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We present PyOECP, a Python-based flexible open-source software for estimating and modeling the complex permittivity obtained from the open-ended coaxial probe (OECP) technique. The transformation of the measured reflection coefficient to complex permittivity is performed based on two different models, including the capacitance model and the antenna model. The software library contains the dielectric spectra of common reference liquids, which can be used to transform the reflection coefficient into the dielectric spectra. Several Python routines that are commonly employed (e.g., SciPy and NumPy) in the field of science and engineering are only required so that the users can alter the software structure depending on their needs. The modeling algorithm exploits the Markov Chain Monte Carlo method for the data regression. The discrete relaxation models can be built by a proper combination of well-known relaxation models. In addition to these models, the electrode polarization, which is a common measurement artifact for interpreting the dielectric spectra, can be incorporated in the modeling algorithm. A continuous relaxation model, which solves the Fredholm integral equation of the first kind (a mathematically ill-posed problem) is also included. This open-source software enables users to freely adjust the physical parameters so that they can obtain physical insight into their materials under test and will be consistently updated for more accurate measurement and interpretation of dielectric spectra in an automated manner. This work describes the theoretical and mathematical background of the software, lays out the workflow, validates the software functionality based on both synthetic and empirical data included in the software., 24 pages, 6 figures, submitted for publication

Capacitive deionization has received significant attention as an energy-efficient technology for brackish water desalination. The capacitive deionization suffers from lower water recovery and high electrode discharge time, that hampers its economics. The low recovery ratio increases the brine disposal cost and is also environmentally polluting. In this paper, the feasibility of capacitive deionization as a brackish water desalination technology is studied. The capacitive deionization performance is first optimized and is later compared with the state-of-the-art reverse osmosis. Both modeling and experimental studies are carried out to optimize the performance of capacitive deionization. A new cost correlation as a function of the capacitive deionization system size is proposed. By optimally designing the system, the treated water cost for capacitive deionization is reduced by 36%. A feasibility map for capacitive deionization is generated and compared to reverse osmosis as a function of brackish water concentration and different brine disposal options (see the graphical abstract). Compared to reverse osmosis, capacitive deionization economics are sensitive to the feed concentrations but becomes superior for salt concentrations less than (a) 70 ± 15 mM (surface brine discharge), (b) 65 ± 13 mM (deep well injection), and (c) 43 ± 10 mM (evaporation pond). For zero liquid discharge, the CDI is not economical compared to RO regardless of salt concentrations. Based on the feasibility map generated in this paper, the optimal technology for desalination can be selected as a function of brackish water concentration and brine disposal.

Diagnosis and monitoring of corrosion at high temperatures are common challenges in many industries, such as conventional power plants and next generation molten-salt reactor (MSR) nuclear power plants. A simple, noninvasive, in situ acoustic technique was developed to monitor wall loss due to corrosion in a model molten-salt vessel, operating at 500°C to 600°C. This work demonstrated the feasibility of high-temperature corrosion monitoring experimentally, and validated the concept with physical and microstructural analysis, modeling, and numerical simulations. The results of this work could form the basis for the development of a general-purpose, extended-range acoustic monitoring and inspection technique for corrosion at high temperatures (with expected upper range of approximately 900°C), which does not currently exist. Such a technique could be critical for the safe operation of MSRs in the future, as well as for rapid, nondestructive testing of new reactor component materials.

Specific conductance and frequency-dependent resistance (impedance) data are widely utilized for understanding the physicochemical characteristics of aqueous and non-aqueous fluids and for evaluating the performance of chemical processes. However, the implementation of such an in-situ probe in high-temperature and high-pressure environments is not trivial. This work provides a description of both the hardware and software associated with implementing a parallel-type in-situ electrochemical sensor. The sensor can be used for in-line monitoring of thermal desalination processes and for impedance measurements in fluids at high temperature and pressure. A comparison between the experimental measurements on the specific conductance in aqueous sodium chloride solutions and the conductance model demonstrate that the methodology yields reasonable agreement with both the model and literature data. A combination of hardware components, a software-based correction for experimental artifacts, and computational fluid dynamics (CFD) calculations used in this work provide a sound basis for implementing such in-situ electrochemical sensors to measure frequency-dependent resistance spectra., Comment: 25 pages, 9 figures, to be submitted for publication

Molecular dynamics (MD) simulations to understand the thermodynamic, dynamic, and structural changes in supercritical water across the Frenkel line and the melting line have been performed. The two-phase thermodynamic model [J. Phys. Chem. B, 2010, 114(24), 8191–8198] and the velocity autocorrelation functions are used to locate the Frenkel line and to calculate the thermodynamic and dynamic properties. The Frenkel lines obtained from the two-phase thermodynamic model and the velocity autocorrelation criterion do not agree with each other. Structural characteristics and the translational diffusion dynamics of water suggest that this inconsistency could arise from the two oscillatory modes in water, which are associated with the bending of hydrogen bonds and intermolecular collisions inside the first coordination shell. The overall results lead us to conclude that the universality of the Frenkel line as a dynamic crossover line from rigid to nonrigid fluids is preserved in water.

Current commercial long-range guided wave inspection and monitoring technologies for pipes usually require establishment of certain specific acoustic modes for wave propagation and use a large number of sensors in a certain geometric arrangement (for example, uniformly-spaced arrays of sensors on a collar, placed around a pipe). This paper, in contrast, presents a long-range corrosion detection method in pipes based on multi-mode guided acoustic waves, generated and received using simple, single-element sensors. In this technique, available guided wave modes in any interrogated zone of the structure are automatically down-selected by the medium, and changes in energy distribution over the selected modes are analyzed through signal processing to monitor material loss or addition. To investigate the feasibility of the proposed method, we have performed both experimental and numerical simulation studies on 50.8-mm (2-in)-diameter schedule-40 carbon steel pipes. In these studies, a linear chirp signal is injected in compression mode, perpendicular to the surface of the pipe, generating multi-mode, multi-directional guided waves that travel within the pipe wall. Corrosion effects in the pipes are simulated numerically and experimentally. To reduce errors in the measurement technique due to changes in the local or global temperature of the measured media, a universal temperature compensation algorithm is introduced. The experimental results show good agreement with simulation results, indicating that the proposed multi-mode wave generation and detection in a pipe could be used for long-range detection and monitoring of corrosion effects, such as pipe wall losses or solid material deposits.

We have performed classical molecular dynamics (MD) simulations of aqueous sodium chloride (NaCl) solutions from 298 to 674 K at 200 bars to understand the influence of ion pairing and ion self-diffusion on electrical conductivity in high-temperature/high-pressure salt solutions. Conductivity data obtained from the MD simulation highlight an apparent anomaly, namely, a conductivity maximum as temperature increases along an isobar, which has been also observed in experimental studies. By examining both velocity autocorrelation and cross-correlation terms of the Green-Kubo integral, we quantitatively demonstrate that the conductivity anomaly arises mainly from a competition between the single-ion self-diffusion and the contact ion pair formation. The velocity autocorrelation function in conjunction with structural analysis suggests that diffusive motion of ions is suppressed at high temperatures due to the persistence of an inner hydration shell. The contribution of velocity cross-correlation functions between oppositely charged ions becomes significant at the onset of the conductivity decrease. Structural analysis based on Voronoi tessellation and pair correlation functions indicates that the fraction of contact ion pairs increases as temperature increases. Spatial decomposition of the electrical conductivity also indicates that the formation of contact ion pairs significantly decreases the electrical conductivity compared to Nernst-Einstein conductivity, but the contribution of distant opposite charges cannot be ignored except at the highest temperature due to unscreened long-range interactions.

Supercritical water desalination (SCWD) is zero liquid discharge technology that can potentially control the solubility of different electrolytes. However, SCWD is an energy-intensive process and requires high-quality thermal heat (> 450 °C). This study proposes the integration of a high-temperature heat pump to reduce the SCWD energy requirement. The integrated system energy consumption improves by 36% for 3.5% feed concentration and 14% for 20% feed, and the distillate cost reduces by 15% and 10%. Another benefit of the proposed integration is the system can be operated using only electricity as a heat source, as is the case with commonly used high-recovery thermal desalination technology. The integrated SCWD-heat pump system shows superior performance compared to the commercially used brine concentrator and crystallizer system. It is approximately 20% more energy-efficient for 25% feed concentration and 8% cheaper. Hence, the integrated SCWD-heat pump has the potential to outperform the pre-existing high-recovery desalination technology.

An open-ended coaxial probe was used to study the dielectric relaxation of neodymium chloride (NdCl3) in water and in methanol at room temperature over the frequency range 0.2–40.0 GHz. An equivalent circuit model based on the antenna model was used to obtain the dielectric spectra with the effective removal of spurious effects. This extends the use of the open-ended coaxial probe technique for highly conductive substances. The structural and thermodynamic parameters obtained from the dielectric spectra of aqueous NdCl3 solutions suggest that solvent-separated ion pairs and solvent-shared ion pairs dominate the low-frequency behavior at low concentrations. In methanol, solvent-shared ion pair relaxation modes were detected. No contact pair relaxation was observed in either solvent. Under all conditions, Nd3+ was strongly solvated, as reflected by its high effective hydration number. The estimated association constant of NdCl3 in water at infinite dilution was within the literature values and was lower than that observed in methanol.

We report properties of polycrystalline MgB2 films deposited on thin flexible yttium-stabilized zirconia (YSZ) substrates by hybrid physical-chemical vapor deposition. The MgB2 films show a transition temperature of 38.9 K with a narrow superconducting transition (0.1 K). The self-field critical current density in the films reaches 107 A/cm2 at low temperatures. These properties do not change after repeated bending over a radius of 10 mm. Low microwave surface resistance comparable to those obtained in epitaxial MgB2 films on single-crystalline sapphire substrate was observed. The result shows promise of polycrystalline MgB2 films for applications in superconducting digital circuits as well as in coated conductor wires.

We report the studies on the effect of grain alignment on lateral carrier transport in nominally 〈001〉-oriented aligned-crystalline silicon (ACSi) films on polycrystalline substrates. With improving grain alignment, energy barrier height at the grain boundaries was reduced from 150 to less than 1 meV, and both conductivity and Hall mobility became less sensitive to hydrogen passivation. This suggests that the dangling bonds in ACSi films are a major source of trapping sites, and that they become less dominant with improving grain alignment. These results demonstrate that improving grain alignment enhances the lateral carrier transport in small-grained (≤1 μm) polycrystalline silicon films, by reducing dangling bond density at the grain boundaries.

We have grown MgB/sub 2/ films using the deposition technique of reactive evaporation. This method allows high-quality, large-area, double-sided films to be grown on a large variety of substrate materials. These films are therefore well suited for applications, several of which may exploit the low-loss high-frequency properties of MgB/sub 2/, including passive microwave resonators and filters, nuclear magnetic resonance coils, and RF cavities for particle accelerators. Determining the surface resistance and nonlinear properties of our films can thus give us an idea of their suitability for these applications, as well as tell us something about their fundamental superconducting nature. We have begun measuring the microwave properties of our films using both a parallel plate technique and by patterning the films into stripline resonators and lumped-element resonators and filters. The films display very low surface resistance values.

The effect of process conditions on the biaxial texture of MgO films grown by ion-beam-assisted deposition (IBAD) was studied. The texture showed a strong dependence on the Ar+/MgO flux ratio, but a weak dependence on the divergence of Ar+ beam. One hundred-nanometer-thick epi-MgO on less than 10-nm-thick textured IBAD-MgO films that were grown on 7-nm-thick Y2O3 layers on fused silica, metal alloy tape, and polished Si substrates showed biaxial texture with in- and out-of-plane orientation distributions of less than 4° and 2°, respectively. These results strengthen the notion that the IBAD technique could serve as a universal technological process to integrate amorphous and polycrystalline substrates with various oxide and semiconductor films that need to be grown with good biaxial texture.

In order to accelerate research and development of coated conductors (CC), a new facility has been developed at Los Alamos National Laboratory (LANL) with labs dedicated to scaled-up fabrication and characterization of CC. These laboratories include facilities for metal tape preparation, ion-beam assisted deposition (IBAD) of template layers, superconductor deposition by laser ablation (PLD), as well as materials characterization including low-temperature transport measurements. The work builds on the prior successes of the LANL CC program, such as the benchmark results of critical currents over 300 A on 1-cm-wide short samples deposited via IBAD and PLD. The new labs have recently been completed and include the ability for reel-to-reel tape processing and characterization. Fabrication of long lengths of tape (>10 m) allow for high-throughput experimentation by linear combinatorial design. This facility is also made to enable collaboration with industrial and other partners.

New discoveries on collective processes in materials fabrication and performance are emerging in the mesoscopic size regime between the nanoscale, where atomistic effects dominate, and the macroscale, where bulk-like behavior rules. For semiconductor electronics and photonics, dimensional control of the architecture in this regime is the limiting factor for device performance. Epitaxial crystal growth is the major tool enabling simultaneous control of the dimensions and properties of such architectures. Although size-dependent effects have been studied for many small-scale systems, they have not been reported for the epitaxial growth of Si crystalline surfaces. Here, we show a strong dependence of epitaxial growth rates on size for nano to microscale radial wires and planar stripes. A model for this unexpected size-dependent vapor phase epitaxy behavior at small dimensions suggests that these effects are universal and result from an enhanced surface desorption of the silane (SiH4) growth precursor near facet edges. Introducing phosphorus or boron dopants during the silicon epitaxy further decreases the growth rates and, for phosphorus, gives rise to a critical layer thickness for single crystalline epitaxial growth. This previously unknown mesoscopic size-dependent growth effect at mesoscopic dimensions points to a new mechanism in vapor phase growth and promises greater control of advanced device geometries.

Our work on tunable rf and microwave devices based on 90° off-axis magnetron sputtered Ba0.6Sr0.4TiO3 epitaxial thin films is reviewed. In particular, we have studied the effects of energetic bombardment during deposition on the structural and electrical properties of these films. The fundamental result of changing the energetic bombardment conditions during deposition is to affect the stress/strain state of the films. We show that high bombardment conditions result in films with significantly extended out-of-plane lattice constants and depressed dielectric constants and tunabilities.

We report the fabrication of SmBa2Cu3O7−δ (Sm123) films on YBa2Cu307−δ(Y123) buffer layers 10–20nm thick using pulsed-laser deposition. Significant improvement in the superconducting properties of Sm 123 such as Tc and Jc has been observed when Y123 buffer layers are used on various substrates (LaAlO3, SrTiO3, NdGaO3 and CeO2/(yttrium-stabilized zirconia)). The buffered Sm 123 films have a high Tc of 93.1 K and a high Jc of 1.9 × 106 Acm−2 at 75 K in zero magnetic field. Compared with Y123, the buffered Sm123 samples have com-parable microwave surface resistance values and pinning characteristics with reduced anisotropy measured by the angle-dependent Ic. The effects of the Y123 buffer layer on the superconducting properties of Sm 123 are investigated and discussed in relation to the initial film growth chemistry and the substitution of Sm on Ba sites.

We present a comprehensive study of broadband (0–2 GHz) electrodynamic properties of coplanar waveguides made from high-temperature superconducting thin-film YBa2Cu3O7−δ electrodes on nonlinear dielectric single-crystal SrTiO3 substrates. The waveguides exhibit strong dielectric nonlinearities, in addition to temperature-, dc-bias-, and frequency-dependent dissipation and refractive index. By using parameters determined from small-signal (linear) transmission characteristics of the waveguides as a function of dc bias, we develop a model equation that successfully predicts and describes large-signal (nonlinear) behavior.

Nonlinear dielectrics, such as SrTiO3 (STO), present unique opportunity not only to develop practical electrically tunable devices, but also to explore novel scientific and technological concepts that exploit strong nonlinearities in these materials. Using prototype device structures, we are currently investigating two interesting phenomena in the realm of nonlinearity: microwave solitons and stochastic resonance. Microwave solitons are similar to optical solitons and are formed when a specific dispersion is introduced into the medium to counteract and balance the effect of nonlinearity for certain waveforms. Stochastic resonance is a phenomenon in which random noise plays a constructive role and enhances a nonlinear system's response to a deterministic signal.

Microwave devices using coplanar waveguide (CPW) structures which incorporate bilayers of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ and nonlinear dielectric SrTiO/sub 3/ on 1 cm/spl times/1 cm/spl times/0.5 mm LaAlO/sub 3/ substrates. The microwave devices include voltage-tunable phase shifters and delay lines, voltage-tunable mixers, and voltage-tunable and adaptive bandpass filters. Under dc voltage bias, these compact CPW devices exhibit more than 360/spl deg/ relative phase shift at 2 GHz, more than 30 dB tunability in mixed microwave power between 0.7 GHz and 5.9 GHz, and fine-tunable symmetric filter profile at around 2.5 GHz with less than 2% bandwidth and more than 15% adaptive range.

We measured the microwave surface resistance R/sub s/ of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/(YBCO) films on buffered polycrystalline alumina and Ni-based alloy substrates using parallel-plate technique. We observed a strong between the low-power R/sub s/ and the in-plane mosaic spread of the YBCO films. A 0.4-/spl mu/m-thick YBCO film with an in-plane mosaic spread of 6.60 (7/spl deg/) on a buffered polycrystalline alloy (buffered polycrystalline alumina) showed an R/sub s/ of 0.51 m/spl Omega/ (1.89 m/spl Omega/) at 76 K and 0.17 m/spl Omega/ (0.21 m/spl Omega/) at 4 K.

Using pulsed-laser deposition, We grew quaternary Ba0.5Sr0.5TiO3 thin films heteroepitaxially on (100) LaAlO3 substrates with conductive SrRuO3 as a bottom electrode. The microstructure of this multilayer of Ba0.5Sr0.5TiO3/SrRuO3/LaAlO3, was characterized by X-ray diffraction and cross-sectional transmission electron microscopy. The heteroepitaxial growth relationship was found to be (h00)Ba0.5Sr0.5TiO3‖(00l)SrRuO3‖(h00)LaAlO3 and (110)Ba0.5Sr0.5TiO3‖⟨100⟩SrRuO3‖⟨110⟩LaAlO3. The high dielectric constant of the crystalline Ba0.5Sr0.5TiO3 thin films and the low leakage current of the Ba0.5Sr0.5TiO3 film sandwiched between a top Au and bottom SrRuO3 electrodes are attributed to the structural perfection of the films and the clean interfaces between layers.

Highly conductive RuO2 thin films were epitaxially grown on (100) LaAlO3 substrates by pulsed laser deposition. The RuO2 film deposited with optimized conditions was (h00) oriented normal to the substrate surface with strong in-plane orientation. The RuO2 thin films deposited at temperatures of above 500 °C demonstrated a room-temperature resistivity of 35 ± 2 μΩ-cm. The Ba0.5Sr0.5TiO3 thin films deposited on epi-RuO2 showed pure (111) orientation normal to the substrate surface, and exhibited dielectric constant above 600 and dielectric loss of 0.03–0.05 at 100 kHz under zero dc bias.

Conductive SrRuO3 thin films were epitaxially grown on (100) LaAlO3 substrates by pulsed laser deposition over a temperature range from 650 °C to 825 °C. Well-textured films exhibiting a strong orientation relationship to the underlying substrate could be obtained at a deposition temperature as low as 450 °C. The degree of crystallinity of the films improved with increasing deposition temperature as confirmed by x-ray diffraction, transmission electron microscopy, and scanning tunneling microscopy. Scanning electron microscopy revealed no particulates on the film surface. The resistivity of the SrRuO3 thin films was found to be a strong function of the crystallinity of the film and hence the substrate temperature during film deposition. A residual resistivity ratio (RRR = ρ300 K/ρ4.2 K) of more than 8 was obtained for the SrRuO3 thin films deposited under optimized processing conditions.

We have studied voltage-tunable (0–200 V) broadband (0.1–5.1 GHz) microwave properties at room temperature and the liquid nitrogen temperature of two coplanar waveguide devices made from a Au / Sr0.5Ba0.5TiO3 bilayer and a YBa2Cu3O7-x / SrTiO3 bilayer, respectively. The experimental results agree well with the predictions of simple quasistatic and quasi-TEM models. © 1995 John Wiley & Sons, Inc.

We present a summary of our work on the dc electric field effect on the microwave properties of YBa2Cu3O7/SrTiO3 (YBCO/STO) layered structures. We briefly describe the fabrication of these layered structures, their structural and electrical properties related to the microwave response, and experimental methods to investigate dc electric field effects at microwave frequencies. Analysis of microwave measurements shows that dc electric field modulated changes in both the complex conductivity of YBCO layers and the dielectric properties of the STO layers contribute to the overall device response. At low temperatures (

A noncontact cryogenic microwave measurement system has been developed for the characterization of passive and active superconducting devices by means of an unloaded quality factor measurement technique. The measurement system was designed specifically for the characterization of planar thin film resonant structures as a function of temperature (4–300 K), frequency (100 MHz–26.5 GHz), and dc voltage bias (≤100 V). It has been used for basic device studies of novel active superconducting lumped components made of metal‐oxide superconductor/insulator heterostructures.

We report on experiments using compact coplanar waveguide devices, incorporating thin-film superconducting YBa2Cu3O7 electrodes. The substrate is strontium titanate, whose nonlinear dielectric properties are dependent on temperature and applied electric field. Close to zero dc bias, the frequency-doubled microwave power output increases by several orders of magnitude with modest broadband noise input. Experimental results are supported by analytical and numerical calculations based on a nonlinear wave equation.

The growth of epitaxial semiconductor nanostructures and films at low temperatures is important for semiconductor technology because it allows the possibility of monolithically integrating different high-performance single-crystalline semiconductor structures directly onto low cost technologically important substrates. At sufficiently low temperatures this can enable, for example, Si or Ge device fabrication on flexible substrates such as plastics. We have studied the reduced-temperature liquid-mediated growth of Ge nanostructures and films on crystalline template layers on non-single-crystalline substrates in a low-pressure chemical vapor deposition (LPCVD) system. The heteroepitaxial process is implemented by the Au seeded vapor-liquidsolid (VLS) catalytic growth technique with germane below 400 ºC. Crystalline template layers were prepared with ion-beam-assisted-deposition (IBAD) texturing and electron-beam evaporation on glass substrates. A thin layer of e-beam evaporated Au forms the catalyst layer, upon which we grew Ge films at 386 ºC. Scanning electron microscopy and x-ray diffraction results indicated that both Ge islands and nanowires grew heteroepitaxially on the crystalline template layers on glass substrates with good alignment over large areas.

Using pulsed laser deposition, the authors have prepared epitaxial heterostructures of a new insulating perovskite Sr/sub 2/AlTaO/sub 6/ (SAT) and the high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) on LaAlO/sub 3/ substrates. X-ray rocking curve and Rutherford backscattering channeling measurements on

Dynamic time expansion or compression of a small-amplitude input signal generated with an initial scale is performed using a nonlinear waveguide. A nonlinear waveguide having a variable refractive index is connected to a bias voltage source having a bias signal amplitude that is large relative to the input signal to vary the reflective index and concomitant speed of propagation of the nonlinear waveguide and an electrical circuit for applying the small-amplitude signal and the large amplitude bias signal simultaneously to the nonlinear waveguide. The large amplitude bias signal with the input signal alters the speed of propagation of the small-amplitude signal with time in the nonlinear waveguide to expand or contract the initial time scale of the small-amplitude input signal.

We report a systematic study of the microstructure and dielectric properties of barium strontium titanate, Ba1−xSrxTiO3, films grown by laser ablation on LaAlO3 substrates, where x=0.1–0.9 at an interval of 0.1. X-ray diffraction analysis shows that when x 0.4, compared with the peak temperatures of the bulk Ba1−xSrxTiO3. At room temperature, the dielectric constant and tunability are relatively high when x⩽0.4 but start to decrease rapidly as x increases.

Fundamental issues in preparing high-quality high-T/sub c/ YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films are addressed. The techniques of inverted cylindrical magneton sputtering and pulsed laser deposition are chosen as successful examples to illustrate how the key problems can be solved. The fabrication of YBa/sub 2/Cu/sub 3/O/sub 7-x//PrBa/sub 2/Cu/sub 3/O/sub 7-x/ superlattices where superconductivity in a single unit cell layer of YBa/sub 2/Cu/sub 3/O/sub 7-x/ was observed demonstrates the state of the art of thin-film deposition of high-T/sub c/ materials. Systematic variations of the deposition parameters result in changes of superconducting and structural properties of the films that correlate with their microwave and infrared characteristics.

We have used a coplanar waveguide structure to study broadband electrodynamic properties of single-crystal and thin-film strontium titanate. We have incorporated both time- and frequency-domain measurements to determine small-signal effective refractive index and loss tangent as functions of frequency (up to 4 GHz), dc bias (up to 106 V/m), and cryogenic temperature (17 and 60 K). The large-signal impulse response of the devices and the associated phenomenological nonlinear wave equation illustrate how dissipation and nonlinearity combine to produce the overall response in the large-signal regime.

We have studied electromagnetic pulse shaping in coplanar waveguide delay lines made from superconducting YBa2Cu3O7−δ electrodes on nonlinear dielectric SrTiO3 single-crystal substrates. The delay lines exhibited bias- and temperature-dependent nonlinearity and dispersion, with associated pulse-shaping effects. At low temperatures and under certain bias conditions, the interplay of dispersion and nonlinearity has led to stable and compact wave forms, reminiscent of microwave solitons.

Biaxially oriented nonlinear dielectric Ba0.6Sr0.4TiO3 (BST) films have been grown on polycrystalline ferrite yttrium iron garnet (YIG) substrates. We use a structurally and chemically compatible MgO buffer to improve the crystallinity of the BST on polycrystalline YIG substrates, where the biaxially oriented MgO is deposited by an ion-beam assisted-deposition technique. The biaxially oriented BST has a dielectric loss of less than 0.01 and a capacitance tunability of greater than 25% at a direct current bias voltage of 40 V at room temperature.

We summarize recent progress in growth and characterization of aligned-crystalline silicon (ACSi) films on polycrystalline metal and amorphous glass substrates. The ACSi deposition process uses, as a key technique, ion-beam-assisted deposition (IBAD) texturing on a non-single-crystalline substrate to achieve a biaxially-oriented (i.e., with preferred out-of-plane and in-plane crystallographic orientations) IBAD seed layer, upon which homo- and hetero-epitaxial buffer layers and hetero-epitaxial silicon (i.e., ACSi) films with good electronic properties can be grown. We have demonstrated the versatility of our approach by preparing ACSi films on customized architectures, including fully insulating and transparent IBAD layer and buffer layers based on oxides on glass and flexible metal tape, and conducting and reflective IBAD layer and buffer layers based on nitrides on flexible metal tape. Optimized 0.4-μm-thick ACSi films demonstrate out-of-plane and in-plane mosaic spreads of 0.8° and 1.3°, respectively, and a room-temperature Hall mobility of ∼90 cm2/V.s (∼50% of what is achievable with epitaxial single-crystalline Si films, and ∼1000 times that of amorphous Si films) for a p-type doping concentration of ∼4×1016 cm−3. By using various experimental techniques, we have confirmed the underlying crystalline order and the superior electrical characteristics of low-angle (+–type diode fabricated using a 4.2-μm-thick ACSi film shows minority carrier lifetime of ∼3 μs, an estimated diffusion length of ∼30 μm in the p-Si layer with a doping concentration of 5×1016 cm−3, and external quantum efficiency of ∼80% at 450 nm with the addition of an MgO film anti-reflector.

We report structural and electronic properties of Aligned-Crystalline Si (ACSi) films on glass substrates. These films show enhanced majority carrier mobilities and minority carrier lifetimes with increasing crystallinity, i.e., with improving alignment and connectivity of the grains. A 0.4-μm-thick ACSi film with a total grain mosaic spread of 4.2° showed Hall mobility of 47 cm2/V.s for a p-type doping concentration of 1.9×1018 cm−3. A prototype n+/p/p+–type diode fabricated using a 4.2-μm-thick ACSi film showed minority carrier lifetime of ∼3.5 μs and estimated diffusion length of ∼30 μm in the p layer with a doping concentration of 5×1016 cm−3.

We present an ion-beam based fabrication method for growth of single-crystal-like films that does not utilize epitaxy on single crystal substrates. We use ion-beam assisted texturing to obtain biaxial crystalline alignment in a film. This ion-beam assisted deposition (IBAD) texturing can be done on arbitrary, but smooth substrates, including flexible polycrystalline metal tapes. With IBAD texturing of MgO and subsequent homoepitaxial growth we have demonstrated an in-plane mosaic spread FWHM as low as 2° and out-of-plane alignment of 1°. The deposition system we use includes reel-to-reel tape transport for a linear transport of substrate materials through the deposition zones. This allows for high-throughput experimentation via a linear combinatorial experimental design.