High-rate sputtering of thick PZT thin films for MEMS

Crack and void free polycrystalline Lead Zirconate Titanate (PZT) thin films in the range of 5 µm to 10 µm have been successfully deposited on silicon substrates using a novel high rate sputtering process. The sputtered PZT layers show a high dielectric constant ε_r between 1,000 and 1,800 with a moderate dissipation factor tan (δ) = 0,002???0,01 measured at f = 1 kHz, a distinct ferroelectric hysteresis loop with a remanent polarisation of 17 µC/cm² and coercive field strength of 5.4 kV/mm. The piezoelectric coefficients d_33,f = 80 pm/V are measured by using a Double Beam Laser Interferometer (DBLI). Based on this deposition process a membrane actuator mainly consisting of a SOI layer and a sputtered PZT thin film was prepared. The deflection of this membrane actuator depending on the driving voltage was measured with a white light interferometer and compared to the results of finite element analysis (FEA). With this approach a transverse piezoelectric coefficient of about e₃₁?=??11.2 C/m² was calculated, whereas all the other material parameters in the model were lent from PZT-5A.     

Characterization of the phases and morphology in synthesizing Cu2-xSe and CuSe films

ABSTRACT

Copper Selenides are important semiconductor materials with excellent performance. Cu_2-xSe and CuSe films were synthesized by spin-coating and chemical co-reduction method. The phases of product films were analyzed by X-ray diffraction (XRD) and the morphology was characterized by scanning electron microscopy (SEM), and the compositions of products were analyzed by energy dispersive spectroscopy (EDS). The surface resistance of the product film was measured using a four-probe resistance instrument. When Copper chloride was chosen as copper source, the products contain Cu_2-xSe, CuSe and a small amount of NaCl. When the reacting temperature is below 180 °C, the XRD intensity of impurity phase NaCl is obviously increased, while it is easier to produce Cu₂Se film at 200 or 220 °C. The sample obtained at 160 °C for 20 h consists of about 0.3 ～ 0.5 µm particles, while the sample obtained at 220 °C shows about 2 ～ 4 µm flake crystals; When the copper nitrate is used as a raw material, the XRD peaks of the product obtained at 200 °C for 20 h are much high and sharp, the phases obtained are mainly CuSe. The sample obtained at 200 °C consists of hexagonal flaky crystals with about 2 ～ 3 µm diameters, while it consists of particles with about 0.3 ～ 0.5 µm diameters for the sample obtained at 220 °C. In addition, the longer reaction time is conducive to the copper selenide formation, for example the single phase CuSe film can be obtained at 220 °C. The average resistivity of Cu-Se films synthesized at 200 °C for 20 h is 2.12E-3 Ω·cm.     

High performance thin film PZT ultrasonic transducer by CSD for distance measurements in water

Piezoelectric thin film ultrasonic transducers were realised and tested for short range distance measurements. Displacements in air and water as a function of frequency were modelled by Comsol Multiphysics finite element modelling (FEM) and transducer configurations with a two electrode layout were manufactured to enable larger displacements than with the conventional design. The transducer was fabricated on a silicon wafer by chemical solution deposition (CSD) with total PZT (Pb(Zr_0.53Ti_0.47)O₃) thickness of 2 µm. Subsequently, a cavity underneath the PZT was wet etched creating a bending membrane with a total thickness of ??13 µm. The displacements of the transducers as a function of frequency were modelled and measured by fiber-optic laser vibrometer. The effective piezoelectric d₃₃ coefficient of 300 nm/V and 144 nm/V in air and 48 nm/V and 18 nm/V in water was obtained for 260?×?260 µm² and 390?×?390 µm² membranes, respectively. The accuracy of the modelled resonance frequencies both in air and water was relatively good, of ??4-13% and ??5-20%, respectively.     

Silicon nanorods‐based all‐dielectric waveguides with long decay‐length at the telecommunication band

We investigate subwavelength waveguides composed of silicon nanorods array in straight and nonstraight regimes deposited on a silica (SiO₂) substrate. It is shown that using all‐dielectric nanorods with high permittivity to design an all‐dielectric optical waveguide provides several advantages such as low‐dissipation coefficient and long decay length for the distributed fields. Exploiting silicon arrays in touching and nontouching arrangements, we examined the optical response of the structure to the guiding of magnetic and electric fields with transverse and longitudinal polarization modes. We studied the decay length for all propagated modes in both nanochain orientations numerically. Simulation results for straight arrays showed that the averaged decay length for the structure with dielectric particles in touching regime is 1.6 µm (for the waveguide with the length of 2.2 µm), and for the nontouching array is 2.2 µm (for the array with the length of 3.1 µm). Calculating transmission loss factors and considering decay length of the proposed waveguide, we verified the strong potential of the proposed structure to design all‐dielectric photonic devices to operate at telecommunication spectra (λ~1310 nm and 1550 nm). Also, we computed bending losses [dB] for the examined structures based on the bends degree. Copyright © 2015 John Wiley & Sons, Ltd.     

Fine patterning of ceramic thick layer on aerosol deposition by lift-off process using photoresist

Ceramic fine patterning using aerosol deposition (AD) method and lift-off process was reported. Pre-baking conditions and thickness of photoresist layer were selected carefully to minimize the dimensions of the patterned structure. As a result, a pattern width less than 10 µm for 2 µm thick PZT and α-Al₂O₃ AD-deposited layers was obtained on Si substrate at room temperature.     

Effect of BaTiO3 size on dielectric property of BaTiO3/PVDF composites

The BaTiO₃/polyvinylidene fluoride (BaTiO₃/PVDF) polymer-based composites with different size and concentration of BaTiO₃ particles were fabricated via a simple physical mixing and subsequently hot-press processing. Effect of the filler size and frequency on the dielectric properties of the BaTiO₃/PVDF binary composites was discussed. The result shows that the BaTiO₃ size has an effect on the morphology of the BaTiO₃/PVDF composites. The composites with 0.2 and 0.3 μm BaTiO₃ exhibit high dielectric permittivity than those with 0.4 and 0.5 μm BaTiO₃. The composite with 0.4 μm BaTiO₃ has a minimum dielectric permittivity except one with 0.1 μm BaTiO₃. Dielectric loss of the BaTiO₃/PVDF binary composites changes slightly with the BaTiO₃ sizes. The ternary BaTiO₃/PVDF composites with 0.1 and 0.7 μm BaTiO₃ in coexistence exhibit good dielectric properties. As a result, the BaTiO₃/PVDF ternary composites in this study may have a promising application as dielectric material in embedded capacitor.     

Mode‐matching analysis of a spit‐circular cavity resonator for measurement of the dielectric constant for film on a substrate

In this paper, we apply the mode‐matching technique (eigenmode expansion) to formulate an analytical model for a split cylindrical cavity resonator with a thick ceramic film layer sandwiched between two‐layer alumina substrates. We then compute the resonant frequencies with the TE₀₁₁ mode with an eigenvalue problem approach using the model formula. The quality factor (Q ‐factor) of the resonator is also calculated by applying the perturbation method to the analytical model. The validity of the proposed analytical technique is confirmed by applying this method to the estimation of permittivity of thick films as an inverse problem. Ceramic films (2 µm thickness) were synthesized using a chemical solution method onto 200‐µm‐thick, 50‐mm‐diameter alumina substrates. The complex permittivity of the films was then determined using the TE₀₁₁ mode split cylindrical cavity resonator in the 10‐GHz band. The extent of the edge effect at a sample insertion space was evaluated by comparing the estimated results through TE wave analysis using the mode‐matching method when the transverse resonance technique and the perturbation method were applied to calculate the resonant frequency and the dielectric Q ‐factor. The results obtained indicate that a difference of 0.153% in the permittivity of the alumina substrate causes differences of 6.10 and 3.75% in the measured permittivity and loss tangent, respectively, of 2‐µm‐thick ceramic film with a permittivity of ∼50. Differences in permittivity and loss tangent were more pronounced with thinner films. It was also confirmed that the estimated results for permittivity and the loss tangent values of these ceramic films were affected by the estimated permittivity value of the alumina substrate. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Harmonic Effects in Electrostatic Induction Motors

Abstract

Electrostatic Induction motors are closely connected in theory to the familiar Tesla induction machine. In practice, designs are constrained by dielectric breakdown. Stator and rotor electrodes must be positioned to avoid breakdown rather than to provide sinusoidal distributions. The result is that Space and time harmonics are important in electrostatic machines. A cylindrical and in experimental electrostatic Induction motor is described. The electric field the air gap is used to compute theoretical torque, which is less than 4 mN · m under most conditions. Experimental operation with balanced three-phase excitation and bearing friction as the only load agrees with the theory more closely than in previous work.     

Size control of monodisperse silica particles by modified Stöber method

ABSTRACT

Monodispersed silica spheres were prepared by an effective method, which an ethanolic solution of tetraethyl orthosilicate (TEOS) was continuously supplied to the reaction mixture containing KCl electrolyte, water, TEOS, ethanol and ammonia. The particle size of the silica spheres ranged from 2.0 to 4.5 µm. In addition, the effects of reaction conditions such as temperature and amount of ammonia on microsphere morphology were studied.     

Design and implementation of combline bandpass tunable filter using barium-strontium-titanate thin-film capacitors

The design, fabrication and microwave properties of tunable fifth-order combline bandpass filter using etched barium-strontium-titanate (BST) thin films on sapphire (0001) substrates were investigated. At 1 MHz and 1000 kV/cm electric field, the dielectric tunability, the remanent polarization (2P_r) and the coercive electric field (2E_C) of BST films were 45.96%, 2.26 µC/cm² and 81.83 kV/cm, respectively. The loss tangent was 1.36% at zero electric field. After the BST parallel plate capacitors characterization, BST capacitors were loaded at the end of parallel coupled resonators in the design of the tunable filter. With the application of 20 V DC voltage, the center frequency of the filter varied from 1.17 GHz to 1.34 GHz which corresponds to a relative shift of 13.5%.     

Structural and dielectric properties of BaCexTi1-xO3 ceramics

ABSTRACT

In this paper, we prepare silver nanowires circuit graphics by UV-curing technology. The optimal condition of preparation of the silver nanowires circuit graphics are examined. Experiment results show that the UV-curing technology is a kind of individual, low-cost and environment-friendly method to prepare silver nanowires circuit graphics. The main influence factors on the lines' width are the UV beam power and scanning speed. And we also study the influence of the hot pressing temperature on the resistivity of the circuit graphics. In the experiments, the optimal condition is that the UV beam power is 190 mW and the scanning rate is 6 cm/s, then we get the minimum line width, which is 0.25 mm. The thickness of silver nanowires layer is 100 µm and the hot pressing temperature is 100°C, we will get the sample whose resistivity is 21× 10^?5 Ω·cm.     

Phosphorus magnetic resonance spectroscopic imaging using flyback echo planar readout trajectories

Object

To present and evaluate a fast phosphorus magnetic resonance spectroscopic imaging (MRSI) sequence using echo planar spectroscopic imaging with flyback readout gradient trajectories.

Materials and Methods

Waveforms were designed and implemented using a 3 Tesla MRI system. ³¹P spectra were acquired with 2 × 2 cm² and 3 × 3 cm² resolution over a 20- and 21-cm field of view and spectral bandwidths up to 1923 Hz. The sequence was first tested using a 20-cm-diameter phosphate phantom, and subsequent in vivo tests were performed on healthy human calf muscles and brains from five volunteers.

Results

Flyback EPSI achieved 10× and 7× reductions in acquisition time, with 68.0 ± 1.2 and 69.8 ± 2.2% signal-to-noise ratio (SNR) per unit of time efficiency (theoretical SNR efficiency was 74.5 and 76.4%) for the in vivo experiments, compared to conventional phase-encoded MRSI for the 2 × 2 cm² and 3 × 3 cm² resolution waveforms, respectively. Statistical analysis showed no difference in the quantification of most metabolites. Time savings and SNR comparisons were consistent across phantom, leg and brain experiments.

Conclusion

EPSI using flyback readout trajectories was found to be a reliable alternative for acquiring ³¹P-MRSI data in a shorter acquisition time.

     

An integrated microelectromechanical microwave switch based on piezoelectric actuation

In the field of microwave applications, microelectromechanical systems (MEMS) are attractive devices in order to force miniaturization by on chip integration. Here, we describe the design, fabrication and testing of a silicon based micromachined switch using piezo-electrically actuated elements. The microwave circuit consists of a coplanar waveguide (CPW) design with two piezoelectric activated beams integrated between the middle line and the ground planes. During operation the beams short the CPW by two overhanging bridge contacts and therefore the transmission characteristics of the microwave circuit change. The CPW is realized by 3 µm thick electroplated copper to yield good transmission characteristics, whereas the clamped—clamped beams benefit from a 250 nm thin PZT film between 100 nm thin Pt electrodes on top of a SiO₂ layer. By the use of double side clamped beams awkward stress compensation of the piezoelectric stack is omitted. Instead the system relies on some initial mechanical stress. Measurements prove deflections of more than 13 µm for a 1400 µm long beam with operation voltages below 10 V. This is in good agreement with finite element simulations. The novel RF-MEMS is predicted to reach an isolation (in “on” state) of more than 20 dB up to 15 GHz.     

Development of anisotropic phantoms using wood and fiber materials for diffusion tensor imaging and diffusion kurtosis imaging

Objective

Several studies have demonstrated that anisotropic phantoms can be utilized for diffusion magnetic resonance imaging. The purpose of our study was to examine whether wood is suitable as an anisotropic phantom material from the viewpoints of affordability and availability. In the current study, wood was used for restricted diffusion, and fibers were used for hindered diffusion.

Materials and methods

Wood and fiber phantoms were made. Diffusion kurtosis images were acquired with three magnetic resonance scanners. Fractional anisotropy, radial diffusivity, axial diffusivity, radial kurtosis and axial kurtosis values were measured. The wood phantom was imaged, and its durability was confirmed. The phantoms were imaged in varying orientations within the magnetic field. The wood was observed using an optical microscope.

Results

Ten kinds of wood and the fiber had a diffusion metrics. The wood diffusion metrics suggested low variation over a period of 9 months. Changing the orientation of the phantoms within the magnetic field resulted in changes in diffusion metrics. Observation of wood vessels and fibers was conducted.

Discussion

Wood and fibers have anisotropy and are promising as phantom materials. The development of anisotropic phantoms that anyone can use is useful for diffusion magnetic resonance imaging research and clinical applications.

     

Electromechanical performance of structurally graded monolithic piezoelectric actuator

In this paper, the effect of structural gradients in monolithic piezoelectric actuators is investigated. Different cross-section profiles were micro-machined with a laser into commercial PZT 5H bulk discs with thicknesses of 375 µm and 500 µm (? 25 mm). Profiles and curvatures of the actuators were measured which showed both concave and convex structures, thus indicating pre-stress of the actuators. After poling, the distribution of out-of-plane displacement was scanned by a fibre-optic laser vibrometer. Maximum displacements of ～6.3 µm and ～24.8 µm were obtained from a freely moving and clamped ～375 µm thick actuator, respectively, in a ±0.5 V/µm electric field at 10 Hz frequency without load. Furthermore, deflection in the centre of the actuators was measured up to 184 mN load using the same electric field and frequency. Bending of the bulk actuators without any additional layer was a consequence of the gradient in poling and driving electric field via thickness variation of the material. Hence, different regions produced strain distribution and bending in a similar fashion to other benders. Actuators with the highest arch height exhibited the highest displacement and load bearing capabilities derived from the increased area moment of inertia and enhanced piezoelectric response due to pre-stress. The results show that the monolithic bending actuators can be realised by simple structural designing of the actuator. Such structural gradients can be one reason contributing to the higher displacement of RAINBOW actuators compared to other pre-stressed actuators. In a further development, the structural gradients can be utilized in high displacement pre-stressed actuators and in miniaturized monolithic piezoelectric devices.     

Dielectric and polarization switching studies in nickel nanoparticles dispersed ferroelectric liquid crystal mixtures

ABSTRACT

We have investigated the effect of nickel nanoparticles (NiNPs) in a pure ferroelectric liquid crystal (FLC) mixture. Dielectric spectroscopy was done in the frequency range of 20 Hz–10 MHz. Switching time, spontaneous polarisation, rotational viscosity has been measured using field reversal technique in SmC^* phase. The spontaneous polarisation increases for NiNPs-FLC sample which may be due to the induced dipole moments around FLC molecules. Response time decreases with temperature and NiNPs dispersion. The relaxation frequency and dielectric strength of observed mode in SmC^* phase is also discussed in pure FLC and NiNPs-FLC samples. The relaxation frequency in NiNPs-FLC sample decreases than pure FLC sample and found ～120 Hz.     

Metal‐bonding‐based hermetic wafer‐level MEMS packaging technology using in‐plane feedthrough: Hermeticity and high frequency characteristics of thick gold film feedthrough

Au–Au‐bonding‐based wafer‐level vacuum packaging technology using in‐plane feedthrough of thick Au signal lines was developed for high‐frequency micro electromechanical system (RF MEMS). Compared with conventional technology based on glass frit bonding, the developed technology is advantageous in terms of smaller width of sealing frames, lower process temperature, and smaller amount of degas. To guarantee the hermetic sealing, the adhesion between the thick Au lines and a SiOx dielectric frame is improved by an Al₂O₃ interlayer by atomic layer deposition. The steps of the dielectric frame above the thick Au lines are absorbed by an electroplated Au seal ring planarized by fly cutting. The thermocompression bonding of the Au seal rings of 20‐100 μm width was done at 300 ºC. A cavity pressure of about 500 Pa or lower was measured by “zero balance method” using Si diaphragms. Vacuum sealing was maintained for more than 19 months, and the leak rate is less than 8×10‐16 Pa m3/s. The isolation of open signal lines was measured up to 10 GHz for different designs of the sealing ring and SiOx dielectric frame. The influence of the in‐plane feed through to the isolation is as low as 2‐3 dB, if the width of the sealing ring is 20 μm and the thickness of SiOx dielectric frame is larger than 10 μm. The developed wafer‐level packaging technology is ready for applications to an radio frequency (RF) MEMS switch.     

Endoluminal high-resolution MR imaging protocol for colon walls analysis in a mouse model of colitis

Objective

An endoluminal magnetic resonance (MR) imaging protocol including the design of an endoluminal coil (EC) was defined for high-spatial-resolution MR imaging of mice gastrointestinal walls at 4.7 T.

Materials and methods

A receive-only radiofrequency single-loop coil was developed for mice colon wall imaging. Combined with a specific protocol, the prototype was first characterized in vitro on phantoms and on vegetables. Signal-to-noise ratio (SNR) profiles were compared with a quadrature volume birdcage coil (QVBC). Endoluminal MR imaging protocol combined with the EC was assessed in vivo on mice.

Results

The SNR measured close to the coil is significantly higher (10 times and up to 3 mm of the EC center) than the SNR measured with the QVBC. The gain in SNR can be used to reduce the in-plane pixel size up to 39 × 39 µm² (234 µm slice thickness) without time penalty. The different colon wall layers can only be distinguished on images acquired with the EC.

Conclusion

Dedicated EC provides suitable images for the assessment of mice colon wall layers. This proof of concept provides gains in spatial resolution and leads to adequate protocols for the assessment of human colorectal cancer, and can now be used as a new imaging tool for a better understanding of the pathology.

     

Dielectric behaviour of neutrophil gelatinase associated lipocalin detected by alpha relaxation process

ABSTRACT

We have investigated alpha (α) relaxation process and its temperature evolution in electrical double layer (EDL) around neutrophil gelatinase-associated lipocalin (NGAL), anti-lipocalin2 (anti-LCN-2) and their conjugate in phosphate buffer. The dielectric permittivity (20 Hz to 1 MHz) of α-relaxation process for LCN-2 and anti-LCN-2 shows variation with temperature. This happens due to unfolding of various microstates of protein at measured temperature intervals. The DSC thermograms of LCN-2, anti-LCN-2 and their conjugate predict that the multiple unfolding domains are parallel to the shifts in real dielectric permittivity at a particular temperature.     

Enhancement in the physical properties of K0.5Na0.5NbO3 ceramics by the addition of 0.5 Li2O – 0.5K2O – 2B2O3 glass

The addition of powdered 0.5 Li₂O–0.5K₂O–2B₂O₃ (LKBO) glass (0.5 to 2 wt%) to potassium sodium niobate, K_0.5Na_0.5NbO₃ (KNN) powder facilitated higher densification which resulted in improved physical properties that include dielectric, piezoelectric and ferroelectric. The required polycrystalline powders of KNN were synthesized through solid-state reaction route, while LKBO glass was obtained via the conventional melt-quenching technique. Pulverized glass was added to KNN powders in different wt% and compacted at room temperature and these were sintered around 1100°C. Indeed the addition of optimum amount (1 wt %) of LKBO glass to KNN ceramics facilitated lowering of sintering temperature accompanied by larger grains (8 µm) with improved density. The dielectric constant (?_r) measured at room temperature was 475 (at 10 kHz), whereas it was only 199 for the LKBO glass free KNN. The piezoelectric coefficient (d₃₃) was found to be 130 pC/N for 1 wt% LKBO added glass, which was much higher than that of pure KNN ceramics (85 pC/N). Indeed, the LKBO glass added samples did exhibit well saturated P versus E hysteresis loops at room temperature. Though there was no particular trend observed in the variation of P_r with the increase in glass content, the P_r values were higher than that obtained for KNN ceramics. The improved physical properties of KNN ceramics encountered in these studies were primarily attributed to enhancement in density and grain size.