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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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Electrochemical capacitance-voltage profiling of nonuniformly doped GaAs heterostructures with SQWs and MQWs for LED applications
摘要： Light-emitting heterostructures with single and multiple GaAs/InGaAs quantum wells have been investigated by means of electrochemical capacitance-voltage (ECV) profiling. Capacitance-voltage characteristics were measured; concentration profiles of free charge carriers over the heterostructure depth as well as the intensity of quantum well filling by charge carriers were obtained. In heterostructures with a single quantum well (QW) we considered limitations of capacitance techniques for undoped QW profiling, which is situated near the metallurgic border of the p–n –junction. We made a detailed consideration of phenomena related to Debye smearing and we developed and analyzed the dependence of the space charge region width on the doping. Special attention was paid to investigation of the “blind” area. This was inspired by the practical problem from capacitance spectroscopy of semiconductors, when the researcher poses the task of obtaining a free charge carrier depth distribution profile as deep as possible in the space charge region, i.e. where the intensity of the electric field is maximum. Generally, the active QW of a LED heterostructure is placed deep in the space charge region, so reaching these regions is extremely important for practical problems. We present an evolution of capacitance-voltage characteristics during ECV profiling of nonuniformly doped p – n– heterostructures. For a heterostructure with multiple quantum wells we registered a response from 6 QWs.
关键词： capacitance-voltage profiling,heterostructure,quantum well,nonuniform doping,Electrochemical capacitance-voltage profiling,quantum dot,light-emitting diodes
更新于2025-11-14 17:28:48
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Effect of Dielectric Charging on Capacitance Change of an SOI Based CMUT
摘要： Effect of dielectric charging on the performance of SOI based Capacitive Micromachined Ultrasonic Transducers (CMUT) has been investigated. Measurements on an SOI based CMUT show that that the capacitance change as a function of DC bias is considerably higher than analytically calculated values. Investigation shows that this deviation in capacitance from analytically calculated values is due to the combined effects of different dielectric charging phenomena due to a strong electric field, trap charges in the SOI oxide layer, the charge motion associated with the leakage current through the buried oxide layer, and the air in the CMUT cavity. Additionally, this charging effect degrades the transduction efficiency as the induced polarization reduced the effective bias across the CMUT. It is concluded that the buried oxide (BOX) layers in SOI wafers are not suitable for use as dielectric spacers in electrostatic MEMS devices.
关键词： SOI,dielectric charging,Capacitance,microfabrication,MEMS,CMUT,leakage current
更新于2025-11-14 17:28:48
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Full capacitance model, considering the specifics of amorphous oxide semiconductor thin film transistors structures
摘要： A full capacitance model for Amorphous Oxide Semiconductor Thin Film Transistors (AOSTFTs), considering the effect of the drain contact overlap in bottom gate passivated structures is presented. It is shown that this drain overlap, on top of the passivation layer, serves as a second gate with an applied voltage equal to VDS. When VDS>VT the semiconductor-passivation (S-P) interface will be in accumulation and the behavior of the different capacitance is affected. An expression to represent this effect is included in the present model. The overlap capacitance between gate and drain/source, as well as the effect of reducing the channel capacitance as the drain is increased, are also considered by the model. The calculated capacitance is a function of the threshold voltage, (VT), the mobility and saturation parameters (γα,αs), and the sharpness of the knee region m, which are extracted using the Unified Model and Extraction Method (UMEM) for AOSTFTs. Results are compared with simulated and experimental data.
关键词： AOSTFT modeling,Capacitance model,Dynamic modeling
更新于2025-11-14 17:28:48
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Determination of physical mechanism responsible for the capacitance-voltage weak inversion “hump” phenomenon in n-InGaAs based metal-oxide-semiconductor gate stacks
摘要： Weak inversion capacitance-voltage (C-V) “hump” is a widely observed phenomenon at n-InGaAs based metal oxide semiconductor (MOS) structures. The mechanism responsible for this phenomenon is still under discussion. The C-V hump can be explained as an interaction of interface states with either one or both semiconductor energy bands. Each of the proposed mechanisms leads to a different interpretation of C-V hump. Simulating the mechanisms by relevant equivalent circuits, the capacitance and conductance characteristics of the MOS structure were calculated and compared with experimental results. The mechanism responsible for the C-V hump was determined.
关键词： interface states,equivalent circuits,n-InGaAs,metal-oxide-semiconductor,capacitance-voltage hump
更新于2025-11-14 17:28:48
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Reinforced photoelectrochemical properties of nanostructural TiO2/C/SiO2 integrated on conductive Ti3SiC2
摘要： Herein, we constructed an ordered nanoporous embedding nanoparticles composite by anodic oxidation of Ti3SiC2 in fluorine containing organic electrolyte. Compared to anodized Ti which resulted in TiO2 nanotubes, the anodized Ti3SiC2 (ATSC) led to the formation of nanostructured TiO2/C/SiO2 composite. The morphologies of oxides in the composite also varied with different anodization parameters. The ATSC could be directly used as an electrode without further processes, which possessed a superior structure and composition with a visible-light photocurrent density of 7.56 μA cm?2, initial reversible area capacity of 6.18 F cm?2, which were respectively 1.32 and 6.87 times higher than those of the anodized Ti (AT), respectively. The ATSC synthesized by such a feasible fabricating strategy shows favorable photoelectrochemical properties and remarkable stability, and may broaden the bifunctional material prospects of anodized MAX phases.
关键词： Nanostructure,Photocurrent,Capacitance,Anodized Ti3SiC2,Photoelectrochemical
更新于2025-11-14 17:04:02
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Synthesis of N-CuMe2Pc nanorods/graphene oxide nanocomposite for symmetric supercapacitor electrode with excellent cyclic stability
摘要： Recent progress in the construction of non-peripheral octamethyl-substituted copper(II) phthalocyanine (N-CuMe2Pc) has opened up new strategies for energy storage applications. Since metal phthalocyanines can deliver excellent redox activities, we have prepared composite based on different ratios of N-CuMe2Pc and graphene oxide (GO) through a simple ultrasound process and evaluated their electrochemical performance for supercapacitor applications. As-prepared composites exhibit superior electrochemical activities as the results of the synergistic effect. A maximum specific capacitance of 291.6 F g?1 is achieved for the G10P2 electrode (Graphene oxide 10 mg and N-CuMe2Pc 2 mg) at 0.5 A g?1 which two times higher than their individual components. Further, the fabricated symmetric device shows that the excellent cyclic stability of about 100.1% over 5000 cycles. The experimental findings ensure the potential application of copper-phthalocyanine/GO composite as an electrode material for the next-generation supercapacitor applications.
关键词： Nanocomposite,Specific capacitance,Cyclic stability,Graphene oxide,Phthalocyanine
更新于2025-09-23 15:23:52
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Incorporating Mn <sup>2+</sup> /Ni <sup>2+</sup> /Cu <sup>2+</sup> /Zn <sup>2+</sup> in the Co <sub/>3</sub> O <sub/>4</sub> Nanorod: To Investigate the Effect of Structural Modification in the Co <sub/>3</sub> O <sub/>4</sub> Nanorod and Its Electrochemical Performance
摘要： The major key component for developing a high-efficiency supercapacitor device is electrode and electrolyte material. This research paper demonstrates the structural modification of Co3O4 nanorod and the electrochemical behavior of Co3O4 nanorod in different aqueous electrolytes such as KOH, PVA/KOH, NaOH, KCl, and Na2SO4. The pseudocapacitive behavior of Co3O4 is varying in the order of KOH > NaOH > PVA/KOH > Na2SO4 > KCl. The storage capability of MCo2O4 (where M = Mn, Ni, Cu, and Zn) nanorods has been compared with Co3O4 nanorod in the KOH electrolyte environment. The material in the form of nanorods is beneficial for an efficient pathway to penetrate an OH- ion into the electroactive material. Among other cobaltite (MCo2O4), NiCo2O4 nanorod exhibits the outstanding capacitance value of 2041.7 F g-1 at a current density of 1 A g-1. NiCo2O4 || NiCo2O4 symmetric supercapacitor system delivers the maximum energy density of 25.42 W h kg-1 at a current density of 0.5 A g-1.
关键词： KOH electrolyte,MCo2O4 nanorod,High specific capacitance,Symmetric device
更新于2025-09-23 15:23:52
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Effect of solvents on the self-assembly of long chain alkylphosphonic acids on indium tin oxide surface - In situ studies on the adsorption kinetics and electron transfer process
摘要： The spontaneous self-assembly process of phosphonic acids (PAs) onto indium tin oxide (ITO) surface has been studied in this work. We have carried out in situ adsorption kinetics studies of phosphonic acids in ethanol as a solvent using electrochemical impedance spectroscopy (EIS). Further, the effect of different solvents like ethanol, water, toluene and hexane on the structural integrity of the alkylphosphonic acid (CH3 (CH2)n PO3H2, n = 15,17) thin films on ITO surface has been investigated by using [Fe(CN)6]3-/4- as a redox probe. From the study of formation kinetics, it is concluded that molecular self-assembly process follows two adsorption steps, a fast first step followed by a slower second step. The results of cyclic voltammetric (CV) and impedance measurements show that phosphonic acids form a highly impermeable surface film on ITO when polar solvents like ethanol and water are used.
关键词： self assembly,Adsorption Kinetics,microelectrode array,Contact Angle,Capacitance,ITO,Phosphonic acid
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Va?ster?s (2018.9.3-2018.9.6)] 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Overview On Functional Materials for Frequency Tunable Antennas
摘要： We report the integration of different kind of materials with improved and adapted properties within antenna designs. In this framework, an overview of three frequency tunable antennas will be presented. Two of them are based on radiating slot elements integrating a Ba2/3Sr1/3TiO3 (BST)-based tunable capacitance and therefore present a continuous tunability for the first one while the second one is integrating a VO2-based switch for a discrete tuning. The third design presented in this paper propose a frequency reconfigurable composite GeTe-metal patch antenna operating at the millimeter-waves (24-30 GHz) whose resonant frequency can be tuned and repeatedly changed upon the application of successive laser pulses.
关键词： Frequency tunable antenna,VO2 switches,BST tunable capacitance,Phase Change Materials
更新于2025-09-23 15:23:52
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Voltage-Induced Charge Redistribution in Cu(In,Ga)Se <sub/>2</sub> Devices Studied With High-Speed Capacitance–Voltage Profiling
摘要： Devices made from Cu(In,Ga)Se2 (CIGS) solar cell material have been evaluated with high-speed capacitance–voltage pro?ling after stepwise voltage changes. The changes primarily affect near-interface charge at deep acceptors within the CIGS absorber layer and generate temperature-dependent capacitance changes observed in deep-level transient spectroscopy measurements. SCAPS device modeling indicates that the deep acceptor concentration is up to the two orders of magnitude higher than the shallow doping level. High deep acceptor concentrations are found in all materials studied here. The large deep defect levels are high enough to limit minority carrier lifetime and cell ef?ciency.
关键词： CuInx Ga1 ?x Se2 (CIGS),capacitance methods,solar cells
更新于2025-09-23 15:23:52