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- 2018
- medical application
- electrical capacitance tomography
- electrical impedance tomography
- Optoelectronic Information Science and Engineering
- University of Manchester
- Chiba University
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Capacitance–Resistive PEDOT:PSS Cotton Fabric Satisfied Jonscher’s Law with Index Exceeding One
摘要： Jonscher’s law is investigated in the context of PEDOT:PSS impregnated conductive cotton fabric for frequencies from 10 Hz to 13 MHz and temperatures from 30°C to 100°C using complex impedance spectroscopy. The drop-casting and drying method was used to prepare samples of conductive cotton fabric with low and high concentrations of dopant. Argand plots of the ratio of AC–DC conductivities of the conductive fabric demonstrated the presence of reactance at high frequencies at each concentration of dopant. Regression analysis demonstrated that Jonscher’s power law was obeyed over a significant range of high frequencies. The hopping frequency and Jonscher index are found to depend on the concentration of dopant, but are insensitive to temperature over the range used in this study. By contrast with numerous experimental studies reporting that the Jonscher index is less than one, this experimental investigation found that Jonscher’s index exceeded one. We further investigated whether or not the hopping frequency identified by regression corresponded to a natural frequency arising in the Argand plot of the complex conductivity ratio. Considerations of curvature and phase angle identified two candidate frequencies, but neither was close to the hopping frequency identified by regression.
关键词： capacitance,Argand,regression,conductivity,Cotton
更新于2025-09-19 17:15:36
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Role of metallic dopants on the properties of copper (1) iodide nanopod-like structures
摘要： The addition of impurities as dopants to any material affects the properties of the material where the dopant modulates the optical and structural properties of the material. Copper (1) iodide films which were successfully doped with Al, Pb and Zn (as metallic dopants) were synthesized by the successive ionic layer adsorption and reaction (SILAR) technique while the morphological, structural, optical and electrochemical properties were investigated using the scanning electron microscope (SEM), X-ray diffraction (XRD), UV–Vis spectrophotometer and potentiostat respectively. The SEM image revealed a nanopod-like structure for the deposited CuI films while the XRD results confirmed the crystalline nature of the films with a face centered cubic structure. The optical results showed a progressive decrease of the absorbance values at increasing wavelengths while the optical bandgap energy of the undoped CuI film reduced from 2.47eV to 1.90eV, 1.75eV and 1.8eV for the Al-doped, Pb-doped and Zn-doped CuI films respectively. The undopedCuI film also showed a higher extinction coefficient value than the metallic-doped CuI films. The Zn-doped film had the maximum specific capacitance of 116 F g?1 at 2 mV/s.
关键词： Bandgap energies,Metallic dopants,CuI,SILAR,Specific capacitance
更新于2025-09-19 17:15:36
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Electronic Traps and its Correlations to Perovskite Solar-Cell Performance via Compositional and Thermal-Annealing Controls
摘要： Herein, underlying factors for enabling efficient and stable performance of perovskite solar cells are studied through nanostructural controls of organic-inorganic halide perovskites. Namely, MAPbI3, (FA0.83MA0.17)Pb(I0.83Br0.17)3, and (Cs0.10FA0.75MA0.15)Pb(I0.85Br0.15)3 perovskites (abbreviated as MA, FAMA, and CsFAMA, respectively) are examined with a grain growth control through thermal annealing. FAMA- and CsFAMA- based cells result in stable photovoltaic performance while MA cells are sensitively dependent on the perovskite grain size dominated by annealing time. Micro-/nanoscopic features are comprehensively analysed to unravel the origin that is directly correlated to the cell performance with the applications of electronic-trap characterizations such as photoconductive noise microscopy and capacitance analyses. It is revealed that CsFAMA has a lower trap density compared to MA and FAMA through the analyses of 1/f noises and trapping/detrapping capacitances. Also, an open-circuit voltage (Voc) change is correlated to the variation of trap states during the shelf-life test: FAMA and CsFAMA cells with the negligible change of Voc over weeks exhibit trap states shifting toward the bandedge, although the power-conversion efficiencies are clearly reduced. It is discussed about the origins that critically affect the solar cell performance through the characterizations of shallow/deep traps with additional mobile defects in the perovskite and interfaces.
关键词： 1/f noise,Organic-inorganic halide perovskite,Perovskite solar cell,Capacitance,Electronic trap
更新于2025-09-19 17:15:36
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FPGA Implementation of ECT Digital System for Imaging Conductive Materials
摘要： This paper presents the hardware implementation of a stand-alone Electrical Capacitance Tomography (ECT) system employing a Field Programmable Gate Array (FPGA). The image reconstruction algorithms of the ECT system demand intensive computation and fast processing of large number of measurements. The inner product of large vectors is the core of the majority of these algorithms. Therefore, a reconfigurable segmented parallel inner product architecture for the parallel matrix multiplication is proposed. In addition, hardware-software codesign targeting FPGA System-On-Chip (SoC) is applied to achieve high performance. The development of the hardware-software codesign is carried out via commercial tools to adjust the software algorithms and parameters of the system. The ECT system is used in this work to monitor the characteristic of the molten metal in the Lost Foam Casting (LFC) process. The hardware system consists of capacitive sensors, wireless nodes and FPGA module. The experimental results reveal high stability and accuracy when building the ECT system based on the FPGA architecture. The proposed system achieves high performance in terms of speed and small design density.
关键词： electrical tomography,image reconstruction algorithm,capacitance measurements,FPGA,LFC
更新于2025-09-19 17:15:36
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Photodetectors [Working Title] || a-Si:H p-i-n Photodiode as a Biosensor
摘要： The p-i-n a-Si:H photodiode is a promising device as a transducer in biosensors. The native and light-induced localized state density and energy distribution in the energy gap of a-Si:H have a large effect on the photoconductivity of thin-film photodiodes. Depending on their nature, they play a crucial role in trapping and recombination processes and consequently influence the photodiode capacitance. The optical bias dependence of modulated photocurrent, OBMPC, method using the blue LED light is applied to clarify the nature and energy distribution of the energy gap density of states and their influence on the photodiode capacitance, from photodiodes transient response. It is observed that the deep defect states of the i-layer contribute to the capacitance at various bias voltages. Also, the capacitance achieves the upper limit around the built-in potential. Based on this method and obtained results, the a-Si:H p-i-n photodiode is used as a biosensor transducer in the detection of mammalian cell chemiluminescence.
关键词： blue light,biosensor,transient response,defects,a-Si:H p-i-n photodiode,density of states,capacitance,LED
更新于2025-09-19 17:13:59
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Influence of Silicon-Doping in n-AlGaN Layer on the Optical and Electrical Performance of Deep Ultraviolet Light-Emitting Diodes
摘要： The influence of two different methods of silicon doping in AlGaN layer, that is, modulation-doping (MD) and delta-doping (DD), on the optical and electrical performance of deep ultraviolet light-emitting diodes (DUV-LEDs) has been investigated. Both the photoluminescence and electroluminescence intensities in the Si-DD structure are stronger than those obtained by the Si-MD method, while the forward voltage and reverse leakage current are slightly smaller in the DD structure than that in the MD structure. Compared with the MD structure, the DD structure shows higher capacitance-voltage characteristics. This study suggests that the DD method can improve the optical and electrical performance of DUV-LEDs.
关键词： bias voltage,n-AlGaN layer,ultraviolet light-emitting diodes,capacitance,Si-doping,current
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 28th International Symposium on Industrial Electronics (ISIE) - Vancouver, BC, Canada (2019.6.12-2019.6.14)] 2019 IEEE 28th International Symposium on Industrial Electronics (ISIE) - Digital Holography for Industrial Applications
摘要： Metal–insulator–metal (MIM) capacitors with full atomic-layer-deposition Al2O3/ZrO2/SiO2/ZrO2/Al2O3 stacks were explored for the first time. As the incorporated SiO2 film thickness increased from 0 to 3 nm, the quadratic and linear voltage coefficients of capacitance (α and β) of the MIM capacitors reduced significantly from positive values to negative ones. For the stack with 3-nm SiO2 film, a capacitance density of 7.40 fF/μm2, α of ?121 ppm/V2, and β of ?116 ppm/V were achieved, together with very low leakage current densities of 3.08 × 10?8 A/cm2 at 5 V at room temperature (RT) and 5.89 × 10?8 A/cm2 at 3.3 V at 125 °C, high breakdown field of 6.05 MV/cm, and high operating voltage of 6.3 V for a 10-year lifetime at RT. Thus, this type of stacks is a very promising candidate for next generation radio frequency and analog/mixed-signal integrated circuits.
关键词： metal-insulator-metal,Al2O3/ZrO2/SiO2/ZrO2/Al2O3,Atomic-layer-deposition,voltage coefficients of capacitance
更新于2025-09-19 17:13:59
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[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - An Air-filled Circularly Polarized Monochromatic Multimode Helical Beam Antenna
摘要： The authors previously succeeded in reducing the shaft voltage of a PWM driven motor with a rotor which had an outer core and an inner core (and the shaft), electrically insulated each other by a resin (hereafter, the insulated rotor). This paper proposes a new method for further reduction of the shaft voltage of a motor with an insulated rotor by adding a capacitor between brackets and N line of the dc link of the inverter. A common-mode equivalent circuit of the system with an ungrounded motor is examined, and the effect of further reduction by the new method is veri?ed by calculation of the shaft voltage from the equivalent circuit and measurement of the shaft voltage of the motor.
关键词： shaft voltage,Bearing current,common-mode voltage,stray capacitance
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Personalized Adaptation of Learning Environments
摘要： The authors previously succeeded in reducing the shaft voltage of a PWM driven motor with a rotor which had an outer core and an inner core (and the shaft), electrically insulated each other by a resin (hereafter, the insulated rotor). This paper proposes a new method for further reduction of the shaft voltage of a motor with an insulated rotor by adding a capacitor between brackets and N line of the dc link of the inverter. A common-mode equivalent circuit of the system with an ungrounded motor is examined, and the effect of further reduction by the new method is veri?ed by calculation of the shaft voltage from the equivalent circuit and measurement of the shaft voltage of the motor.
关键词： shaft voltage,Bearing current,stray capacitance,common-mode voltage
更新于2025-09-19 17:13:59
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Can we see defects in capacitance measurements of thin‐film solar cells?
摘要： Thermal admittance spectroscopy and capacitance‐voltage measurements are well established techniques to study recombination‐active deep defect levels and determine the shallow dopant concentration in photovoltaic absorbers. Applied to thin‐film solar cells or any device stack consisting of multiple layers, interpretation of these capacitance‐based techniques is ambiguous at best. We demonstrate how to assess electrical measurements of thin‐film devices and develop a range of criteria that allow to estimate whether deep defects could consistently explain a given capacitance measurement. We show that a broad parameter space, achieved by exploiting bias voltage, time, and illumination as additional experimental parameters in admittance spectroscopy, helps to distinguish between deep defects and capacitive contributions from transport barriers or additional layers in the device stack. On the example of Cu(In,Ga)Se2 thin‐film solar cells, we show that slow trap states are indeed present but cannot be resolved in typical admittance spectra. We explain the common N1 signature by the presence of a capacitive barrier layer and show that the shallow net dopant concentration is not distributed uniformly within the depth of the absorber.
关键词： admittance spectroscopy,deep defects,doping profile,thin films,capacitance
更新于2025-09-19 17:13:59