A piezoelectric microvalve with a flexure-hinged driving frame and microfabricated silicon sealing pair

This paper describes a piezoelectric microvalve for attitude control of micro-satellite with a mass in the range of 20–100 kg. The microvalve comprises of a driving mechanism with a flexure-hinged frame and a valve body with a silicon sealing pair. The silicon valve core with sealing rings can achieve a low leak rate with a small structural deformation. The driving mechanism using a flexure-hinged frame and piezoelectric actuators assures the microvalve normally closed and leads to a fast response of the microvalve. The response time of the driving mechanism is characterized to be as small as 0.6 ms. A maximum flow rate of 3100 mL/min is achieved at an inlet pressure of 0.6 MPa while applied with a maximum voltage of 200 V. The static power consumption is 48 mW with a driving voltage of 200 V, and the dynamic power consumption is approximately 0.9 W at 100 Hz.     

Design and quasi-static characteristics study on a planar piezoelectric nanopositioner with ultralow parasitic rotation

This paper presents a particular mechanism design which is inherently inclined to have no parasitic rotation. The flexure-based stage comprises symmetric flexure guiding mechanism and two piezoelectric stack actuators. The layout of the stage is evaluated by finite element analysis, and the results indicate that the proposed design exhibits ultralow parasitic rotation. A prototype of the stage is then fabricated, and its performance is tested. Experimental results show that the stage has a stroke of 500 μm × 500 μm and the crosstalk is less than 1%. The maximum parasitic rotation is ±1.2 arcsec at a stroke of 500 μm.     

Optimal design of high precision XY-scanner with nanometer-level resolution and millimeter-level working range

This article presents the design and performance evaluation of a compact high precision XY-scanner providing nanometer-level resolution and a millimeter-level travel range. The proposed XY-scanner is composed of a voice coil motor (VCM) and double compound linear spring flexure guide mechanism. The challenge was to determine design variables properly while simultaneously satisfying the requirements of high resolution, long working range, high response speed, and compact size, because the relationships between the design variables and the system parameters are complex. Therefore, we developed a design that would provide the optimal tradeoff in terms of design variables. The objective was to maximize the first resonant frequencies of the XY-scanner to increase response speed while limiting the size of the scanner to 100 mm × 100 mm × 50 mm. The XY-scanner was fabricated with optimally-designed values, and its performance was evaluated. From the experimental results, the first resonant frequencies of XY-scanner were 26.68 Hz for the X-axis and 22.79 Hz for the Y-axis. The measured results of the 10 nm resolution and 2 mm working range confirmed that the designed scanner could be successfully used in precision fields requiring nanometer-level resolution and millimeter-level travel range.     

Solid-state synthesis of modified (Bi0.5Na0.5)TiO3 piezoelectric nanocrystalline ceramics and evaluating their properties

The piezoelectric nanocrystalline ceramics of (Bi_0.5Na_0.5) TiO₃, 0.94(Bi_0.5Na_0.5) TiO₃–0.06BaTiO₃, 0.82(Bi_0.5Na_0.5) TiO₃–0.18(Bi_0.5K_0.5) TiO₃ and 0.85(Bi_0.5Na_0.5) TiO₃–0.144(Bi_0.5K_0.5)TiO₃–0.006BaTiO₃ (abbreviated as BNT, BNBT6, BNKT18 and BNT–BT–BKT, respectively) have been synthesized by a modified solid state approach using high-energy planetary ball-milling. The crystal structures of ceramics were determined using X-ray diffraction (XRD) method and that the microstructures as well as the morphology of the sintered ceramic specimens were observed using scanning-electron microscopy (SEM). The dielectric coefficient was also calculated based on its relation with a constant capacitance measured by an electrical circuit on the basis of the Wetston–Bridge and the piezoelectric coefficient (d₃₃) measured with a d₃₃-meter. On the calcination of powders the XRD results showed that the perovskite phase was formed perfectly and the crystallite sizes of BNT, BNBT6, BNKT18 and BNT–BT–BKT were estimated at about >100, 55, 36 and 63 nm, respectively. Also, the crystallite sizes of the calcinated BNT powders over the course of 5, 10, 20, 30 and 40 h of ball-milling were estimated at about 86, 82, 72, 53, 81 nm, respectively. Moreover, the results of XRD and SEM analysis of the sintered powders at 750–1150 °C confirmed the positive effect of nanocrystalline formation during ball-milling in decreasing the sintering temperature and increasing the density of the sintered samples. Furthermore, electrical calculations such as dielectric and piezoelectric coefficients showed that the modified BNKT18 nanocrystalline ceramic sintered at 1150 °C was to have the best values of dielectric (ε_r=792 at 1 kHz) and piezoelectric coefficients (d₃₃=85.9 pC/N) in comparison with the other synthesized piezoelectric ceramics.     

Energy harvesting from radio frequency propagation using piezoelectric cantilevers

This work reports an induced strain in a piezoelectric cantilever due to radio frequency signal propagation. The piezoelectric actuator is coupled to radio frequency (RF) line through a gap of 0.25 mm. When a voltage signal of 10 Vpp propagates in the line it sets an alternating current in the actuator electrodes. This flowing current drives the piezoelectric cantilever to mechanical movement, especially when the frequency of the RF signal matches the mechanical resonant frequency of the cantilever. Output voltage signals versus frequency for both mechanical vibrational and RF signal excitations have been measured using different loads.     

Mapping etching induced damages on GaN surfaces using scanning internal photoemission microscopy

In this study, we used scanning internal photoemission microscopy (SIPM) to investigate damage on the n-GaN surface, which were induced by inductive coupled plasma (ICP) etching in conjunction with a recovery process by annealing. We formed Pd Schottky electrodes on n-GaN surfaces including selectively ICP-etched regions, and conducted two-dimensional mapping of the photoyield (Y). With SIPM, we could clearly visualize the etched regions in the Y map, where Y increased 1.4 times and the Schottky barrier height (qϕ_B) decreased by 0.32 eV, as compared with unetched regions. Upon annealing at 700 °C and 800 °C, both Y and qϕ_B values recovered. When we increased the annealing temperature to 900 °C, Y decreased remarkably in the both etched and unetched regions, and the etching patterns in the Y maps disappeared. These results indicate that SIPM is effective for mapping etching damage and recovery processes with high sensitivity.     

An I-shape linear piezoelectric actuator using resonant type longitudinal vibration transducers

Resonant type longitudinal vibration transducers are used in this work to construct a linear piezoelectric actuator with four driving feet. Totally three longitudinal transducers are integrated in I-shape to form the proposed actuator, which contains one vertical transducer and two horizontal transducers. These three transducers vibrate under longitudinal modes with certain temporal sequence, whose vibrations are superimposed in the actuator to generate elliptical motions on the four driving feet. The three transducers are tuned to be suitable dimensions, under which they have very close 1st longitudinal resonance frequencies; the working frequency of the piezoelectric actuator is designed to be about 31.3 kHz. The vibration coupling problem between the longitudinal transducers are studied by calculating the motion trajectories of the four feet. It is found that the temporal shift of the longitudinal vibrations can be used to tune the movement trajectories; the four feet can get nearly the same vertical displacements under a phase shift of 105°. At last, the vibration characteristics and mechanical output performances of a prototype are measured. The working frequency of the prototype, the maximum speed, and the maximum thrust force are measured to be 33.15 kHz, 1563 mm/s, and 158.2 N, respectively.     

Improving electroactive polymer actuator by tuning ionic liquid concentration

We have fabricated actuators from a blend of fluoropolymer (FP) with ionic liquid (IL). Here a combination of graphene, graphite, and silver nanoparticles is used to raise the electrode conductivity. As the electrode composition is fixed, we found that the actuator displacement increases with decreasing amount of ionic liquid in the polymer gel electrolyte. A maximum strain of 0.48% was observed from peak-to-peak displacement for an actuator with IL/FP = 0.3 in the polymer gel electrolyte. The simulation results indicate that lowering IL concentration leads to a more compact ion distribution in the electrode layers and hence explains the increased strain in the actuators.     

Analysis of recursive convolutional codes and turbo codes as sources with memory

The paper proposes a general method to analyze discrete sources with memory. Besides the classical entropy, we define new information measures for discrete sources with memory, similar to the information quantities specific to discrete channels. On the base of this method, we show for the first time that, as result of convolutional and turbo encoding, sources with memory are obtained. We apply this information analysis method for the general case of a recursive convolutional encoder of rate R_CC = 1/n₀ and memory of order m, and for a turbo encoder of rate R_TC = 1/3, with two systematic recursive convolutional component encoders. Each component encoder has memory of order m, and is built based on the same primitive feedback polynomial. For the convolutional and turbo codes, the information quantities H(Y/S), H(S,Y), H(S/Y), H(Y), H(S) and I(S,Y) have been computed, where S and Y denote the set of states and the set of messages of the encoder, respectively. The analysis considered two cases: n₀ ≤ m + 1 and n₀ > m + 1. When n₀ = m + 1, the mutual information I(S,Y) is maximum and equal to m, as is the entropy of the set of states. For turbo codes, the quantity I(S,Y) also depends on the input bit and on its probability.     

Impact of crystallization on ferro-, piezo- and pyro-electric characteristics in thin film P(VDF–TrFE)

In this paper, the impact of the crystallization and polymer chain length of the P(VDF–TrFe) on its dielectric, ferroelectric, piezoelectric and pyroelectric properties are studied. X-rays diffraction (XRD) analysis have revealed that a higher β crystalline phase is obtained with a lower polymer chain length corresponding to a higher grain size for a P(VDF–TrFe) composition of 72.2/27.8 mol.%. The polymer chain morphology was characterized by scanning electron microscopy (SEM) where the fibrils orientation and width were extracted. By coupling both XRD analysis and chain morphology analysis, we have established that an increase of the grain size of the polymer chain enhances the ferroelectric and piezoelectric effects of the P(VDF–TrFe) layer. On the other hand, we observed a slight degradation of its pyroelectric properties. In addition, the piezoelectric coefficient (d₃₃) of the P(VDF–TrFe) was enhanced by decreasing the molecular weight (M_w) of the copolymer, exhibiting a maximum value around −50 pC/N for the composition 72.2/27.8 with a molecular weight of 470 kg/mol. On the opposite, the pyroelectric properties were enhanced for the lowest polymer crystalline grain size studied and obtained with the composition 71/29 mol.% with a molecular weight of 505 kg/mol. A pyroelectric coefficient of 37.8 μC/m² K was measured.     

Magnetic,optical, microscopic and electrical behavior of Ca2−xYxCo2O5 prepared by a molten flux method

In this present study, we have reported the preparation of yttrium doped polycrystalline Ca_2−xY_xCo₂O₅ (x=0.0–1.0) material by a molten flux method and its various properties like electrical, optical, dielectric and magnetic behaviors. Characterization techniques have been adopted to confirm its physical nature and properties. X-ray diffraction results confirmed the crystal structure of prepared Ca_2−xY_xCo₂O₅ as orthorhombic and the scanning electron microscope pictured the presence of platelet-shaped particles with the dimensions of 150–300 nm. It also reveals the state of higher concentration of yttrium (Y³⁺) controls the grain size of Ca_2−xY_xCo₂O₅ ceramics. Further, we find out that the higher concentration of yttrium (Y³⁺) increases the optical band gap due to the occurrence of metal–insulator transition and also the same in electrical resistivity from 0.2 mΩ cm to 0.5 mΩ cm, which is due to the replacement of holes by Y³⁺ ions. The result of dielectric studies proves that the conduction mechanism of yttrium doped calcium cobalt oxide is due to space charge polarization. The magnetic saturation behavior shows the decreasing area in the hysteresis curve while the Y³⁺ concentration is increased, which is due to the phase transition of ferromagnetic to paramagnetic.     

New challenges for 300 mm Si technology: 3D interconnects at wafer scale by aligned wafer bonding

A new alignment technique is proposed for wafer level 3D interconnects fabrication: the SmartView^®. This original procedure is using alignment keys located in the bonding interface and enables an alignment precision of 1 μm. The method uses two top–bottom microscope pairs for observing the alignment keys and a minimal Z-axis travel during wafer alignment procedure. After the alignment procedure, the wafers are secured for subsequent wafer bonding procedures. The alignment process is presented in detail, as well as the integration of such an equipment in high production systems able to run wafers up to 300 mm diameter.     

Design and control of a piezoelectric driven reticle assist device for prevention of reticle slip in lithography systems

This paper presents a device for managing the inertial loads on photoreticles of lithography scanners. At high scan accelerations, the reticle inertial load can approach the clamp force limit. As a result, nanometer-level presliding slip can occur. Reticle slip is one limitation on increasing the throughput of the lithography scanners. In this paper, we present a reticle assist device which can eliminate reticle slip by compensating better than 95% of the inertial loads when tested in a bench-top tester. The reticle assist device consists of a coarse approach mechanism, for accommodating reticle load/unload, and a piezoelectric stack for fine actuation. The device utilizes a sensorless control system design. The control system uses a self-sensing contact detection method, which is inspired by self-sensing scanning probe microscopy, to find the reticle edge. It also uses a charge amplifier with a novel hybrid hysteresis compensation technique to linearly control the piezoelectric actuator extension, without the need for closed-loop position control. When tested with a replicated force profile with 60 N peak force and 6400 N/s force rate, the assist device compensated better than 95% of the inertial load.     

Growth features and intergranular connectivity of melt processed YBCO

Large grain melt processed Y-Ba-Cu-O (YBCO) samples have been prepared by seeded and unseeded growth techniques. The current carrying ability within individual grains and across grain boundaries has been investigated and correlated with features in the microstructure of samples fabricated by both techniques. The development of an inhomogeneous, cell-like growth microstructure in seeded samples at distances ≈4 mm from the seed is related to a saturation in inclusion density and volume proportion of Y₂BaCuO₅ (Y211) particles. A significant decrease in critical current density is associated with this change over a wide temperature range. The resistance of high angle c-axis grain boundaries is observed to depend critically on the magnitude of the injection current whereas the intra-granular resistance is not influenced significantly by this variable. J_c of a grain boundary fabricated by unseeded melt growth is estimated to be less than 100 A cm⁻² at 77 K in zero applied field, which is more than two orders of magnitude lower than the intragranular J_c. Field screening measurements suggest that low angle grain boundaries do not form weak links between grains in modest magnetic fields and hence do not present a significant barrier to current flow.     

Structure,charge-transfer and luminescent properties of bis(2-(2-hydroxyphenyl)benzothiazolate)beryllium

A luminescent Be(II) complex of aromatic N, O-chelate ligand, namely Be(BTZ)₂ (BTZ = 2-(2-hydroxyphenyl)benzothiazolate), has been synthesized and characterized by X-ray crystallography. Its charge-transfer and luminescent properties were studied. The results indicated that the single crystal of Be(BTZ)₂ is monoclinic, space group C2/c. With larger the electron-transfer rate than hole-transfer rate, Be(BTZ)₂ may serve as candidate for electron-transport material. The highest occupied molecular orbital energy level (E_HOMO) and the lowest unoccupied molecular orbital energy level (E_LUMO) are −5.79 eV and −2.98 eV, respectively. Be(BTZ)₂displays strong photoluminescence (PL) in the blue region at 456 nm, and the electroluminescent (EL) peak wavelength is located at 460 nm, CIE coordinates are X = 0.1525, Y = 0.1803.     

Piezoelectric energy harvesting from vibrations induced by jet-resonator system

Inspired by musical instruments that create high amplitude tones corresponding to resonator acoustic modes when subjected to airflow, a new piezoelectric energy harvester for powering the electronic system of aircrafts is developed. It converts the incoming airflow energy into electricity via a piezoelectric transducer during the flight. With the airflow simulated by an air cylinder, prototypes of the developed energy harvester are fabricated and tested. Experimental results show that the curve of sound pressure, corresponding to the first resonator acoustic mode, is a regular sinusoidal pattern. Within the study range of airflow velocity, a linear relationship can be found not only between sound pressure and airflow velocity but also between open circuit voltage and airflow velocity. A power of above 85 mW is released on a passive electric load of 3 kΩ by using a single piezoelectric element of 10 mm diameter at relative airflow velocity of 159 m/s. And the maximum total energy conversion efficiency of the piezoelectric energy harvester is about 1.2‰. It has laid a solid foundation for powering sensors or other devices, thus eliminating a need for batteries.     

Broadband proximity fed ring microstrip antenna arrays

Various gap-coupled array configurations of ring microstrip antennas and rectangular slot cut ring microstrip antennas with proximity fed slot cut ring microstrip antenna for larger bandwidth and gain are proposed. The rectangular slot in ring patch reduces its orthogonal TM₀₁ and TM₀₂ mode resonance frequencies and along with TM₁₀ modes of fed and parasitic ring patches, yields broadband response. The gap-coupled configuration with ring patch and slot cut ring patch yields bandwidth of nearly 430 MHz with broadside radiation pattern and peak gain of more than 9 dBi. By gap-coupling ring patches along all the edges of proximity fed pair of slot cut ring patch, a 3 × 3 ring microstrip antenna array is realized. It yields bandwidth of more than 460 MHz with peak gain of more than 10 dBi. To further improve upon the bandwidth, a 3 × 3 array of ring patches in which rectangular slot is first cut on the edges of ring patch which are gap-coupled along x-axis and further cut inside the patches which are gap-coupled along x and diagonal axes, is proposed. Both of these configurations yield bandwidth of more than 500 MHz (>45%) with a peak gain of around 10 dBi.     

Post-annealing modification in structural properties of ZnO thin films on p-type Si substrate deposited by evaporation

Zinc oxide (ZnO) films of thickness ∼380 nm were deposited on p-type Si (1 1 1) substrate maintained at 300 °C under 3×10⁻⁶ Torr by a radio frequency (RF) heating source. Transmission Fourier transform infrared (FTIR) spectrum exhibited a clear Zn–O bond excitation frequency of ∼408 cm⁻¹. X-ray diffraction spectrum demonstrated four peaks (P₁–P₄) at 2θ (deg) ∼36±0.06, 40±0.09, 82±0.17 and 86±0.2, which originated from (1 0 0), (0 0 2), (2 0 1) and (0 0 4) hexagonal planes, respectively. P₂ being the highest intensity peak indicated that the growth of ZnO predominantly occurred along the c-axis i.e. (0 0 2) plane. Micrographs of the samples obtained from scanning electron microscopy (SEM) and atomic force microscopy (AFM) identically displayed scattered nanocrystallites, which grew bigger with the increase of sample annealing temperature (°C) in the range of 400–1000. AFM pictures, in particular, exposed the hexagonal structure of the deposited films along with voids. However, ZnO composition ∼6:1 (Zn:O) as calculated from the energy dispersive spectrum (EDS) revealed that the formation of ZnO was not stoichiometric, rather of Zincsuboxide structure ZnO_x (x<1). Arrhenius plot of the resistivity data yielded a donor level (zinc interstitial and/or Zn–on–O site) with ionization energy E_c–1.26 eV, thereby it supports our measured results, in general.     

Processing,device fabrication and electrical characterization of LaMnO3 nanofibers

Lanthanum manganite (LaMnO₃) nanofibers were synthesized using electrospinning technique. The size and uniformity of these nanofibers were optimized by varying PVP concentration. X-ray diffraction analysis revealed the formation of single phase LaMnO₃ nanofibers (average diameter ~400 nm) when the composite nanofibers were calcined at 600 °C. M″ and Z″ spectroscopic plots of impedance spectroscopy data confirmed the presence of two distinct electro-active regions referred to as the grain and grain boundary regions. The activation energies of the grain and grain boundary regions were 0.27 eV and 0.41 eV, respectively; which suggested two different transport mechanisms in these fibers.