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The Au-Al alloy system was investigated via a combinatorial thin film sputtering method for its potential as a plasmonic material. Au x Al 1- x combinatorial libraries were cosputtered from Au and Al elemental targets and the composition, phase, and dielectric function of a ∼350 nm film was determined using energy dispersive spectroscopy (EDS), grazing incidence X-ray diffraction (GIXRD), and spectroscopic ellipsometry, respectively. The phase evolution and optical properties were analyzed after annealing various compositions under a vacuum. The phases present matched the expected phases based on the published Al-Au binary phase diagram at all compositions. Interestingly, the mixed phase Al-AuAl 2 region showed the most optical tunability, where a maximum in the real part of the dielectric function progressively shifted to higher energy for increasing gold concentration. For almost pure AuAl 2 , the imaginary component is largely reduced in the visible range and is comparable to that of pure Al in the UV region. A 20-nm-thick film with composition Au 0.74 Al 0.26 was studied using a (scanning) transmission electron microscope with an in situ laser heating system. The structures of the as-deposited and laser annealed films were determined using selected area diffraction and the bulk plasmon of AuAl 2 and Al realized with electron energy loss spectroscopy. Last, the Au-rich solid solution region was investigated as a surface enhanced Raman spectroscopy (SERS) substrate using the benezenethiol (BT) molecule. Good SERS intensity was maintained up to 30% Al addition where enhancements of 10 5 to 10 7 were still observed.

We synthesized a combinatorial library of CuxNi1−x alloy thin films via co-sputtering from Cu and Ni targets to catalyze graphene chemical vapor deposition. The alloy morphology, composition, and microstructure were characterized via scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and X-ray diffraction (XRD), respectively. Subsequently, the CuxNi1−x alloy thin films were used to grow graphene in a CH4-Ar-H2 ambient at atmospheric pressure. The underlying rationale is to adjust the CuxNi1−x composition to control the graphene. Energy dispersive x-ray spectroscopy (EDS) analysis revealed that a continuous gradient of CuxNi1−x (25 at. % < x < 83 at.%) was initially achieved across the 100 mm diameter substrate (~0.9%/mm composition gradient). The XRD spectra confirmed a solid solution was realized and the face-centered cubic lattice parameter varied from ~3.52 to 3.58 A ˙ , consistent with the measured composition gradient, assuming Vegard's law. Optical microscopy and Raman analysis of the graphene layers suggest single layer growth occurs with x > 69 at.%, bilayer growth dominates from 48 at.% < x < 69 at.%, and multilayer (≥3) growth occurs for x < 48 at.%, where x is the Cu concentration. Finally, a large area of bi-layer graphene was grown via a CuxNi1−x catalyst with optimized catalyst composition and growth temperature. [ABSTRACT FROM AUTHOR]

In this study, the optical properties of Au 1-x Ni x alloy thin films are investigated by employing a combinatorial sputtering approach. The dielectric function is measured using spectroscopic ellipsometry and is correlated to the composition, determined by energy dispersive spectroscopy, and phases present, determined via x-ray diffraction. As-deposited alloys form a metastable solid solution, however, annealed alloys exhibited phase separation into Au-rich and Ni-rich phases due to the large miscibility gap in the Au-Ni material system. The optical properties are then rationalized by modeling the dielectric function of the solid solution alloys with a Drude-Critical Point analytical model. Lastly, the efficacy of the model is demonstrated which shows that the dielectric function of the phase separated alloys can be approximated using a composition-weighted average of two solid solution dielectric functions. Image 1 • Sputter deposited Au-Ni alloys are a metastable solid solution initially. • A unique trend in the dielectric function exists with changing composition. • The drude – critical point model describes the solid solution dielectric function. • Annealed alloys phase separate into Au-rich and Ni-rich grains. • Anneal temperature controls the dielectric function of phase separated alloys. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) are inherently complex and potentially span a vast composition space, making their research and discovery challenging. In the present study, high-throughput synthesis of an Al x (CoCrFeNi) 100- x combinatorial material library covering x = 4.5–40 atomic percent Al is achieved, using magnetron co-sputtering. The effects of Al on the microstructure and corrosion behavior are investigated. With the increased amount of Al, crystal-structures of thin films transform from face-centered cubic (FCC) to body-centered cubic (BCC). Both the FCC and BCC thin films demonstrate a uniform elemental distribution. Corrosion characteristics of combinatorial samples immersed in the 3.5 wt% (wt%) NaCl solution are evaluated via electrochemical tests. Complementary X-ray photoelectron spectroscopy analysis reveals the compositional variation of passivated films formed on the sample surface after immersion. The results show that the Al x (CoCrFeNi) 100- x HEA thin films possess outstanding corrosion-resistant properties, but the resistance diminishes with the increasing Al content. The decreased corrosion resistance is revealed to be directly related to the constituents of passivated films. Unlabelled Image • High-throughput synthesis of Al x (CoCrFeNi) 100- x high-entropy alloys is achieved. • The influences of Al on the microstructure and corrosion behavior are evaluated. • Al x (CoCrFeNi) 100- x thin films possess outstanding corrosion-resistant properties. [ABSTRACT FROM AUTHOR]

Al x Ce 100−x thin films with a composition range of ~75.0 < x < 99.5 at% (36.5 < x < 97.5 wt%) were synthesized via combinatorial co-sputtering from an Al and an Al 50 Ce 50 target. The crystal structure, phase fraction, film morphology, electrical resistivity, and temperature-dependent coefficients of thermal expansion (CTE) are all correlated to the Al x Ce 100−x composition. The as-deposited films form a metastable solid-solution, and annealing leads to the formation of the thermodynamically stable two-phase system of Al and the α-Al 11 Ce 3 intermetallic. Temperature dependent x-ray diffraction (XRD) reveals that the two phases expand independently of one another, and the thin film Al temperature-dependent CTE is similar to bulk Al. The thin film Al 11 Ce 3 intermetallic phase has a nearly constant CTE of ~1.5 × 10−5/°C within the temperature range studied (25–550 °C). To confirm the thin film Al 11 Ce 3 results, bulk stoichiometric Al 11 Ce 3 and +/- 1 wt% Ce samples were prepared and the CTE of each was measured with the same conditions. A Rietveld analysis of the bulk data enabled an estimation of the CTE in each of the 3 orthorhombic lattice parameters, which displayed anisotropic behavior. The thin film and bulk CTE measurements were in very good agreement. Estimations of the temperature dependent CTE of the two-phase alloys are made via the Reuss and Voigt models. By demonstrating the efficacy of the approach, more complex multi-component rapid materials discovery of low CTE Al-alloys can be pursued via the combinatorial thin film synthesis and XRD measurement. • Combinatorial thin film library of Al x Ce 1 00 −x sputter deposited covering a range of 75< x <99.5. • As-deposited Al-Ce alloys form metastable solid solution; annealing induces phase-separation to equilibrium Al and Al 11 Ce 3. • Temperature dependent x-ray diffraction used to determine coefficients of thermal expansion (CTE) for Al and Al 11 Ce 3. • Thin films and bulk alloy CTE show good agreement. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ionization effects and the associated chemical complexity should be considered to understand radiation effects in complex alloys. • The coupled elastic and inelastic thermal spikes both contribute to the grain growth of nanocrystalline high-entropy alloys (HEAs). • The much slower radiation-induced microstructural evolution in nanocrystalline HEAs is attributed to the sluggish diffusion and the resulting slower kinetics. High-entropy alloys (HEAs) and some complex alloys exhibit desirable properties and significant structural stability in harsh environments, including possible applications in advanced reactors. Energetic ion irradiation is often used as a surrogate for neutron irradiation; however, the impact of ion electronic energy deposition and dissipation is often neglected. Moreover, differences in recoil energy spectrum and density of cascade events on damage evolution must also be considered. In many chemically complex alloys, the mean free path of electrons is reduced significantly, thus their decreased thermal conductivity and slow dissipation of localized radiation energy can have noticeable effects on displacement cascade evolution that is greatly different from metals with high thermal conductivity. In this work, nanocrystalline HEAs of Ni 20 Fe 20 Co 20 Cr 20 Cu 20 and nonequiatomic (NiFeCoCr) 97 Cu 3 , both having much lower room-temperature thermal conductivity than pure Ni or Fe, are chosen as model HEAs to reveal the role that electronic energy loss during ion irradiation has in complex alloys. The response of nanocrystalline HEAs is investigated under irradiation at room temperature using MeV Ni and Au ions that have different ratios of electronic energy to damage energy, which is the energy dissipated in displacing atoms. Different from previously reported amorphization of nanocrystalline SiC, experimental results on these HEAs show that, similar to the process in nanocrystalline oxide materials, both inelastic thermal spikes via electron–phonon coupling and elastic thermal spikes via collisions among atomic nuclei contribute to the overall grain growth. The growth follows a power law dependence with the total deposited ion energy, and the derived value of the power-exponent suggests that the irradiation-induced instability at and near grain boundaries leads to local rapid atomic rearrangements and consequently grain growth. The high power-exponent value can be attributed to the sluggish diffusion and delayed defect evolution arising from the chemical complexity intrinsic to HEAs. This work calls attention to quantified fundamental understanding of radiation damage processes beyond that of simplified displacement events, especially in simulating neutron environments. [ABSTRACT FROM AUTHOR]

• Combinatorial thin film synthesis of bimetallic Ag x Fe 1−x alloy for rapid materials characterization. • Correlation of composition and structure to the optical and magnetic properties of Ag x Fe 1-x thin films. • Magnetic measurements reveal Ag x Fe 1−x has an antiferromagnetic phase Néel temperature of ≈120 K. • Controlled phase separation in immiscible Ag-Fe system results in tunable magneto-optical properties. Bimetallic alloys with large discrepancies in atomic radii and crystal structure typically yield systems that are highly immiscible, even at high temperatures. The Ag x Fe 1−x binary system has limited solid and liquid solubility and thus phase separated Ag + Fe alloys should result. Furthermore, Ag has interesting plasmonic properties and Fe is a strong ferromagnet, thus magneto-plasmonic nanoparticles/films should result due to their phase separation. We have leveraged a combinatorial sputter deposition to synthesize thin films with a large Ag x Fe 1−x (0.19 < x < 0.84) phase space to correlate the composition and structure to the optical and magnetic properties for both as-deposited and annealed compositions. [ABSTRACT FROM AUTHOR]