Electrochemical Capacitance Voltage Research Articles

Electrochemical Etching of Nitrogen Ion‐Implanted Gallium Nitride – A Route to 3D Nanoporous Patterning

Dopant‐selective electrochemical etching (ECE) of gallium nitride (GaN) results in well‐defined porous layers with tunable refractive index, which is extremely interesting for integrating photonic components into nitride technology. Herein, the impact of nitrogen implantation with and without subsequent rapid thermal annealing (RTA) on the porosification process of highly n‐doped GaN ([Si] 3 × 1019 cm−3) is investigated. Implantation is expected to compensate the donors of the n‐GaN layer to spatially suppress porosification during ECE. Optical transmission, electrochemical capacitance–voltage, and X‐Ray diffractometry of as‐grown and as‐implanted GaN suggest successful compensation of n‐dopants. Cross‐sectional scanning electron microscopy reveals the presence of mesopores (diameter 2–50 nm) after ECE of the as‐grown n‐GaN. In the case of implanted n‐GaN, it is found that ECE results in macropores (diameter > 50 nm), which can be suppressed by an intermediate RTA step. The implanted and annealed n‐GaN layers solely exhibit mesopores at the top and bottom, while the intermediate region remains unimpaired. Chronoamperometry and gravimetry provide additional insight and confirm the presence of macro‐ and mesopores in samples without and with RTA, respectively. The results demonstrate a successful implementation of etch‐resisting subsurface layers, which are required for 3D refractive index engineering in porous GaN.

Low-temperature aluminum doped and induced polysilicon and its application as partial rear contacts on p-type silicon solar cells

Low-temperature contact techniques offer benefits for various solar cells, including tandem solar cells, which risk degradation from high-temperature contact fabrication for top cell materials, such as in III-V/Si multijunction cells. This paper presents aluminum (Al) doped and induced poly-Si (formed through annealing at 190 °C for 5 min) as localized contacts on p-type silicon absorbers. This approach avoids the high-temperature processes required for poly-Si formation and the toxic gases involved in in-situ doping through chemical vapor deposition. Raman spectroscopy confirms poly-Si formation due to Al-induced recrystallization of a-Si:H(i), with electrochemical capacitance-voltage (ECV) measurements validating Al doping in the newly-formed poly-Si. The contact stack of p-Si/a-Si:H(i)/Al exhibits ohmic behavior after annealing at 190 °C for 5 min, achieving a contact resistivity of ∼13.2 mΩ⋅cm2. Finally, a cell featuring a localized Al-doped poly-Si contact structure is fabricated, realizing a 3% absolute efficiency improvement compared to a full-area Al back contact cell.

Revisiting Open Circuit Corrosion of Cr in Unpurified Molten FLiNaK Salts with a Multi-Modal Approach

Corrosion and mitigation of environmental degradation of structural materials in high-temperature Gen IV molten salt reactors, are critical issues. However, any corrosion studies have historically been forensic post-test examinations and materials development has occurred mainly by trial and error until recently. Meanwhile, a fundamental understanding can only be achieved by recognizing how the corrosion system of model materials in molten fluoride salts evolves as a function of time. A number of in-situ spectroscopy techniques to identify corrosion product compositions in molten salts have been suggested in recent years. Raman, high-temperature UV-Vis absorption spectroscopy, and X-ray absorption spectroscopy are a few of them [1,2]. These techniques' major limitations include the fact that they are mainly qualitative, and complex hardware requiring a beam focusing inside the glove box is needed. At the same time, electrochemical techniques have been presented which can provide the information on behavior of both metal and its corrosion product in the continuously evolving corrosion system in molten salts. However, use of single isolated methods renders it difficult to obtain mechanistic information on instantaneous, time-dependent processes and phenomena during corrosion. These are needs gaps opportunities. In this work we present a detailed electrochemical analysis of the corrosion of polycrystalline chromium at 600°C in FLiNaK over 50 h including an electrochemical analysis of in-situ near-instantaneous corrosion rates corroborated with other methods.A variety of corroborating methods including (1) in-situ electrochemical diagnostic techniques, (2) static immersion exposure with gravimetric and SEM analysis, (3) electrochemical impedance spectroscopy, (4) XRD, (5) ICP-OES, was utilized to study the corrosion behavior in unpurified FLiNaK at 600°C. The focus was to evaluate the viability of using an external non-reactive electrode to measure the concentration of corrosion products via redox process analysis in order to determine the corrosion rate during the process of OCP corrosion of Cr in FLiNaK. This work reports the possibility of using of electrochemical techniques such as CV for the instantaneous determination of Cr corrosion rates when Cr is exposed to a 600oC FLiNaK salts for 50 h. It was found that the concentration of dissolved corrosion products, in the more likely possible forms of CrF3 - and CrF6 3- , might be calculated by established analytical approaches to CV analysis such as Berzins-Delahay (soluble/insoluble) and Randles-Ševcik equations (soluble/soluble). The calculated values showed the definite concentration of Cr(II)/Cr(III) corrosion products at the distance of the external electrode (due to the static corrosion conditions). These finding supported by XRD and ICP-OES. A semi-infinite diffusion model was employed in this study to adjust the calculated concentrations assuming a stagnant solution and diffusion based one-dimensional concentration diffusion profile in order to calculated the Cr(III) concentration at a fixed position in the Cr(III) concentration gradient. It was shown that the semi-infinite diffusion model helps correctly describe this profile between 10 and 50 h, based on the geometry of the working electrode and corrosion cell. Based on these results the OCP corrosion rate was interpreted to switch over 50 h from initially charge transfer control Cr(II) oxidation at early times with likely HF and Cr(III) reduction, followed by mass transport control regulated by a salt film and then possible stifling due to depletion of HF and Cr(III) solubility limits.The results of half-cell redox potentials and peak currents pertaining to oxidation/reduction of Cr corrosion products were correlated to the concentrations of particular Cr species and compared with the results of mass loss experiment and ex-situ ICP-OES of post-exposed FLiNaK. The mass loss of the Cr(II)/Cr(III) metal that was approximated by spatially integrating the concentration profiles at a selected time, and the result of Cr mass loss separately obtained from gravimetric measurements showed a reasonable agreement. Furthermore, the rate of accumulation of Cr ions in the residual FLiNaK salt after 50 h of exposure determined by ICP-OES, correlated with the electrochemical CV and EIS analysis. In addition to this, the oxidation and reduction peak potentials pertaining to Cr/CrF3 - and CrF3 -/CrF6 3- redox reactions (measured on Pt wire) were compared with the OCP (measured on Cr) to provide insights on the predominant anodic and cathodic reactions. Acknowledgments This research was supported as part of the fundamental understanding of transport under reactor extremes (FUTURE), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Utilization of the Malvern-Panalytical Empyrean diffractometer was supported by Nanoscale Materials Characterization Facility with National Science Foundation under award CHE-2102156. References Y. Liu et al., (2020) Corrosion Science. 169 108636. https://doi.org/10.1016/j.corsci.2020.108636.S. Fayfar, et al., (2022). https://doi.org/10.26434/chemrxiv-2022-3nspm.

Interlaced Micro-Fibrous Hard Carbon As Superior Anode for Na-Ion Battery: Insights into the Sodium Storage Mechanism and Solid Electrolyte Interface

Hard carbon has been proved to be a promising negative electrode material for sodium-ion battery (SIBs) application. In this study, we have synthesized carbonaceous anode material by pyrolysis of tissue paper waste at different temperatures ranging from 800° to 1400°C. The tissue paper pyrolyzed at 1400°C has shown highest desodiation capacity of 350 mAhg-1 at 20 mAg-1 with stable cyclic performance and 70% capacity retention after 400 cycles at 200 mAg-1. The morphology, structure and surface chemistry of the cycled hard carbon electrodes were examined by ex-situ FE-SEM, XRD, Raman and XPS. The characterization results obtained reveal the detailed insights of the solid electrolyte interface and sodium storage mechanism of the hard carbon. The parameters of diffusion kinetics were evaluated by Electrochemical Impedance Spectroscopy (EIS) and CV analysis at different sweep rates. The results obtained in the study establish tissue paper waste as a promising precursor material to synthesize carbonaceous anode for SIBs by a simple one-step pyrolysis process.

Highly-Efficient Ni@CuS/SGCN Nanocomposite with Superior Bifunctional Electrocatalytic Activity for Water Splitting

The contemporary world faces significant challenges with the depletion of non-renewable energy sources and the escalation of global temperatures. Using H2 as an energy source is a sustainable, renewable, and environmentally friendly alternative. Electrochemical water splitting using an efficient electrocatalyst is an optimistic approach for hydrogen production. The primary concern is the development of a durable, cost-effective, and highly efficient bifunctional electrocatalyst to enhance electrochemical water splitting. The present investigation employs CuS as the electrocatalyst, followed by the implementation of two techniques, doping and composite material synthesis, to enhance its electrocatalytic characteristics. CuS samples doped with varying weight percentages of Ni (2, 4, 6, 8, and 10 wt.%) and a composite material of 6% Ni@CuS with SGCN were synthesized using the co-precipitation method. The electrocatalysts were studied by characterization techniques such as SEM, EDX, FTIR, and XRD. Doping and composite material synthesis enhance the electrochemical water-splitting activity, as LSV, CV, EIS, and Chronopotentiometry analyses demonstrated. The electrochemical water splitting process exhibits maximum performance when utilizing Ni@CuS/SGCN, resulting in a low overpotential of 380 mV for OER and 178 mV for HER, achieving a current density of 10 mA cm−2. The findings indicate that composite Ni@CuS/SGCN can potentially serve as an electrocatalyst for water splitting.

Multicrystalline, Highly Oriented Thick‐Film Silicon from Reduction of Soda‐Lime Glass

AbstractThe study describes synthesis and characterization of > 10 µm thick multicrystalline (mc), highly oriented, p‐doped silicon layers by aluminothermic reduction of low‐cost soda‐lime glass. X‐ray diffraction shows a highly preferred (111)‐orientation and excellent crystallinity. Low compressive stress and very good crystallinity are confirmed by the peak position and width of the Raman LO‐phonon line, approaching the one of bulk single‐crystalline wafer material. Due to strong bonding to the glass substrate layer, spalling is not observed. A conductive aluminum‐rich oxide layer is formed underneath the silicon, serving as an electrical back‐contact for electronic devices. Using secondary ion mass spectrometry very low concentrations of 1014–1015 cm−3 of impurities are found originating from the soda‐lime glass with an iron content below the detection limit. Furthermore, a plateau‐like, very homogenous Al concentration of ≈4 × 1018 cm−3 over a thickness of ≈10 µm is found, which corresponds to the solubility of Al in Si at the process temperature. Complete electronic activation within the plateau region is confirmed by carrier concentration measurements using electrochemical capacitance–voltage profiling and Raman spectroscopy. Hole concentrations in the range of few 1018 cm−3 are beneficial for the p‐type base material of full‐emitter cell mc‐silicon photovoltaic devices.

Fabrication and characterization of heavily doped n-type GaAs for mid-infrared plasmonics

N-type doping in GaAs is a self-limited process, rarely exceeding a carrier concentration level of 1019 cm−3. Here, we investigated the effect of intense pulsed light melting on defect distribution and activation efficiency in chalcogenide-implanted GaAs by means of positron annihilation spectroscopy and electrochemical capacitance–voltage techniques. In chalcogenide-doped GaAs, donor–vacancy clusters are mainly responsible for donor deactivation. Using positrons as a probe of atomic scale open volumes and DFT calculations, we have shown that after nanosecond pulsed light melting the main defects in heavily doped GaAs are gallium vacancies decorated with chalcogenide atoms substituting As, like VGa–nTeAs or VGa–nSAs. The distribution of defects and carriers in annealed GaAs follows the depth distribution of implanted elements before annealing and depends on the change in the solidification velocity during recrystallization.

High Uniformity 6-Inch InGaP Epitaxial Growth

The growth of 6-inch In0.485Ga0.515P has been examined in this study. The effects of growth temperature, the V/III ratio, and the H2 total flow on solid composition, growth rate, and crystal quality have been systematically investigated and discussed. Additionally, the effect of growth conditions on doping efficiency has been investigated. Finally, the relationship between electrical uniformity, optical uniformity, and the growth conditions of the 6-in epitaxial layer is discussed. At a growth temperature of 600 °C and a V/III of 250, a high uniformity 6-in InGaP epitaxial layer with an electrical uniformity of 0.33% and optical uniformity of 0.03% was produced. InGaP was grown by the metal-organic chemical vapor deposition method in an Aixtron 2800G4 reactor. High resolution X-ray diffraction (HRXRD), photoluminescence (PL), sheet resistance, electrochemical capacitance-voltage (ECV), and the Hall effect were used to characterize the characteristics of InGaP epitaxial layers.

Construction of isoniazid pharmaceutical logic system based on poly(N, N-diethylacrylamide) hydrogel films

In this work, poly(N,N-diethylacrylamide) (PDEA) hydrogel films were polymerized on glassy carbon (GC) electrode surface, and isoniazid (INH) was chosen as an electroactive pharmaceutical molecule probe, aiming to investigate the switchable electrochemical behaviors of INH. Determining the contents of INH tablets under different external stimuli conditions and constructing its logic gate computing systems. The triple-sensitive electrochemical CV behaviors of INH on this film system toward pH, temperature and salt concentration were observed and explored. Thus, a 3-input/8-output combinational pharmaceutical logic gate network and a 3-to-8 decoder were designed and constructed based on the stimulus-responsive characteristics of the electrochemical response of INH on PDEA hydrogel-modified electrodes. Besides, the relationship between the oxidation peak current (Ipa) and concentration of INH (CINH) was studied by the differential pulse voltammetry (DPV) method. Apply this film system, and the INH tablets could be switchable detected. The construction of the logic-gate computing system based on isoniazid drug molecule may provide a novel approach and model to design new style drug sensors, which might be applied to intelligent medical diagnostics and drug release.

Polypyrrole Modified Carbon Nanotube/Polyimide Electrode Materials for Supercapacitors and Lithium-ion Batteries

Lithium-ion batteries have evolved and transcended in recent years to power every device across the spectrum, from watches to electrical vehicles and beyond. However, the lithium-ion battery requires the use of heavy and expensive transition metal oxides that have limited life cycles. Conductive polymer nanocomposites have been shown to possess good electrochemical and thermomechanical properties and are considered to be effective alternatives to transition metal oxides. The fabrication and properties of polyimide matrix-single wall carbon nanotube, SWCNT composite electrode materials, modified by the electrodeposition of polypyrrole, PPy was successfully carried out. The doping of PPy with p-Toluene sulfonic acid, T resulted in a dramatic transformation of the morphology and specific capacitance of the electrode material. Electrochemical impedance spectroscopy, EIS, cyclic voltammetry, CV, and galvanic charge–discharge tests were used to measure the electrode’s specific capacitance and specific capacity. Maximum specific capacitance values of up to 84.88 F/g and 127.13 F/g were obtained by CV and charge–discharge tests, respectively. A capacitance retention of over 80% was obtained after over 500 cycles of testing. The insertion of doped PPy into the electrode material by electrochemical polymerization was shown to positively correlate to the improved electrochemical performance of the nanocomposite. An increase in the porosity of about 34.68% over the non-doped polypyrrole was obtained from EIS measurement and supported by the optical microscope pictures. Increasing the process parameters, such as pyrrole, Py concentration and the amount of dopants, lead to a dramatic increase in the specific capacitance and capacity of the composite electrodes.

Sensitive detection of acetaminophen in body fluids, pharmaceuticals and herbal medicines at un-doped mesoporous carbon nitride film electrode

Electrochemical sensing of acetaminophen (ACT) was made using un-doped mesoporous (average pore size 33.2 nm) carbon nitride (mGCN) modified glassy carbon electrode (GCE) in physiological buffer (PBS, pH 7.4). GCN was prepared by pyrolysis of agriculture urea precursor and characterized using XRD, UV–visible, FTIR, XPS and HRTEM techniques and observed 3D mesoporous structure. The electrochemical methods CV, EIS, and DPV were employed to explore the behaviour of mesoporous carbon nitride thin film modified electrode and its acetaminophen electrochemical sensing. The sensor showed a linear range from 0.1 to 1400 µM with sensitivity and limit of detection 0.0180 mA cm−2 mM−1 and 93.22 nM. Practical electrochemical sensing of ACT was demonstrated using unprocessed pharmaceutical tablet, body fluids (urine, blood serum), and herbal (ayurvedic Ocimumtenuifrum and Coleus amboinicus plants) samples. These electrochemical data were very well corroborated with results obtained from UV–Visible detection.

Fabrication of a new rGO@PPy/SS composite electrode with high energy storage and long cycling life for potential applications in supercapacitors

Electrochemical synthesized PPy/SS and rGO@PPy/SS electrodes are individually characterized from the point of their morphological and structural properties by the SEM, EDX and FTIR techniques. Electrochemical measurements, for instance, CV, EIS, and MS are performed to obtain the supercapacitive behaviour of the electrodes in an aqueous solution of 0.1 M KOH. All the morphological and structural studies confirm the molecular occurrence of PPy and rGO@PPy, and the homogenous distribution of the material onto the SS substrate. The specific capacitances of the electrodes show up as 104.22 F g−1 and 122.53 F g−1 respectively for PPy/SS and rGO@PPy/SS at 10 mV s−1 scan rate. The energy density of rGO@PPy/SS is 212.5 Wh kg−1 at the current density of 6 A g−1 while the energy density of PPy/SS is 116.66 Wh kg−1 at the same scan rate. This considerable increase is also shown for the power densities of the electrodes as from 4516.12 W kg−1 to 6219.51 W kg−1 at 6 A g−1 by insertion of rGO into PPy/SS. Likewise, with this insertion, an impressive improvement in the cyclic stability of the electrode is seen from 59.5% to 97.6%. In the light of these results, rGO@PPy/SS is considered an extremely promising material for supercapacitor investigations.

Depolarization of Cu electrodeposition in the presence of Ag: A cyclic-voltammetry study

Cyclic voltammetry profiles of Cu-Ag acidic sulfate deposition baths at Cu, Cu-Ag, Au or Ru substrates have been systematically studied, revealing the existence of an early Cu reduction peak before the bulk Cu deposition peak. The Cu deposit thickness produced by this early Cu reduction peak is estimated to decrease with scan rate and increase with the [Ag+] concentration in the electrolyte. The early Cu reduction peak generates Cu deposits thicker than 3 nm for the Cu-Ag electrolyte with 2 mM Ag(I). Electrochemical quartz crystal microbalance (EQCM) and CV reveal that the early Cu reduction peak is associated with a Cu(II)/Cu(0) reaction at 65% Coulombic efficiency, slightly smaller than that of the main Cu(II)/Cu(0) reduction peak (∼78%). Directly observing the linear regions in the polarization curves produced by CV, the early Cu reduction peak is estimated to show a Tafel slope ∼30 mV/dec. We hypothesize that the early Cu reduction peak is caused by the catalytic effect of Ag in the substrate or in the initial deposit on the intermediate reduction step of Cu(II)/Cu(I), leading to a shift of the rate determining step of Cu(II)/Cu(0) reduction.

V2O5 Nanosheets as an Efficient, Low‐cost Pt‐free Alternate Counter Electrode for Dye‐Sensitized Solar Cells

AbstractThe search for cost‐effective and efficient counter electrode finds its way in choosing vanadium pentoxide, an abundant and low‐cost material with good electrocatalytic property and stability. Two‐dimensional vanadium pentoxide nanosheets (V2O5 NS) were prepared by a simple hydrothermal method followed by calcination at 350 °C. The morphology of the synthesized material provides an excellent surface property with good surface area and a wide range of porosity distribution helps in enhancing the electrocatalytic active sites for effective reduction of I3−. The electrochemical studies performed with V2O5 NS showed good electrocatalytic activity with high current density, low series and charge transfer resistance. The electrochemical techniques CV, EIS and Tafel polarization performed with V2O5 NS gave an enhanced electrocatalytic activity and charge transfer kinetics with a low value of Rs and Rct. Furthermore, the photocurrent voltage studies done with V2O5 NS CE DSSC achieved a PCE of 5.1% ( Open circuit voltage (Voc)=0.65 V, short ciruit photocurrent density (Jsc)=11.67 mA/cm2 and fill factor (FF)=66.46%) and the conventional thermal decomposed Pt CE DSSC reached the PCE of 7.4% (Open circuit voltage (Voc)=0.78 V, short circuit photocurrent density (Jsc)=15.03 mA/cm2 and fill factor (FF)=57.39%) under similar test conditions, appreciably good performance than previous reports on V2O5 CE DSSC. The present work encourages further extensive research to develop nanostructures of V2O5 as a low‐cost alternate counter electrode to Pt CE for large‐scale production.

An In-Depth Study of the Boron and Phosphorous Doping of GeSn

We have investigated the in situ doping of GeSn with Ge2H6, SnCl4, B2H6 (p-type) or PH3 (n-type) at 349 °C, 100 Torr on Ge Strain-relaxed Buffers, themselves on Si(001) substrates. Our aim was to replace the boron and phosphorous doped Ge layers used in previous pin structures with GeSn:B and GeSn:P. The Sn content from Wavelength Dispersive X-ray Fluorescence (WDXRF) was constant around 6.5% for low F(B2H6)/F(Ge2H6) and F(PH3)/2*F(Ge2H6) Mass-Flow Ratios (MFRs). It fell down to 4.9% (GeSn:B) and 6.0% (GeSn:P) for higher MFRs due to the dopant precursors that catalyzed the Ge Growth Rate component. The B atomic concentrations (from Secondary Ion Mass Spectrometry (SIMS)) increased almost linearly with the MFR, reaching values of at most 6.3 × 1019 cm−3. B atoms were almost fully electrically active based on Electrochemical Capacitance Voltage (ECV) measurements. WDXRF and SIMS also gave us access to the atomic P concentrations, with values as high as 3.9 × 1020 cm−3. Maybe because of the formation of SnmPnV nanoclusters, the P electrical activation decreased for the highest flows. Only the GeSn:B layers grown at the three highest MFRs exhibited some B and/or Sn surface segregation. Otherwise, a smooth surface with a cross hatch along 〈110〉 was present.

Evaluation of secondary electron intensities for dopant profiling in ion implanted semiconductors: a correlative study combining SE, SIMS and ECV methods

This study evaluates the secondary electron (SE) dopant contrast in scanning electron microscopy (SEM) and helium ion microscopy (HIM) on boron implanted silicon sample. Complementary techniques like secondary ion mass spectrometry and electrochemical capacitance voltage (ECV) measurements are used to understand the dopant profile and active dopant distribution before and after a thermal firing, a step carried out to remove implantation damage and to electrically activate the implanted boron. Thermal firing resulted in an activation efficiency of 33%. HIM showed higher contrast than SEM having more defined peak with a lower background contribution. Variations in dopant concentration near the peak maximum were observed in ECV measurements, which was not observed in the intensity profiles from both SEM and HIM. This study demonstrates the effectiveness of SE dopant profiling as a quick tool to map the electrically active dopant concentrations even in far-from-equilibrium materials such as ion implanted samples.

Improved performance on multi-crystalline silicon solar cells by optimizing aluminum back surface field process

Traditional aluminum back surface field (Al-BSF) multi-crystalline silicon (mc-Si) solar cells have been favored by the market for a long time due to their low cost. However, the Al-BSF formed after Al screen printing and firing restrict the doping profile and the passivation effect. Here we report a scheme to produce the Al-BSF in advance (before phosphorus diffusion) by using the additional preparation processes consisting of three successive steps, namely Al screen printing, annealing and Al removing. The Al removing process helps optimize the depth of Al-BSF, while the annealing process and the subsequent diffusion process helps improve the doping profiles. As a result, the passivation performance of such improved Al-BSF is greatly improved in terms of electrochemical capacitance voltage measurements (ECV) and minority carrier lifetime characterizations. Also the average conversion efficiency for such mc-Si cells with improved Al-BSF reaches 18.73%, which is 0.27% higher than that of the same batch of traditional Al-BSF solar cells. This approach represents an efficient method for further improving mc-Si solar cells.

Electrochemical synthesis of binder-free interconnected nanosheets of Mn-doped Co3O4 on Ni foam for high-performance electrochemical energy storage application

• Simple electrochemical CV method for the synthesis of different nanostructures by tuning the scan rate. • Binder free preparation of different nanostructures of Mn-doped Co 3 O 4 on Ni foam. • Superior electrochemical performance of interconnected nanosheets exhibiting maximum specific capacitance of 1005F g −1 in KOH. • Aqueous asymmetric supercapacitor assembly with activated carbon showed enhanced electrochemical performance. In this study, various nanostructures of Mn-doped Co 3 O 4 were synthesized on Ni foam using binder-free electrochemical technology for electrochemical energy storage applications. Using the cyclic voltammetry method with different scan rates, diverse nanostructures, i.e., irregularly oriented nanooctahedra, interconnected standing nanosheets, and nanopetals of Mn-doped Co 3 O 4 , were obtained. The standing interconnected nanosheets on the Ni foam exhibited remarkable supercapacitive performance due to the void space between the sheets and mesoporous structure, which provided additional active sites for faradic transitions. The nanosheets exhibited excellent electrochemical performance with a maximum specific capacitance of 1005F g −1 and a cyclic stability of 88% during 5000 charge–discharge cycles. Moreover, an asymmetric supercapacitor was assembled comprising activated carbon on Ni foam and interconnected nanosheets of Mn-doped Co 3 O 4 on Ni foam as negative and positive electrodes, respectively. This assembled device exhibited an improved potential of 1.6 V, a maximum specific energy of 20.6 Wh kg −1 , and a maximum specific power of 16 kW kg −1 with 80.6% capacity retention after 2000 charge–discharge cycles, which is superior for SC devices.

Corrosion behavior of aluminum-Fiber Glass composite fabricated through surface mechanical alloying in alkaline media

Dissolution reaction control of aluminum in 2M KOH alkaline media was achieved through surface mechanical alloying SMA with dielectric Fiber glass ‘FG’ powder. A significant decrease corrosion rate from 0.867 for blank Al to 0.0002 mm y−1 for SMA Al with FG powder previously etched after 15 min; surface mechanical attrition treatment ‘SMAT’; Formed surface metal matrix Al/FG composites layers on Al anodes have attractive electrical properties. Its analysis obtained using X-Rays Diffraction XRD, scanning electron microscopy SEM. Used three electrochemical techniques EIS, CV and PDP indicate corrosion resistance improvement in 2M KOH correspond to inhibition efficiency reaches 99.81%. Such inhibition encourage for forming efficient and safe air batteries for interesting applications using Al anodes after consecutive SMAT & SMA processing.

Delta-doped β-(AlxGa1−x)2O3/Ga2O3 heterostructure field-effect transistors by ozone molecular beam epitaxy

Heterojunction field-effect transistors based on the β-(AlxGa1−x)2O3/Ga2O3 heterostructure grown by ozone-assisted molecular beam epitaxy were demonstrated for the first time. Al composition ratios in the 14%–23% range were validated using x-ray diffraction on the three samples grown for this study. Electrochemical capacitance-voltage (ECV) measurements showed the presence of a charge sheet in the delta-doped (AlxGa1−x)2O3 barrier layer. Secondary ion mass spectroscopy and ECV measurements also revealed an unintentional Si peak at the (AlxGa1−x)2O3/Ga2O3 interface. Direct current (IDS-VGS) and transconductance (Gm-VGS) measurements demonstrated depletion-mode transistor operation as well as the presence of a parallel conduction channel. A one-dimensional Poisson model suggested that dopant redistribution in the delta-doped region could cause a secondary channel to form in the barrier in addition to the primary channel near the (AlxGa1−x)2O3/Ga2O3 interface under certain conditions met in these samples. Fabricated devices on sample A did not exhibit breakdown up to the measurement limit of 1100 V, with stability after ten cycles. A maximum output drain current density of 22 mA/mm was measured on sample B. Room temperature Hall measurements yielded a sheet carrier density of 1.12 × 1013 cm−2 with corresponding Hall mobility of 95 cm2/V s in sample C.