Microstructure and magnetic properties of aerosol‐deposited Sm‐Fe‐N thick films

In this study, the relationship among magnetic properties, Aerosol Deposition (AD) conditions, and microstructures in Sm‐Fe‐N AD films was investigated. The maximum thickness of 145µm was obtained under AD conditions of gas flow rate (gfr)=6liters/min for 10 min. The density of Sm‐Fe‐N films was in the range of 5.43 to 6.24g/cm³, that is, 71 to 81% of the X‐ray density of the Sm₂Fe₁₇N₃ compound reported (7.67g/cm³). The Sm‐Fe‐N AD films showed remanence in the range of 0.38 to 0.42 T, that is, 61 to 68% of that of the Sm‐Fe‐N host powder (0.62 T). The coercivities increased from 1.16 to between 1.74 and 1.79 T after the deposition because the grain size decreased from 1.94µm to 0.32µm. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(1): 8–13, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20214     

Magnetic properties of Pr‐Fe‐Co‐V‐W‐Si‐B system exchange spring magnets

The melt‐spun ribbons of Pr‐Fe‐Co‐V‐W‐Si‐B system alloys were prepared by single roller rapid‐quenching method. The effects of composition, surface velocity, and heat treatment on the magnetic properties were investigated. The P₉sFe₇₁Co₈V_0.5W_0.5Si_0.5B_10.5 alloy ribbons prepared at a surface velocity of 12.5 m/s were crystallized by heat treatment, and the optimum heat‐treatment condition was found to be at 575°C for 3 min, for which the magnetic properties were (BH)_max = 136.1 kJ/m³, J_r = 0.93 T, H_cJ = 652.2 kA/m, and H_cB = 528.3 kA/m. The temperature coefficients of J_r and H_cJ for the ribbons crystallized from melt‐spun ribbons of Pr₉Fe₇₁Co₈V_0.5W_0.5Si_0.5B_10.5 alloy were α(J_r)_ave = ?0.057%/°C and α(H_cJ) = ?0.450%/°C. The value of (B)_max for the compression molding Pr₉Fe₇₁Co₈V_0.5W_0.5Si_0.5B_10.5 isotropic bonded magnet prepared by using the ribbons annealed at 575°C for 3 min is 80.0 kJ/m³, and the density is 6.24 Mg/m³. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(3): 10–16, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20211 Copyright © 2006 Wiley Periodicals, Inc.     

Vertical‐type organic device using thin‐film ZnO transparent electrode

We propose a double heterojunction organic light‐emitting diode (OLED) using a zinc oxide (ZnO) film, which works as a transparent and electron injection layer. The crystal structure of the ZnO films as a function of Ar/O₂ flow ratio and the basic characteristics of the OLED depending on the ZnO sputtering conditions are investigated. Excellent characteristics of the novel OLED were obtained, as high as 470 cd/m² at 22 V and 7.6 mA/cm². The results obtained here demonstrate that the vertical organic light‐emitting transistor (OLET) using a ZnO layer as an electron injection layer is promising as a key element for flexible sheet displays. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 49–55, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20151     

Nd–Fe–B thick films prepared at the high deposition rate of 90 µm/h

After a postannealing process, the magnetic properties of pulsed laser deposition (PLD)‐made Nd–Fe–B film magnets prepared at the deposition rate of 20–90 µm/h showed constant values, and the average values of H_c, B_r and (BH)_max were 1050 kA/m, 0.6 T, and 60 kJ/m³, respectively. The obtained results were comparable to those previously reported. In conclusion, it was found that a maximum deposition rate of 90 µm/h could be achieved without deterioration of magnetic and mechanical properties. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Fabrication of flat micro‐gap electrodes for molecular electronics

Recently, organic molecular electronic devices such as molecular thin‐film transistors have received considerable attention as possible candidates for next‐generation electronic and optical devices. This paper reports on fabrication technologies of flat metallic electrodes on insulating substrates with a micrometer separation for high‐performance molecular device evaluation. The key technologies of fabricating planar‐type electrodes are the liftoff method by the combination of bilayer photoresist with overhang profile, electron beam evaporation of thin metal (Ti and Au) films, and SiO₂‐CMP (Chemical Mechanical Polishing) method of CVD (Chemical Vapor Deposition)‐deposited TEOS (tetraethoxysilane)–SiO₂ layer. The raggedness of the electrode/insulator interface and the electrode surface of the micro‐gap electrodes were less than 3 nm. The isolation characteristics of fabricated electrodes were on the order of 10¹³ ohms at room temperature, which is sufficient for evaluating electronic properties of organic thin‐film devices. Finally, pentacene FET (Field Effect Transistor) characteristics are discussed fabricated on the micro‐gap flat electrodes. The mobility of this FET was 0.015 cm²/Vs, which was almost on the order of the previous results. These results suggest that high‐performance organic thin‐film transistors can be realized on these advanced electrode structures. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(2): 39–46, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20152     

Low‐resistive and transparent AZO films prepared by PLD in magnetic field

Al₂O₃‐doped ZnO (AZO) thin films have been deposited onto glass substrates using a split target consisting of AZO (1 wt%) and AZO (2 wt%) by pulsed laser deposition with an ArF excimer laser (λ = 193 nm, 15 mJ, 10 Hz, 0.75 J/cm²). By applying a magnetic field perpendicular to the plume, the lowest resistivity of 8.54 × 10^?5Ω·cm and an average transmittance exceeding 91% over the visible range were obtained at a target‐to‐substrate distance of 25 mm for approximately 279‐nm‐thick AZO film (1.8 wt%) grown at a substrate temperature of 230 °C in vacuum. From cross‐sectional TEM observations and the XRD spectrum, a reason why the low resistivity (54 × 10^?5Ω·cm) was reproducibly obtained was considered to be due to the fact that a disorder of crystal growth originating in the vicinity of the interface between the substrate and the film was suppressed by application of the magnetic field and the c‐axis orientation took preference, giving rise to the increase of mobility. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(2): 40–45, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20026     

Electron‐beam‐pumped light sources using graphite nanoneedle field emitters and Si electron‐transparent films

Sputter‐induced carbon nanoneedle field emitters and Si electron‐transparent films have been developed for electron‐beam‐pumped light sources. The sputter‐induced carbon nanoneedle field emitters exhibited a stable electron emission of 0.1 mA at an average field of 13 V/µm. The 1.5‐µm thick Si electron‐transparent films achieved an electron transmittance of about 60% at an acceleration voltage of 27 kV. An electron‐beam‐pumped light source was demonstrated from the excitation of N₂ gas, and a N₂ gas spectrum was clearly observed. The increase of the beam current is important for increasing the light intensity. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A low‐voltage band‐gap reference circuit with second‐order analyses

A new band‐gap reference (BGR) circuit employing sub‐threshold current is proposed for low‐voltage operations. By employing the fraction of V_BE and the sub‐threshold current source, the proposed BGR circuit with chip area of 0.029mm² was fabricated in the standard 0.18µm CMOS triple‐well technology. It generates reference voltage of 170 mV with power consumption of 2.4µW at supply voltage of 1 V. The agreement between simulation and measurement shows that the variations of reference voltage are 1.3 mV for temperatures from ?20 to 100^°C, and 1.1 mV per volt for supply voltage from 0.95 to 2.5 V, respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

A new modeling approach for circuit‐field‐coupled time‐stepping electromagnetic analysis of saturated interior permanent magnet synchronous motors

This paper proposes a new modeling approach for circuit‐field‐coupled time‐stepping electromagnetic analysis of a saturated interior permanent magnet synchronous motor (IPMSM). To predict the drive performance quickly, the proposed approach consists of a dynamic simulator based on a new analytical model of the d‐ and q‐axis magnetization characteristics (λ‐i_d‐i_q‐θ). The model can take into account not only cross‐saturation but also the harmonics of the inductance distributions and EMF waveforms. The validity of the model is verified from suitable simulation results for the instantaneous current and torque waveforms of the IPMSM. The proposed analysis leads to a dramatic reduction in the computation time compared to circuit‐field‐coupled time‐stepping FEA, while maintaining analytical accuracy. The effectiveness of the proposed method is experimentally verified using a 10‐kW, 15,000‐rpm concentrated‐winding IPM motor. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 49–58, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21024     

High‐tuning‐range CMOS band‐pass IF filter based on a low‐Q cascaded biquad optimization technique

A design procedure for high‐order continuous‐time intermediate‐frequency band‐pass filters based on the cascade of low‐Q biquadratic cells is presented. The approach is well suited for integrated‐circuit fabrication, as it takes into account the maximum capacitance spread dictated by the available technology and maximum acceptable sensitivity to component variations. A trade‐off between noise and maximum linear range is also met. A novel, wide‐tuning‐range transconductor topology is also described. Based on these results, a 10‐pole band‐pass filter for a code division multiple‐access satellite receiver has been designed and tested. The filter provides tunable center frequency (f₀) from 10 to 70 MHz and exhibits a 28‐MHz bandwidth around f₀ = 70 MHz with more than 39‐dB attenuation at f₀/2 and 2f₀. Third‐order harmonic rejection is higher than 60 dB for a 1‐Vpp 70‐MHz input, and equivalent output noise is lower than 1 mV_rms. The circuit is fabricated in a 0.25‐µm complementary metal oxide semiconductor process, and the core consumes 12 mA from a 2.5‐V supply, offering the best current/pole ratio figure. The die area resulted to be 0.9 × 1.1 mm². Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of Activation Energies and Electric Dipole Moment of In‐Plane Highly Electrically Conductive Hetero‐C12TCNQ/C20 LB Films Using Thermally Stimulated Current

The activation energies of in‐plane highly electrically conductive 2‐dodecyl‐7,7,8,8‐tetracyanoquinodimethane (C₁₂ TCNQ)/arachidic acid (C₂₀) hetero‐LB films and C₁₂TCNQ homo‐LB films were determined by thermally stimulated current (TSC) measurement. The TSC curves for the upper Al electrode/C₁₂TCNQ/C₂₀/lower Al electrode were nearly of the same shape as those for the upper Al electrode/C₁₂TCNQ/lower Al electrode. The activation energies of the upper Al electrode/C₁₂TCNQ/C₂₀/lower Al electrode and upper Al electrode/C₁₂TCNQ/lower Al electrode were 0.9–1.3 eV at 55–80^°C and 1.6–1.8 eV at 105–120^°C, respectively. The TSC curves for the upper Al electrode/C₁₂TCNQ/C₂₀/lower Al electrode and upper Al electrode/C₁₂TCNQ/lower Al electrode had two peaks at 55–80^°C owing to the depolarization of the electric dipole and two peaks at 105–120^°C owing to the movement of space charges in the C₁₂TCNQ molecule. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Implementation of the symmetric doped double‐gate MOSFET model in Verilog‐A for circuit simulation

Recently we developed a model for symmetric double‐gate MOSFETs (SDDGM) that, for the first time, considers the doping concentration in the Si film in the complete range from 1×10¹⁴ to 3×10¹⁸ cm⁻³. The model covers a wide range of technological parameters and includes short channel effects. It was validated for different devices using data from simulations, as well as measured in real devices. In this paper, we present the implementation in Verilog‐A code of this model, which allows its introduction in commercial simulators. The Verilog‐A implementation was optimized to achieve reduction in computational time, as well as good accuracy. Results are compared with data from 2D simulations, showing a very good agreement in all transistor operation regions. Copyright © 2009 John Wiley & Sons, Ltd.     

A gain/efficiency‐enhanced bidirectional switched‐capacitor DC‐DC converter

A closed‐loop gain/efficiency‐enhanced bidirectional switched‐capacitor converter (BSCC) is proposed by combining an adaptive‐conversion‐ratio (ACR) phase generator and pulse‐width‐modulation (PWM) controller for bidirectional step‐up/down DC‐DC conversion and regulation. For realizing gain‐enhanced, the power part consists of one m_c‐stage cell and one n_c‐stage cell in cascade between low‐voltage (LV) and high‐voltage (HV) sides to boost HV voltage into m_c × n_c times voltage of LV source at most, or convert LV voltage into 1/(m_c × n_c) times voltage of HV source at most. For realizing efficiency‐enhanced, the ACR idea with adapting stage number m, n is built in the phase generator to obtain a suitable step‐up/down gain: m × n or 1/(m × n) (m = 1, 2, …, m_c, n = 1, 2, …, n_c). Further, the output regulation and robustness to source/loading variation can be enhanced by PWM on the LV/HV sides. Some theoretical analysis and control design are included as: modeling, steady‐state analysis, conversion ratio, efficiency, capacitance selection, and control design. Finally, the performance of this scheme is verified experimentally on a BSCC prototype, and all results are illustrated to show the efficacy of this scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

Fabrication and characterization of β−FeSi2 thin films prepared by PLD method using Nd:YAG laser

β?FeSi₂ thin films were grown on Si(111) substrates by pulsed laser deposition (PLD) method using a Nd:YAG laser (λ=1064nm, laser energy=50mJ, laser energy density=1.65J/cm², repetition frequency=10Hz). In the fabrication process, three targets of (a) Fe(5N), (b) FeSi₂(3N), and (c) Fe(5N)+FeSi₂(3N) were used. The β?FeSi₂ thin films having the best properties of crystallinity were obtained in the case of (c), in which the first layer as the template was formed with the target of Fe(5N) and then, on top of that, the second layer was deposited with the target of FeSi₂(3N). At this time, it was found that by XRD measurement, the degree of crystallinity of the films of case (c) in which the first layer was introduced as the template improved 1.4 times as much compared with case (a), and that by SEM and AFM observations, surface morphologies also improved. Moreover, it was found that by TEM observation, the β?FeSi₂ thin films grew uniformly along the direction of (220) or (202) from the interface of the Si substrate and the film to the free surface and that by EDS analysis, the compositions of Fe and Si were uniformly distributed. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(2): 39–45, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ eej.20238     

Crank‐shaped and Y‐shaped through‐hole interconnections filled with Au‐Sn solder

Crank‐shaped and Y‐shaped through‐hole interconnections (THI) filled with Au‐Sn solder are demonstrated in this study. They are expected to realize a higher‐density wafer‐level package (WLP) for electrical devices including the fields of MEMS (Micro Electro‐Mechanical Systems) and MOEMS (Micro Optical Electro‐Mechanical Systems) compared with conventional WLP using THI consisting of straight through‐holes. In this paper, formation techniques for crank‐shaped and Y‐shaped THI are described. In order to make crank‐shaped and Y‐shaped through‐holes in a substrate, both femtosecond laser irradiation and wet chemical etching are used. Crank‐shaped through‐holes with an 80‐μm opening and 400 μm deep have also been achieved. Gold (Au)‐tin (Sn) solder was filled into the holes using the molten metal suction method (MMSM). Airtightness of the THI was examined using the helium leakage test, and the estimated leakage rate was less than 1.0 × 10^?9 Pa·m³/s, which is sufficient for use in WLP applications. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(1): 54–62, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com) . DOI 10.1002/eej.21134     

Nonlinear optical properties and morphologies of vanadyl‐phthalocyanine thin films prepared on polyethylene‐terephthalate film

Vanadyl phthalocyanine (VOPc) crystal thin films were prepared on poly(ethylene terephthalate) (PET) film. The VOPc film prepared on PET substrate at 120 °C had Phase II. The third harmonic (TH) intensity of the VOPc film was measured by the marker fringe method. The third optical susceptibility (χ⁽³⁾) estimated from TH intensity is 3.5 × 10^?9 esu. The transition from Phase I to Phase II of the VOPc film was enhanced with corona charging. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 36–43, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10022     

Characteristics evaluation of a CO2‐capturing power generation system with reheat cycle utilizing regenerative oxygen‐combustion steam‐superheater

A new CO₂‐capturing power generation system is proposed that can be easily realized by applying conventional technologies. In the proposed system, the temperature of medium‐pressure steam in a thermal power plant is raised by utilizing an oxygen‐combusting regenerative steam‐superheater. The CO₂ generated by combusting the fuel in the superheater can be easily separated and captured from the exhaust gas at the condenser outlet, and is liquefied. The superheated steam is used to drive a steam turbine power generation system. Using a high‐efficiency combined cycle power generation system as an example, it is shown that the proposed system can increase the power output by 10.8%, and decrease the CO₂ emissions of the entire integrated system by 18.6% with a power generation efficiency drop of 2.36% compared with the original power plant without CO₂ capture, when the superheated steam temperature is 750 ^°C. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(1): 35–41, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20575     

A 5‐MHz AT‐cut quartz crystal oscillating circuit functioning in 350 nA

An oscillating circuit functioning at ultra low power (350 nA) for a 5‐MHz AT‐cut quartz crystal oscillator was investigated. This circuit has a resistance between the power terminal of the CMOS‐IC and the power supply, and another between the earth terminal of the CMOS‐IC and the ground (GND). These resistances discourage an inrush of current, and set a gain (g_m) necessary for oscillating the circuit at minimum. The developed circuit is quite simple, but enables driving at once‐unthinkable, low power (below 1 µA). © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

High‐performance pMOSFETs with high Ge fraction strained SiGe‐heterostructure channel and ultrashallow source/drain formed by selective B‐doped SiGe CVD

The improvement of current drivability and short‐channel effect is very important for ultrasmall MOS device technology. SiGe‐channel pMOSFETs are one of the most promising devices because hole mobility in the SiGe layers is enhanced. In the previous work, it has been reported that Super Self‐aligned Shallow junction Electrode (S³E) MOSFETs formed by selective B‐doped SiGe CVD are effective for the suppression of short‐channel effect. In this paper, it is clarified that the (S³E) pMOSFETs with Si_0.65Ge_0.35 channel are realized not only with suppression of punch‐through due to the ultrashallow B‐diffused source/drain but also with enhancement of maximum linear transconductance due to the low parasitic resistance, compared to that with the Si channel fabricated by the same process conditions. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(3): 46–50, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20597     

0.3‐V bulk‐driven programmable gain amplifier in 0.18‐µm CMOS

A new solution for an ultra low voltage bulk‐driven programmable gain amplifier (PGA) is described in the paper. While implemented in a standard n‐well 0.18‐µm complementary metal–oxide–semiconductor (CMOS) process, the circuit operates from 0.3 V supply, and its voltage gain can be regulated from 0 to 18 dB with 6‐dB steps. At minimum gain, the PGA offers nearly rail‐to‐rail input/output swing and the input referred thermal noise of 2.37 μV/Hz^1/2, which results in a 63‐dB dynamic range (DR). Besides, the total power consumption is 96 nW, the signal bandwidth is 2.95 kHz at 5‐pF load capacitance and the third‐order input intercept point (IIP₃) is 1.62 V. The circuit performance was simulated with LTspice. Copyright © 2016 John Wiley & Sons, Ltd.