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Hafnium silicates (HfO2:SiO2, HSO) have recently attracted much interest in the fields of fundamental science and technology because they have high dielectric constant and low leakage current. The structure and properties of HSO gate oxides were studied using a combinatorial continuous-compositional-spread method. HSO material libraries were synthesized on a 4-inch wafer at room temperature and at 200°C using a custom-built radio-frequency (RF) sputtering system. The electrical properties of HSO material libraries were measured using metal-oxide-semiconductor structure. X-ray diffraction (XRD) was utilized to characterize the structure and compositions of HSO material libraries. The effects of sputtering conditions on the properties of the HSO gate oxides were investigated. The dielectrics constants (εr) of HSO material libraries treated with rapid thermal annealing (600°C/1min/N2) were in the range 5∼23, as determined by C-V measurement, and the dielectric constant was observed to increase with HfO2 content. The I-V relations of the HSO material libraries indicate that the leakage current decreases as the amount of Si in the HSO films increases. The structural characteristics of HSO films with RTA treatment (1000°C/10sec/N2) varied from the amorphous to the crystalline state (tetragonal and monoclinic phase), according to the composition of material libraries. The correlation among the electrical properties, the composition and the crystal structure of the HSO films is discussed.
In this study, we produced Au-Sn alloy electroplated from a single solution and optimized the composition. The composition of electroplated Au-Sn alloy was Au-31.02 at.% Sn at the condition of 6 ms on - 4 ms off pulse current, 50 °C and 10 mA/cm2. Results in XRD analysis showed that Au-Sn alloy electroplated at DC 10 mA/cm2 had AuSn phase (δ) only and Au5Sn phase (d) appeared with decreasing the pulsed current on time. Also micro-patterned Au-Sn solder bump was produced by photolithography. Though it’s composition of Au-35.98 at.% Sn was not optimum, we tried to bond between Au-Sn solder bump and Si wafer that was coated with Ti (100 nm)/Au (300 nm).
The study and application of antimicrobial peptides is a growing niche field in the areas of pharmaceutics and medicinal chemistry. As a result, the majority of testing and development is completed under in vitro conditions. The use of synthetically derived antimicrobial peptides in applications outside the medical realm is a relatively untapped field, with the significance of interactions between antimicrobial oligopeptides and the ingredients of polymer systems being largely unknown. Water-based polymer coatings systems are attractive targets for microbial invasion because of their inherent material properties. Water-based polymer latex coatings contain a number of components which aide in stabilization and coalescence of the polymer particles, such as surfactants and polymeric cellulose-derived molecules, with several types of molecular structures existing for each. Microbes are able to flourish within the water phase of the latexes while taking sustenance from these dispersion components, resulting in a loss of properties commonly known as ‘spoilage’. This work addresses the impact of formulation variables, specifically surfactant structure, on the solution and antimicrobial behavior of a model antimicrobial oligopeptides through the use of HT absorbance measurements.
Formulators of complex mixtures have long known that the characteristics of their final formulation and the position of “equilibrium” often depends critically upon the order of addition of ingredients and the precise processing conditions under which the formulation was made. The large variety of possible outcomes derive from the many eigenstates that are available to each composition of a complex mixture due to the fact that the bonds between the component molecules are weak physical bonds and therefore a potential multitude of nanostructures can be formed. This is especially true of systems comprising polyelectrolytes and oppositely charged surfactants in the semi-dilute regime, because both polyelectrolyte conformation and surfactant micellar association structures are strongly influenced by the ionic environment of the polymer and surfactant molecules. This is especially important for 2-in-1 shampoos that depend upon the spontaneous creation of a polyelectrolyte/surfactant coacervate to deposit active conditioning, styling or antidandruff ingredients during the shampoo process. The investigation of the effects of order of addition requires exanimation of a myriad of samples and it is virtually impossible by conventional techniques. This task is ideally suited to investigation by a combinatorial approach aimed at the generation of libraries of pseudo-phase diagrams. In this study we developed a high-throughput screening method to generate phase diagrams over a large range of concentrations for cationic polysaccharide interaction with anionic surfactant in the presence and absence of dissolved electrolyte. Using a liquid handling system for sample preparation, we are able to analyze nearly 1000 samples per day, making the above goals of understanding electrolyte effects and coacervate structure-property relationships attainable.
Shape memory alloy (SMA) thin films are used as actuator materials in MEMS due to their unique properties. Binary thin films with a composition close to Ni50Ti50 are well-established materials, whereas ternaries like NiTiCu, NiTiPd, NiTiHf are less studied. Furthermore, new alloys are being developed which show a magnetic shape memory effect, e.g. Ni2MnGa. For the optimization of known, and the development of new, SMA thin films, a fast and reliable characterization technology is needed, which rapidly identifies the transformation temperatures (i.e. martensite and austenite start and finish temperatures) for a range of material compositions deposited on a whole wafer. In this paper, automated temperature-dependent resistance measurements are discussed as a means which yields the thermal hysteresis of the investigated thin films. Results of monitoring the uniformity of shape memory film depositions on the wafer level, as well as results on the use of this method as a tool for screening for new SMA films by characterization of materials libraries are reported.
Zirconium silicate is an extremely durable materials with the variety of useful optical and electronic properties and broad range of existing and potential applications. Using Density Functional Theory (DFT) in local density approximation (LDA) and generalized gradient approximation (GGA) with plane wave (PW) basis set we have revealed eight new polymorphs of ZrSiO4 within the energy range ∼1 eV above the most stable zircon which have higher and lower density than experimentally known zircon and reidite. Two structures, which have both silicon and zirconium atoms six-fold coordinated, orthorhombic AlTaO4-like (alumotantite) and monoclinic PbWO4-like (raspite), have similar energies at GGA level ∼0.35 eV above reidite and density intermediate between zircon and reidite. Among two low-density structures, which can be potentially revealed experimentally in the nanocrystalline thin films, the orthorhombic CaSO4-like form has energy similar to reidite but much lower density. We also conducted a comparative study of existing ZrO2 and SiO2 polymorphs, which demonstrates the higher accuracy of GGA approach.
By means of insertion of thin pentacene buffer layer, we have succeeded in the fabrication of highly c-axis oriented rubrene (5,6,11,12-tetraphenylnaphthacene) thin films and their field effect transistors (FETs). In the case without pentacene buffers, only amorphous rubrene films were obtained and their FETs did not show operation. After optimization of pentacene buffer by using combinatorial thickness-gradient method, we obtained the crystalline rubrene thin films and their FETs showed p-type operation with a mobility of 0.05 cm2/V·s and an on-off ratio of 106.
In order to optimize low electrical resistivity compositions of Pd-based thin film metallic glass (TFMG), Combinatorial arc plasma deposition (CAPD) was employed. A Pd-based continuous compositionally-graded thin film was deposited using CAPD in the experiments. To deposit the composition-grade of the Pd-rich thin film, the number of shots and the plasma strength were controlled. The deposited thin film was separated into 1,089 samples for measurements. The thickness, composition, phase and relative resistivity of these samples were measured respectively. And three amorphous CAPD samples exhibiting low relative resistivity were selected. To determine whether these were TFMG compositions, their compositions were reproduced on sputter-deposited samples and their Tg and Tx were measured. It was found that the sample of Pd81Cu5Si14 at.% showed the lowest absolute resistivity (60 μΩ·cm) and the largest temperature range of supercooled liquid region (SCLR) i.e., 60 K among all samples. The resistivity was 19% lower than conventional Pd-based TFMG and SCLR was two and half times as large. The tensile strength was higher than the conventional TFMG and the Young's modulus was lower than the conventional one.
This paper presents a preliminary investigation on the effectiveness of the new data management technique of data warehousing in organizing dental materials data in order to provide the efficient information services such as data retrieval and materials selection. A scaled-down version of the data warehouse for dental materials is constructed and an English Query application, which allows the end users to formulate their queries in natural English language, is developed on top of the data warehouse. The data warehouse supports five types of queries from basic practice of data retrieval to more advanced information service of materials selection. The results have demonstrated that the data warehousing technique is of a great potential in storing, processing and managing dental materials data.
Non-uniformity in the thickness of thin films can severely distort their transmission spectra as compared to those of flat, smooth films. Methods that extract properties such as refractive index, thickness, and extinction coefficient of such films can suffer inaccuracies when applied to wedged or rough films. In order to accurately extract optical properties of non-uniform films, we have developed a novel numerical method and efficient constitutive relations that can determine film properties from just the transmission spectrum. The Optimum Parameter Extraction (OPE) method can accommodate transparent or absorbing films thickness variations that result in significant errors in the values of refractive index and film thickness if not considered. A packing-density model was proposed and used for refractive index to accelerate the fitting routine and to avoid finding local minima instead of the global minimum. In this model, refractive index has one fitting parameter, the packing density, p. Therefore, the OPE method takes a shorter time and produces more accurate results than many other methods. We show that for actual PLD (Pulsed Laser Deposition) AlN thin films, properties such as refractive index, extinction coefficient, and film thickness were very accurately determined using our OPE method. These results are compared with two previous techniques to determine properties of thin films, and the accuracy and applicable conditions for all of these methods are discussed.
Combinatorial approaches are successfully applied for the optimization of electric write-once, thin-film Si antifuse memory devices, as well as for studying the solid-phase epitaxy kinetics of amorphous silicon on c-Si. High forward, low reverse current thin film Si diode deposition recipes are selected using cross-strips of different combinations of amorphous and microcrystalline doped layers, as well as a thickness-wedged intrinsic a-Si:H buffer layer. By studying switching in thickness-wedged a-Si:H layers, it is found that switching requires both a critical field and a critical bias voltage across the metallic contacts. Solid-phase epitaxy speed has a non-linear dependence on the film thickness, which is easily observed by optical image monitoring and analysis in wedged a-Si:H films on c-Si wafers.
This study focuses on the application of an image processing technique known as texture analysis to provide a complementary method to process non-contact atomic force microscopy data. For the current study, SrBi2Ta9O9 (SBT) thin films (∼200nm) on silicon samples were prepared via MOD and imaged via nc-AFM. Previous studies have qualitatively chosen grain size or grain density to quantify the surface characteristics of SBT but for this study texture analysis was used. Results obtained from the texture analysis and the subsequent stepwise discriminant analysis illustrated the importance of grain density and its effect on the statistics obtained from the gray scale cooccurrence matrix.
The need for fast and low-cost processes for compound development is obvious when “bespoke” products are required in small quantities. In a typical development workflow, many experiments are needed for the systematic study of the effects of additives and their potential synergistic interactions. This is usually accomplished using the one-variable-at-a-time variational principle. However, if the complexity of the formulation is high, the number of experiments that needs to be conducted soon becomes prohibitive. Therefore, new, but potentially more effective additives are not easily introduced. To address this problem, the plastics processing industry is turning to the notion of combinatorics, which has been shown to accelerate R&D times both in the pharmaceutical industry as well as in other areas of materials science such as catalysis and polymer chemistry.
The contribution discusses the development of a combinatorial compounding line, consisting of a production-size twin screw extruder with four gravimetric feeding units for the addition of additives. Furthermore, the development of fast on-line and in-line analytics for compound characterization is discussed.
The combinatorial fabrication of nanocrystalline Si particles embedded in a SiO2 matrix (nc-Si:SiO2) by RF co-sputtering of Si and SiO2 targets is described. The peak of the photoluminescence (PL) spectra of the films varies systematically from 760 to 600 nm, consistent with the presumed systematic variation in the size distribution of the embedded Si particles. The correlation between the optical properties of the samples and the formation parameters is also analyzed.
Predicting the properties and behavior of materials by computer simulation from a fundamental, ab initio perspective has long been a vision of computational material scientists. The key to achieving this goal is utilizing hierarchies of paradigms and scales that connect macrosystems to first principles quantum mechanics (QM). Here we describe a new software environment, the “Computational Materials Design Facility” (CMDF), capable of simulations of complex materials studies using a variety of simulation paradigms. The CMDF utilizes a Python scripting layer to integrate different computational tools to develop multi-scale simulation applications. We have integrated DFT QM methods, the first principles ReaxFF reactive force field, empirical all atom force fields (FFs), mesoscale and continuum methods. The central data structure Extended OpenBabel (XOB) plays a critical role as glue between applications. We demonstrate the usefulness of CMDF in examples that couple complex chemistry and mechanical properties during dynamical failure processes, as for example in a study of cracking of Ni under presence of O2.
With our present concern for a secure environment, the development of new radiation detection materials has focused on the capability of identifying potential radiation sources at increased sensitivity levels. As the initial framework for a materials-informatics approach to radiation detection materials, we have explored the use of both supervised (Support Vector Machines – SVM and Linear Discriminant Analysis – LDA) and unsupervised (Principal Component Analysis – PCA) learning methods for the development of structural signature models. Application of these methods yields complementary results, both of which are necessary to reduce parameter space and variable degeneracy. Using a crystal structure classification test, the use of the nonlinear SVM significantly increases predictive performance, suggesting trade-offs between smaller descriptor spaces and simpler linear models.
While measurement of magnetostriction in bulk materials is readily accomplished using a strain gauge, measurement of this quantity for thin films presents a greater challenge, and typically involves measurement of the overall wafer curvature (for a film of uniform composition) as a function of field. In order to evaluate magnetostriction locally in composition-spread samples, we have developed a method using a dense array of pre-fabricated cantilever beams on a silicon substrate prepared using MEMS techniques. Differential strain in the thin film/cantilever system results in curvature which is detected using an optical (laser/position-sensitive-detector) system. A magnetic field is applied using two orthogonal Helmholtz coils, and the resulting deflection-field curves are used to determine the saturation magnetostriction λs as well as dλ/dH. Our composition-spread films are prepared using a three gun on-axis magnetron cosputtering system. The position-dependent composition is inferred using rate calibrations and verified with electron microprobe and Rutherford Backscattering Spectroscopy. Preliminary experiments have validated the technique and the system has been used to measure magnetostriction in the Ni-Fe system. Our approach can also be used to measure properties of giant magnetostrictive materials (e.g. TbFe/Fe multilayers) as a function of layer thicknesses, or thin film shape-memory alloys, including magnetic shape-memory alloys.
This paper presents the characteristics of Mo-based (Mo-Zr based) amorphous alloys exhibiting a high crystallization temperature. In order to investigate the alloy composition showing an amorphous state in the Mo-Zr-X (X=Si and Al) alloy system, thin film libraries were prepared at first by combinatorial arc plasma deposition (CAPD). The composition region corresponding to the amorphous state was identified in the libraries with X-ray diffraction. On the basis of the alloy composition and phase distribution of the thin film libraries, additional amorphous Mo-Zr-Si and Mo-Zr-Al thin films were prepared by a carousel sputtering system. The crystallization temperature Tc of the amorphous Mo50Zr(50-x)Six thin films exceeded 1073 K. However, the Mo-Zr-Si thin films were so brittle that they could not be subjected to tensile testing. In the Mo-Zr-Al thin films, Tc of the Mo-rich MoxZr(90-x)Al10 and MoxZr(76-x)Al24 thin films exceeded 973 K. Although the toughness of Mo-based amorphous alloy thin films could be improved slightly by adding Al, the amorphous Mo-Zr-Al thin films were also brittle.
Combinatorial pulsed laser deposition approach is suitable to study complex effects such as composition, thickness and surface structure on thin film-based photocatalysis in high-throughput manner. We fabricated composition spreads and thickness gradient films of transition metal-doped SrTiO3(001) on various oxide single crystal substrates and evaluated their photocatalytic activity by the use of photoreduction of Ag+ in AgNO3 solution. We found anomalous film thickness and substrate effects on the Ag-photodeposition in the V-doped SrTiO3 epitaxial thin films grown on the Nb:SrTiO3(001) substrate.
Aluminum nitride (AlN), a wide band gap semiconductor (Eg = 6.2eV), has potential applications in microelectronics due to its excellent insulating properties and compatibility with silicon [1,2]. More recently, the use of AlN thin films in high electron mobility transistors, light emitting diodes and UV sources is explored by altering the band gap of the material . The present work describes the combinatorial synthesis of (Al,Ti)N thin films via pulsed laser deposition (PLD) technique to obtain desirable compositional spreads and corresponding variations in the electrical properties. Films of AlN, TiN and (Al,Ti)N were deposited on 6H-SiC (0001) substrates held at a temperature of 680°C. The surface quality of the films examined using an AFM revealed island growth of SiO2 and other growth patterns possibly related to substrate defects.
X-ray diffraction studies indicated that the growth of AlN and TiN films occurred with corresponding habit planes of (0002) and (111) parallel to the substrate surface. Compositional investigations conducted using energy dispersive spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS) showed systematic changes in the Al and Ti composition across the thickness of the compositional spread film. Cross-sectional analysis of (Al,Ti)N films conducted in a high-resolution transmission electron microscope revealed that the films were multi-layered. Several orders of magnitude decrease in the measured resistivity across a 15 mm length (Al,Ti)N film was noted corresponding to a systematic increase in the Ti content. Further optimization of deposition conditions is essential for producing thicker films.