Decrease In Capacitance Research Articles

Exploring the Bio-inspired Corrosion Inhibition Properties of Eco-friendly Limonia Acidissima Leaves Extract for Mild Steel in Acidic Media: Computational, Electrochemical and Spectroscopic Insights

This study investigates the corrosion inhibition properties of Limonia acidissima leaves extract (LALE) on mild steel in a 1.0 M HCl medium. Utilizing mass loss measurements, potentiodynamic polarization, AC impedance spectroscopy, and surface characterization methods like SEM, AFM, UV-Vis, and fluorescence spectroscopy, the study reveals significant findings. The maximum inhibition efficiency of LALE was attained to be 92.26% at a 1.0% concentration. Potentiodynamic polarization studies show a marked decrease in corrosion current density (Icorr) from 3.102 × 10-3 A/cm² for the blank solution to 3.165 × 10-4 A/cm² with 1.0% LALE, indicating mixed-type inhibition. AC impedance measurements show an increase in charge transfer resistance (Rct) from 2.1410 Ω in the blank solution to 8.6580 Ω with 1.0% LALE, and a decrease in double-layer capacitance (Cdl) from 7.757 × 10-7 μF/cm² to 1.926 × 10-7 μF/cm², suggesting the formation of a protective film. SEM and AFM analyses confirm that LALE-treated steel surfaces are smoother with fewer pits and cavities compared to untreated steel. Furthermore, DFT analysis complemented well with the empirical findings. This research highlights the potential of plant extracts in industrial applications for corrosion protection, contributing to the growing body of knowledge on sustainable corrosion inhibitors and offering practical insights for future research and application in various corrosive environments.

Li-ion solvation structure at electrified solid-liquid interface: Understanding solvation structure dynamics and its role in electrochemical energy storage through binary ethylene carbonate and dimethyl carbonate solvent.

Binary solvent electrolytes can provide interpretations for designing advanced electrolytes of next generation batteries. This study investigates the adsorption mechanisms of solvated lithium ions in binary solvents near charged electrodes. Molecular dynamic simulations are performed for lithium hexafluorophosphate (LiPF6) in ethylene carbonate and dimethyl carbonate (EC:DMC) solvent sandwiched between two electrodes. Results show that lithium ions form a tetrahedral solvation structure with two EC and two DMC molecules. The solvated lithium ion shows anti-electrostatic interaction with electrodes. This can be attributed to the electrostatic attraction of the polar end of the DMC molecule, which keeps the cation anchored to the positive electrode. Meanwhile, the solvation structure adopts a fix orientation at the negative electrode, which leads to unchanged electrostatic interaction at high charge density. Finally, EC molecules are swapped by DMC molecules near the negative electrode at high charge density. This leads to a decrease in local relative permittivity and, therefore, a decrease in differential capacitance. The differential capacitance of the positive electrode continuously decreases with increasing charge density. This is caused by the partial anchoring of solvent molecules holding the cations, which cancels the adsorption of anions near the positive electrode. This study provides insights into designing better electrolytes for efficient battery performance.

Impact of voltage and frequency on electrical characteristics of MIS capacitors with triphenylamine layer

This study examines the effect of triphenylamine (TPA) interlayers on the electrical properties of Al/TPA/p-Si metal-interlayer/insulator material-semiconductor (MIS) capacitors. Using Gaussian software, TPA molecular structure was optimized, and HOMO-LUMO energy levels were simulated. Capacitance-conductance-voltage (C-G-V) measurements were performed at room temperature over −4 V to +4 V and 50 kHz–700 kHz. AFM and SEM analysis showed TPA films were smooth with a uniform thickness of about 178 nm. The C-V characteristics revealed a frequency-dependent decrease in capacitance, indicating a continuous distribution of interface states. Barrier height (ΦB) increased from 0.305 eV at 50 kHz to 0.655 eV at 700 kHz, while the active interface trap density (Dit) decreased from 6.73 × 1012 eV−1 cm−2 to 3.23 × 1011 eV−1 cm−2. Additionally, the accumulating region exhibited low series resistance values (between 6.88 and 8.44 Ω). These results suggest that TPA thin films are effective for MIS capacitors.

Enhanced Schottky barrier engineering in silver-doped TiO2/p-Si heterojunctions: Insights into electrical behavior and charge carrier dynamics

Heterojunctions were fabricated through the deposition of silver-doped Titanium dioxide (Ag–TiO2) onto p-type crystalline silicon, employing the sol-gel technique. Electrical characterization was conducted with varying Ag concentrations. The investigation revealed that the Schottky barriers at each interface (Ag/TiO2 and Si/Ag), along with the built-in potential at the TiO2/p-Si junction, increase proportionally with the Ag concentration. This observed trend was attributed to the reduction in the TiO2 bandgap due to Ag incorporation, resulting in a concurrent shift in both valence and conduction bands. Consequently, there is a growth of the conduction energy discontinuity and a reduction in the valence one, facilitating hole diffusion while impeding electron transfer across the depletion layer. Furthermore, the introduction of Ag leads to a decrease in both electron and hole concentrations. However, Ag incorporation within the TiO2 matrix manifests as nanoparticles and clusters, resulting in a nonhomogeneous distribution of charge carriers across the sample. Impedance analysis indicates an increase in device resistance and a decrease in effective capacitance.

Comprehensive Study on the Corrosion Inhibition of Aluminum in HCl by N1, N1'-(Ethane-1,2-diyl)di(ethane-1,2-diamine): Experimental and Theoretical Approaches

The inhibitory effects of the novel molecule N1, N1'-(ethane-1,2-diyl)di(ethane-1,2-diamine) (TETA) on aluminum (Al) corrosion were investigated in 0.2, 0.3, and 0.4 M HCl solutions. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation (PDP), quantitative techniques, and surface morphology characterisation were utilised. Surface morphology characterisation via atomic force microscopy (AFM) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS) confirmed the efficacy of the inhibitor in preventing corrosion. Weight loss research revealed that the protective efficacy of TETA grows with increasing concentration but shrinks with increasing temperature of the acidic solution. The findings indicate a marked increase in inhibition efficiency as TETA content rises, reaching 99.0 % when measured by the weight loss method, 98.34% through EIS, and 94.13% via electrochemical polarization. Polarization curves show that TETA stops hydrochloric acid from acting on the anodic type. Both the charge-transfer resistance and the double-layer capacitance decrease with increasing inhibitor concentration, as shown by the adsorption mechanism and supported by the EIS results. "The Langmuir isotherm and negative Gibb's free energy values demonstrate that the inhibitor molecules cling to the metal and that they adsorb to the aluminium spontaneously. In addition to analysing TETA via density functional theory (DFT), the adsorption of TETA on the surface of aluminium (Al) was examined via molecular dynamics (MD) simulations. The results show that the TETA molecule successfully blocks the corrosion process.

Characterization of Mn3O4/(x)Nb2O5 thin films as a promising material for supercapacitors

The thin films of Mn3O4/(x)Nb2O5 oxides (x = 0, 2, 4, and 6 %) were prepared by the electron beam evaporation method and then annealed at 400 °C. The structural analysis showed a tetragonal phase of Mn3O4, according to X-ray diffraction results. The quantitative elemental analysis of films confirms the stoichiometry of the Mn3O4, while the Nb2O5 couldn’t be recognized using energy dispersive X-ray fluorescence. The chemical speciation of the films was investigated using X-ray photoelectron spectroscopy. Three oxidation states of Mn were recognized at average binding energies of 645.70±0.35, 642.99±0.40, and 641.58±0.48 eV that correlated to Mn4+, Mn3+, and Mn2+, respectively. As the Nb2O5 increases, a slight decrease in the binding energy of Mn4+ is recognized, whereas it is nearly constant for the deconvoluted Mn3+ and Mn2+. Two electronic transitions (Eg1 and Eg2) of the optical band gap showed an increase with increasing Nb2O5 dopant from 2 % to 6 %. The optical parameters such as Eosc, the single oscillator energy, Edis, the dispersion energy, both moments (M−1) and (M−3), the ratio of carrier concentration/effective mass (N/m*), and the lattice dielectric constant (εL) were determined. From electrochemical measurements of pure Mn3O4 films, it is found that the voltammetric current density is directly proportional to the scan rates of cyclic voltammetry CV, with good cyclic stability, and by increasing the scan rates, the values of specific capacitance decrease while the values of specific power increase. In doped thin films, no potential drop is observed in the discharging process, which indicates good interfacial contact between the active material and the substrate during the charge/discharge process. These results suggest that the obtained Mn3O4 nanoparticles are a better candidate for supercapacitor applications.

Rapeseed cake meal extract as an eco-friendly green sustainable inhibitor for the corrosion of cold rolled steel in trichloroacetic acid solution

The inhibitory properties of rapeseed cake meal extract (RCME) on the corrosion of cold rolled steel (CRS) in trichloroacetic acid (TCA) were systematically investigated using gravimetric, electrochemical, surface characterizations and theoretical calculations. The results demonstrate that RCME exhibits excellent inhibitory performance with a maximum inhibition efficiency of 92.7% for 100 mg L−1 RCME at 20°C. The adsorption of RCME obeys Langmuir isotherm at 20 and 30°C, Temkin isotherm at 40°C, and Freundlich isotherm at 50°C. RCME acts as a cathodic inhibitor. The charge transfer resistance is increased with the addition of RCME, while the double-layer capacitance decreases. SEM, AFM, CLSM, XPS, XRD and TOF-SIMS analyses confirm that the active components in RCME adsorb onto the surface of CRS, forming a protective film that effectively inhibits the corrosion of CRS by TCA. Along with the increase in the concentration of RCME, the surface tension of the inhibited solution gradually decreases, while the electrical conductivity increases before stabilizing. HPLC-MS and FTIR analyses reveal rutin, linolenic acid, linoleic acid and adenine are the effective substances in RCME. Quantum chemical (QC) calculations and molecular dynamic (MD) simulations indicate that the active centers of the effective inhibitor molecules are predominantly located on benzene rings, O- or N-containing heterocyclic rings, and functional groups such as C=O and C=C. Additionally, their main chains adsorb onto the Fe (001) surface in an approximately flat manner, involving both chemical and physical adsorption processes.

Effect of Interfacial Ionic Defects in Perovskite Solar Cells and their Mitigation Mechanism: A Comprehensive Theoretical Analysis with Experimental Validation

AbstractInterfacial ionic defects in perovskite solar cells (PSCs) significantly influence the efficiency and long‐term stability. In this study, primarily simulation‐assisted analyses are conducted to explore the capacitive effect of these defects on the performance of PSCs through impedance analysis. Simulated data indicate a decrease in capacitance with increasing frequency, leading to a higher built‐in potential (ΔVbi = 150 mV). Moreover, an increase in capacitance with increasing light intensity is observed. Additionally, reducing the ionic defect concentration at the interfaces (from 1019 to 1016 cm−3) results in more significant band bending and a higher Vbi. Potential solutions to mitigate interfacial ionic defects, including doping at transport layer interfaces are proposed. Doping at both interfaces introduces an energy spike (valence band offset) of 0.21 eV and a cliff (conduction band offset) of 0.16 eV, respectively, for holes and electrons, leading to an improvement in the open circuit voltage (VOC). Finally, experimental results demonstrate a notable enhancement in VOC of 0.04 V with the introduction of Li+ doping at the electron transport layer/perovskite interface. These findings provide essential perceptions for effectively mitigating the effect of interfacial ionic defects on the performance of PSCs and enhance their overall performance.

Anticorrosive activity of Melothria perpusilla: A renewable and sustainable inhibitor

Anticorrosive activity of Melothria perpusilla extract on mild steel in H2SO4 was examined by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy methods. The results revealed that mild steel corrosion was effectively controlled by the extract with 99.4 % efficiency at 3000mg/L concentration. The efficiency was improved with higher extract concentration but decreased as the temperature increased. The Tafel plots and its corrosion potential value (<85 mV) inferred that Melothria perpusilla acts as a mixed type inhibitor. Adsorption of phytochemicals onto the surface of mild steel is the primary factor in reducing corrosion. The increase in activation energy for adsorption from 22.73 kJ mol−1 in acid to 133.74 kJ mol−1 in extract's presence confirms the active role of phytochemicals in adsorption process. The increase in charge transfer resistance from 3.21 Ω cm2 in acid to 369.2 Ω cm2 in extract's presence, coupled with a decrease in double layer capacitance in the EIS investigation, suggests that a charge transfer mechanism is active at the mild steel-solution interface. Gas chromatography-Mass spectroscopy revealed the presence of five major phytochemicals along with other organic compounds in the extract. Fourier transform infrared and UV–visible spectroscopies indicated the active functional moieties (-COOH, –CONH2, -C-O-C-, –C=C- and long chain alkyl groups) are involved in the inhibition. Scanning electron microscopy confirmed the existence of shielding film of phytochemicals on mild steel. Density functional theory validated the inhibitory properties of the constituents. Therefore, it is concluded that Melothria perpusilla is an efficient green inhibitor in acidic condition.

Suppression of irradiation effect on electrical properties of silicon diodes by iron in p-silicon

Radiation-hardness of silicon (Si) has been the subject of interest due to the damage of the material-based detectors during and after operation. In this work, the effects of 4 MeV proton-irradiation on the electrical properties of devices fabricated on undoped and Fe-doped p-Si were investigated using current-voltage (I-V) and capacitance-voltage (C-V) techniques. A decrease in current and capacitance is less pronounced and the conduction mechanism remains unchanged on Fe-doped p-Si diode after proton-irradiation. This insignificant change of electrical parameters of the Fe-doped diode after proton-irradiation indicates the suppression of the radiation effect by Fe in Si. The electrical properties of the diode are less dependent on incident radiation, because of the possible prevention of further dislodgement of atoms by incident radiation. As a result, the material becomes resistant to radiation damage, making the electrical properties of the diode independent of incident radiation due to Fe atoms in Si. As a result of the ohmic behaviour displayed by the Fe-doped Si diode, it is possible that in Si, Fe is responsible for generation-recombination (g-r) centres, which are defect levels positioned at the middle of the energy gap of Si. The possibility of these defects being responsible for the suppression of the radiation effect is explained in this work, making Fe a promising dopant to improve the radiation-hardness of Si.

Electrochemical Investigation of the Stability of Poly-Phosphocholinated Liposomes.

Poly[2-(methacryloyloxy)ethyl phosphorylcholine] liposomes (pMPC liposomes) gained attention during the last few years because of their potential use in treating osteoarthritis. pMPC liposomes that serve as boundary lubricants are intended to restore the natural lubrication properties of articular cartilage. For this purpose, it is important that the liposomes remain intact and do not fuse and spread as a lipid film on the cartilage surface. Here, we investigate the stability of the liposomes and their interaction with two types of solid surfaces, gold and carbon, by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). With the aid of a hydrophilic species used as an electroactive probe in the solution, the charge transfer characteristics of the electrode surfaces are obtained. Additionally, from EIS, the capacitance characteristics of the surfaces are derived. No decrease of the peak currents and no displacement of the peak potentials to greater overpotentials are observed in the CV experiments. No decrease in the apparent capacitance and increase in the charge transfer resistance is observed in the EIS experiments. On the contrary, all parameters in both CV and EIS do change in the opposite direction. The obtained results confirm that there is only physical adsorption without fusion and spreading of the pMPC liposomes and without the formation of lipid films on the surfaces of both gold and carbon electrodes.

Influence of Oxygen Vacancies Introduced via Acceptor (Gadolinium) Doping to the Pseudocapacitive Properties of Nano-Sized Cerium Oxide.

The voluntary introduction of defects can be considered an effective strategy for enhancing the electrochemical properties of metal oxide electrodes. In this study, the enhanced pseudocapacitive properties of an acceptor (Gd) doped cerium oxide nanoparticle-a sustainable metal oxide with low environmental and human toxicity-are investigated in depth using ex situ X-ray photoemission spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Interestingly, with 15at% Gd doping (15GDC), the specific capacitance of the nanoparticles measured at 1Ag-1 enhanced to 547.8Fg-1, which is fivefold higher than undoped CeO2 (98.7Fg-1 at 1Ag-1). The rate-dependent capacitance is also improved for 15GDC, which showed a 31.0% decrease in the specific capacitance upon a tenfold increase in the current density, while CeO2 showed a 49.9% decrease. The enhanced electrochemical properties are studied in depth via ex situ XPS and EIS analysis, which revealed that the oxygen vacancies at the surface of the nanoparticles played important roles in enhancing both the specific capacitance and the high-rate performance of 15GDC by acting as the active site for pseudocapacitive redox reaction and allowing fast diffusion of oxygen ions at the surface of 15GDC nanoparticles.

Parylene Double-Layer Coated Screen-Printed Carbon Electrode for Label-Free and Reagentless Capacitive Aptasensing of Gliadin.

Celiac patients are required to strictly adhere to a gluten-free diet because even trace amounts of gluten can damage their small intestine and leading to serious complications. Despite increased awareness, gluten can still be present in products due to cross-contamination or hidden ingredients, making regular monitoring essential. With the goal of guaranteeing food safety for consuming labeled gluten-free products, a capacitive aptasensor was constructed to target gliadin, the main allergic gluten protein for celiac disease. The success of capacitive aptasensing was primarily realized by coating a Parylene double-layer (1000 nm Parylene C at the bottom with 400 nm Parylene AM on top) on the electrode surface to ensure both high insulation quality and abundant reactive amino functionalities. Under the optimal concentration of aptamer (5 μM) used for immobilization, a strong linear relationship exists between the amount of gliadin (0.01-1.0 mg/mL) and the corresponding ΔC response (total capacitance decrease during a 20 min monitoring period after sample introduction), with an R2 of 0.9843. The detection limit is 0.007 mg/mL (S/N > 5), equivalent to 0.014 mg/mL (14 ppm) of gluten content. Spike recovery tests identified this system is free from interferences in corn and cassava flour matrices. The analytical results of 24 commercial wheat flour samples correlated well with a gliadin ELISA assay (R2 = 0.9754). The proposed label-free and reagentless capacitive aptasensor offers advantages of simplicity, cost-effectiveness, ease of production, and speediness, making it a promising tool for verifying products labeled as gluten-free (gluten content <20 ppm).

Spatially resolved capacitance-based stress self-sensing in concrete

Spatially resolved capacitance-based stress self-sensing in unmodified concrete has been demonstrated. The spatial resolution is 45 mm in one dimension, which is in the direction of the capacitance measurement. Parallel coplanar component electrodes (aluminum, 5-mm wide), attached to the concrete using double-sided adhesive tape) separated by 45 mm are used to measure the in-plane capacitance in the direction perpendicular to the length of the electrodes. Combinations of component electrodes are electrically connected to form an electrode. The capacitance ranges from ∼200 pF to ∼750 pF. The greater is the number of component electrodes in an electrode, the higher is the capacitance. The compressive loading is applied at selected areas located between adjacent component electrodes. The stress (defined as load divided by the 300 ×300-mm2 concrete area) is up to 3000 Pa. The load decreases the capacitance monotonically and reversibly. The fractional decrease in capacitance ranges from ∼0.1 % to ∼0.5 %. More spatially concentrated loading, as for loading near the edges of the specimen, gives greater fractional decrease in capacitance. The capacitance decreases with increasing inter-electrode distance. Embedded steel rebars with a 20.0-mm concrete cover do not affect the capacitance or capacitance-based sensing.

The inhibitive action of lemon verbena plant extract as an economical and eco-friendly corrosion inhibitor for mild steel in acidic solutions

The inhibitive effect of lemon verbena (lemon v.) extract as a green corrosion inhibitor (CI) for mild steel (st37) in 0.5 M H2SO4 and 1 M HCl media at room temperature is investigated by employing electrochemical current noise (ECN), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and scanning electron microscopy (SEM). The achievements demonstrated that the inhibition efficiency increases with increasing the extract concentration up to 2000 ppm in 0.5 M H2SO4 and up to 2500 ppm in 1 M HCl solutions and decreases with an increase in temperature. The ECN results show when Lemon V. extract is included to both acidic media, the values of commotion charges (Q) diminished. The least value of the Q is 15 and 60 mCoul in H2SO4 and HCl media, respectively. The EIS measurements depicted that by addition of the inhibitors up to a certain concentration, the charge transfer resistance increases up to 186 Ω cm−2 in H2SO4 and 350 Ω cm−2 in HCl, besides the double layer capacitance (Cdl) decreases. Potentiodynamic polarization assessments indicated that Lemon V. acts as mixed type inhibitor. Certain thermodynamic parameters were determined based on the temperature impact on inhibition and corrosion processes. The extract adsorption on the surface of the alloy follow the Langmuir adsorption pattern. A mixed mode of adsorption was observed, wherein the extract in H2SO4 and HCl predominantly underwent chemisorption. Thermodynamic parameters indicated spontaneous adsorption and exothermic process with increasing entropy in H2SO4 and decreasing entropy in HCl. SEM investigation also validated the adsorption performance of the inhibitor.

Capacitance-based structural self-sensing of stress: effect of water/cement

The compressive stress self-sensing properties of mortars with different water-cement ratios are investigated without the need for any conductive additives. Mortar specimens are cyclically loaded and the corresponding capacitance and resistance are measured. The aluminum foil that is used as the electrode is wrapped around the prismatic sample. A coplanar configuration of electrodes is used. Capacitance and resistance increase with increasing water/cement (W/C) ratio. Stress causes decrease in capacitance and increase in resistance. The relationship between stress and fractional capacitance-resistance (except for the sample with 0.30 W C−1 ratio) change is reasonably consistent. The effectiveness of stress sensing (the fractional change in capacitance-resistance per unit of stress) decreases monotonically as the maximum stress increases, regardless of the W/C ratio. It is found that the dependence of the effectiveness of the stress sensing on the W/C ratio decreases with an increase in the maximum stress.

Quantum capacitance behavior of Ti2CO2/MoS2 heterostructures with 3d and 4d transition-metal doping

The storage capacity of capacity, quantum capacitance behavior, and atomic stability of O-defected, S-defected, 3d and 4d transition-metal (3d-TMs: Sc, Ti, V, Cr, Mn, Fe, Co, and Ni; 4d-TMs: Y, Zr, Nb, Mo, Ru, Rh, Pd, and Ag) doped Ti2CO2/MoS2 heterostructures were studied by density functional theory (DFT). Pristine Ti2CO2/MoS2 exhibited a high quantum capacitance of 1038.62 μF/cm2 at the positive potential. The appearance of O-vacancy in Ti2CO2-layer enhanced the capacitance of Ti2CO2/MoS2 at negative bias, and S-vacancy induced an obvious improvement of quantum capacitance at 0 V. After introducing various transition metals into modified Ti2CO2/MoS2 heterostructures, the doping in pristine structures increased the capacitance value to be 1182.71 μF/cm2 (Y-doping), while TM-doping in S-vacancy defected Ti2CO2/MoS2 systems induced a slight decrease of capacitance at positive potentials. For TM-doped O-defected Ti2CO2/MoS2, only Sc- and Y-doped systems exhibited higher quantum capacitance than the pristine Ti2CO2/MoS2, which were 1093.60 and 1096.26 μF/cm2. Due to the obvious advantage of capacitance of pristine Ti2CO2/MoS2 than Ti2CO2 or MoS2 single-layer at the positive bias, it can be used as effective anodes for high-capacitance supercapacitors, while 3d or 4d TM-doping had no significant enhancement in capacitance behaviors. The findings in this study were supposed to be theoretical data base to design high-performance supercapacitors.

Influence of Microwave and Magnetic Fields on the Electrophysical Parameters of a Tunnel Diode

In this paper, we studied the effect of an electromagnetic field of an ultrahigh frequency on the I–V characteristics of tunnel diodes. The influence of thermionic current on the change in the ratio of the values of tunnel currents at depth and the peak formed in the tunnel diode as a result of a strong electromagnetic field and on the change in the ratio of the values of tunnel currents at the highest and lowest points without exposure to a strong electromagnetic field. The I–V characteristics of a tunnel diode under the action of a microwave field is determined based on the theory of Knott and Demassa and the Tsu-Esaki model. The characteristics of the Tsu-Esaki and Karlovsky models used to determine the effect of the tunnel current in the extremely high frequency field (EHF) are shown. Chynoweth's model and Knott and Demassa's theory have shown that in germanium-based tunnel diodes, under an extremely high frequency (EHF) field, the amount of excess current generated in the tunnel diode increases. According to the Tsu-Esaki theory and Knott and Demassa theory is found to decrease the value of the differential resistance of a tunnel diode with a p-n junction under the action of a microwave field, regardless of the type of heterostructure or doping level. According to the Tsu-Esaki theory and Knott and Demassa found decrease in the diffusion capacitance of a tunnel diode with a p-n junction under the action of a microwave field, regardless of the type of heterostructure or doping level. A decrease in the transparency coefficient due to an increase in the internal field at the p-n junction boundary of a Ge-based tunnel diode under the action of a microwave field has been established. A formula is determined for determining the total current of a tunnel diode under the action of both microwave and magnetic fields, taking into account the transparency coefficient of the tunnel diode.

Long cycle life achieved in polyaniline/SP based self-healing supercapacitor

Polyaniline (PANI) has emerged as a promising electrode material for supercapacitors due to its low cost and high specific capacitance. However, during the charge and discharge process, PANI undergoes volume changes, leading to structural damage at the molecular level. This results in material pulverization, causing a loss of electronic contact with the electrode and, consequently, a decrease in capacitance. In this study, we employed ultrasonication-assisted growth of PANI on super-P (PANI/SP-US) to enhance the structural stability. At 1 A g−1, a high specific capacitance of 639 F g−1 was achieved. After 5000 charge-discharge cycles at 2 A g−1, the material retained 75.9% of its capacitance. More importantly, we further developed an effective strategy to incorporate a self-healing polymer (SHP) to fabricate a self-healing electrode. Due to the self-healing ability, the pulverized PANI/SP-US was able to be reconnected and restore electronic contact with the electrode substrate, thereby regaining specific capacitance and achieving excellent cycle life. The sphere-like shape of PANI/SP-US is also of benefit to the self-healing process. Symmetric and asymmetric self-healing devices based on PANI/SP-US and the self-healing polymer exhibited outstanding cyclic stability, retaining 107.9% and 108% of their capacitance, respectively, after 10,000 cycles at 2 A g−1. The self-healing device also exhibits good flexibility under bending, folding deformations. In addition, the device also shows good capacitance retention as the temperature shifted from 50°C to 0°C. This work underscores the significance of microstructure self-repair in enhancing cyclic stability and extends the application of self-healing devices to flexible and variable-temperature conditions.

Imaginary impedance due to hopping phenomena and evaluation of dopant ionization time in cryogenic metal-oxide-semiconductor devices on highly doped substrate

MOS capacitors fabricated on substrates with doping concentrations as high as 1018 cm−3 were characterized at 4.2 K. The highly doped substrate exhibited an intrinsic imaginary component of impedance at 4.2 K. The imaginary component is attributed to the time delay induced by hopping phenomena, leading to a decrease in the gate capacitance. Furthermore, we investigated the time constant associated with dopant ionization under depletion conditions and determined it to be 0.35 μs. An equivalent circuit model of the highly doped substrate at 4.2 K is also shown.