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Nanocrystalline NbMoTaW high entropy alloys (HEAs) have attracted significant attention due to their superior mechanical properties at elevated temperatures. However, the fracture behavior of nanocrystalline HEAs is still unknown. In this study, the fracture behavior of thin HEA films was investigated using micro-cantilever bending. The nanocrystalline films demonstrated critical stress intensities of ~3 MPa√m, which is significantly higher than previous single- and bi-crystalline values. This work demonstrates the capability of ion beam assisted deposition to strengthen nanocrystalline thin films with only minor losses in toughness.

Most refractory high-entropy alloys (HEAs) are brittle and suffer from limited formability at ambient temperature. Previous studies imply that grain boundaries affect their fracture behavior, but quantitative studies on the fracture properties of body-centered-cubic HEAs are scarce. Here, using in situ micro-cantilever tests, we show that the fracture toughness of a bi-crystal HEA, Nb 25 Mo 25 Ta 25 W 25 , is one order of magnitude lower than that of single crystalline ones. Atom probe tomography of the bi-crystal HEA reveals element segregation and formation of oxides and nitrides at grain boundaries, suggesting that minimizing grain boundary segregation is critical to improving fracture properties in refractory HEAs.

Sample geometries for micro-mechanical testing, e.g. micro-pillars and micro-cantilevers are primarily produced using gallium focused ion beam technology. However, the effects of the gallium ions on the mechanical properties of metals which are embrittled by liquid metal gallium are still unknown. In this work, micro-compression samples from single crystalline and ultrafine-grained aluminum are fabricated using both xenon and/or gallium ions. The different ions have little effect on the yield strength of single crystalline aluminum. However, for the ultrafine-grained aluminum, the strength is reduced with increasing Ga dose, and considerable differences in the deformation morphology and resulting microstructures are observed.

Diffusion-controlled deformation mechanisms may become relevant for nanocrystalline and nanostructured materials at room temperature. In this paper, the stress–strain behavior of gold nanowires 40 nm wide, 20 nm high and 1 mm long on a flexible substrate was investigated in the temperature range of 173–393 K. For decreasing temperatures, the yield strength and the fracture resistance increase. Both can be qualitatively explained by diffusion-driven deformation. The activation energy at room temperature indicates diffusion on (1 1 1) surfaces.

Metallic conductors on polymeric substrates are frequently used for printed circuit boards or flexible displays. Optimization of these devices is mostly associated with the miniaturization of the conductors which changes their electrical and mechanical properties. We focus on crack formation in gold nano-interconnects about 20 nm high, 40 nm wide and 1 mm long on flexible substrates. The fracture toughness of the gold nanolines is decreased significantly compared to bulk gold.

Dealloying of Au–Ag films has been investigated by quantitative electron probe microanalysis and scanning electron microscopy. For film compositions greater than 44 at.% Au, dissolution of Ag is limited, with individual pores distributed randomly on the surface. Dealloying is enhanced as the initial Au content decreases below 44 at.%. The dealloying threshold, or parting limit, below which the fully nanoporous structure evolves, is 35 at.% Au. Dealloying also causes a slight decrease in film thickness, which is readily measured using the technique discussed here.

The reliability of microelectronic devices is critically affected by the texture of the thin films. It has been demonstrated that ion bombardment during film growth, a process known as ion beam assisted deposition, is an effective tool for texture control. In particular, the use of two beams allows selection of both the in-plane and the out-of-plane texture. In this paper we show that post-deposition ion bombardment of strongly (1 1 1)-fiber textured Au films leads to the preferred growth of a single orientation, thus proving that single crystalline thin films can be fabricated without the use of molecular beam epitaxy technologies.

Ion bombardment leads to grain growth in thin metal films. This phenomenon is usually attributed to thermal spikes during ion–crystal interaction, which enhances grain-boundary mobility, but does not bias the migration process. In this work we show instead that local ion channeling with a focused ion beam can reversibly bias grain-boundary motion.

In their comment (M. Lagos et al., Scripta Mater. (2012), http://dx.doi.org/10.1016/j.scriptamat.2012.04.018 ), Lagos et al. propose a two-dimensional plasticity model based on grain boundary sliding to explain the deformation behavior of ultrathin Cu and Ta/Cu film systems on polyimide substrates. Here, we critically discuss their comments and include new results obtained by peak profile analysis of the original in situ diffraction data; they strongly suggest that the deformation behavior of the different film systems is very likely not self-similar as claimed by Lagos et al.