Electro-mechanical behavior of Al/Mo bilayers studied with in situ straining methods

Kreiml, Patrice; Rausch, Martin; Terziyska, Velislava L.; Köstenbauer, Harald; Winkler, Jörg; Mitterer, Christian; Cordill, Megan J.

doi:10.1016/j.tsf.2018.07.054

Cited by 24 publications

(19 citation statements)

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“…A 135 nm Al film on 50 nm Mo film on 125 µm Upilex-S polyimide was sputter deposited onto precut strips with dimensions 9 mm  60 mm. The sputter deposition was performed in an industrial sized chamber as previously described (9). All samples were deposited at the same time to ensure no differences between deposition runs.…”

Section: Methodsmentioning

confidence: 99%

10‐1: Invited Paper: An In Depth Comparison of Methods to Evaluate Bending Failure for Flexible Electronics

Cordill

Kreiml

2021

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For flexible electrical systems there are no standardized evaluation methods or failure criteria. This study compares in‐situ and ex‐situ bending under similar conditions (2.5% tensile bending strain, 10,000 cycles) in combination with optical and electrical evaluation methods on a 135/50 nm thick Al/Mo bilayer on 125 μm polyimide material system. The results show that under most circumstances the two bending tests studied show inhomogeneous, but comparable damage distribution. The test of electrical conductivity is more meaningful than crack density, as similar crack densities may yield vastly different conductivities when reached with different cycle speeds.

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Section: Methodsmentioning

confidence: 99%

10‐1: Invited Paper: An In Depth Comparison of Methods to Evaluate Bending Failure for Flexible Electronics

Cordill

Kreiml

2021

Symp Digest of Tech Papers

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“…For brittle films a strong and sudden increase in R / R 0 or Δ R / R 0 signals that at least one TTC is long enough to hinder the electric current flow ( Figure 5 a). Many researchers have reported that the sudden increase in resistance is correlated to the observed crack formation in brittle films [ 77 , 78 , 79 , 80 , 81 , 82 , 83 ]. The increase in the electrical resistance of ductile film systems, on the other hand, does not always signal a fracture.…”

Section: Electro-mechanical Testingmentioning

confidence: 99%

“…DOS occurs somewhere between necking and TTCs’ formation because TTCs are much shorter in ductile films and necks can still conduct currents. In the case of ductile film systems, a 10–20% deviation from the constant volume approximation has been used as a failure criterion [ 80 ]. This criterion avoids any opinions as to how “an increase” from the constant volume approximation could be defined ( Figure 5 a).…”

Section: Electro-mechanical Testingmentioning

confidence: 99%

“…Several studies have demonstrated that brittle interlayers cause the early electrical and mechanical failure of ductile films. From experiments and simulations [ 64 ], the early failure of normally ductile films with brittle interlayers, such as Cr, Ti, or Mo [ 64 , 67 , 80 , 122 , 132 , 133 ], has been observed, again independent of the deposition method. In-situ resistance measurements note a deviation from the constant volume approximation well before that of the same film without the interlayer and are dependent on the ductile film thickness [ 80 ].…”

Section: Materials Influencesmentioning

confidence: 99%

“…It should be noted that the thickness ratio between the ductile layer and brittle layer can be used as a design criterion, but it is not universal and is different for every material system. Under monotonic tensile straining in order to suppress TTC formation in the ductile layer, a thickness ratio of 20:1 is best for the Cu/Cr on PI [ 64 ], and for Al/Mo on PI a thickness ratio of 10:1 works well [ 80 ]. However, for Au/Cr also on PI, 5:1 is not enough to hinder TTC formation, especially when the films are 50 nm and 10 nm, respectively [ 67 , 78 ].…”

Section: Materials Influencesmentioning

confidence: 99%

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Materials Engineering for Flexible Metallic Thin Film Applications

2022

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More and more flexible, bendable, and stretchable sensors and displays are becoming a reality. While complex engineering and fabrication methods exist to manufacture flexible thin film systems, materials engineering through advanced metallic thin film deposition methods can also be utilized to create robust and long-lasting flexible devices. In this review, materials engineering concepts as well as electro-mechanical testing aspects will be discussed for metallic films. Through the use of residual stress, film thickness, or microstructure tailoring, all controlled by the film deposition parameters, long-lasting flexible film systems in terms of increased fracture or deformation strains, electrical or mechanical reliability, can be generated. These topics, as well as concrete examples, will be discussed. One objective of this work is to provide a toolbox with sustainable and scalable methods to create robust metal thin films for flexible, bendable, and stretchable applications.

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Electromechanical Behavior of Al/Al₂O₃Multilayers on Flexible Substrates: Insights from In Situ Film Stress and Resistance Measurements

et al. 2022

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In recent years, nanoscale metal/ceramic multilayers have come into greater focus as they exhibit promising mechanical, physical, and chemical properties, useful for a wide range of thermal, mechanical, and environmental conditions. Main efforts include manufacturing and characterization [1][2][3][4][5][6] of such structures as well as different experimental [4,5,[7][8][9][10][11][12][13][14][15] and modeling [9,13,[16][17][18][19] approaches to understand their deformation mechanisms and optimize mechanical properties. Enhancement in both, multilayer hardness and ductility, is achieved compared to rule of mixture values, depending on the bilayer thickness, the thickness ratio between ceramic and metal layers, and interfacial properties. [9,13] For thin layers (>10 nm) the metal can undergo elasticplastic deformation while the ceramic layer deforms elastically until it fails due to cracking; [4] alternatively, highly localized shear deformation may occur as a result of localized stresses at the interfaces. [5,9,15,17,19] When the layer thickness is reduced to a few nanometers, ultra-thin ceramics can plastically co-deform with metal layers, as has been demonstrated for Al/TiN. [4,18] Substantial intrinsic ductility at small scales has also been demonstrated for amorphous oxides (40 nm Al 2 O 3 ) [20] provided that the material is dense and free of geometrical flaws, whereby mechanical characterization remains experimentally challenging.Metal/ceramic multilayers are of interest for flexible thin-film applications, providing a unique combination of high strength, good conductivity, and potential damage tolerance due to sublayer fragmentation and crack deflection at interfaces.

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Electro-mechanical behavior of Al/Mo bilayers studied with in situ straining methods

Cited by 24 publications

References 24 publications

10‐1: Invited Paper: An In Depth Comparison of Methods to Evaluate Bending Failure for Flexible Electronics

10‐1: Invited Paper: An In Depth Comparison of Methods to Evaluate Bending Failure for Flexible Electronics

Materials Engineering for Flexible Metallic Thin Film Applications

Electromechanical Behavior of Al/Al₂O₃Multilayers on Flexible Substrates: Insights from In Situ Film Stress and Resistance Measurements

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Electro-mechanical behavior of Al/Mo bilayers studied with in situ straining methods

Cited by 24 publications

References 24 publications

10‐1: Invited Paper: An In Depth Comparison of Methods to Evaluate Bending Failure for Flexible Electronics

10‐1: Invited Paper: An In Depth Comparison of Methods to Evaluate Bending Failure for Flexible Electronics

Materials Engineering for Flexible Metallic Thin Film Applications

Electromechanical Behavior of Al/Al2O3Multilayers on Flexible Substrates: Insights from In Situ Film Stress and Resistance Measurements

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Electromechanical Behavior of Al/Al₂O₃Multilayers on Flexible Substrates: Insights from In Situ Film Stress and Resistance Measurements