Thermo mechanical properties and plastic deformation of gold nanolines and gold thin films

Under mechanical loading, nanocrystalline metals show unique behaviour, among the most common of which are high strength, mechanically induced grain growth and twin formation. However, mechanically induced grain growth is seldom correlated with twins. Here we report a clear relationship between grain growth and nanoscale twins in 20-nm-thick gold films with a grain size of B19 nm under cyclic loading based on atomic-scale observations and analyses. We find that the formation of nanotwins is an effective way to assist grain coarsening, following a fundamental process that the mutual formation of nanotwins in two neighbouring grains changes the local grain orientation and dissociates the grain boundary into new segments, which become more mobile. The proposed mechanism of nanotwin-assisted grain growth may have important implications for understanding the interface-mediated mechanisms of cyclic plastic deformation and for the interface engineering design of nanostructured metals with both high strength and good fatigue resistance.

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“…Such a strain range is expected to cause a high stress range 33 . Features of fatigue damage in the gold film (Fig.…”

Section: Resultsmentioning

confidence: 99%

Nanotwin-assisted grain growth in nanocrystalline gold films under cyclic loading

2014

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“…The ultimate tensile strength of the gold thin film at room temperature varies from 0.7 to 1.45 GPa. 45 Even though a very small free oscillation amplitude is chosen, the maximum compressive stress is larger than the ultimate tensile strength of the gold, predicting that tip wear will occur.…”

Section: Resultsmentioning

confidence: 99%

Practical Method to Limit Tip–Sample Contact Stress and Prevent Wear in Amplitude Modulation Atomic Force Microscopy

Vahdat

Carpick

2013

ACS Nano

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Amplitude modulation atomic force microscopy (AM-AFM) is one of the most popular AFM modes because of the reduced tip-sample interaction, compared to contact mode AFM, and the ability to acquire high-resolution images while interrogating the sample's material composition through phase imaging. Despite the reduced tip-sample interaction, tip and sample wear can occur through gradual atomic scale processes that can significantly accumulate due to the high frequency of the tip-sample interaction and through high intermittent contact stresses. Starting from existing analytical formulations, we introduce a method for selecting an appropriate probe and free oscillation amplitude that avoids exceeding a critical contact stress to minimize tip/sample damage. The approach is presented for the case of both a Hertzian- and a Derjaguin-Müller-Toporov-like tip-sample contact. Stress maps and related simplified formulas are provided that enable one to determine allowable free oscillation amplitudes to stay below a target contact stress for given cantilever and sample parameters (combined into a single "cantilever-sample constant" that we introduce). Experimental results show how sharp silicon tips, either uncoated or coated with diamond-like carbon and silicon nitride, interacting with a hard and wear-resistant sample (ultrananocrystalline diamond) can be preserved while attaining high-quality AM-AFM images by using our proposed scheme. We also show that using our analysis to select parameters that exceed the target contact stress indeed leads to significant tip wear. This method provides AM-AFM users with a better understanding of contact stresses and enables selection of AM-AFM cantilevers and experimental parameters that preserve the tip for long periods of use and prevents the sample from damage.

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“…To further enhance the reliability and lifetime of such devices, it is important to understand the deformation behavior with respect to the film thickness or grain size. A multitude of studies concerning the deformation behavior of thin films with a face-centered cubic (FCC) or bodycentered cubic (BCC) structure like Cu, Au or Cr can be found in literature [9][10][11][12][13][14][15]. However, a thorough understanding of the deformation mechanism of hexagonal close-packed (HCP) thin films like cobalt, especially for nanocrystalline cobalt, is still lacking.…”

Section: Introductionmentioning

confidence: 99%

Effect of annealing on the size dependent deformation behavior of thin cobalt films on flexible substrates

et al. 2017

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Thermo mechanical properties and plastic deformation of gold nanolines and gold thin films

Cited by 17 publications

References 39 publications

Nanotwin-assisted grain growth in nanocrystalline gold films under cyclic loading

Nanotwin-assisted grain growth in nanocrystalline gold films under cyclic loading

Practical Method to Limit Tip–Sample Contact Stress and Prevent Wear in Amplitude Modulation Atomic Force Microscopy

Effect of annealing on the size dependent deformation behavior of thin cobalt films on flexible substrates

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