Composition Spread Thin Films Research Articles

Combinatorial search of superconductivity in Fe-B composition spreads

We have fabricated Fe-B thin film composition spreads in search of possible superconducting phases following a theoretical prediction by Kolmogorov et al. [Phys. Rev. Lett. 105, 217003 (2010)]. Co-sputtering was used to deposit spreads covering a large compositional region of the Fe-B binary phase diagram. A trace of superconducting phase was found in the nanocrystalline part of the spread, where the film undergoes a metal to insulator transition as a function of composition in a region with the average composition of FeB2. The resistance drop occurs at 4 K, and a diamagnetic signal has also been detected at the same temperature. From the field-dependent resistive transition behavior, we estimate the upper critical field to be approximately 2 T.

High-Throughput Measurement of Ionic Conductivity in Composition-Spread Thin Films

This paper demonstrates the feasibility of high-throughput investigation of ionic conductivity in oxygen-ion conductors. Yttria stabilized zirconia (YSZ) composition-spread thin films with nanometer-size grains were prepared by 90° off-axis reactive RF cosputtering. We compare results for two electrode configurations, namely, out-of-plane (parallel plate) and in-plane (planar interdigitated electrode) and find that the contribution from the intragrain conductivity in YSZ thin films (150 nm) is more explicit in the latter configuration because it greatly diminishes electrode effects. The intragrain oxygen ion conductivity of thin film YSZ was systematically measured as a function of yttria concentration over the range 2 mol % to 12 mol %. The results show that the measured conductivity of the YSZ thin films is close to that of corresponding bulk materials with a peak value around 3 × 10⁻⁴ S cm⁻¹ at 440 °C at the optimum Y₂O₃ concentration of 8 mol %. Validation of this technique means that it can be applied to novel chemical systems for which systematic bulk measurements have not been attempted.

Synthesis of Au microwires by selective oxidation of Au–W thin-film composition spreads

We report on the stress-induced growth of Au microwires out of a surrounding Au–W matrix by selective oxidation, in view of a possible application as ‘micro-Velcro’. The Au wires are extruded due to the high compressive stress in the tungsten oxide formed by oxidation of elemental W. The samples were fabricated as a thin-film materials library using combinatorial sputter deposition followed by thermal oxidation. Sizes and shapes of the Au microwires were investigated as a function of the W to Au ratio. The coherence length and stress state of the Au microwires were related to their shape and plastic deformation. Depending on the composition of the Au–W precursor, the oxidized samples showed regions with differently shaped Au microwires. The Au48W52 composition yielded wires with the maximum length to diameter ratio due to the high compressive stress in the tungsten oxide matrix. The values of wire length (35 μm) and diameter (2 μm) achieved at the Au48W52 composition are suitable for micro-Velcro applications.

Ultrafast elemental mapping of materials combinatorial libraries and high-throughput screening samples via pulsed glow discharge optical emission spectroscopy

Combinatorial and high-throughput techniques have become well-established in materials science to aid in the accelerated discovery of novel functional materials. Thin film composition spreads are frequently used for this purpose by performing localized measurements and exploring different properties throughout the phase diagram. Nevertheless, the thin film composition map has to be determined to understand the behavior of the compound or alloy of interest. There are several established techniques that can give elemental composition maps of large areas but the total mapping time can range from several hours to tens of hours or more. Thus, faster elemental mapping techniques are needed. In this study, the applicability of GDOES elemental mapping towards combinatorial and high-throughput screening samples is explored by characterizing a CuNi thin film composition spread. Qualitative analysis images show that Cu and Ni composition gradients can be obtained in a matter of seconds. In addition, the use of reference materials allowed quantitative elemental analysis maps to be extracted from the emission intensity images. The images of emission intensities and curve fitting parameters are discussed. Finally, the GDOES results are compared to profiles obtained via EDX. The GDOES figures-of-merit relevant to elemental mapping are contrasted against selected alternative techniques from the literature to put the potential impact into perspective.

Combinatorial search of structural transitions: Systematic investigation of morphotropic phase boundaries in chemically substituted BiFeO3

Abstract

High-throughput study of martensitic transformations in the complete Ti–Ni–Cu system

The shape memory properties of the complete Ti–Ni–Cu thin film system were investigated using combinatorial methods, i.e. fabrication and high-throughput characterization of thin film materials libraries. Thin film composition spreads were deposited using a wedge-type multilayer technique and annealed at 500 °C, 600 °C and 700 °C for 1 h for alloy formation. The complete composition regions showing reversible phase transformations were identified for each annealing temperature. These regions are well extended in comparison to prior knowledge. Furthermore, the composition-structure-property relations governing the phase transformation characteristics in the thin film samples were determined. For films annealed at 500 °C and 600 °C the transformation temperatures are highest for compositions close to Ti50Ni50−xCux and decrease as the thin film compositions deviate. Similarly, the thermal transformation hysteresis is found to be smallest for “stoichiometric” (Ti50Ni50−xCux) compositions. Precipitation of Ti-rich and (Ni,Cu)-rich phases is found to be responsible. With increasing annealing temperature the transformation temperatures increase and the thermal hysteresis values decrease for compositions showing B2→B19 phase transformation paths, due to coarsening of the precipitate phases. The alloying process of the multilayer thin films leads to the formation of the equilibrium phases. The formation of Guinier–Preston zones is suppressed. For thin films annealed at 700 °C the transforming composition region is comparatively smaller and the phase transformation properties are influenced by Ti2Ni precipitates.

High Throughput Thin Film Pt-M Alloys for Fuel Electrooxidation: Low Concentrations of M (M = Sn, Ta, W, Mo, Ru, Fe, In, Pd, Hf, Zn, Zr, Nb, Sc, Ni, Ti, V, Cr, Rh)

Eighteen Pt-M binary (M = Sn, Ta, W, Mo, Ru, Fe, In, Pd, Hf, Zn, Zr, Nb, Sc, Ni, Ti, V, Cr, Rh) thin film composition spreads were deposited at low M concentrations using magnetron sputtering and screened for methanol and ethanol electrooxidation activity using a fluorescence assay. Characterization of these thin films was performed using high energy X-ray diffraction and X-ray fluorescence. The electrochemical fluorescence assay revealed highest activity in the films with M = Sn, Zn, In, Fe, and Ru. Pt-M (M = Sn, Zn, In) showed highest activity at concentrations below 5 atom-% with a high fraction of Pt fcc(111) texturing and Pt-Fe showing the best activity at 10 atom-% Fe. On the other hand, the best (most negative) fluorescence onset potential in the Pt-Ru system was observed at a concentration of 35 atom-% Ru with only slight texturing of the film. To explore the potential origins of the observed catalytic activity, preliminary calculations on the d-band center shift with alloying were performed for bulk concentrations of up to 30 atom-% for Fe and 16 atom-% for M = Sn, Zn.

A combinatorial characterization scheme for high-throughput investigations of hydrogen storage materials

In order to increase measurement throughput, a characterization scheme has been developed that accurately measures the hydrogen storage properties of materials in quantities ranging from 10 ng to 1 g. Initial identification of promising materials is realized by rapidly screening thin-film composition spread and thickness wedge samples using normalized IR emissivity imaging. The hydrogen storage properties of promising samples are confirmed through measurements on single-composition films with high-sensitivity (resolution <0.3 μg) Sievert’s-type apparatus. For selected samples, larger quantities of up to ∼100 mg may be prepared and their (de)hydrogenation and micro-structural properties probed via parallelin situ Raman spectroscopy. Final confirmation of the hydrogen storage properties is obtained on ∼1 g powder samples using a combined Raman spectroscopy/Sievert’s apparatus.

Dielectric properties of continuous composition spreaded MgO–Ta2O5 thin films

The dielectric properties of MgO–Ta2O5 continuous composition spread (CCS) thin films were investigated. The MgO–Ta2O5 CCS thin films were deposited on Pt/Ti/SiO2/Si substrates by off-Axis RF magnetron sputtering system, and then the films were annealed at 350°C with rapid thermal annealing system in vacuum. The dielectric constant and loss of MgO–Ta2O5 CCS thin films were plotted via 1500 micron-step measuring. The specific point of Ta2O5–MgO CCS thin film (post annealed at 350°C) showing superior dielectric properties of high dielectric constant (k∼28) and low dielectric loss (tanδ<0⋅004) at 1MHz were found in the area of 3–5mm apart from Ta2O5 side on the substrate. The cation's composition of thin film was Mg:Ta=0.4:2at%.

A wavelet transform algorithm for peak detection and application to powder x-ray diffraction data

Peak detection is ubiquitous in the analysis of spectral data. While many noise-filtering algorithms and peak identification algorithms have been developed, recent work [P. Du, W. Kibbe, and S. Lin, Bioinformatics 22, 2059 (2006); A. Wee, D. Grayden, Y. Zhu, K. Petkovic-Duran, and D. Smith, Electrophoresis 29, 4215 (2008)] has demonstrated that both of these tasks are efficiently performed through analysis of the wavelet transform of the data. In this paper, we present a wavelet-based peak detection algorithm with user-defined parameters that can be readily applied to the application of any spectral data. Particular attention is given to the algorithm's resolution of overlapping peaks. The algorithm is implemented for the analysis of powder diffraction data, and successful detection of Bragg peaks is demonstrated for both low signal-to-noise data from theta-theta diffraction of nanoparticles and combinatorial x-ray diffraction data from a composition spread thin film. These datasets have different types of background signals which are effectively removed in the wavelet-based method, and the results demonstrate that the algorithm provides a robust method for automated peak detection.

Microstructural and dielectric properties of Ba0.6Sr0.4Ti1−xZrxO3 based combinatorial thin film capacitors library

Epitaxial growth of Ba0.6Sr0.4Ti1−xZrxO3 (0≤x≤0.3) composition spread thin film library on SrRuO3/SrTiO3 layer by combinatorial pulsed laser deposition (PLD) is reported. X-ray diffraction and energy dispersive x-ray spectroscopy studies showed an accurate control of the film phase and composition by combinatorial PLD. A complex evolution of the microstructure and morphology with composition of the library is described, resulting from the interplay between epitaxial stress, increased chemical pressure, and reduced elastic energy upon Zr doping. Statistical and temperature-related capacitive measurements across the library showed unexpected variations in the dielectric properties. Doping windows with enhanced permittivity and tunability are identified, and correlated to microstructural properties.

Phase Behavior of Pseudobinary Precious Metal−Carbide Systems

Transition metal carbides exhibit a variety of interesting material properties, including electrochemical stability. When combined with precious metals, Ta and W carbides have shown promise as fuel cell electrode materials; yet, the phase behavior of these precious metal−carbide systems is largely unexplored. We investigated P-M-C phase behavior with P = Pt, Pd, and Ru and M = Ta and W using composition spread thin films. We attained limited control of the deposited carbide phase through variation of the sputter atmosphere and demonstrated decreased corrosion of W−C materials with increasing C content. A high-throughput X-ray diffraction and X-ray fluorescence experiment was employed for thin film characterization, which revealed solubility of Pt, Pd, and Ru in cubic WC. Density functional calculations of the lattice parameter dependence on carbon concentration enabled the determination of carbon concentration from the X-ray data as a function of transition metal stoichiometry. Our measurement of variatio...

Cosputtered composition-spread reproducibility established by high-throughput x-ray fluorescence.

We describe the characterization of sputtered yttria-zirconia composition spread thin films by x-ray fluorescence (XRF). We also discuss our automated analysis of the XRF data, which was collected in a high throughput experiment at the Cornell High Energy Synchrotron Source. The results indicate that both the composition reproducibility of the library deposition and the composition measurements have a precision of better than 1 atomic percent.

Competing electronic orders in anisotropically strained(Pr0.6Ca0.4)1−x(La0.6Sr0.4)xMnO3thin films

We have explored the competing phases in the anisotropically strained manganese oxide with use of a composition-spread thin film where two contrastive ground states, i.e., ferromagnetic metal and charge/orbital-ordered insulator, are designed to compete with a continuous variation in the chemical composition. Taking advantage of a systematic inspection of the phase evolutions, we have confirmed that competing electronic orders could be realized in thin-film form. In particular, we found a possibly one-dimensional orbital-ordered insulating state near the metal-insulator phase boundary which can be disturbed by a relatively low magnetic field.

High energy x-ray diffraction/x-ray fluorescence spectroscopy for high-throughput analysis of composition spread thin films

High-throughput crystallography is an important tool in materials research, particularly for the rapid assessment of structure-property relationships. We present a technique for simultaneous acquisition of diffraction images and fluorescence spectra on a continuous composition spread thin film using a 60 keV x-ray source. Subsequent noninteractive data processing provides maps of the diffraction profiles, thin film fiber texture, and composition. Even for highly textured films, our diffraction technique provides detection of diffraction from each family of Bragg reflections, which affords direct comparison of the measured profiles with powder patterns of known phases. These techniques are important for high throughput combinatorial studies as they provide structure and composition maps which may be correlated with performance trends within an inorganic library.

R-phase formation in Ti 39Ni 45Cu 16 shape memory thin films and bulk alloys discovered by combinatorial methods

The combinatorial fabrication and high-throughput characterization of a Ti–Ni–Cu shape memory thin film composition spread led to the discovery of the shape memory alloy Ti 39Ni 45Cu 16, which exhibits a single B2 → R-phase transformation above 25 °C with a thermal hysteresis width <1 K. Here we show that the thin film results correctly predict the phase transformation behavior of bulk material upon cooling from the high temperature phase. For both thin film and bulk, a two-step B2 → R-phase → B19′ transformation was found. The B2 → R-phase transformation can be exploited independently, due to a significant temperature separation of the two transformation steps. The shape memory effect in both thin film and bulk samples is limited due to the two-phase microstructure. Transmission electron microscopy investigations revealed the existence of Ti(Ni,Cu) 2 precipitates within the TiNi(Cu) matrix, which are concluded to be responsible for the R-phase formation and separation of the transformation steps.

C-16 High Energy XRD/XRF for High-Throughput Analysis of Composition Spread Thin Films

C-16 High Energy XRD/XRF for High-Throughput Analysis of Composition Spread Thin Films

High-throughput synthesis and characterization of anodic oxides on Nb–Ti alloys

Composition spread thin film samples of Nb and Ti were prepared by co-sputtering. The composition range from Nb–5 at.% Ti to Nb–78 at.% Ti was achieved and characterized by high resolution field emission scanning electron microscopy and grazing angle X-ray diffraction. Nb stabilized the β-Ti phase over the entire range studied. The structure was cubic with a continuous change in the lattice constants with composition. Several distinct compositional zones were identified in the as-deposited film morphology. Then, anodic oxides were grown potentiodynamically and characterized by electrochemical impedance spectroscopy using a scanning droplet cell to yield a comprehensive description of oxide film properties including dielectric permittivity, resistivity, thickness and film formation factor. Mott–Schottky analysis of potentiostatically grown oxides showed how the alloy composition influences the flat band potential and the donor density of the mixed n-type semiconducting oxides. Complementary X-ray photo electron spectroscopy as a chemical analysis revealed differences in the oxide compositions as compared to the as-deposited metal resulting from the different ion transport numbers.

437 サーモグラフィによる薄膜アモルファス合金ライブラリの結晶化開始温度測定法(複合機能化材料・デバイスとその加工プロセス)

In this paper, we develop a novel high-throughput characterization method of crystallization temperature on a thin film library with thin film composition spread. Crystallization temperature of thin film amorphous alloy can be detected as a change of emissivity using a thermography. For this method, a particular thin film library which has temperature reference area and tantalum covered grid is proposed and fabricated by MEMS process. Here, Pd-Cu-Si thin film library is deposited using combinatorial arc plasma deposition and 107 amorphous samples are confirmed on the library by X-ray diffraction as deposition with wide distribution of Pd at.%. The thin film library is heated by IR heater with thermography monitoring and crystallization temperature of 95 amorphous samples on the library can be detected at once.

Combinatorial Fabrications and Electronic-state Evaluations of Functional Complex Metal Oxides

We have developed a continuous composition spread-pulsed laser deposition (CCS-PLD) system of scanning laser for exploring new functional complex metal oxides. Our new CCS-PLD system is based on a precisely controlled synchronization between the laser firing, target exchange, linear mask motion and mirror swinging, and provides more flexibility and control than earlier PLD-based approaches. Most importantly, the deposition energetics and the film thickness are kept constant across the entire composition range by using scanning laser. In this study, we fabricated binary composition-spread films composed of LaNiO3 and LaMnO3. Synchrotron radiation-photoemission spectroscopy of LaNiO3-LaMnO3 composition spread films was carried out to evaluate the valence band electronic structures. Here we report on the high-throughput fabrications and evaluations using the combination of composition spread thin film growth techniques and synchrotron radiation-photoelectron spectroscopy.