In-situ TEM tensile testing of DC magnetron sputtered and pulsed laser deposited Ni thin films

Hugo, Richard; Kung, H.; Weertman, J.; Mitra, Rahul; Knapp, J. A.; Follstaedt, D. M.

doi:10.1016/s1359-6454(02)00599-2

Cited by 211 publications

(86 citation statements)

References 13 publications

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“…Stress vs. strain curves of two free-standing Au film specimens tested at the same strain rate of 6 Â 10 À3 s À1 using a strain gauge and a piezoresistive loadcell. [3,27]. Hugo et al [27] reported that DC magnetron-sputtered (DCMS) Cu films had a lower elastic modulus compared to pulsed laser-deposited films.…”

Section: Resultsmentioning

confidence: 99%

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Strain rate sensitivity of nanocrystalline Au films at room temperature

et al. 2010

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Dimitrios, "Strain rate sensitivity of nanocrystalline Au films at room temperature" (2010) AbstractThe effect of strain rate on the inelastic properties of nanocrystalline Au films was quantified with 0.85 and 1.76 lm free-standing microscale tension specimens tested over eight decades of strain rate, between 6 Â 10 À6 and 20 s À1 . The elastic modulus was independent of the strain rate, 66 ± 4.5 GPa, but the inelastic mechanical response was clearly rate sensitive. The yield strength and the ultimate tensile strength increased with the strain rate in the ranges 575-895 MPa and 675-940 MPa, respectively, with the yield strength reaching the tensile strength at strain rates faster than 10 À1 s À1 . The activation volumes for the two film thicknesses were 4.5 and 8.1 b 3 , at strain rates smaller than 10 À4 s À1 and 12.5 and 14.6 b 3 at strain rates higher than 10 À4 s À1 , while the strain rate sensitivity factor and the ultimate tensile strain increased below 10 À4 s À1 . The latter trends indicated that the strain rate regime 10 À5 -10 À4 s À1 is pivotal in the mechanical response of the particular nanocrystalline Au films. The increased rate sensitivity and the reduced activation volume at slow strain rates were attributed to grain boundary processes that also led to prolonged (5-6 h) and significant primary creep with initial strain rate of the order of 10 À7 s À1 .

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Section: Resultsmentioning

confidence: 99%

“…[3,27]. Hugo et al [27] reported that DC magnetron-sputtered (DCMS) Cu films had a lower elastic modulus compared to pulsed laser-deposited films. Based on TEM images, the authors concluded that the reduced stiffness was a result of porosity in DCMS films due to gas entrapment.…”

Section: Resultsmentioning

confidence: 99%

Strain rate sensitivity of nanocrystalline Au films at room temperature

et al. 2010

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“…Gradual, and not sudden, change of contrast was observed in some grains (grain A, Fig. 2) over many strain increments, perhaps induced by grain rotation and or global tilting of the film (30,31). The specimens behaved as macroscopically brittle and failed at Ϸ680 MPa with a crack initiating from the edge and advancing both through the grain boundaries and grain interiors.…”

Section: Experimental Methodsmentioning

confidence: 95%

“…We overcome the difficulty by developing microinstrumentation that combines quantitative tensile testing of thin films with the qualitative capabilities of the transmission electron microscope (TEM) so that one can simultaneously measure the stress-strain states in solids and observe the deformation mechanisms during materials testing. Although the TEM has so far been a major analytical instrument in materials research (29), nonuniformity in specimen cross-section and space restrictions for the accommodation of force and displacement sensors have limited its application to qualitative in situ straining without simultaneous measurement of stressstrain response (30)(31)(32). Our experimental setup consists of a free-standing tensile sample with uniform width and thickness, cofabricated with a microtensile stage with force and displacement sensors.…”

Section: Experimental Methodsmentioning

confidence: 99%

Deformation mechanisms in free-standing nanoscale thin films: A quantitative in situ transmission electron microscope study

Haque

Saif

2004

Proc. Natl. Acad. Sci. U.S.A.

240

115

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We have added force and displacement measurement capabilities in the transmission electron microscope (TEM) for in situ quantitative tensile experimentation on nanoscale specimens. Employing the technique, we measured the stress-strain response of several nanoscale free-standing aluminum and gold films subjected to several loading and unloading cycles. We observed low elastic modulus, nonlinear elasticity, lack of work hardening, and macroscopically brittle nature in these metals when their average grain size is 50 nm or less. Direct in situ TEM observation of the absence of dislocations in these films even at high stresses points to a grain-boundary-based mechanism as a dominant contributing factor in nanoscale metal deformation. When grain size is larger, the same metals regain their macroscopic behavior. Addition of quantitative capability makes the TEM a versatile tool for new fundamental investigations on materials and structures at the nanoscale.N anomechanical behavior of materials has gained considerable attention because of the ever-shrinking dimensions of thin-film materials in microelectronics, data storage, and microelectromechanical sensors͞actuators, and also the advancements in bulk nanostructured materials. Mechanical properties of materials are influenced by their length-scales. For example, yield stress of polycrystalline metals increases with a decrease in grain size [Hall-Petch behavior (1, 2)], and strain-gradientdependent strengthening (3-6) occurs when the specimen size is reduced to the micrometer scale. Dislocations have been attributed to cause both of these behaviors as long as the grain size or the thickness is Ͼ100 nm. At smaller length-scales, straingradient-dependent strengthening disappears (7) and reverse Hall-Petch behavior is observed (8-13). Another less understood size effect observed at nanoscale is the reduction of Young's modulus, which has been attributed to specimen density (13) and grain boundary compliance (14,15). Models that attempt to explain the nanoscale size effect are of two basic types: (i) models describing nanocrystalline materials as twophase composites with grain interiors and boundaries, where the mechanical properties are averaged by simple ''rule of mixtures '' (16, 17); and (ii) models considering dislocation motion (10,18,19), grain boundary sliding (20, 21), and diffusion (12, 22) as competing deformation mechanisms. Although the literature has compelling evidence of these size-effects, the underlying deformation mechanisms are not yet well understood (23). Experimental MethodsDirect experimental observations of the deformation mechanisms mentioned above while the materials behavior is measured quantitatively is difficult at the nanoscale even with the recent novel existing approaches (24-28). We overcome the difficulty by developing microinstrumentation that combines quantitative tensile testing of thin films with the qualitative capabilities of the transmission electron microscope (TEM) so that one can simultaneously measure the stress-strain state...

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“…Some experimental investigations [13][14][15][16] indicate that grain boundary sliding is the prevailing mechanism of deformation for nc and ufg materials. Hugo et al [17] and Kumar et al [18] performed in situ tensile tests in a transmission electron microscope. Their observations reveal that dislocationmediated plasticity plays a dominant role in the deformation of nc Ni.…”

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confidence: 99%

Shear bands at the fatigue crack tip of nanocrystalline nickel

Xie

Hong

2007

Scripta Materialia

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Fatigue crack growth rates in electrodeposited nanocrystalline Ni and its coarse counterpart were experimentally investigated in this paper. The shear bands, called the epsilon plastic zone, were observed on the surface of nanocrystalline Ni samples. The length of the shear bands is close to the estimated size of the plastic zone at the crack tip. Atomic force microscopy measurements indicate that the shear strain in the shear bands and the width of shear bands increase with related crack length.

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In-situ TEM tensile testing of DC magnetron sputtered and pulsed laser deposited Ni thin films

Cited by 211 publications

References 13 publications

Strain rate sensitivity of nanocrystalline Au films at room temperature

Strain rate sensitivity of nanocrystalline Au films at room temperature

Deformation mechanisms in free-standing nanoscale thin films: A quantitative in situ transmission electron microscope study

Shear bands at the fatigue crack tip of nanocrystalline nickel

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