Papers by Keyword: Capacitance

Abstract: Through a simple electrodeposition technique, SnO₂/MnO₂ nanocomposite films were directly deposited onto ultrathin stainless-steel (SS) foils for use in electrochemical supercapacitors. The materials were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Electrochemical experiment revealed that the SnO₂/MnO₂ electrodes exhibited a high gravimetric capacitance of 876 F/g at a current density of 1 A/g. Furthermore, an asymmetric supercapacitor was fabricated using the SnO₂/MnO₂ nanocomposite as the positive electrode and activated carbon as the negative electrode. This asymmetric device demonstrated a capacitance of 72.2 F/g at 1 A/g and retained approximately 87.5% of its initial capacitance after 28,000 cycles, highlighting its excellent cycling stability and practical application potential. The combination of high capacitance and robust stability makes this SnO₂/MnO₂ nanocomposite a promising candidate for high-performance supercapacitor electrodes.

Abstract: Graphene, a 2D carbon allotrope with remarkable characteristics like high conductivity, large surface area has shown potential as a good candidate for high-performance supercapacitors. The processability of its derivative, graphene oxide, into fibers enables the development of miniaturized wearable energy storage devices. However, the synthesis of pure graphene oxide and its subsequent reduction to restore conductivity remain a focus for research. Herein, we employ the improved Hummers’ method for graphene oxide synthesis, followed by meticulous washing to remove residual acids. The obtained graphene oxide was then transformed into conductive graphene fibers through a wet-spinning and hydroiodic acid (HI) reduction process. The resulting fibers showed a high areal capacitance of 175 mA cm⁻² in a three-electrode system. When assembled into a flexible supercapacitor, these fibers delivered an energy density of 8 μWh cm⁻² and areal capacitance of 60 mA cm⁻². This study demonstrates the potential of our strategy for fabricating fiber-based energy storage devices based on graphene.

Abstract: There are some technological issues in SiC MOSFETs that are still unsolved. One of the main problems is the high density of traps/defects at the SiC/SiO₂ interface. Traps distribution at such interface is complex and it affects the overall performance of the device. The high-density of defects at the SiC/SiO₂ interface is a relevant problem since it can influence the overall performance of the device, causing detrimental impacts on threshold voltage stability, channel mobility and leakage current amplitude. Due to the fundamental importance of the SiC/SiO₂ interface characterization, several techniques have been employed to investigate defects properties related to this region. In this work non-classical C-V measurements are performed. Capacitance is measured between Gate and Source terminals while a fix DC voltage is imposed on the Drain. This latter is considered among positive values in the first case, while it is chosen as a negative voltage in the second case. The arising capacitances in both cases show an unexpected behavior which can be related to interface properties. To this aim numerical analysis is performed in Sentaurus TCAD environment.

Abstract: SiC MOSFETs still suffers from some open issues, such as the high density of defects existing at the SiC/ SiO₂ interface. In order to characterize such interface, a non-destructive investigation technique should be employed. In this work, we investigate the measurement of Gate capacitance with biased Drain. More in detail, the effect of frequency on such curves is considered. The analysis is performed using both in experimental setup and numerical framework. Experimental and numerical results both exhibit a sharp capacitance peak in the inversion region which reduces its height as frequency increases.

Abstract: The investigation of biomass-based, cost-effective, efficient, and environmentally materials with high power density and fast ion/electron transfer is intensively carried out for the development of renewable energy storage devices. Pyrolysis and hydrothermal carbonization (HTC) are two common methods of thermochemical conversion to synthesize biomass-derived based carbon. Compared to the pyrolysis method, HTC is a more promising strategy because it can be carried out without a pre-drying process, has a high yield, low ash content, and requires a relatively low temperature (180-250 °C). The carbon produced from the HTC process is known as hydrochar. This study reports the acid-assisted hydrothermal carbonization temperature on the hydrochar properties and its application for supercapacitor electrodes. Hydrochar was synthesized from extracted avocado seed waste with potassium permanganate and sulfuric acid catalyst solution at 200 °C for 12 h. The effect of one- and two-stage HTC temperature on the hydrochar properties were compared. The hydrochar characterization includes yield, SEM, XRD, FTIR, and cyclic voltammetry analysis. According to the characterization and analysis results, hydrochar produced has the 3D porous network morphology and the highest specific capacitance of 73.54 F/g. In conclusion, hydrochar derived from avocado seed through the acid-assisted HTC can be a potential way for supercapacitor electrodes.

Abstract: The anatase titanium dioxide nanotube array (TiO₂ NTA) with short and independent nanotube film structure is applied as stable metal oxide electrode substrate. The influence of different proton acid electrolytes is fully investigated on the electrical double-layer capacitance. The anatase TiO₂ NTA electrode substrate conducts reversible protonation-deprotonation process of dissociation hydrogen ion and electrostatic adsorption-desorption process of equilibrium anion in the cycling charge-discharge process. The reversible properties could be well proved by highly symmetric characteristic of positive-negative sweeping current and charge-discharge potential. The protonated TiO₂ NTA electrode substrate reveals cyclic voltammetry-based capacitances of 0.147 and 0.124 mF cm^-2, galvanostatic charge-discharge-based capacitances of 0.167 and 0.148 mF cm^-2 when similar dissociation proton concentration is maintained in 1.0 M H₂SO₄ and 1.0 M HCl. The TiO₂/H₂SO₄ exhibits similar capacitance enhancement ratio of 1.19 and 1.13 in comparison with of the TiO₂/HCl. The corresponding electrical double-layer capacitance at the same dissociation proton condition is mostly dependent on the electrostatic interaction between the protonated TiO₂ and equilibrium anions in different proton acid electrolytes rather than anion diffusion. The theoretical simulation calculation reveals that TiOOH⁺-HSO₄^- shows lower interaction interface energy and higher total densities of states than TiOOH⁺-Cl^-. Accordingly, TiO₂/H₂SO₄ conducts more feasible protonation and electrostatic adsorption process rather than TiO₂/HCl, contributing to its superior electrical double-layer capacitance.

Abstract: SiC MOSFETs have already replace silicon-based device in power applications, even if some technological issues are still not solved. The most important of them is related to the complex traps distribution at SiC/SiO₂ interface. Interface traps affect the overall device behavior, modifying channel mobility and introducing hysteresis. In this work experimental C-V and I-V curves are carried out on various commercial SiC MOSFET at different temperatures. The focus is the comparison of hysteresis arising in trench and planar SiC MOSFETs.

Abstract: SiC MOSFETs have already replaced silicon-based device in power applications, even if some technological issues are still not solved. Among others, the complex traps distribution at SiC/SiO₂ interface is of foremost importance. Interface traps affect the overall device behavior, modifying channel mobility and introducing hysteresis. In this work, the capacitance behavior, when the Drain terminal is floating, is studied through numerical analysis. The effects of traps distribution and its properties on such curves has been studied along with temperature effects. Experimental curves are carried out at various temperatures and compared to the same trends of numerical results.

Abstract: In this paper, we consider the technological features of the formation of thin ferroelectric films of lead zirconate titanate (PZT) by the method of plasma high-frequency reactive sputtering. The crystal structure, morphology and elemental composition of films deposited on silicon and oxidized silicon substrates are investigated. It is shown that the obtained PZT films have a perovskite structure and are polycrystalline with a predominant crystallite growth in the (110) direction. An automated test bench has been designed and manufactured for measuring the electrophysical parameters of ferroelectric films. The measured CV characteristics of the Ni/PZT/Si structure show the hysteresis caused by the polarization of the PZT film. It is noted that the asymmetry of the dependence of the spontaneous polarization on the applied voltage can be caused by the presence of surface states at the PZT/Si interface.

Abstract: The detection of volatile organic compounds (VOCs), humidity and toxic industrial chemicals is important for various environmental and industrial applications. The design of interdigital capacitor (IDCs) sensor is carried out in such a way that it would be suitable for microelectronic technology. The basic geometry of IDCs is defined by some parameters such as: number of electrodes N, electrode width W, electrode length L and the separation between electrodes G. The interactions between IDCs sensitive coating and analyte induced a change in the sensors capacitance due to the permittivity variation of the sensitive layer and to the change in polymer thickness (swelling). In this work, a fairly new approach of IDCs based sensor in terms of capacitance calculation has been presented. The results have been obtained from the modeling of the sensors geometry 2D and 3D using multi-physics simulation software COMSOL. The effects of some geometry parameters coupled with swelling measurements for polymeric films have been studied.