It is known that the room-temperature plastic deformation of bulk metallic glasses is compromised by strain softening and shear localization, resulting in near-zero tensile ductility. The incorporation of metallic glasses into engineering materials, therefore, is often accompanied by complete brittleness or an apparent loss of useful tensile ductility. Here we report the observation of an exceptional tensile ductility in crystalline copper/copper-zirconium glass nanolaminates. These nanocrystalline-amorphous nanolaminates exhibit a high flow stress of 1.09 ؎ 0.02 GPa, a nearly elastic-perfectly plastic behavior without necking, and a tensile elongation to failure of 13.8 ؎ 1.7%, which is six to eight times higher than that typically observed in conventional crystallinecrystalline nanolaminates (<2%) and most other nanocrystalline materials. Transmission electron microscopy and atomistic simulations demonstrate that shear banding instability no longer afflicts the 5-to 10-nm-thick nanolaminate glassy layers during tensile deformation, which also act as high-capacity sinks for dislocations, enabling absorption of free volume and free energy transported by the dislocations; the amorphous-crystal interfaces exhibit unique inelastic shear (slip) transfer characteristics, fundamentally different from those of grain boundaries. Nanoscale metallic glass layers therefore may offer great benefits in engineering the plasticity of crystalline materials and opening new avenues for improving their strength and ductility.metallic glass ͉ size-dependent plasticity ͉ nanocrystalline materials ͉ amorphous-crystalline interface ͉ tensile ductility A traditional strategy to develop ultrahigh-strength crystalline materials is to limit or inhibit the motion of dislocations required for plastic deformation (1-3) so that a higher applied stress is necessary. Examples of such advanced materials include thin films (4), nanocrystalline metals (5-7), and nanolaminates (8-10). As dislocation motion in high-strength crystalline materials becomes increasingly difficult (11), the ductility, i.e., the ability of a material to change shape without catastrophic failure, is often reduced dramatically (6, 7). In bulk metallic glasses, plastic deformation is not enabled by dislocations (12-21) but rather by clusters of atoms that undergo cooperative shear displacements [shear transformation zones (STZs)] (16); in the extreme limit of homogeneous-toinhomogeneous flow transition, shear bands of nanoscale width form (17,(19)(20)(21). The formation of such shear bands causes large strain softening and abrupt rupture of the metallic glasses. By way of contrast, large compressive plastic strains have been obtained in several bulk metallic glasses (12)(13)(14). Nonetheless, they show nearzero macroscopic ductility when subjected to tensile loading. To our knowledge, there is no experimental evidence currently suggesting that macroscopic metallic glass samples can sustain large tensile plasticity. An interesting question arises whether shear banding remains...

We present results of the first measurements of density, shock speed and particle speed in compressed liquid deuterium at pressures in excess of 1 Mbar. We have performed equation of state (EOS) measurements on the principal Hugoniot of liquid deuterium from 0.2 to 2 Mbar. We employ high-resolution radiography to simultaneously measure the shock and particle speeds in the deuterium, as well as to directly measure the compression of the sample. We are also attempting to measure the color temperature of the shocked D2. Key to this effort is the development and implementation of interferometric methods in order to carefully characterize the profile and steadiness of the shock and the level of preheat in the samples. These experiments allow us to differentiate between the accepted EOS model for D2 and a new model which includes the effects of molecular dissociation on the EOS.

Coherent twin boundaries (CTBs) are widely described, both theoretically and experimentally, as perfect interfaces that play a significant role in a variety of materials. Although the ability of CTBs in strengthening, maintaining the ductility and minimizing the electron scattering is well documented [1][2][3] , most of our understanding of the origin of these properties relies on perfect-interface assumptions. Here we report experiments and simulations demonstrating that as-grown CTBs in nanotwinned copper are inherently defective with kink-like steps and curvature, and that these imperfections consist of incoherent segments and partial dislocations. We further show that these defects play a crucial role in the deformation mechanisms and mechanical behaviour of nanotwinned copper. Our findings offer a view of the structure of CTBs that is largely different from that in the literature 2,4,5 , and underscore the significance of imperfections in nanotwinstrengthened materials.CTBs formed during growth, deformation or annealing exist broadly in many crystalline solids with low or medium stackingfault energies 1,5,6 . The strengthening behaviour and other attractive properties of CTBs have been studied in nanotwinned metals (with an average twin spacing <100 nm; refs 7-9). One prevalent view is that CTB-strengthened materials have certain advantages over nanocrystalline or ultrafine-grained materials; that is, materials strengthened through traditional grain boundaries (GBs) that are considered incoherent and defective 10 . GBs not only scatter electrons, but can migrate and slide under shear stresses 11 , leading to a maximum in strength in nanocrystalline materials 12,13 . In contrast, such migration/sliding mechanisms may not be operative in CTBs despite some reports of detwinning evidence 7,14,15 and the observation of a similar maximum strength in a nanotwinned copper 3 (nt-Cu). Existing models widely assume perfect CTBs and rationalize flow softening due to CTB migrations and detwinning as caused by nucleation and motion of partial dislocations parallel to CTBs (ref. 4). These mechanisms are informative as long as CTB lengths are limited to the tens of nanometres typically used in molecular dynamics simulations 4,[16][17][18] . It still remains difficult through molecular dynamics simulations to validate the migrations/detwinning of the much longer CTBs seen in experiments (500 nm; ref. 3). There could be alternative mechanisms that are intricately related to the potential structures of CTBs and the characteristics of GBs, both of which are not accounted for in the literature.Recent studies of nanotwinned copper pillars without GBs revealed strong deformation anisotropy and a brittle-to-ductile transition behaviour (where CTBs are considered intrinsically brittle) 2 , suggesting that CTBs alone are not sufficient for increased plasticity despite their strong strengthening effect, and that a reasonable mix of GBs is helpful to mediate the plasticity and achieve high ductility. Experiments and simulations have f...

Recent developments in thin film technology have made possible the construction of multilayered thin film structures that act as efficient Bragg diffractors for x rays and extreme ultraviolet (EUV) radiation. These structures (which we term layered synthetic microstructures or LSMs) are analogous to multilayer interference filters for the visible spectral region and have important potential applications in many areas of x-ray/EUV instrumentation. In this paper the theory of x-ray diffraction by periodic structures is applied to LSMs, and approximate formulas for estimating their performance are presented. A more complete computation scheme based on optical multilayer theory is described, and it is shown that, by adjusting the refractive indices and thicknesses of the component layers, the diffracting properties may be tailored to specific applications. Finally, it is shown how the theory may be modified to take account of imperfections in the LSM structure and to compute the properties of nonperiodic structures.

Commercial EUV lithographic systems require multilayers with higher reflectance and better stability then that published to date. Interface-engineered MoISi multilayers with 70% reflectance at 13.5 nm wavelength (peak width of 0.545 nm) and 71% at 12.7 nm wavelength (peak width of 0.49 nm) were developed. These results were achieved with 50 bilayers. These new multilayers consist of Mo and Si layers separated by thin boron carbide layers. Depositing boron carbide on interfaces leads to reduction in silicide formation on the Mo-on-Si interfaces. Bilayer contraction is reduced by 30% implying that there is less intermixing of Mo and Si to form silicide. As a result the Mo-on-Si interfaces are sharper in interface-engineered multilayers than in standard Mo/Si multilayers. The optimum boron carbide thicknesses have been determined and appear to be different for Mo-on-Si and Si-on-Mo interfaces. The best results were obtained with 0.4 nm thick boron carbide layer on the Mo-on-Si interface and 0.25 nm thick boron carbide layer on the Si-on-Mo interface. Increase in reflectance is consistent with multilayers with sharper and smoother interfaces.A significant improvement in oxidation resistance of EUV multilayers has been achieved with ruthenium terminated MoISi multilayers. The best capping layer design consists of a Ru layer separated from the last Si layer by a boron carbide layer. This design achieves high reflectance and the best oxidation resistance in a water vapor (i.e. oxidation) environment. Electron beam exposures of 4.5 hours in the presence of 5~1 0 -~ torr water vapor partial pressure show no measurable reflectance loss and no increase in the oxide thickness of Ru terminated multilayers. Longer exposures in different environments are necessary to test lifetime stability of many years.. I