Optical bandgap tailoring through compositional tuning in thermally evaporated antimony sulphoselenide solid solution thin films

Influence of strain on the dielectric properties of Bi–Zn–Ti–Nb–O solid solution thin films

The detachment and migration of colloidal particles is an important cause of permeability decline in the near wellbore region. It is shown that polymerizable ultra thin film can be utilized to immobilize fines on pore surfaces. The Surface Adsorption Polymerization (SAP) process developed here is a three step process requiring a sequential injection of a specific concentration of the surfactant, monomer, and initiator. An ionic surfactant is first adsorbed on the solid substrate or the porous medium. In the second step, a monomer is injected that preferentially resides in the surfactant layer. In the final step, an initiator is used to polymerize the monomer on the surface to form a solid ultra thin film which is very stable and effectively holds the colloids on the surface. There are three major advantages of such a treatment. Firstly, there is a great deal of flexibility in the choice of monomers and surfactants used so that the mechanical and chemical properties of the film, can be tailored to meet the needs of a particular application. Secondly, when applied to porous media or microporous membranes the ultra thin film does not cause pore closure. The film is extremely thin and the thickness of the film can be controlled by using appropriate concentrations of the monomer and surfactant. Lastly, the polymerization does not occur in the bulk solution, resulting in minimal waste or damage caused by polymer formation in the bulk solution. The SAP process can be potentially applied to stabilizing fines in high rate producers, as a post flush after acidizing and in specialized applications such as steam huff and puff wells.

Preparation and properties of Al1–xTixN solid solution thin films by multiple cathode sputtering

An electron impact spectrometer designed for measurement of energy loss spectra of low-energy electrons reflected from thin solid films is described. The spectrometer operates at impact energies as low as 1 eV and is capable of monitoring dynamic changes in electronic excitation cross-sections in the important threshold region. Spectra of benzene demonstrate a progression from vibrational excitation through electronic excitation to ionization as the most prominent energy loss mode as incident electron energy is increased. Excitations of benzene to the optically forbidden B1u3 or B2u1 states, while highly probable near threshold, show a rapid falloff in excitation probability at higher impact energies as compared to the optically allowed E1u1 ← A1g1 transition. In studies on 1-hexene, losses involving excitation to the lowest triplet state are also prominent near threshold.

Compound semiconductor based power devices such as SiC and GaN require high temperature operating passive devices such as a capacitor. SiC-based active devices can operate above 250 °C. The development of high-temperature operational passives is urgently needed to advance to the module and system level. In the case of capacitors, currently available capacitors can only operate efficiently up to 175 °C. Therefore, a thin film capacitor that can operate at high temperatures and be monolithically integrated near the active device should be developed. In this talk, I will present our achievements in the development of high-temperature operating dielectric film materials using the solid solution system. One topic is A2B2O7 pyrochlore ferroelectrics. The ferroelectric materials with the pyrochlore structure such as Sr2Nb2O7 exhibited the high dielectric constant above 100 at high and low temperature ranges. However, due to the crystallographic direction dependence of the Curie-Weiss temperature, the temperature stability of the dielectric constant from room temperature to 300 °C was not available. In order to obtain the high temperature stability of dielectric constant from room temperature to 300 °C with high dielectric constant over 100, the pyrochlore ferroelectric solid solution thin films were investigated by employing the combinatorial synthesis. Composition spread thin films of solid solution of two or three kinds of materials were deposited on substrates by physical vapor deposition technique, which provided the systematic physical properties. High-throughput combinatorial synthesis method is effective in the rapid optimization of the correlation between the crystallization and the dielectric property change behavior. For the composition spread solid solution film, the Sr- or La-containing A2B2O7 pyrochlore ferroelectrics were selected from the viewpoints of ion radios and crystallographic direction dependence of the Curie-Weiss temperature. The composition spread films were formed on a Pt/Ti/SiO2/Si substrate by combinatorial RF sputtering with stoichiometric composition targets. The X-ray fluorescence spectrum of the composition-spread film showed a linear variation of the metal composition. After deposition, the samples were annealed at different temperatures under oxygen atmosphere to reduce oxygen vacancies and improve crystallinity. The crystallization of the composition-spread solid solution thin film was confirmed by X-ray diffraction patterns, indicating the composition dependence of the crystallographic orientation. Some compositions showed high dielectric constant over 100 and high temperature stability from room temperature to 300 °C. In the presentation, the correlation between film composition, orientation and dielectric constant will be discussed in detail. In the presentation, we also introduce our achievement of the BaTiO3 based relaxor ferroelectrics and other dielectric materials development using the solid solution system. For the relaxor ferroelectrics, among the BaTiO3 based relaxor ferroelectrics, we have selected x[BaTiO3]-(1-x)[Bi(Mg2/3Nb1/3)O3] . The permittivity of 400 and the stability <8% from room temperature to 400 °C were obtained, which are promising as high-temperature dielectric medium.

The formation of the metastable orthorhombic phase (Pca21) in CeO2-HfO2 solid solution epitaxial thin films has been demonstrated. The films were deposited at room temperature on (001)yttria stabilized zirconia substrates by an Ar ion-beam sputtering method and subsequent annealing, where the Ce content of the films was controlled by changing the composition, x = [CeO2]/([HfO2]+[CeO2]), of the sputtering target. The chemical states of cations in xCeO2 − (1 − x)HfO2 (x = 0–0.5) thin films have been investigated by X-ray photoelectron spectroscopy, which confirmed the coexistence of Ce4+ and Ce3+. The crystal structure has been investigated by using X-ray diffraction and transmission electron microscopy. These analyses revealed that the metastable orthorhombic phase was formed in the films with x = 0.03–0.1, and the lattice constants of that phase increased with the Ce content. Microstructural analysis has been performed by using scanning transmission electron microscopy, which revealed a multidomain structure consisting of the orthorhombic phase. The polarization-electric field loop for the film with x = 0.1 indicated ferroelectricity, demonstrating that CeO2-HfO2 solid solution thin films are candidates for fluorite-type ferroelectrics.

Electrochemical analysis of thin film electrolytes and electrodes for application in rechargeable all solid state lithium microbatteries

BiFeO3–PbTiO3 (BF–PT) solid solution thin films were deposited on LaNiO3/SiO2/Si substrates by a sol–gel multilayer deposition method in a super clean room with rapid thermal annealing (RTA) technique. XRD patterns of all the films demonstrate a single perovskite phase. The induced orientation of LaNiO3 substrates leads to highly (100) oriented texture. Cross-section SEM and EDS pictures confirmed that the BFPT-based films are about 230 nm thickness and had formed a dense and uniform solid solution. Film with a ratio of BF:PT = 1:2 (BFPT1-2) possesses best ferroelectric properties. A saturated hysteresis loop with a remnant polarization of 66 μC/cm2 measured at room temperature was obtained, much higher than that of BFPT7030 thin film, which was prepared by depositing BFPT7030 sol directly on LaNiO3/SiO2/Si substrates without multilayer deposition. BFPT1-2 thin films also showed better dielectric and leakage current properties than BFPT7030 thin film in the test range of electric field and frequency. BFPT1-2 thin films exhibit lowest leakage current and loss tangent, indicating that a high quality of BFPT1-2 thin film was successfully prepared by multilayer deposition method with a RTA technique with heating rate of 1 °C/s.

Stimulus-responsive microporous solid thin films were successfully fabricated by simple molecular self-assembly via an amphiphilic block polymer, polystryene–b–polyacrylic acid (PS–b–PAA). The solid thin films exhibit different surface morphologies in response to external stimuli, such as environments with different pH values in aqueous solutions. The experiments have successfully applied atomic force microscope (AFM) technology to observe in-situ surface morphological changes. There is a reversible evolution of the microstructures in buffer solutions over a pH range of 2.4–9.2. These observations have been explained by positing that there is no conventional PAA swelling but that the PAA chains in the micropores stretch and contract with changes in the pH of the solution environment. The hydrophobicity of the solid thin film surface was transformed into super-hydrophilicity, as captured by optical contact angle measurements. The stimulus-responsive dynamics of pore sizes was described by a two-stage mechanism. A promising electrochemical application of this film is suggested via combination with an electrochemical impedance technique. This study is aimed at strategies for the functionalization of stimulus-responsive microporous solid thin films with reversible tunable surface morphologies, and exploring new smart materials with switch-on/switch-off behavior.

We investigated the fabrication conditions of a solid electrolyte Ta2O5 thin film suitable for an electrochromic (EC) all-solid-state switchable mirror glass to reduce material and processing costs. The film was deposited by reactive dc magnetron sputtering in a mixture gas of argon and oxygen. The electrochemical properties of the film on a WO3/ITO/glass substrate and the optical switching properties of the EC switchable mirror device were investigated, considering the thickness of the Ta2O5 thin film. All the films on WO3/ITO/glass substrates in this work exhibited similar current density, as measured by cyclic voltammetry. The electrochemical properties of the film with thickness reduced by 75% were almost the same as those of the conventional film. However, the device constructed with the thinner film displayed poor optical switching properties. Switching from the reflective state to the transparent state upon application of a voltage, the device with a 100-nm-thick film required a switching time that was 3 times longer than that of the conventional device constructed with a 400-nm-thick film. These results indicate that suitable fabrication conditions for the solid electrolyte Ta2O5 thin film of EC all-solid-state switchable mirror glass can potentially be found that reduce consumption of materials and shorten processing time.

Hafnia-zirconia (HfO2-ZrO2) solid solution thin films have emerged as viable candidates for electronic applications due to their compatibility with Si technology and demonstrated ferroelectricity at the nanoscale. The oxygen source in atomic layer deposition (ALD) plays a crucial role in determining the impurity concentration and phase composition of HfO2-ZrO2 within metal-ferroelectric-metal devices, notably at the Hf0.5Zr0.5O2 /TiN interface. The interface characteristics of HZO/TiN are fabricated via sequential no-atmosphere processing (SNAP) with either H2O or O2-plasma to study the influence of oxygen source on buried interfaces. Time-of-flight secondary ion mass spectrometry reveals that HZO films grown via O2-plasma promote the development of an interfacial TiOx layer at the bottom HZO/TiN interface. The presence of the TiOx layer leads to the development of 111-fiber texture in HZO as confirmed by two-dimensional X-ray diffraction (2D-XRD). Structural and chemical differences between HZO films grown via H2O or O2-plasma were found to strongly affect electrical characteristics such as permittivity, leakage current density, endurance, and switching kinetics. While HZO films grown via H2O yielded a higher remanent polarization value of 25 μC/cm2, HZO films grown via O2-plasma exhibited a comparable Pr of 21 μC/cm2 polarization and enhanced field cycling endurance limit by almost 2 orders of magnitude. Our study illustrates how oxygen sources (O2-plasma or H2O) in ALD can be a viable way to engineer the interface and properties in HZO thin films.

Phase-matched second-harmonic generation in solid thin films has been achieved by using gratings etched onto the surface of a nonlinear substrate to modulate the nonlinear susceptibility.

The temperature dependence of the capacitance of (111)c-oriented (0.90–x)BaTiO3-0.10Bi(Mg0.5Ti0.5)O3-xBiFeO3 solid solution films is investigated. These films are prepared on (111)cSrRuO3/(111)Pt/TiO2/SiO2/(100)Si substrates by the chemical solution deposition technique. All the films have perovskite structures and the crystal symmetry at room temperature varies with increasing x ratio, from pseudocubic when x = 0–0.30 to rhombohedral when x = 0.50–0.90. The pseudocubic phase shows a high relative dielectric constant (εr) (ranging between 400 and 560 at room temperature and an operating frequency of 100 kHz) and a low temperature dependence of capacitance up to 400°C, while maintaining a dielectric loss (tan δ) value of less than 0.2 at 100 kHz. In contrast, εr for the rhombohedral phase increases monotonically with increasing temperature up to 250°C, and increasingly high tan δ values are recorded at higher temperatures. These results indicate that pseudocubic (0.90–x)BaTiO3-0.10Bi(Mg0.5Ti0.5)O3-xBiFeO3 solid solution films with (111) orientation are suitable candidates for high-temperature capacitor applications.

The linear stability of freestanding thin films under the influence of attractive van der Waals forces is investigated for three rheological models, viz., Newtonian viscous films, viscoelastic solid films, and Jeffreys viscoelastic liquid films, with the aim of studying the role of rheology on the instability. Thin freestanding viscous films are unconditionally unstable, whereas the shear modulus in thin freestanding solid viscoelastic films governs the onset of instability. Interestingly, elasticity plays a dual role with regard to the stability of freestanding solid and liquid films: while it has a stabilizing influence on the former, it is destabilizing in the latter. Linear stability results of Jeffreys viscoelastic freestanding films are compared with those from supported films in the inertialess limit. The instability of Jeffreys viscoelastic freestanding film is unaffected by the relaxation time, but is enhanced with decrease in the viscosity ratio (μr, the ratio of solvent viscosity to total viscosity). The dominant length scale of instability in Jeffreys viscoelastic freestanding film shifts toward shorter wavelengths with decrease in μr. For μr→0, the maximum growth rate remains bounded in a freestanding viscoelastic film in the presence of inertia, but diverges in its absence, similar to supported viscoelastic films. In general, our results show that freestanding thin films exhibit faster dynamics than supported thin films. The mode of deformation of the freestanding film (viz., bending or squeezing) is not imposed a priori in our analysis and is found to be a squeezing (symmetric) mode with equal amplitudes at the interfaces.

Download options Please wait... Article information DOI https://doi.org/10.1039/B111035G Article type Paper Submitted 03 Dec 2001 Accepted 29 Jan 2002 First published 18 Mar 2002 Download Citation J. Mater. Chem., 2002,12, 1250-1255 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Stabilization of naphthalene-1,8:4,5-dicarboximide radicals in zirconium phosphonate solid materials and thin films S. Brochsztain, M. A. Rodrigues, G. J. F. Demets and M. J. Politi, J. Mater. Chem., 2002, 12, 1250 DOI: 10.1039/B111035G To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Sergio Brochsztain Magali A. Rodrigues Gregoire J. F. Demets Mario J. Politi