Microstructure, stability and thermomechanical behavior of crack-free thin films of nanoporous gold

Sun, Ye; Kucera, Kalan P.; Burger, Sofie; Balk, T. John

doi:10.1016/j.scriptamat.2008.01.036

Cited by 58 publications

(39 citation statements)

References 22 publications

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“…Thermal annealing offers a convenient way to systematically tune the ligament size, which in turn modulates the mechanical properties. After thermal coarsening, a sample-size-dependent ductile-brittle transition was observed in NPG beam [7], and the yield strength of NPG foil was found to decrease when the ligament size increases [11], similar result was obtained in nanoporous Pt-Ni film [15] and NPG film [16]. As the annealing temperature increases, the residual stress for the freestanding NPG beam and the NPG films on substrates was found to increase, while the elastic modulus increases dramatically after a slight initial decrease [4].…”

Section: Introductionsupporting

confidence: 56%

Effect of thermal coarsening on the thermal conductivity of nanoporous gold

et al. 2012

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The thermal conductivities of nanoporous gold (NPG) microwires annealed at different temperatures have been measured in the temperature range from 100 to 320 K. Considering the electron-surface scattering, the thermal conductivity is expected to increase with the increase of ligament diameter. However, the thermal conductivity of NPG microwire is found to decrease after thermal coarsening, and has a maximum value at around 250 K for the as-dealloyed sample. We suggest that the defects accumulating at a relatively high temperature and the reduction in defect spacing may cause these temperature behaviors of thermal conductivity. Taking into account the electron scattering on ligament surfaces and defects, a modified theoretical model for the thermal conductivity of nanoporous metal is proposed to agree with our experimental results.

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Section: Introductionsupporting

confidence: 56%

Effect of thermal coarsening on the thermal conductivity of nanoporous gold

et al. 2012

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“…Within the same time interval, extensive cracking also occurred (Figure 3). In a separate study of crack-free np-Au films, [29] the dissolution of Ag was accompanied by an increase in stress, instead of by the relaxation observed here, implying that the initial formation of nanoporous structure does not reduce film stress. It is, therefore, proposed that the tensile stress expected from the dealloying process was relaxed by cracking, in the films studied here.…”

Section: Dealloying-induced Stress Changesmentioning

confidence: 47%

Evolution of Structure, Composition, and Stress in Nanoporous Gold Thin Films with Grain-Boundary Cracks

Sun

Balk

2008

Metall Mater Trans A

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Nanoporous gold (np-Au) thin films were fabricated from Au-Ag alloy films sputtered onto substrates. At several stages of dealloying, the evolution of the microstructure and Ag content were analyzed and stress in the np-Au thin films was measured. A nanoporous structure evolved almost immediately throughout the film thickness, and the ligament width coarsened during further dealloying, with a time dependence of t 1/8 . The initial alloy films, which contained 25 at. pct Au, became stress free after extended dealloying and during thermal cycling up to 200°C. Preferential dissolution caused cracking at grain boundaries, which accommodated a portion of the volume contraction from dealloying, but the films nonetheless remained attached to their substrates.

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“…The ~35 nm thick Au layer improves adhesion and prevents delamination of the Ag x Au 1-x alloy layer during de-alloying. 25 In addition any potential redox activity of the underlying Ti layer is suppressed. Each metal was sputtered at a constant sputtering rate to produce a ~300 nm thick Ag 67 Au 33 alloy layer with a uniform distribution of Ag throughout the alloy.…”

Section: Methodsmentioning

confidence: 99%

Characterization of Nanoporous Gold Electrodes for Bioelectrochemical Applications

Scanlon¹,

Salaj-Kośla²,

Belochapkine³

et al. 2011

Langmuir

104

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ABSTRACT. The high surface areas of nanostructured electrodes can provide for significantly enhanced surface loadings of electroactive materials. The fabrication and characterisation of nanoporous gold (np-Au) substrates as electrodes for bioelectrochemical applications is described.Robust np-Au electrodes were prepared by sputtering a gold-silver alloy onto a glass support and subsequent de-alloying of the silver component. Alloy layers were prepared with either a uniform or non-uniform distribution of silver and, post de-alloying, showed clear differences in morphology on characterisation with scanning electron microscopy. Redox reactions under kinetic control, in particular measurement of the charge required to strip a gold oxide layer, provided the most accurate measurements of the total electrochemically addressable electrode surface area, A real .Values of A real up to 28 times that of the geometric electrode surface area, A geo , were obtained. For diffusion controlled reactions overlapping diffusion zones between adjacent nanopores established limiting semi-infinite linear diffusion fields where the maximum current density was dependent on A geo . The importance of measuring the surface area available for the immobilisation was determined 2 using the redox protein, cyt c. The area accessible to modification by a biological macromolecule, A macro , such as cyt c was reduced by up to 40 % compared to A real , demonstrating that the confines of some nanopores were inaccessible to large macromolecules due to steric hindrances. Preliminary studies on the preparation of np-Au electrodes modified with osmium redox polymer hydrogels and Myrothecium verrucaria bilirubin oxidase (MvBOD) as a biocathode were performed; current densities of 500 A cm -2 were obtained in unstirred solutions.

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Microstructure, stability and thermomechanical behavior of crack-free thin films of nanoporous gold

Cited by 58 publications

References 22 publications

Effect of thermal coarsening on the thermal conductivity of nanoporous gold

Effect of thermal coarsening on the thermal conductivity of nanoporous gold

Evolution of Structure, Composition, and Stress in Nanoporous Gold Thin Films with Grain-Boundary Cracks

Characterization of Nanoporous Gold Electrodes for Bioelectrochemical Applications

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