ⌳ ‫ס‬ 240 nm to a semicoherent one at ⌳ ‫ס‬ 40 nm. Remarkably, (001) multilayers were observed to solutionize at 1373 K, which is approximately 100 K below that predicted by the Ni-Al phase diagram.

Defect-interface interactions

“…In some materials, stability at elevated temperature further depends on interface crystallography. For example, the temperature to solutionize Ni/Ni 3 Al multilayers is 100 K lower for multilayers with Ni-Ni 3 Al interfaces formed along {100} planes than along {111} planes [424]. The effect of stresses and interface crystallography on the morphological stability of irradiated materials has yet to be investigated in detail.…”

X-Ray Diffraction Studies of Forward and Reverse Plastic Flow in Nanoscale Layers During Thermal Cycling

“…The layer structure remains intact (a) and layer thickness is unchanged (b), suggesting that large-scale diffusion and morphological instability does not occur. [35] The initially planar Si-Cu seed layer interface becomes nonplanar and nearby regions become polycrystalline (c), suggesting formation of copper silicides as in [36]. Diffusion is aided by lack of an appropriate barrier layer.…”

Correlation of stress state and nanohardness via heat treatment of nickel-aluminide multilayer thin films

“…Films are detached from the substrate and viewed in (a) as-is condition, prior to heat treatment; after heating in argon at (b) 673 K for 36 h and (c) 1073 K for 10 h work. 18 The ⌳ ‫ס‬ 50-nm films were encapsulated and then heat-treated at 673 K for 1/36 the time used for ⌳ ‫ס‬ 300-nm films. A 1/36 ratio was chosen because the time t for grain growth driven by reduction of area energy scales as (grain size) 2 which is proportional to ⌳ 2 .…”

“…The ⌳ ‫ס‬ 50-nm samples were not heat-treated at 1073 K due to rapid thermal grooving and pinch-off of layers. 18 Following heat treatment, all samples were air-cooled by removal from the furnace. Figure 1(b) shows that a layered morphology with sharp interfaces is retained after the 673 K heat treatment.…”

“…18 This relation is applicable over a range of temperatures for which the films are morphologically stable with a planar arrangement of phases.…”