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Exploring nanoscale metallic multilayer Ta/Cu films: Structure and some insights on deformation and strengthening mechanisms

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journal contribution
posted on 2024-05-28, 13:13 authored by Daniel Karpinski, Tomas Polcar, Andrey BondarevAndrey Bondarev

Nanoscale metallic multilayer (NMM) films are systems offering insight into the role of interfaces in metal plasticity, deformation, and strengthening mechanisms. Magnetron sputtering was used to fabricate the Ta/Cu NMM films with a periodicity (equal Ta and Cu layer thickness) from 6 to 80 nm, and with the structure exhibiting immiscible tetragonal β-Ta and face-centred cubic Cu phases. Transmission electron microscopy and X-ray diffraction analyses revealed that, irrespective of the period, all films manifested a polycrystalline structure. The growth direction of both Cu and Ta layers was found to be along 〈001〉 β-Ta || 〈111〉 Cu directions, with the crystallite size constrained by the layer thickness. The studies showed that the Ta/Cu NMMs exhibited compressive residual macro-stress and flow strength, and enhanced elastic recovery at the periodicity of ≤12 nm. Activation volume V* value of 11 to 20 b3 as determined from the indentation creep test under a constant load, may indicate a mixed deformation mechanism. This mechanism likely involves the emission of dislocations from the incoherent Ta/Cu interfaces, as well as the formation of screw dislocations within Cu grains. The high-load indentation test, TEM studies, and the rCLS model collectively demonstrate that all NMM films predominantly undergo plastic deformation. This plastic deformation primarily occurs within the soft Cu layer, while the propagation of dislocations across the incoherent interface is largely excluded.


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Materials Characterization, 2024, 212, 113933



Other Funding information

CzechNanoLab project LM2018110 funded by MEYS CR is gratefully acknowledged for the financial support of the measurements at CEITEC Nano Research Infrastructure and Institute of Physics of the Czech Academy of Sciences. This work was co-funded by the European Union under the project Robotics and advanced industrial production (reg. no. CZ.02.01.01/00/22_008/0004590)

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