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Issue 29, 2018
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Unraveling the discrepancies in size dependence of hardness and thermal stability in crystalline/amorphous nanostructured multilayers: Cu/Cu–Ti vs. Cu/HfO2

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Abstract

Crystalline/amorphous interfaces (CAIs) confer outstanding mechanical properties on crystalline/amorphous nanostructured multilayers (C/ANMs), which are widely used in micro/nanodevices, because their unique interfacial structure possesses high strain compatibility. In this study, Cu/X (X = Cu–Ti, HfO2) C/ANMs with equal layer thicknesses (h) were comparatively investigated in terms of size-dependent hardness (H) and thermal stability to uncover the fundamental difference(s) between Cu/Cu–Ti and Cu/HfO2. It was found that both as-deposited Cu/Cu–Ti and Cu/HfO2 C/ANMs exhibited a maximum hardness at a critical thickness of h ∼30 nm, which was caused by a transition from confined dislocation gliding to dislocation transmission across the interface. Specifically, the Cu/Cu–Ti C/ANMs exhibited annealing hardening, whereas the Cu/HfO2 C/ANMs exhibited annealing softening associated with a minimum softening at h ∼ 30 nm, which was closely correlated with their thermal stability. In comparison with monolithic amorphous X thin films, the glassy X nanolayers in the present Cu/X C/ANMs exhibited reduced thermal stability and a trend that smaller sizes led to higher stability. The underlying mechanism of the size-dependent crystallization behavior of X nanolayers is discussed in terms of the constraining effects of the interface. These findings provide deep insights into the design of Cu/metallic-glass and Cu/ceramic-glass C/ANMs with optimal performance.

Graphical abstract: Unraveling the discrepancies in size dependence of hardness and thermal stability in crystalline/amorphous nanostructured multilayers: Cu/Cu–Ti vs. Cu/HfO2

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Publication details

The article was received on 21 Mar 2018, accepted on 04 Jul 2018 and first published on 05 Jul 2018


Article type: Paper
DOI: 10.1039/C8NR02327A
Citation: Nanoscale, 2018,10, 14331-14341
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    Unraveling the discrepancies in size dependence of hardness and thermal stability in crystalline/amorphous nanostructured multilayers: Cu/Cu–Ti vs. Cu/HfO2

    T. Yue, Y. Q. Wang, J. Y. Zhang, K. Wu, G. Li, J. Kuang, G. Liu and J. Sun, Nanoscale, 2018, 10, 14331
    DOI: 10.1039/C8NR02327A

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