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Title: Solid-state dewetting of Au/Ni bilayers: The effect of alloying on morphology evolution

Abstract

The solid-state dewetting of thin Au/Ni bilayers deposited onto SiO{sub 2}/Si substrates is investigated. A rapid thermal treatment is used to induce the dewetting process by an increase in temperature. The evolution of the (111) peaks of X-ray diffraction reveals a characteristic change due to mixing of Au and Ni. At low temperature, the Au-Ni thin film is found to break up at the phase boundaries and growing voids are shown to be surrounded by a Ni-rich phase. Branch-like void growth is observed. Upon annealing at increasing temperatures, Au-Ni solid solutions are formed well above the bulk equilibrium solubility of Au and Ni. It is found that this metastable phase formation makes the Au-Ni thin film less vulnerable to rupturing. Moreover, growth mode of still evolving voids changes into a more regular, faceted one due to alloying. Finally, it is shown that annealing above the miscibility gap forms supersaturated, well-oriented Au-Ni solid solution agglomerates via dewetting.

Authors:
; ; ;  [1]
  1. Institute of Materials Engineering and Institute of Micro- and Nanotechnologies MacroNano, Chair Materials for Electronics and Electrical Engineering, TU Ilmenau, Ilmenau 98693 (Germany)
Publication Date:
OSTI Identifier:
22308555
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; CRYSTAL GROWTH; EQUILIBRIUM; EVOLUTION; GOLD; LAYERS; NICKEL; SILICON; SILICON OXIDES; SOLID SOLUTIONS; SOLIDS; SUBSTRATES; THIN FILMS; X-RAY DIFFRACTION

Citation Formats

Herz, A., Wang, D., E-mail: dong.wang@tu-ilmenau.de, Kups, Th., and Schaaf, P.. Solid-state dewetting of Au/Ni bilayers: The effect of alloying on morphology evolution. United States: N. p., 2014. Web. doi:10.1063/1.4891448.
Herz, A., Wang, D., E-mail: dong.wang@tu-ilmenau.de, Kups, Th., & Schaaf, P.. Solid-state dewetting of Au/Ni bilayers: The effect of alloying on morphology evolution. United States. doi:10.1063/1.4891448.
Herz, A., Wang, D., E-mail: dong.wang@tu-ilmenau.de, Kups, Th., and Schaaf, P.. Mon . "Solid-state dewetting of Au/Ni bilayers: The effect of alloying on morphology evolution". United States. doi:10.1063/1.4891448.
@article{osti_22308555,
title = {Solid-state dewetting of Au/Ni bilayers: The effect of alloying on morphology evolution},
author = {Herz, A. and Wang, D., E-mail: dong.wang@tu-ilmenau.de and Kups, Th. and Schaaf, P.},
abstractNote = {The solid-state dewetting of thin Au/Ni bilayers deposited onto SiO{sub 2}/Si substrates is investigated. A rapid thermal treatment is used to induce the dewetting process by an increase in temperature. The evolution of the (111) peaks of X-ray diffraction reveals a characteristic change due to mixing of Au and Ni. At low temperature, the Au-Ni thin film is found to break up at the phase boundaries and growing voids are shown to be surrounded by a Ni-rich phase. Branch-like void growth is observed. Upon annealing at increasing temperatures, Au-Ni solid solutions are formed well above the bulk equilibrium solubility of Au and Ni. It is found that this metastable phase formation makes the Au-Ni thin film less vulnerable to rupturing. Moreover, growth mode of still evolving voids changes into a more regular, faceted one due to alloying. Finally, it is shown that annealing above the miscibility gap forms supersaturated, well-oriented Au-Ni solid solution agglomerates via dewetting.},
doi = {10.1063/1.4891448},
journal = {Journal of Applied Physics},
number = 4,
volume = 116,
place = {United States},
year = {Mon Jul 28 00:00:00 EDT 2014},
month = {Mon Jul 28 00:00:00 EDT 2014}
}
  • Self-assembly of ultrathin Au, W, and Au-W bilayer thin films is investigated using a rapid thermal annealing technique in an inert ambient. The solid-state dewetting of Au films is briefly revisited in order to emphasize the role of initial film thickness. W films deposited onto SiO{sub 2} evolve into needle-like nanocrystals rather than forming particle-like agglomerates upon annealing at elevated temperatures. Transmission electron microscopy reveals that such nanocrystals actually consist of tungsten (VI) oxide (WO{sub 3}) which is related to an anisotropic oxide crystal growth out of the thin film. The evolution of W films is highly sensitive to themore » presence of any residual oxygen. Combination of both the dewetting of Au and the oxide crystal growth of WO{sub 3} is realized by using various bilayer film configurations of the immiscible Au and W. At low temperature, Au dewetting is initiated while oxide crystal growth is still suppressed. Depending on the stacking sequence of the Au-W bilayer thin film, W acts either as a substrate or as a passivation layer for the dewetting of Au. Being the ground layer, W changes the wettability of Au which clearly modifies its initial state for the dewetting. Being the top layer, W prevents Au from dewetting regardless of Au film thickness. Moreover, regular pattern formation of Au-WO{sub 3} nanoparticles is observed at high temperature demonstrating how bilayer thin film dewetting can create unique nanostructure arrangements.« less
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  • During solid-state dewetting of thin single crystal films, film edges retract at a rate that is strongly dependent on their crystallographic orientations. Edges with kinetically stable in-plane orientations remain straight as they retract, while those with other in-plane orientations develop in-plane facets as they retract. Kinetically stable edges have retraction rates that are lower than edges with other orientations and thus determine the shape of the natural holes that form during solid-state dewetting. In this paper, measurements of the retraction rates of kinetically stable edges for single crystal (110) and (100) Ni films on MgO are presented. Relative retraction ratesmore » of kinetically stable edges with different crystallographic orientations are observed to change under different annealing conditions, and this accordingly changes the initial shapes of growing holes. The surfaces of (110) and (100) films were also characterized using low energy electron diffraction, and different surface reconstructions were observed under different ambient conditions. The observed surface structures were found to correlate with the observed changes in the relative retraction rates of the kinetically stable edges.« less