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• Pb(ZrxTi1-x)O3 (PZT) thin films synthesized on Si by physical vapor deposition. • TiO2 used as a buffer layer on Si resulted in a crack free surface of PZT. • We have investigated the transition from rhombohedral to tetragonal PZT structure. • This research explores the potential to use PZT films on Si devices. The integration of lead zirconate titanate (Pb(Zr x Ti 1-x)O 3) (PZT) compounds on Si substrates with a smooth surface would provide a key technology for silicon photonic devices. The quality of the deposited thin film is critical in order to integrate Pb(Zr x Ti 1-x)O 3 on Si substrates for applications such as pyroelectric mid-infrared detectors or optical modulators. Here, we have applied physical vapour deposition technique using a modified molecular beam epitaxy tool to deposit perovskite Pb(Zr x Ti 1-x)O 3 on Si and Pt substrates. We have developed a method to grow crack-free PZT films on Si substrates. The fabrication procedure entailed the use of TiO 2 as a buffer layer and post annealing of the PZT/TiO 2 /Si films under oxygen atmosphere. Cross section Scanning Electron Microscopy images enabled the identification of two distinct layers: PZT and TiO 2 , which was also confirmed by Spectroscopic Ellipsometry. X-Ray Diffraction patterns indicated the transition from the rhombohedral to the tetragonal phase and the formation of the perovskite phase of Pb(Zr 0.44 Ti 0.56)O 3. [ABSTRACT FROM AUTHOR]

The development of functional perovskites for future technologies can be achieved though the combinatorial synthetic method of evaporative physical vapour deposition (HT-ePVD) which provides a direct low temperature route to anion stoichiometric materials. When combined with the ability to control and vary precisely the composition of thin film libraries of materials, high-throughput methods of screening and characterisation provides a rapid experimental determination of the structure/function relationship. This review of the use of HT-ePVD shows that controlled cationic substitutions in A and/or B sites can easily be explored, as can the effect of anionic substitution. This is exemplified in using this approach for a wide range of perovskite systems, where the tuning of the functional properties through cation substitution has application in a broad range of technologies. [ABSTRACT FROM AUTHOR]

Abstract: A range of Ni–W thin film alloys have been synthesised by evaporation from atomic sources to produce a compositional gradient across the substrate, and characterised by X-ray diffraction (phase identification and crystallite size) and EDX (composition). The corrosion resistance of 100 discrete alloy compositions has been measured simultaneously in identical environments using a high-throughput screening protocol based on cyclic voltammetry. The corrosion resistances and potentials are extracted from potentiodynamic data by both the linear polarisation resistance (LPR) and Tafel extrapolation methods; results from these are shown to be self-consistent. The high-throughput approach allows, for the first time, a direct correlation to be made between the bulk crystalline phases and morphology, and the corrosion behaviour of Ni–W alloys. The incorporation of W in the Ni–W solid solution at low W compositions results in a continuous reduction in crystallite size, a small cathodic shift in corrosion potential, and a small reduction in corrosion resistance. A large cathodic shift in corrosion potential together with a significant increase in the corrosion resistance is observed for alloy compositions greater than 24%at. W. This composition range coincides with the formation of the amorphous phase. [Copyright &y& Elsevier]

Abstract: The corrosion behaviour of a series of NiCr thin film alloys were characterised through the high-throughput electrochemical measurement of their polarisation resistance on a micro-fabricated array of electrodes. The linear polarisation resistance (LPR) method has been compared to the results from Tafel extrapolation, and the alloy compositional dependence of the polarisation resistance as a function of composition is consistent. There are, however, some systematic differences in the absolute values extracted using the two methodologies which are likely to be a result of the smaller current densities associated with the LPR method. In the case of the NiCr alloys deposited at 300K, the observed bulk phases closely agree with those expected from the literature. The polarisation resistance behaviour is shown to be directly related to the bulk alloy structures. Besides the b.c.c. α-Cr(Im3m) phase and its Ni solid solutions which exhibit the highest polarisation resistances, the σ-Cr3Ni2(P42/mnm) phase exhibits the next best polarisation resistance, and its co-existence with the σ-Cr7Ni3 (P42/mnm) phase at higher Cr content results in a lowering of that resistance. [Copyright &y& Elsevier]

A study of the lithium ion conductor Li3xLa2/3-xTiO3 solid solution and the surrounding composition space was carried out using a high throughput physical vapor deposition system. An optimum total ionic conductivity value of 5.45 x 10-4 S cm-1 was obtained for the composition Li0.17La0.29Ti0.54 (Li3xLa2/3-xTiO3 x = 0.11). This optimum value was calculated using an artificial neural network model based on the empirical data. Due to the large scale of the data set produced and the complexity of synthesis, informatics tools were required to analyze the data. Partition analysis was carried out to determine the synthetic parameters of importance and their threshold values. Multivariate curve resolution and principal component analysis were applied to the dim-action data set. This analysis enabled the construction of phase distribution diagrams, illustrating both the phases obtained and the compositional zones in which they occur. The synthetic technique presented has Significant advantages over other thin film and bulk methodologies. In terms of both the compositional range covered and the nature of the materials produced. [ABSTRACT FROM AUTHOR]

Abstract: Most high throughput studies focus on assessing the effect of composition within a single known fundamental structure type, such as perovskite. Here we demonstrate how high throughput synthesis and screening can be used to establish structure–property relations in the PbO–Nb2O5 system, for which eight distinct fundamental structure types are known to exist. PbNb4O11, PbNb2O6 and pyrochlore could be easily distinguished by X-ray diffraction (XRD). However, XRD was insensitive to distortions of the pyrochlore structure and instead Raman spectroscopy was utilized to determine changes in symmetry from cubic to rhombohedral as the PbO concentration increased. High throughput screening of the capacitance revealed permittivity (εr ) maxima in the PbNb4O11 (εr =700) and cubic pyrochlore phases (εr =450). The εr of PbNb4O11 has not to date been reported but the value for cubic pyrochlore is higher than that reported for bulk ceramics (εr =270). Initial high electric field studies also revealed exceptionally high tunability (four times that reported for bismuth zinc niobate-based pyrochlores) of the capacitance in the pyrochlore phase. [Copyright &y& Elsevier]

Polycrystalline thin-film libraries of Bi2O3-TiO2-Na2O system have been synthesised over a wide composition region using elemental molecular beam epitaxy sources combined with an oxygen plasma source. Structural characterisation and the screening of both dielectric and ferroelectric properties of fabricated compounds have been carried out. The bismuth sodium titanate perovskite-type phases exhibited a high relative permittivity (up to 375), a loss tangent lower than 0.02 and ferroelectric properties superior to thin films synthesised using other deposition methods: a remnant polarization, Pr, approximately 22 μC/cm2 was observed in the optimal composition range. The high throughput approach allowed us to establish clearly the compositional boundaries of the ferroelectric perovskite phase in the system. [ABSTRACT FROM AUTHOR]

Memory structures play a basic role in providing integrated circuits of powerful processing capabilities. Even most powerful processors have nothing to offer without an accompanying memory and importantly, the development of mobile devices is dependent on the continual improvement of memory technology. Herein, we report the synthesis of TiO 2 thin films on SSTOP (Pt/TiO 2 /SiO 2 /Si) substrate via physical vapour deposition process for the first time. The layers consisted of Si, SiO 2 , TiO 2 and Pt, hence the SSTOP shorthand is used throughout the text. Three different phases of TiO 2 thin films were obtained, i.e. amorphous, anatase and rutile phases, by controlling the reaction parameters which were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM) and Raman-scattering spectroscopy in order to understand the crystallographic, morphological, compositional and scattering properties. The detailed studies confirmed the formation of various crystal phases of titania. The grown thin films on SSTOP substrates were further utilized to fabricate resistive random access memory (ReRAM) devices and the initial electrical screening was performed on capacitor-like structures which were prepared using platinum top electrodes (diameter = 250 μm) on a 14 × 14 array metal contact mask. Current-Voltage (I–V) measurements were implemented employing a range of current compliances (IC). The detailed electrical characterizations revealed that the forming field for a switchable unipolar device was found to be greatest on rutile titania and lowest on the amorphous titania phase. Similarity, the resistive contrast was greatest on the rutile titania phase and lowest on the anatase titania phase. Design for ReRAM device based on Pt/TiO 2 /SiO 2 /Si (SSTOP) substrate. Image 1 [ABSTRACT FROM AUTHOR]