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Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application and in doing so, open a new path for the development of complex metal-oxide nano-structures.

Manipulation of electrons in a solid through transmitting, storing and switching is the fundamental basis for the microelectronic devices. Recently, the electroresistance effect in the ferroelectric capacitors has provided a novel way to modulate the electron transport by polarization reversal. Here, we demonstrate a giant electroresistive ferroelectric diode integrating a ferroelectric capacitor into two-dimensional electron gas (2DEG) at oxide interface. As a model system, we fabricate an epitaxial Au/Pb(Zr0.2Ti0.8)O3/LaAlO3/SrTiO3 heterostructure, where 2DEG is formed at LaAlO3/SrTiO3 interface. This device functions as a two-terminal, non-volatile memory of 1 diode-1 resistor with a large I+/I− ratio (>108 at ±6 V) and Ion/Ioff ratio (>107). This is attributed to not only Schottky barrier modulation at metal/ferroelectric interface by polarization reversal but also the field-effect metal-insulator transition of 2DEG. Moreover, using this heterostructure, we can demonstrate a memristive behavior for an artificial synapse memory, where the resistance can be continuously tuned by partial polarization switching and the electrons are only unidirectionally transmitted. Beyond non-volatile memory and logic devices, our results will provide new opportunities to emerging electronic devices such as multifunctional nanoelectronics and neuromorphic electronics.

Recently, piezoelectric and triboelectric energy harvesting devices have been developed to convert mechanical energy into electrical energy. Especially, it is well known that triboelectric nanogenerators have a simple structure and a high output voltage. However, whereas nanostructures improve the output of triboelectric generators, its fabrication process is still complicated and unfavorable in term of the large scale and long-time durability of the device. Here, we demonstrate a hybrid generator which does not use nanostructure but generates much higher output power by a small mechanical force and integrates piezoelectric generator into triboelectric generator, derived from the simultaneous use of piezoelectric and triboelectric mechanisms in one press-and-release cycle. This hybrid generator combines high piezoelectric output current and triboelectric output voltage, which produces peak output voltage of ~370 V, current density of ~12 μA·cm−2 and average power density of ~4.44 mW·cm−2. The output power successfully lit up 600 LED bulbs by the application of a 0.2 N mechanical force and it charged a 10 μF capacitor to 10 V in 25 s. Beyond energy harvesting, this work will provide new opportunities for developing a small, built-in power source in self-powered electronics such as mobile electronics.

The thickness dependence of ferroelectric permittivity of (Ba, Sr)TiO3 has been investigated. The BST films could be obtained to have a simple cubic perovskite structure, space group Pm3m, and practically c-axis epitaxial structure deposited at 800∘C. Through post-annealing process, we have improved the dielectric properties; dielectric permittivity, dielectric loss, and tunability. The change in dielectric properties before and after annealing is attributed to the change in film strain and the contraction in film lattice. As the thickness of BST films increases from 55 nm to 350 nm, the dielectric constant of BST films increases from about 100 to above 670 due to the reduction of interfacial dead layers with low dielectric constant between films and top electrodes. The dielectric loss of BST thin films decreased as the thickness increases. The existence of interfacial dead layers in a thinner film had a larger effect on the effective dielectric constant than tensile strain between the BST films and MgO substrate.

Characteristics of piezoelectric thick films on various bottom electrodes prepared by screen printing method were investigated. The composition of the ceramics used in this study was 0.01Pb(Mg1/2W1/2)O3–0.41Pb(Ni1/3Nb2/3)O3–0.35PbTiO3–0.23PbZrO3 + 0.1wt% Y2O3 +2.0 wt.%ZnO(PMW-PNN-PT-PZ). The Ag and the Ag-Pd electrodes were coated on SiO2/Si substrate by screen printing method and Pt electrode was deposited on Ti/ SiO2/Si substrate by DC sputtering system. The piezoelectric PMW-PNN-PT-PZ thick films were fabricated on each electrode and annealed by rapid thermal annealing (RTA). The PMW-PNN-PT-PZ piezoelectric thick films on Ag/SiO2/Si has higher remanent polarization (P r) of 22.4 μC/cm2.

Recently, a novel tiny piezoelectric ultrasonic linear motor driven by impact force which converts a radial mode vibration into a longitudinal one was developed for camera optical modules. This tiny piezoelectric motor consists of a shaft, mobile element and piezoelectric transducer. In this work, the frictional properties of the interface between the shaft and mobile element were investigated according to their respective materials. Five types of materials were used for the shaft, viz. stainless steel coated with DLC (Diamond like carbon) and PTFE (Polytetrafluoroethylene), uncoated stainless steel, Pyrex and Graphite. Bakelite and stainless steel (SUS) were used for the mobile elements. It was found that two combinations, namely Pyrex glass or stainless steel for the shaft and stainless steel for the mobile element, exhibited good dynamic behaviors in a tiny piezoelectric ultrasonic linear motor, which was newly developed based on operating concepts based on Newton’s law.

This paper presents properties of saw acoustic wave (SAW) gas sensors to detect volatile gases such as acetone, methanol, and ethanol by measuring phase shift. A dual-delay-line saw sensors with a center frequency of 100 MHz were fabricated on 128∘ Y-Z LiNbO3 piezoelectric substrate. In order to improve sensitivity of SAW sensors, a thin titanium (Ti) film as mass sensitive layer was deposited using e-beam evaporation on the surface of the SAW sensors. In our investigation the response time and sensitivity of SAW sensors were measured. The response time and sensitivity of SAW sensor with thin Ti film were strongly improved because of changing electrical and mechanical properties in the mass sensitive layer. As a result, high sensitivity and fast response time could be achieved by deposition of thin Ti film as mass sensitive layer on the surface of SAW sensor. It can be applied for high performance electronic nose system by assembling an array of different sensors.

The modifications of microwave slot transmission lines formed on the (Ba,Sr)TiO3 ferroelectric films were investigated to realize high quality factor millimeter-wavelength devices tunable by low bias voltages. The narrow inner electrodes inserted to a slot line form the novel type of the transmission lines, which was called multislot line (MSL). The MSL short-circuited and tunable resonators were tested at frequency ∼30 GHz. The MSL phase shifter merit factor was evaluated higher than 100 degree/dB at bias voltage lower 100 V. The comparatively high quality factors of tunable MSL resonators and phase shifters evidence on real prospects of novel topology approach to the development of such microwave devices as tunable band-pass filters and electronically steerable antennas.

The effect of the addition of glass on the densification, low temperature sintering, and microwave dielectric properties of the Ca[(Li1/3Nb2/3)1−x Tix]O3−δ(CLNT) was investigated. Addition of glass (B2O3-ZnO-SiO2-PbO system) improved the densification and reduced the sintering temperature from 1150∘C to 900∘C of Ca[(Li1/3Nb2/3)1−x -Tix]O3−δ microwave dielectric ceramics. As increasing glass contents from 10 wt% to 15 wt%, the dielectric constants (er) and bulk density were increased. The quality factor (Q⋅f0), however, was decreased slightly. The temperature coefficients of the resonant frequency (τf) shifted positive value as increasing glass contents over Ti content is 0.2 mol. The dielectric properties of Ca[(Li1/3Nb2/3)0.75Ti0.25]O3−δ with 10 wt% glass sintered at 900∘C for 3 h were er = 40 Q·f0 = 11500 GHz, τf = 8, ppm/°C. The relationship between the microstructure and dielectric properties of ceramics was studied by X-ray diffraction (XRD), and scanning electron microscope (SEM).

A tiny ultrasonic linear motor with a structure has been developed, and various shaft materials were tested in the motor in order to improve its dynamic properties. We found that the shaft material has direct influence on efficiency, reliability and quality of the motors and their dynamic properties and is crucial to the achievement of high motor performance. The use of shafts of various materials such as stainless steel, stainless steels coated with DLC (Diamond Like Carbon) and PTFE (Teflon), a Pyrex, and a graphite, can make it possible to improve dynamic properties of the motors over a wide range of tribological conditions. In a motor with a stainless steel shaft coated with DLC driven at 44 kHz, its velocity was 4 mm/s with a force of 75 mN. When a motor used the Pyrex shaft was used a force of 110 mN was attained at 51 kHz. Thus the maximum force produced by a motor with a graphite shaft is estimated to be 120 mN with a velocity of 8 mm/s. We found that graphite has the appropriate surface conditions and directional texture to promote the linear motion of the moving element. Finally, the use of a cap resulted in significant improvements in the stability of the motor’s operation. Motor with graphite and Pyrex shafts were found to exhibit very stable operation and improved dynamic characteristics.

Recently, a tiny piezoelectric linear motor using a vibration mode of the transducer has been invented. The motor consists of a shaft, mobile element, and piezoelectric transducer using a piezoelectric radial mode bimorph disk. The fringe of the bimorph disk is fixed firmly which means this area has no degree of freedom. Therefore, the radial mode of the transducer transfers to the flexure mode. The mobile elements move along the Pyrex shaft by the impact force generated by the flexure mode of the piezoelectric transducer. The motors are operated at their resonant frequencies. The dynamic properties of the motor have been intensively measured and analyzed according to the applied voltage waveforms at the resonant frequencies. As the sawtooth and rectangular voltage waveforms are applied, the velocity, the thrust force, and the velocity dependence of the mobile position are measured. The dynamic characteristics are also analyzed within a period of each wave using laser vibrometer. The velocity of the mobile is moderately constant along the shaft. The better dynamic characteristics are obtained in the case of applying the rectangular waveform.

Microwave multislot transmission lines formed on (Ba,Sr)TiO3–BST ferroelectric films were studied using full-wave analysis and resonator measurements. The BST films were grown on sapphire, MgO and alumina substrates in the process of RF sputtering. The multislot resonators formed on different types of BST films were measured at frequency ∼30 GHz. The slot and multislot resonator topologies measured in rectangular waveguide had similar quality factor (100–120). The BST film dielectric characteristics were obtained: ϵ = 1100–1800; tan δ = 0.02–0.03. The coupled multislot structures were simulated to realize tunable band-pass filters of various tunability range, pass band and microwave losses in the band.

A modified structure for tiny ultrasonic linear motors has been developed, and various shaft materials have been tested in order to improve dynamic properties. The shaft material has a direct influence on efficiency, reliability, and quality of the motors and their dynamic properties. The shaft material is crucial to achieve high performance. Shafts of with various materials, such as a stainless steel, stainless steel coated with diamond like carbon (DLC), a Pyrex, and a graphite, can make it possible to improve dynamic properties of the motors over a wide range of tribological conditions. For the motor with a stainless steel shaft coated with DLC at 47 kHz, its velocity is 6.5 mm/s and its force is 110 mN. When the motor has a Pyrex shaft, a force of 140 mN is reached at 52 kHz. Accordingly, the maximum force produced by a motor with a graphite shaft is estimated as 97 mN. The velocity of this motor was 15 mm/s. We found that graphite has a fine surface and a directional texture which can help a moving element achieve linear motion. Finally, the use of a cap resulted in significantly improving stable operation. A motor with a graphite or a Pyrex shaft showed very stable operation and improved dynamic characteristics.

The change in dielectric constant of ferroelectric materials as a function of electric field is the key to wide range of applications such as tunable oscillators, delay lines, and phase shifters. The effect of the post-annealing on the dielectric properties of (Ba0.6Sr0.4)(Ti0.9Zr0.1)O3 (BSTZ) thin films deposited by Pulsed Laser Deposition is studied. BSTZ ferroelectric thin films showed simple cubic perovskite structure having (200) preferred orientation independent on deposition conditions. Preferred orientation slightly increased after post-annealing. With increasing the oxygen pressure, the dielectric loss of ferroelectric thin films decreased due to the oxygen vacancies. The reason why the dielectric constant increased was due to expansion of unit cell volume leading the increase of ion polarizability. The structure of ferroelectric thin film did not change after post-annealing. The grain size, dielectric constant and tunability were increased; however dielectric loss was decreased after annealing. The microstructure of ferroelectric thin film was one of the important facts(stress between thin films and substrates, thermal conductivity etc) effecting the dielectric properties such as dielectric constant, dielectric loss and tunability etc. Microwave dielectric properties of (Ba0.6Sr0.4)(Ti0.9Zr0.1)O3 ferroelectric thin film were obtained at deposition temperature 750 ◦ C, oxygen pressure 200 mTorr, and post-annealing conditions 1100 ◦ C for 1h : dielectric constant 2060, dielectric loss 0.0026 and tunability 25.3%.

Novel design of microwave four-pole band-pass filter based on the tunable waveguide dielectric resonators with the embedded planar (Ba,Sr)TiO3 film ferroelectric varactors is presented. The following operational parameters were obtained after the experomental test in Ka-band: the bandwidth at 1 dB level is about 350 MHz (1.2%), the range of tuning is 570 MHz (1.9%) and insertion losses are no more than 5.0 dB.

The microwave electrodeless measuring techniques for the determination of the characteristics of the ferroelectric (Ba, Sr)TiO3 thin films in the millimeter wavelength region were studied. The partialy filled cavity resonator based on the rectangular waveguide of Ka and V bands was theoretically and experimentally investigated. At the frequency around 90–100 GHz the technique of multiple signal reflections from the interface film/substrate was developed and implemented. As the result of microwave measurements of BST films the frequency dependence of dielectric loss factor was build up for the region 1–100 GHz, which had practically linear character.

The new-typed tiny ultrasonic motor has been introduced to have compact and simple structure. The linear motion of a new-type linear motor is operated by a principle of inertia displacement. The motor can be realized by the central movement of transducing part, which is the maximum displacement of the up-and-down movement. The transducing parts, using different diameters, 3.0 and 5.0 mm and thickness of 0.1 and 0.2 mm metal disks, were fabricated and the dynamic characteristics of the motors were measured. The motor with piezoelectric ceramic of O3 needs higher operating voltage than the motor with the piezoelectric ceramic of O5.

In recent years, a novel tiny piezoelectric linear motor converting a radial mode vibration to a longitudinal mode vibration driven by the impact force has been developed for a camera optical module. The tiny piezoelectric motor is consisted of a shaft, mobile element, and piezoelectric transducer. In this work, the frictional coefficient and static friction force of the interface between the shaft and the mobile element have been investigated according to their respective materials. It was found that two combinations, namely Pyrex glass or stainless steel for the shaft and stainless steel (SUS) for the mobile element, exhibited good dynamic behaviors in the tiny ultrasonic linear motor, which was newly developed based on operating concepts based on Newton`s law.

In order to develop a tunable resonator which can be easily operated by DC bias and applied for microwave tunable filters and devices using ferroelectric thin or thick films, the non conductor backed-and conductor backed- coplanar stripline resonators have been designed and analyzed. They have been designed to be operated at 25 GHz which involve coplanar stripline input and output ports. The resonators have been simulated and analyzed using Ansoft HFSS. The research has been focused on the Quality factor of the coplanar stripline resonator. The conductor Q, box Q, and radiation Q of the resonators have been analyzed and calculated according to the substrate thickness & conductor width of the resonators. From these parameters, the loss factors of the coplanar stripline resonator have been investigated. The conducting Q of the coplanar stripline resonator has no relation with the thickness of dielectric substrate and increases as the conductor width increases. The box Q has no much relation with the thickness of substrate and the conductor width, which is above 2000. The radiation loss increases as the thickness of substrate and the conductor width increase. To decrease the radiation loss of the coplanar stripline resonator, a conductor backed coplanar stripline resonator has been proposed which has the unloaded Q of 170.

This paper describes the development of a surface acoustic wave gas sensor that is designed to detect volatile gas by monitering phase change of output signal as a function of time. The sensor consists of SAW oscillators with a center frequency of 100 MHz fabricated on Y-Z substrates. Experimental results, which show the phase change of output signal under the absorption of volatile gas onto sensors, are presented. The proposed sensor has the properties of high sensitivity compare to the conventional SAW gas sensor and chemical selectivity. Thus, it is thought these results are applicable for use in sensor array of an high performance electronic nose system.

The contact kinetics of piezoelectric linear motors determines the operational characteristics like speed and torque or transmitted mechanical power and efficiency. Piezoelectric linear motors are driven by tangential stress in the interface between tip of shaking beam and slider. A good contact between the tip and slider is necessary for a reliable analysis of the motor, which is needed for the optimization of its performance. The piezoelectric linear motor was fabricated and the characteristics of the motor were investigated by external conditions such as tip shape with different curvatures and contact force between the tip and the slider. It was found in this investigation that the optimal curvature of the tip and the contact force are curvature of 1 and 10, respectively, for the high actuating speed, and curvature of 1 and 40 N, respectively, for the high actuating force. Finally, tip shape has an influence on the characteristics of linear motor.

Characteristics of piezoelectric actuator on Si membrane were investigated. Si membranes were fabricated as a function of size using bulk micromachining method. Bottom electrode Ag–Pd and piezoelectric thick films were fabricated using screen printing method, respectively. Piezoelectric thick films were sintered by rapid thermal annealing (RTA). Top electrodes Pt were deposited by DC sputtering system. We analyzed micro structure by scanning electron microscope (SEM) and investigated dynamic properties by MTI2000. Therefore, piezoelectric thick film on Si membrane had Pr of 15.7 μC cm−2. The maximum displacement of micro actuator had 0.05 μm. We find the combination of thick film printing and MEMS process to form a Si membrane micro actuator.

The microstructure and piezoelectric properties of the 0.01Pb(Mg1/2W1/2)O3–0.41Pb(Ni1/3Nb2/3)O3–0.35PbTiO3–0.23PbZrO3 + 0.1 and 0.3 wt.% Y2O3 + x ZnO ceramics were investigated. The crystal structure changed from psudocubic to tetragonal when ZnO added. The average grain size increased from 4 μm to 8 μm with the addition of ZnO by oxygen diffusion, even if the growth rate was low. When ZnO added until 0.5 wt.%, the e 33 T / e 0 , kp and d33 values of specimens were slightly increased regardless Y2O3 contents. The curie point of PMW–PNN–PT–PZ ceramics were increased from 162 °C to 232 °C, as increasing the ZnO contents. When ZnO added, the kp of specimens slightly was increased regardless Y2O3 contents. The mechanical quality factors were abruptly decreased regardless Y2O3 contents, when ZnO added until 0.75 wt.%. The optimized piezoelectric properties were obtained; d33 = 730 (pC/N), kp = 60, Qm = 50, and e 33 T / e 0 = 4750, when PMW–PNN–PT–PZ + 0.3 wt.% Y2O3 + 0.5 wt.% ZnO sintered at 1200 °C for 1 h.

The single-layer 400 μm × 200 μm sized Ba0.6Sr0.4TiO3 thin-film embedded chip capacitors with two external electrodes fabricated on the surface of the chip capacitors have been demonstrated. The structure of the external electrodes placed on the same surface allows the reduction of connection length, resulting in low parasitic loss and noise of elecronic devices. The fabricated chip capacitors exhibited excellent electrical properties such as high capacitance density and dielectric constant (1687 nF/cm2 and 452) and a low dielectric loss of 0.052 at 1 kHz, respectively. In addition, the chip capacitors exhibited the superior temperature stability of X5R (ΔC/C = ±15% at -55°C to +85°C) characteristics. Such a low leakage current density of ~ 0.15 μA/cm2 at 3 V and a high breakdown voltage of 19.75 V were obtained as well. In conclusion, the chip capacitors are suggested as a candidate for the applications of embedded passive components.

In this paper, a novel design of multilayer ceramic-based Transmit/Receive (T/R) switch using Low Temperature Co-fired Ceramic (LTCC) technology have been presented. Compact T/R switch has been designed by transforming quarter-wave transmission line to its lumped equivalent circuit. Especially, high-Q three dimensional inductors with double strip have been proposed and incorporated. The proposed inductor has been modeled by multi-conductor coupled lines. A measured inductor quality factor (Q) of 80 and a Self-Resonance Frequency (SRF) of 6.6 GHz have been demonstrated. The inductor library has been incorporated into the design of WCDMA T/R switch.

The microwave dielectric properties of (1− x )(Al 1/2 Ta 1/2 )O 2 − x (Mg 1/3 Ta 2/3 )O 2 (AMT) (0≤ x ≤1.0) ceramics and design of small coplanar waveguide fed antenna (CPWFA) have been investigated. As (Mg 1/3 Ta 2/3 )O 2 concentration increased, dielectric constant ( e r ) and quality factor ( Q ) significantly increased and the temperature coefficient of resonant frequency ( τ f ) changed from negative to positive value. The τ f of 0 ppm °C −1 was realized at x =0.65 and the Qf 0 value and e r for this composition were 112 470 GHz and 26.1, respectively. A newly developed 0.35(Al 1/2 Ta 1/2 )O 2 –0.65(Mg 1/3 Ta 2/3 )O 2 dielectric materials were used for 1.5 GHz band CPWFA design and fabrication. The size of the CPWFA can be reduced by using AMT ceramics with high dielectric constant, insetting slits into patch, and fabricating CPW feed line in the ground plane. The slits play roles in not only lowering a center frequency but also fine-tuning for the proposed CPWFA together with open stub of CPW feed line. The CPWFA with slits has the lower center frequency than the conventional CPWFA, which suggests that an antenna size can reduce as large as 16.3%. Experimental results of the fabricated device were in good agreement with the simulation.

The crystal structure and microstructure of microwave dielectric (1−x)(Al1/2Ta1/2)O2–x(Mg1/3Ta2/3)O2 (0.2≤x≤1.0) ceramics have been investigated. It is reported in the JCPDS cards that (Al1/2Ta1/2)O2 and (Mg1/3Ta2/3)O2 have orthorhombic and tetragonal structure, respectively. (1−x)(Al1/2Ta1/2)O2–x(Mg1/3Ta2/3)O2 ceramics had two phases of orthorhombic and tetragonal at low (Mg1/3Ta2/3)O2 concentration but as (Mg1/3Ta2/3)O2 concentration increased, (1−x)(Al1/2Ta1/2)O2–x(Mg1/3Ta2/3)O2 transformed into tetragonal structure. Specimens having tetragonal single phase could be obtained over x=0.6. As (Mg1/3Ta2/3)O2 concentration increased, the cell parameters, X-ray density, and the grain size increased. However, apparent density increased from 0.2 to 0.65 concentration of (Mg1/3Ta2/3)O2 and then decreased over 0.65 concentration of (Mg1/3Ta2/3)O2. The number and size of pores in grains also decreased from 0.2 to 0.65 concentration of (Mg1/3Ta2/3)O2 and then increased over 0.65 concentration of (Mg1/3Ta2/3)O2. It is expected that the relationship between structural characteristics and microwave dielectric characteristics have a good correlation.

In the paper, the design of the multilayer helical dipole antenna (MHDA) for International Mobile Telecommunications-2000 (IMT-2000) handset, which is compact and has a wide impedance bandwidth, is demonstrated. The MHDA can obtain size-reduction and wide impedance bandwidth by using dielectric material (er=7.8), fabricating helical conductor pattern, and designing the structures with high radiation resistance. The MHDA consists of a rectangular-parallelepiped ceramic body and helical conductor patterns are embedded in the body using LTCC technology. The simulations are performed to obtain a good impedance matching by high frequency structure simulator (HFSS). A 3D structure design of MHDA suitable for IMT-2000 (1920–2170 MHz) handset has been implemented, and experimental results are presented and discussed.

The design method for a small lowpass filter (LPF) having a multilayer structure, which can be embedded in RF modules, is presented. Low loss, three dimensional inductors and capacitors have been investigated and incorporated to design a chip-type LPF. The Chebyshev LPF has been designed with a cutoff frequency of 2 GHz, a ripple of 0.1 dB, and a high attenuation (

We report the fabrication of organic thin-film transistors (OTFTs) with high-k gate dielectrics of Mn-doped Bi2Ti2O7 (BTO) films. 3% Mn-doped BTO films deposited on polymer substrates by pulsed laser deposition at room temperature exhibit low leakage currents of 2.1 × 10–8 A/cm2 at an applied electric field of 0.3 MV/cm, while undoped BTO films show much higher leakage currents of 4.3 × 10–4 A/cm2. Mn doping effectively reduces the number of oxygen vacancies in the films and improves the electrical properties. Low operation voltage and significantly reduced leakage currents are demonstrated in pentacene-based OTFTs with the Mn-doped BTO gate dielectrics. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper, a small-chip meander antenna for dual-frequency operation is presented. This novel compact dual-frequency antenna uses a meander patch with increased capacity to adjust dual operating frequencies with small size and frequency ratio. The proposed antennas are fabricated by the LTCC-MLC process. The characteristics of return losses, radiation patterns, and gains are discussed. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 274–277, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10580

The effects of substrate temperatures and annealing temperatures on the microstructures and ferroelectric properties of PbZ (PZT) thin fims prepared by pulsed laser deposition (PLD) were investigated. For this purpose, the PZT films were deposited at various substrate temperatures (400~) with post annealing process in oxygen atmosphere. The single perovskite phase was formed at the deposition temperature of 500 to 55 without post annealing and the PZT films deposited below 50 formed the single phase with post annealing at . The grain size of the films increased and the grain boundary of the films was clearly defined as the substrate temperature increased from 400 to 55. The remnant polarization (Pr) and the coercive field (Ec) of the films deposited at 55 and annealed at were 34.3 C/c and 60.2 kV/cm, respectively.y.y.

The microwave dielectric properties of \(\left( {1 - x} \right)\left( {Al_{1/2} Ta_{1/2} } \right)O_2 - x\left( {Mg_{1/3} Ta_{2/3} } \right)O_2\) (AMT) \(\left( {0 \leqslant x \leqslant 1.0} \right)\) ceramics and the design of small coplanar waveguide fed antenna (CPWFA) have been investigated. (\(\left( {Al_{1/2} Ta_{1/2} } \right)O_2\) and (\(\left( {Mg_{1/3} Ta_{2/3} } \right)O_2\) have orthorhombic and tetragonal structure, respectively. As (\(\left( {Mg_{1/3} Ta_{2/3} } \right)O_2\) concentration increased, AMT ceramics transformed into the tetragonal structure. Specimens having tetragonal single phase could be obtained above x=0.6. As (\(\left( {Mg_{1/3} Ta_{2/3} } \right)O_2\) concentration increased, the grain size, dielectric constant \(\varepsilon _r\) and quality factor (Q) significantly increased and the temperature coefficient of resonant frequency \(\tau _f\) changed from negative to positive. The \(\tau _f\) of \(0 ppm ^\circ C^{ - 1}\) was realized at x=0.65 and the Q · fO value and \(\varepsilon _f\) for this composition were 112 470 GHz and 26.1, respectively. Newly developed \(0.35\left( {Al_{1/2} Ta_{1/2} } \right)O_2 - 0.65\left( {Mg_{1/3} Ta_{2/3} } \right)O_2\)dielectric materials were used for 1.5 GHz band CPWFA design and fabrication. The size of the CPWFA can be reduced by using high dielectric constant AMT ceramics, insetting slits into the patch, and fabricating CPW feed line in the ground plane. The slits play a role in not only lowering a center frequency but also fine tuning for the proposed antenna together with the open stub of CPW feed line. The CPWFA with slits has a lower center frequency than the conventional CPWFA, which suggests that the antenna size can be reduced by as much as 16.3%. The structure simulations of the CPWFAs have been performed to obtain impedance matching and to investigate the effects of slits. Experimental results of the fabricated device were in good agreement with the simulation.

Highly sensitive and selective chemiresistive sensors based on graphene functionalized by metals and metal oxides have attracted considerable attention in the fields of environmental monitoring and medical assessment because of their ultrasensitive gas detecting performance and cost-effective fabrication. However, their operation, in terms of detection limit and reliability, is limited in traditional applications because of ambient humidity. Here, the enhanced sensitivity and selectivity of single-stranded DNA-functionalized graphene (ssDNA-FG) sensors to NH3 and H2S vapors at high humidity are demonstrated and their sensing mechanism is suggested. It is found that depositing a layer of ssDNA molecules leads to effective modulation of carrier density in graphene, as a negative-potential gating agent and the formation of an additional ion conduction path for proton hopping in the layer of hydronium ions (H3O+) at high humidity (>80%). Considering that selectively responsive chemical vapors are biomarkers associated with human diseases, the obtained results strongly suggest that ssDNA-FG sensors can be the key to developing a high-performance exhaled breath analyzer for diagnosing halitosis and kidney disorder.

A bio-realistic artificial synapse integrated with a nanogenerator (NG), which can be used in neuromorphic systems, is demonstrated for self-powered biomedical devices in this study. Biocompatible amorphous (Na0.5K0.5)NbO3 (NKN) films are grown on TiN/polyimide substrates to synthesize NKN memristors for use as artificial synapses. Various synaptic functions are realized in NKN memristors, which are driven by a pulse generator and an NG. The synaptic plasticity of the NKN memristor results from the oxygen vacancy movements and the changes in the shape of the oxygen vacancy filaments. As a further step toward developing more bio-realistic artificial synapses, various types of metaplasticity and their mechanisms in the NKN memristors are investigated. Moreover, the metaplasticity of spike-timing-dependent plasticity (a key characteristic of biological synapses) is realized in the NKN memristor with a priming stimulus given by the NKN NG. An electronic component that mimics synapses in the brain has been created by a team in Korea. Mimicking the way the brain processes information in man-made devices could enable an entirely new way of computing that uses far less energy than conventional computers. Sahn Nahm from Korea University and co-workers created a circuit element known as a memristor that can switch between a high and low electrical resistance. They made it from (Na0.5K0.5)NbO3, or NKN, on a flexible substrate. NKN exhibits memristive properties due to the movement of oxygen vacancies and changes in shape of oxygen vacancy filaments. It is also piezoelectric, meaning that it generates an electrical current whenever it is moved, thus opening a route to self-powered biomedical devices. Bio-realistic flexible artificial synapses integrated with a nanogenerator were demonstrated for self-powered neuromorphic biomedical device applications. Biocompatible (Na0.5K0.5)NbO3 (NKN) was used in both memristors as an artificial synapse and a nanogenerator. Biological synaptic functions were produced in the NKN memristor driven by the NKN nanogenerator. Finally, metaplasticity was implemented in the integrated devices to facilitate bio-realistic functions in the artificial synapse.

A fire detector is the most important component in a fire alarm system. Herein, we present the feasibility of a highly sensitive and rapid response gas sensor based on metal oxides as a high performance fire detector. The glancing angle deposition (GLAD) technique is used to make the highly porous structure such as nanocolumns (NCs) of various metal oxides for enhancing the gas-sensing performance. To measure the fire detection, the interface circuitry for our sensors (NiO, SnO2, WO3 and In2O3 NCs) is designed. When all the sensors with various metal-oxide NCs are exposed to fire environment, they entirely react with the target gases emitted from Poly(vinyl chlorides) (PVC) decomposed at high temperature. Before the emission of smoke from the PVC (a hot-plate temperature of 200 °C), the resistances of the metal-oxide NCs are abruptly changed and SnO2 NCs show the highest response of 2.1. However, a commercial smoke detector did not inform any warning. Interestingly, although the NiO NCs are a p-type semiconductor, they show the highest response of 577.1 after the emission of smoke from the PVC (a hot-plate temperature of 350 °C). The response time of SnO2 NCs is much faster than that of a commercial smoke detector at the hot-plate temperature of 350 °C. In addition, we investigated the selectivity of our sensors by analyzing the responses of all sensors. Our results show the high potential of a gas sensor based on metal-oxide NCs for early fire detection.

The decoration of p-type nickel oxide (NiO) with n-type hematite (α-Fe2O3) to achieve vertically ordered 1D nanostructures is an attractive strategy to enhance gas sensing properties. Herein, the authors report a facile method for α-Fe2O3 decoration of the whole surface of vertical NiO nanorods. An NiO/Fe heterostructure is deposited in multiple steps using a glancing angle deposition method, which is followed by the oxidation of Fe into α-Fe2O3. Thermally agglomerated α-Fe2O3 nanoparticles are uniformly distributed on the whole surface of the NiO nanorods. Due to the α-Fe2O3 decoration, the NiO nanorods exhibit a coral-like rough surface and, more interestingly, their preferential crystallographic orientation changed from (111) to (200). Compared to bare NiO nanorods, the α-Fe2O3-decorated NiO nanocorals exhibit a 45.4 times higher response to 50 ppm toluene (C7H8) at 350 °C. Their theoretical detection limit for C7H8 is calculated to be ≈22 ppb. The observed unprecedented synergetic effects of α-Fe2O3-decorated NiO nanocorals for the extremely selective C7H8 sensing, as well as their facile synthetic route, establish a new perspective on heterostructured metal oxide 1D nanostructures for selective gas sensing.

Ca

The effect of B2O3 doping on microwave dielectric properties of Ca[(Li1/3Nb2/3)0.9Ti0.1]O3-δ was investigated. The Ca[(Li1/3Nb2/3)0.9Ti0.1]O3-δ ceramics was sintered at 1150°C. In order to decrease the sintering temperature for using as a low temperature co-firing ceramics (LTCC), B2O3 was added in the Ca[(Li1/3Nb2/3)0.9Ti0.1]O3-δ. As the content of B2O3 increased, the sintered density, the dielectric constant and Q·f0 value increased and the temperature coefficient of resonance frequency (τf) shifted to the negative value. When the B2O3 of 0.7 wt% added, the dielectric properties were ϵr of 35, Q·f0 of 22100 GHz, and τf of-5.6 ppm/°C at the sintering temperature of 1000°C.

We report the fabrication of ZnO based thin-film transistors (TFTs) with high- k gate insulator of Ti-substituted Bi 1.5 ZnNb 1.5 O 7 (BZN) films. (Bi 1.5 Zn 0.5 )(Zn 0.4 Nb 1.43 Ti 0.3 O 7 ) film deposited on Pt/Ti/SiO 2 /Si substrate by pulsed laser deposition at room temperature exhibits high dielectric constant of 73 at 100 kHz, while BZN film shows much lower dielectric constant of 50, respectively. The increasing dielectric constant with increasing Ti substitution can be attributed to the presence of a highly polarizable TiO 6 octahedra and its strong correlation with the NbO 6 octahedra. All room temperature processed ZnO based TFTs using Ti-substituted BZN gate insulator exhibited filed effect mobility of 0.75 cm 2 /Vs and low voltage device performance less than 2.5 V.

A high-density metal-insulator-metal (MIM) capacitor at 300°C with a titanium-substituted Bi1.5 Zn1.0Nb1.5O7 (BZN) dielectric prepared by physical vapor deposition is presented for the first time. Improvements have been achieved in terms of both capacitance density and temperature coefficient of capacitance (TCC) for MIM capacitors. A 67-nm-thick (Bi1.5 Zn0.5)(Zn0.4Nb1.3Ti0.3O7) film has exhibited a high capacitance density of 14.8 fF/cm2 at 100 kHz. The leakage current density is low, which is approximately 7.69 nA/cm2 at 1 V. The values of linear voltage and TCC are approximately 156 ppm/V2 and 98 ppm/°C at 100 kHz, respectively. All these make the Ti-substituted BZN capacitor very suitable for use in silicon RF and mixed-signal IC applications.

Buckling was observed in Bi5Nb3O15 (BiNbO) films grown on TiN/SiO2/Si at 300°C but not in films grown at room temperature and annealed at 350 °C. The 45-nm-thick films showed a high capacitance density and a low dissipation factor of 8.81 fF/?m2 and 0.97% at 100 kHz, respectively, with a low leakage current density of 3.46 nA/cm2 at 2 V. The quadratic and linear voltage coefficients of capacitance of this film were 846 ppm/V2 and 137 ppm/V, respectively, with a low temperature coefficient of capacitance of 226 ppm/°C at 100 kHz. This suggests that a BiNbO film grown on a TiN/SiO2/Si substrate is a good candidate material for high-performance metal-insulator-metal capacitors.

The microwave dielectric properties of Ca[(Li1/3Nb2/3)1−xMx]O3−δ (M = Sn, Ti, 0 ≤ x ≤ 0.5) ceramics were investigated. In general, the ceramics prepared were multiphase materials. However, single-phase specimens having orthorhombic perovskite structure similar to CaTiO3 could be obtained in the vicinity of Sn = 0.2 to 0.3, and Ti = 0.2. As Sn concentration increased, the dielectric constant (εr) decreased and the quality factor (Q) significantly increased within the limited Sn concentration. As Ti concentration increased, the dielectric constant (εr) increased, the quality factor (Q) decreased, and the temperature coefficient of resonant frequency (τf) changed from a negative to positive value. The temperature coefficient of resonant frequency of 0 ppm/°C was realized at Ti = 0.2. The Q · fo value and εr for this composition were found to be 26100 GHz and 38.6, respectively.

The microwave dielectric properties of (Pb1-xCax){(Fe0.5Nb0.5)1-ySny}O3 ceramics (0.4 ≤ x ≤ 0.6, y = 0.05, 0.1) and design of 900 MHz band 2-pole monoblock band pass filter (BPF) have been investigated to fabricate BPF. Single-phase specimens having orthorhombic perovskite structure similar to CaTiO3 could be obtained in the compositions of Pb1-xCax){(Fe0.5Nb0.5)1-ySny}O3 (0.4 ≤ x ≤ 0.6, y = 0.05, 0.1). The substitution of Sn for Fe0.5Nb0.5) significantly increased the quality factor Q and slightly decreased the dielectric constant (ɛr). The temperature coefficient of the resonant frequency of 0 ppm °C−1 was realized at x = 0.55 and y = 0.1. The Q · f0 value and (ɛr) for this composition were found to be 8600 GHz and 86, respectively. A monoblock λ/4 dielectric BPF for 900 MHz band portable telephone terminal is presented. This BPF is a kind of combline filter. Computer-aided design (CAD) was used in the modeling procedure. The equivalent circuit of the monoblock BPF is represented by transmission lines and lumped elements based on Zoe and Zoo. A BPF model was designed for surface mounted device (SMD) types. The simulations of the equivalent circuit and BPF structure have been performed to optimize the filter design. Newly developed Pb0.45Ca0.55){(Fe0.5Nb0.5)0.9Sn0.1}O3 dielectric materials were used for BPF fabrication. Experimental results of the fabricated device were in good agreement with the simulation.

Ferroelectric lithium niobate (LiNbO3) thin films were epitaxially fabricated on sapphire (0001) and polycrystalline diamond substrates using pulsed laser deposition (PLD). Various deposition conditions are investigated to realize deposition of c-axis oriented LiNbO3 thin film. The LiNbO3 thin films were chemically etched after electric poling, being investigated by scanning electron microscope (SEM).

Self-assembled WO3 thin film nanostructures with 1-dimensional villi-like nanofingers (VLNF) have been synthesized on the SiO2/Si substrate with Pt interdigitated electrodes using glancing angle deposition (GAD). Room-temperature deposition of WO3 by GAD resulted in anisotropic nanostructures with large aspect ratio and porosity having a relative surface area, which is about 32 times larger than that of a plain WO3 film. A WO3 VLNF sensor shows extremely high response to nitric oxide (NO) at 200 °C in 80% of relative humidity atmosphere, while responses of the sensor to ethanol, acetone, ammonia, and carbon monoxide are negligible. Such high sensitivity and selectivity to NO are attributed to the highly efficient modualtion of potential barriers at narrow necks between individual WO3 VLNF and the intrinsically high sensitivity of WO3 to NO. The theoretical detection limit of the sensor for NO is expected to be as low as 88 parts per trillion (ppt). Since NO is an approved biomarker of chronic airway inflammation in asthma, unprecedentedly high response and selectivity, and ppt-level detection limit to NO under highly humid environment demonstrate the great potential of the WO3 VLNF for use in high performance breath analyzers.

(Bi2Te3)(1-x)(PbTe)(x) binary systems near eutectic composition were prepared by melting of elemental metals and a sequential water quenching process and their microstructures and thermoelectric properties were investigated. Multiple phases such as Bi2Te3, BiPbTe and PbTe were observed due to phase separation when the composition x was higher than the eutectic point. Also the electrical conduction type of the alloys converted from p-type to n-type in the phase separated alloys. The lattice thermal conductivities in the phase-separated alloys are lower than those in alloys without phase separation, attributable to increased boundary scattering.

Ultrathin (4-6 nm) single-crystal Bi(2)Se(3) nanodiscs and nanosheets were synthesized through a simple and quick solution process. The growth mechanism was investigated in detail. Crystal seeds grew via 2D self-attachment of small nanoparticles followed by epitaxial recrystallization into single crystals. The lateral dimension of the nanodiscs increased and their shape changed from circles to hexagons as the reaction temperature increased. Positively charged polymer surfactants greatly enlarged the lateral dimension to produce nanosheets with uniform thickness.