Combinatorial Materials Libraries Research Articles

Cutting Edge High‐Throughput Synthesis and Characterization Techniques in Combinatorial Materials Science

AbstractThe Materials Genome Initiative is expected to accelerate the materials discovery and design by fundamentally changing the trial‐and‐error research paradigm. However, mass data from high‐throughput experiments is still essential for the revelation of rules and verification of theories. In fact, the development of combinatorial materials science is always on the strength of the upgrade and evolution of high‐throughput techniques in each stage, especially high‐throughput materials synthesis and characterization. Herein, this review summarizes the high‐throughput synthesis methods for combinatorial materials libraries, especially the co‐deposition and masking techniques of thin‐film fabrication; and details the high‐throughput characterization methods for specific material properties and typical material categories, which comes down to the spectroscopy and microscopy techniques. It is considered that high‐throughput concepts will be the predominant lab experimentation in the future, along with advanced experimental techniques and convenient data processing procedures. Before that, more cooperation between multiple researchers from different fields should be conducted to complete the combinatorial materials research, since the high‐throughput technology covers multiple disciplines with a huge span.

High-throughput synthesis and oxidation behavior of a continuous composition spread (Nb–Ti)1-x-ySixCry alloy thin film

High-throughput method of three targets magnetron sputter co-deposition was adopted to prepare (Nb–Ti)1-x-ySixCry composition spread alloy film (CSAF). Early oxidation behavior of the as-deposited alloy thin film was investigated in atmospheric conditions at 1250 °C for 10 min. A (Nb–Ti)1-x-ySixCry combinatorial material library covering (9.34–32.31) Si-(10.43–20.27) Cr (at. %) is obtained and as-deposited film was composed of amorphous phase. The oxidized film was separated into three regions having different oxidation products. The composition range for establishment of a protective scale (SiO2 and CrNbO4) and a small amount of Nb2O5 was ascertained efficiently across the entire alloy thin film.

High-throughput development of tough metallic glass films.

Fast development of metallic glass films with high toughness has been a long-sought goal of humankind in view of their superior properties and great potential for application in the field of soft electronics. However, until now, there has been no effective experimental strategy because of the lack of suitable and precise toughness measurement technology. In the present work, we introduced a feasible route for developing tough metallic glass films using combinatorial material library preparation and high-throughput toughness measurement via nanoindentation. Based on this route, tough metallic glass films for the quaternary Zr-Ti-Cu-Al system were successfully screened out. The corresponding electron work function map was detected to uncover the physical mechanism for the composition dependence of toughness. In addition, the preliminary assessments of the screened tough metallic glass films as strain-sensing materials were also conducted. Our current research not only provides a versatile toolbox for high-throughput development of tough metallic glass films, but also exemplifies their potential as strain-sensing materials.

Combinatorial discovery of irradiation damage tolerant nano-structured W-based alloys

One of the challenges in fusion reactors is the discovery of plasma facing materials capable of withstanding extreme conditions, such as radiation damage and high heat flux. Development of fusion materials can be a daunting task since vast combinations of microstructures and compositions need to be explored, each of which requires trial-and-error based irradiation experiments and materials characterizations. Here, we utilize combinatorial experiments that allow rapid and systematic characterizations of composition-microstructure dependent irradiation damage behaviors of nanostructured tungsten alloys. The combinatorial materials library of W-Re-Ta alloys was synthesized, followed by the high-throughput experiments for probing irradiation damages to the mechanical, thermal, and structural properties of the alloys. This highly efficient technique allows rapid identification of composition ranges with excellent damage tolerance. We find that the distribution of implanted He clusters can be significantly altered by the addition of Ta and Re, which play a critical role in determining property changes upon irradiation.

Mid-infrared complex permittivity in Bi2-Sb Te3-Se thin films synthesized using a combinatorial method

• A combinatorial material library of Bi 2- x Sb x Te 3- y Se y thin films was synthesized. • λ c shifts from 5.346 μm for Bi 2 Se 3 to 9.232 μm for Sb 2 Te 3 . • The compositionally adjustable mid-infrared plasmonic property was carried out. Successful employment of plasmonics-inspired solutions in the mid-infrared frequency range would benefit a number of highly important technologies. As a plasmonic material beyond gold and silver, Bi-based chalcogenide semiconductor alloys exhibit a wide tunability in the spectral dispersion of relative permittivity by varying the composition of their ternary and quaternary compounds. In our investigation, a combinatorial materials library of Bi 2- x Sb x Te 3- y Se y thin films were synthesized. The complete solid solubility and the in-depth chemical composition profile of thin film pixels in the library were confirmed using micro-area X-ray diffraction and secondary ion mass spectroscopy, respectively. The stoichiometries of thin film pixels were acquired using the energy dispersive X-ray analysis. The mid-infrared spectral transmittance was measured using a Fourier-transform infrared spectrometer. The complex permittivity ε ( ω ) in the spectral range from 2.5 to 15 μm was derived by fitting spectral transmittance to the Drude–Lorentz equation. It can be demonstrated that the negative values of real part of permittivity, ε r , emerge at the shorter wavelengths. The crossover wavelength, at which ε r crosses zero from negative to positive, can shift from 5.346 μm for Bi 2 Se 3 to 9.232 μm for Sb 2 Te 3 with the increasing of x and the deceasing of y . Therefore, an exceptionally wide and potentially interesting mid-infrared plasmonic property, which is compositionally adjustable, can be carried out for evaporation-deposited Bi 2- x Sb x Te 3- y Se y solid-solution thin films.

Hypothesis Learning in Automated Experiment: Application to Combinatorial Materials Libraries.

Machine learning is rapidly becoming an integral part of experimental physical discovery via automated and high-throughput synthesis, and active experiments in scattering and electron/probe microscopy. This, in turn, necessitates the development of active learning methods capable of exploring relevant parameter spaces with the smallest number of steps. Here, an active learning approach based on conavigation of the hypothesis and experimental spaces is introduced. This is realized by combining the structured Gaussian processes containing probabilistic models of the possible system's behaviors (hypotheses) with reinforcement learning policy refinement (discovery). This approach closely resembles classical human-driven physical discovery, when several alternative hypotheses realized via models with adjustable parameters are tested during an experiment. This approach is demonstrated for exploring concentration-induced phase transitions in combinatorial libraries of Sm-doped BiFeO3 using piezoresponse force microscopy, but it is straightforward to extend it to higher-dimensional parameter spaces and more complex physical problems once the experimental workflow and hypothesis generation are available.

Magnetization\u2013structure\u2013composition phase diagram mapping in Co-Fe-Ni alloys using diffusion multiples and scanning Hall probe microscopy

Transition metal alloys are essential for magnetic recording, memory, and new materials-by-design applications. Saturation magnetization in these alloys have previously been measured by conventional techniques, for a limited number of samples with discrete compositions, a laborious and time-consuming effort. Here, we propose a method to construct complete saturation magnetization diagrams for Co–Fe–Ni alloys using scanning Hall probe microscopy (SHPM). A composition gradient was created by the diffusion multiple technique, generating a full combinatorial materials library with an identical thermal history. The composition and crystallographic phases of the alloys were identified by integrated energy dispersive X-ray spectroscopy and electron backscatter diffraction. “Pixel-by-pixel” perpendicular components of the magnetic field were converted into maps of saturation magnetization using the inversion matrix technique. The saturation magnetization dependence for the binary alloys was consistent with the Slater-Pauling behavior. By using a significantly denser data point distribution than previously available, the maximum of the Slater-Pauling curve for the Co–Fe alloys was identified at ~ 32 at% of Co. By mapping the entire ternary diagram of Co–Fe–Ni alloys recorded in a single experiment, we have demonstrated that SHPM—in concert with the combinatorial approach—is a powerful high-throughput characterization tool, providing an effective metrology platform to advance the search for new magnetic materials.

Prospect of making XPS a high-throughput analytical method illustrated for a Cu x Ni1-x O y combinatorial material library.

Combinatorial material science crucially depends on robust, high-throughput characterization methods. While X-ray photoelectron spectroscopy (XPS) may provide detailed information about chemical and electronic properties, it is a time-consuming technique and, therefore, is not viewed as a high-throughput method. Here we present preliminary XPS data of 169 measurement spots on a combinatorial 72 × 72 cm2 CuxNi1−xOy compositional library to explore how characterization and evaluation routines can be optimized to improve throughput in XPS for combinatorial studies. In particular, two quantification approaches are compared. We find that a simple integration (of XPS peak regions) approach is suited for fast evaluation of, in the example system, the [Cu]/([Cu] + [Ni]) ratio. Complementary to that, the time-consuming (XPS peak-) fit approach provides additional insights into chemical speciation and oxidation state changes, without a large deviation of the [Cu]/([Cu] + [Ni]) ratio. This insight suggests exploiting the fast integration approach for ‘real time’ analysis during XPS data collection, paving the way for an ‘on-the-fly’ selection of points of interest (i.e., areas on the sample where sudden composition changes have been identified) for detailed XPS characterization. Together with the envisioned improvements when going from laboratory to synchrotron-based excitation sources, this will shorten the analysis time sufficiently for XPS to become a realistic characterization option for combinatorial material science.

High-throughput preparation and electrochemical screening of nanocrystalline Fe-Cr-Ni material libraries with homogeneous element distribution

Magnetron co-sputtering has been widely used for high-throughput preparation of combinatorial material library. However, a large number of alloy compositions in the fabricated material libraries are interconnected with each other, and their element distribution is uneven. Here, we present a high-throughput strategy where 97 independent nanocrystalline alloy samples with homogeneous element distribution can be prepared simultaneously through multi-station rotary sample stage. Using this approach, we synthesized 22 nanocrystalline Fe-Cr-Ni alloy samples covering 10.65–28.36 wt% Cr and 7.47–24.57 wt% Ni and studied their pitting corrosion resistance by electrochemical measurements, thereby quickly establishing the relationship between chemical compositions and corrosion resistance.

In situ compositional mapping of combinatorial materials libraries by scanning low-angle x-ray spectroscopy

A novel in situ diagnostic, scanning low-angle x-ray spectroscopy, has been introduced for compositional mapping of combinatorial thin film libraries. The technique uses high-energy electron beam-generated characteristic x rays from the films as they are deposited. The x-ray intensities are acquired dynamically, layer by layer at different film thicknesses, processed, and analyzed by Neocera-developed software using a unique algorithm. A fully automated four-axis mechanical stage facilitates data acquisition from a 2-in. diameter wafer providing a comprehensive compositional map across the wafer. A ternary materials library of Zn-Ti-Cr oxide has been deposited by continuous composition spread pulsed laser deposition to demonstrate the novel application of scanning low-angle x-ray spectroscopy for compositional mapping in situ. This in situ feedback on composition across the wafer significantly enhances the capability of any physical vapor deposition technique used for depositing combinatorial libraries, by providing compositional feedback during growth as well as the ability to monitor and control deposition processes for composition optimizations.

High-Throughput Synthesis and Characterization of a Combinatorial Materials Library in Bulk Alloys

High-Throughput Synthesis and Characterization of a Combinatorial Materials Library in Bulk Alloys

Compositions, structures, and mid-infrared transparency of Sb–Te–Se thin films synthesized using a combinatorial method

The dielectric function of phase-change materials (PCMs) presents a tremendous difference for the amorphous and crystalline states. Therefore, the measurement of the mid-infrared transparency of thin films of PCMs will provide a cost-efficient method to reveal the dependence of amorphous-crystalline phase transition on their compositions. Although Sb–Te–Se system has shown the advantages of the high speed, low power consumption and long retention life, the information on the mid-infrared transparency of Sb–Te–Se thin films is still insufficient. In our investigation, combinatorial materials libraries of Sb–Te–Se thin films were synthesized. The composition and mid-infrared spectral transmittance of each pixel of Sb–Te–Se thin film in the library were characterized using the energy dispersive X-ray analysis (EDX) and Fourier-transform infrared (FTIR) spectrometer, respectively. The in-depth chemical composition for randomly selected pixels was identified using secondary ions mass spectroscopy (SIMS). The crystallographic structure of some pixels was also identified using micro-area X-ray diffraction (μ-XRD). It can be found that, with the change of composition in Sb–Te–Se thin films, their mid-infrared spectral transmittance can be organized into three distinctive groups, corresponding to amorphous Sb–Se, Sb2Se3 orthorhombic structure and Sb2Te3 rhombohedral structure, respectively. Therefore, the amorphous-crystalline phase transition and the phase-change from the orthorhombic structure of Sb2Se3 to the rhombohedral structure of Sb2Te3 can be completely reflected in the mid-infrared spectral transmittance of Sb–Te–Se thin films.

XPS group array analysis of a combinatorial Ni-Ti-Co thin film library

The last few decades have seen rapid development in computational and theoretical tools for simulating, fabricating, and characterizing material systems. In this report, the potential of surface characterization by x-ray photoelectron spectroscopy (XPS) to provide rapid elemental and chemical state information is presented. The development of the group analysis array functionality is significant for facilitating processing and display of large datasets in the application of XPS analysis to combinatorial materials discovery. We demonstrate that group array analysis provides a more detailed understanding of the chemical distribution across a Ni-Ti-Co combinatorial thin-film materials library.

Fabrication of combinatorial material libraries by flow cell electrodeposition technique

Scanning flow cell is a technique, widely used for rapid screening of electrocatalysts libraries, but not for fabrication of them. In this paper we demonstrate application of the flow cell technique for deposition of material libraries. As an example, a library of Pt-Ni alloy has been fabricated. It is shown that the method allows production of catalyst arrays with variable compositions in a controlled manner.

High-throughput synthesis and corrosion behavior of sputter-deposited nanocrystalline Alx(CoCrFeNi)100-x combinatorial high-entropy alloys

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 Alx(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 Alx(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.

A novel gradient composition spreading and nanolayer stacking process for combinatorial thin-film materials library fabrication.

A novel magnetron sputtering process is proposed to fabricate a combinatorial thin-film materials library with highly precise composition spreading. In order to produce a gradient composition spreading for a specific target, a moving shutter is used to cover the deposition substrate step by step with a fixed step-length. By rotating the substrate and repeating the step-by-step masked deposition with different targets in turn, a heterogeneous precursor structure is obtained with alternate stacking of different material layers, each of which is in a step-by-step wedge-shaped thickness cross section. By controlling the thickness of each layer at the nanometer scale, a multilayer structure is formed to facilitate the interlayer diffusion between different precursor layers. It may also define the boundaries of individual sample pixels, resulting in improved composition spreading resolutions for the prepared materials library. A combinatorial magnetron sputtering system is designed with reciprocating rectangular targets, a narrow slit between the substrate and the target, and a quartz crystal microbalance feedback to control the deposition uniformity, resulting in a variation better than 3% across a 76 × 76 mm substrate. Three individual deposition chambers are designed in an annular distribution with 90° angle between each other. Moreover, a step-by-step moving shutter and a rotating substrate holder are incorporated. Combinatorial materials libraries with more than 10 000 individual compositions could be obtained using this system. A Ti-Zr-Ni ternary alloy library was fabricated for demonstration in which the sheet resistance spreading diagram of the Ti-Zr-Ni library was studied as a function of the composition.

Structure Zone Investigation of Multiple Principle Element Alloy Thin Films as Optimization for Nanoindentation Measurements.

Multiple principal element alloys, also often referred to as compositionally complex alloys or high entropy alloys, present extreme challenges to characterize. They show a vast, multidimensional composition space that merits detailed investigation and optimization to identify compositions and to map the composition ranges where useful properties are maintained. Combinatorial thin film material libraries are a cost-effective and efficient way to create directly comparable, controlled composition variations. Characterizing them comes with its own challenges, including the need for high-speed, automated measurements of dozens to hundreds or more compositions to be screened. By selecting an appropriate thin film morphology through predictable control of critical deposition parameters, representative measured values can be obtained with less scatter, i.e., requiring fewer measurement repetitions for each particular composition. In the present study, equiatomic CoCrFeNi was grown by magnetron sputtering in different locations in the structure zone diagram applied to multinary element alloys, followed by microstructural and morphological characterizations. Increasing the energy input to the deposition process by increased temperature and adding high-power impulse magnetron sputtering (HiPIMS) plasma generators led to denser, more homogeneous morphologies with smoother surfaces until recrystallization and grain boundary grooving began. Growth at 300 °C, even without the extra particle energy input of HiPIMS generators, led to consistently repeatable nanoindentation load–displacement curves and the resulting hardness and Young’s modulus values.

Thin-Film Processing Routes for Combinatorial Materials Investigations-A Review.

High-throughput combinatorial investigations are transforming materials discovery, phase diagram development, and processing optimization. Thin-film deposition techniques are frequently used to fabricate sample libraries employed in these studies. Various adaptations of well-known thin-film chemical vapor deposition (CVD) and physical vapor deposition (PVD) techniques utilized for the synthesis of inorganic combinatorial thin-film materials libraries are reviewed, with novel processing approaches being highlighted. Methods for developing gradients in composition of other film properties are described. Issues and considerations specific to thin-film processing of combinatorial materials libraries are discussed, with some emphasis on catalytic applications.

Unsupervised phase mapping of X-ray diffraction data by nonnegative matrix factorization integrated with custom clustering

Analyzing large X-ray diffraction (XRD) datasets is a key step in high-throughput mapping of the compositional phase diagrams of combinatorial materials libraries. Optimizing and automating this task can help accelerate the process of discovery of materials with novel and desirable properties. Here, we report a new method for pattern analysis and phase extraction of XRD datasets. The method expands the Nonnegative Matrix Factorization method, which has been used previously to analyze such datasets, by combining it with custom clustering and cross-correlation algorithms. This new method is capable of robust determination of the number of basis patterns present in the data which, in turn, enables straightforward identification of any possible peak-shifted patterns. Peak-shifting arises due to continuous change in the lattice constants as a function of composition and is ubiquitous in XRD datasets from composition spread libraries. Successful identification of the peak-shifted patterns allows proper quantification and classification of the basis XRD patterns, which is necessary in order to decipher the contribution of each unique single-phase structure to the multi-phase regions. The process can be utilized to determine accurately the compositional phase diagram of a system under study. The presented method is applied to one synthetic and one experimental dataset and demonstrates robust accuracy and identification abilities.

High-throughput combinatorial chemical bath deposition: The case of doping Cu (In, Ga) Se film with antimony

The conventional methods for designing and preparing thin film based on wet process remain a challenge due to disadvantages such as time-consuming and ineffective, which hinders the development of novel materials. Herein, we present a high-throughput combinatorial technique for continuous thin film preparation relied on chemical bath deposition (CBD). The method is ideally used to prepare high-throughput combinatorial material library with low decomposition temperatures and high water- or oxygen-sensitivity at relatively high-temperature. To check this system, a Cu(In, Ga)Se (CIGS) thin films library doped with 0–19.04 at.% of antimony (Sb) was taken as an example to evaluate the regulation of varying Sb doping concentration on the grain growth, structure, morphology and electrical properties of CIGS thin film systemically. Combined with the Energy Dispersive Spectrometer (EDS), X-ray Photoelectron Spectroscopy (XPS), automated X-ray Diffraction (XRD) for rapid screening and Localized Electrochemical Impedance Spectroscopy (LEIS), it was confirmed that this combinatorial high-throughput system could be used to identify the composition with the optimal grain orientation growth, microstructure and electrical properties systematically, through accurately monitoring the doping content and material composition. According to the characterization results, a Sb2Se3 quasi-liquid phase promoted CIGS film-growth model has been put forward. In addition to CIGS thin film reported here, the combinatorial CBD also could be applied to the high-throughput screening of other sulfide thin film material systems.