1 of 9) 1605928applications. [8][9][10][11][12][13][14] A spin quantum Hall state is also predicted in the distorted octahedral phase (1T′) of MX 2 in the monolayer limit, further extending applications of TMDs into spintronics and lowdissipation electronics. [13] As a part of the TMDs family, WTe 2 has recently attracted great interest due to its giant, nonsaturating magnetoresistance (MR) observed in bulk crystals, [15] and its predicted Weyl state. [16] Pressure-induced superconductivity and large spin-orbit coupling are also observed. [17,18] In addition, the lattice thermal conductivity of WTe 2 is predicted to be smaller than that of WSe 2 due to the heavier atom mass and the lower in-plane crystal symmetry. [19] Studies on WTe 2 have so far been carried out using bulk crystals or mechanically exfoliated flakes. Although mechanical exfoliation can produce high-quality flakes down to a monolayer, scaling it to obtain large-area thin films for practical applications is challenging. Thus, direct synthesis of WTe 2 thin films is desirable for potential electronic and thermal propertyrelated applications, but has yet to be realized due to the low bonding energy of W-Te. Synthesizing WTe 2 directly into largescale thin films is challenging due to its very small standard Gibbs free energy of reaction (−26.2 kJ mol −1 ) compared to that of WSe 2 (−135.0 kJ mol −1 ). [20,21] Additionally, the low melting point of the forming Te-W binary eutectic and high melting point of W (3422 °C) restrict the reaction efficiency between W and Te. Only recently, direct synthesis of MoTe 2 thin films, another interesting TMD [22] with a lower standard Gibbs free energy of reaction (−64.3 kJ mol −1 ) than WTe 2 , has been demonstrated via chemical vapor deposition synthesis (all values of standard Gibbs free energy of reaction are taken at 1100 K). [21,23,24] So far, no direct synthesis of large-area, highly crystalline WTe 2 thin films has been reported.Here, we demonstrate a large-area, facile synthesis of WTe 2 and MoTe 2 thin films by reacting sputtered metal films with H 2 Te, an intermediate vapor phase formed from Te vapor and H 2 carrier gas, through atmospheric pressure chemical vapor reaction. The synthesized films are polycrystalline whose grain size increases with increasing metal film thickness. Based on time-domain thermoreflectance (TDTR), [25,26] the in-plane thermal conductivity of our polycrystalline WTe 2 thin film is less than 2 W m −1 K −1 , at least 7.5 times smaller than that of single-crystalline exfoliated flakes (15 ± 3 W m −1 K −1 ) at room temperature. Through-plane thermal conductivity of our WTe 2 thin films was measured to be 0.8 W m −1 K −1 at room temperature, which is lower than that of the recently reported Large-scale, polycrystalline WTe 2 thin films are synthesized by atmospheric chemical vapor reaction of W metal films with Te vapor catalyzed by H 2 Te intermediates, paving a way to understanding the synthesis mechanism for low bonding energy tellurides and toward synthesis of single-crystallin...

Metals of hybrid nano-/microstructures are of broad technological and fundamental interests. Manipulation of shape and composition on the nanoscale, however, is challenging, especially for multicomponent alloys such as metallic glasses. Although top–down approaches have demonstrated nanomoulding, they are limited to very few alloy systems. Here we report a facile method to synthesize metallic glass nanoarchitectures that can be applied to a broad range of glass-forming alloys. This strategy, using multitarget carousel oblique angle deposition, offers the opportunity to achieve control over size, shape and composition of complex alloys at the nanoscale. As a consequence, nanostructures of programmable three-dimensional shapes and tunable compositions are realized on wafer scale for metallic glasses including the marginal glass formers. Realizing nanostructures in a wide compositional range allows chemistry optimization for technological usage of metallic glass nanostructures, and also enables the fundamental study on size, composition and fabrication dependences of metallic glass properties.

Metallic alloys are normally composed of multiple constituent elements in order to achieve integration of a plurality of properties required in technological applications. However, conventional alloy development paradigm, by sequential trial-and-error approach, requires completely unrelated strategies to optimize compositions out of a vast phase space, making alloy development time consuming and labor intensive. Here, we challenge the conventional paradigm by proposing a combinatorial strategy that enables parallel screening of a multitude of alloys. Utilizing a typical metallic glass forming alloy system Zr-Cu-Al-Ag as an example, we demonstrate how glass formation and antibacterial activity, two unrelated properties, can be simultaneously characterized and the optimal composition can be efficiently identified. We found that in the Zr-Cu-Al-Ag alloy system fully glassy phase can be obtained in a wide compositional range by co-sputtering, and antibacterial activity is strongly dependent on alloy compositions. Our results indicate that antibacterial activity is sensitive to Cu and Ag while essentially remains unchanged within a wide range of Zr and Al. The proposed strategy not only facilitates development of high-performing alloys, but also provides a tool to unveil the composition dependence of properties in a highly parallel fashion, which helps the development of new materials by design.

A series of noble metal high entropy alloys with up to six constituent elements has been produced by casting. PtPdRhIrCuNi forms single-phase face-centered cubic solid solution, and its stability is confirmed by annealing experiments. This alloy deforms homogeneously to ~30% to a high ultimate compression strength of 1839 MPa. We discuss rules for the formation of single-phase solid solution.