eV Activation Energy Research Articles

First-principles study of Na adsorption and diffusion over substitutionally doped antimonene

The storage of the colossal amount of energy is the eminent research area for the era of eternal need of energy. Sodium-ion (Na-ion) battery emerged as an appropriate alternative to fulfil this. Here, we investigate the functionalities of doped antimonene monolayer (with Ge, Se, Sn and Te atom) as an anode material for Na-ion battery using First-principles Density Functional Theory (DFT) approach. The adsorption and diffusion of Na over the substitutionally doped antimonene is well supported thermodynamically with an adsorption energy of range −2.3 eV to −2.8 eV and minimum activation energy of range 0.1 eV to –0.8 eV. The conductivity of doped antimonene increases with the number of Na atoms adsorbed over it as seen by bandstructure, density of states (DOS) and electron difference density (EDD) plots. Inhomogeneities and structural disturbances were absent during adsorption and diffusion indicating a robust electrode material. The outcomes predict that the doped antimonene monolayer can be a potential candidate for Na-ion battery anode material application.

Electrical characterization of lead-modified bismuth borovanadate glasses

Specifically, the study looks into dielectric characteristics (ε′andε″) and complex modulus formulation and AC conductivity of lead-modified bismuth borovanadate glasses (50-x) V2O5-40 B2O3-10 Bi2O3-xPbO, where x = 5,10, 15, 20 and 25 mol% with sample ID's VPb1, VPb2, VPb3, VPb4 & VPb5 according to different compositions of lead and vanadate. When the PbO content rises, there is a decreasing tendency in both the alternating current conductivity and dielectric constants. In order to fit AC conductivity data, Almond West equation is used to extract parameters, including crossover frequency (ωH), frequency exponent (s), and direct current conductivity (σdc). Direct current conduction mechanism in all glass samples except VPb5 [Correlated Barriers Hopping (CBH) conduction at all frequencies] at lower frequencies might potentially be attributed to large-polaron quantum mechanical tunneling (LQMT). Similar to this, at high frequencies, small polaron quantum mechanical tunnelling is followed by VPb2 & VPb3 while LQMT is followed by VPb1 & VPb4. Activation energy of dc conduction (Edc) at higher frequencies (0.373–0.476 eV) for samples having sample ID VPb1 to VPb4 and sample VPb5 at all frequencies with Edc 0.686 eV and modulus activation energy (ER) (0.382–0.534 eV) are found in good agreement. Dielectric studies reveal non-Debye-type behaviour.

Doping dependence of boron–hydrogen dynamics in crystalline silicon

In this contribution, we investigate the formation and dissociation of boron–hydrogen (BH) pairs in crystalline silicon under thermal equilibrium conditions. Our samples span doping concentrations of nearly two orders of magnitude and are passivated with a layer stack consisting of thin aluminum oxide and hydrogen-rich silicon nitride (Al2O3/SiNx:H). This layer stack acts as a hydrogen source during a following rapid thermal annealing. We characterize the samples using low-temperature Fourier-transform infrared spectroscopy and four-point-probe resistivity measurements. Our findings show that the proportion of hydrogen atoms initially bound to boron (BH pairs) rises with increasing boron concentration. Upon isothermal dark annealing at (163 ± 2) °C, hydrogen present in molecular form, H2, dissociates at a rate directly proportional to the concentration of boron atoms, ∝ [B−], leading to the formation of BH pairs. With prolonged annealing, an unknown hydrogen complex is formed at a rate that is inversely proportional to the square of the boron concentration, ∝ 1/[B−]2, resulting in the disappearance of BH pairs. Based on experimental observations, we derive a kinetic model in which we describe the formation of the unknown complex through neutral hydrogen H0 binding to a sink. Additionally, we investigate the temperature dependence of the reaction rates and find that the H2 dissociation process has an activation energy of (1.11 ± 0.05) eV, which is in close agreement with theoretical predictions.

Orangish-red light emitting LaSr2AlO5:Sm3+ nanophosphors for warm LEDs: Crystallographic, photoluminescence characteristics with high color purity and thermal stability

Gel-combustion method was implemented in current research to generate Strontium Lanthanum Aluminate (LaSr2AlO5) phosphors doped with Sm3+ ions and have a potential to emit orangish-red light. In order to analyze phase characteristics, XRD technique was employed. XRD patterns of synthesized materials were closely resembles the JCPDS pattern indicated on card no. 70–2197, which define the tetragonal symmetry of the material with I4/mcm space group. The morphological, optical band energies and elemental analyses were done via TEM, DRS and EDX investigation respectively. The Sm3+ activated LaSr2AlO5 phosphor's PL spectra monitored at 406 nm excitation indicate intense visible orangish-red emission at 602 nm owing to the 4G5/2 → 6H7/2 transition. Concentration quenching was obtained at 4 mol % content of Sm3+ owed to the dipole-dipole interaction among activated ions. The calculated lifetimes have been observed to shorten as content of Sm3+ ions in the phosphors rises. The CIE (0.6069, 0.3905) value, CCT (1382 K) value, 99.4 % color purity of the optimum sample was calculated which placed in orange-red space. The fabricated phosphor has excellent thermal durability up to 498 K and 0.1686 eV activation energy. Finally, the results of all the research allow us to consider that Sm3+ doped LaSr2AlO5 phosphor is appropriate for warm LEDs.

Synergistic interaction of FeCo anchored on phthalocyanine for efficient CO2 electroreduction to C2 via microkinetic study

It is been thought as an absorbing method to carbon dioxide electroreduction reaction (CO2RR) into worthy products. However, it has been hindered because of the ultrahigh overpotential required, poor selectivity, the inevitably competitive hydrogen evolution reactions and inefficient conversion to C2 for the trouble of C–C coupling. Herein, a dual metal–nitrogen active sites anchored within phthalocyanine (FeCo-Pc) is designed as a perfect synergistic catalyst for capable CO2RR into C2. Because of the strong synergistic interactions of the doped Cobalt and Ferrum dual active sites, the obtained FeCo-Pc catalyst exhibits significantly enhanced capability in substrate adsorption and CO2 activation. The proposed reaction path shows that FeCo-Pc can accelerate CO∗ and CHO∗ intermediates dimerization with 0.70 eV activation energy, forming C2 species. Density functional theory studies have proposed that glycolaldehyde could be a selectivity-determining intermediate. The structure sensitivity and energy difference of the reaction after this intermediate would decide the ascendant C2, ethanol, ethylene, and ethylene glycol. It finds that FeCo-Pc efficiently converts CO2 mainly to ethylene at potentials of −0.66 versus reversible hydrogen electrode. Through analysis the rate constant and rate determining step, ethylene mechanism is judged as the most favorable one. The turnover frequency control degree (XTOF) of the species in four mechanisms is employed as descriptors to enhance the FeCo-Pc catalyst. This work may serve as a new method for CO2RR to C2 products by designing and utilizing multiple catalytic active sites catalysts.

Enhanced densification and ionic conductivity of LLZO by flash sintering

ABSTRACT Flash sintering arouses the interest since high-density ceramics can be obtained at shorter dwell times and lower temperatures than conventional sintering. In this study, the cubic garnet Li6.25Al0.25La3Zr2O12 (Al-LLZO) was successfully synthesised by the solid-state method. The powders were uniaxially pressed and were subjected to flash sintering at 850°C in a tube furnace under a DC bias using various current densities. It is evidenced that control of the flash electric current is a crucial factor for densification of Al-LLZO. The sample sintered in 50 V cm−1 and 200 mA mm−2 showed a cubic LLZO, 94 ± 0.4% relative density, 0.37 mS cm−1 total ionic conductivity and 0.32 eV activation energy. In addition, it was demonstrated that increasing the current density had a considerable impact on the relative density. This outstanding ionic conductivity might be due to the lower lithium loss and higher density as a result of flash sintering method applied.

BN-bicyclohexyl material for enhanced reversible dehydrogenation reaction for hydrogen storage: Density functional theory approach

Hydrogen is considered as an environmentally friendly energy resource to replace fossil fuels. This study aims to enhance the dehydrogenation efficiency of liquid organic hydrogen carrier (LOHC) materials by investigating the dehydrogenation and hydrogenation mechanisms through hetero atom (B and N) substitution of bicyclohexyl, as well as by applying the high-efficiency catalysts, palladium and ruthenium. To achieve this, BN-bicyclohexyl, a novel material based on bicyclohexyl, was proposed using density functional theory (DFT) calculations, and the synthesis of the new material was evaluated through enthalpy and free energy calculations. Mulliken charge analysis showed that the B and N atoms substituted in bicyclohexyl can induce dihydrogen bonding, resulting in efficient dehydrogenation at the substitution site. The dehydrogenation efficiency of BN-bicyclohexyl (1.53 eV in activation energy) surpasses that of bicyclohexyl (2.77 eV) on the Pd(111) surface. However, on the Ru(001) surface, BN-bicyclohexyl exhibits a slightly lower hydrogenation efficiency than bicyclohexyl, with an increase of 0.39 eV in activation energy. This trend highlights BN as a promising candidate for enhancing the capability of LOHCs. Notably, the dehydrogenation efficiency of BN-bicyclohexyl is significantly higher than that of bicyclohexyl, which go beyond slightly lower hydrogenation efficiency than bicyclohexyl.

The Liquid-Mediated Synthesis and Performance Evaluation of Li-Zr-F Composite for Ion-Conduction

Crystalline lithium fluoride (LiF) has been intensively pursued as potential alternative solid electrolytes (SEs) owing to its excellent chemical and electrochemical oxidation stability, and good deformability. However, due to its low ion conductivity, LiF is still challenging for practical SE applications. Herein, Li-Zr-F composite-based SE by liquid-mediated synthesis is proposed to be studied. methanol (CH<sub>3</sub>OH) was mainly evaluated as a liquid-mediated precursor for synthesizing Li-Zr-F composites under the stoichiometric proportion of LiF and ZrF4 (2:1 and 2:0.8) and a subsequent annealing process at 25°C/150°C, 50°C/150°C, and 70°C/150°C, respectively. X-ray diffraction results revealed that the Li-Zr-F composites could be crystallized in the three main types of phase formations, including Li<sub>2</sub>ZrF<sub>6</sub> ( ), Li<sub>2</sub>ZrF<sub>6</sub> ( ), and Li<sub>4</sub>ZrF<sub>8</sub> ( ) octahedron structures. In addition, the effect of cation stack sublattice synthesized by methanol mediator on the ion conduction of Li-Zr-F composites was investigated by using electrochemical impedance spectroscopy (EIS). Through the Zr<sup>4+</sup>-substitution, Li<sub>2</sub>ZrF<sub>6</sub> ( )-based SE exhibited the highest ion conduction which was increased to 2.40 × 10<sup>-8</sup> S/cm and 3.89 × 10<sup>-8</sup> S/cm under the stoichiometric proportion of LiF and ZrF<sub>4</sub> 2:0.8 at a dried temperature of 50°C/150°C with, respectively. A 0.21 eV activation energy ( ) was achieved for a battery with Li<sub>2</sub>ZrF<sub>6</sub> ( )-based SE. Meanwhile, LiF exhibited up to 0.78 eV leading to a low kinetic rate for ion diffusion. These results implied that Li<sub>2</sub>ZrF<sub>6 </sub>( )-based SE was successfully synthesized under the optimal condition of CH<sub>3</sub>OH-50°C/150°C which could improve the ion-conductivity of LiF.

In-situ Neutron Reflectometry to Determine Ge Self-Diffusivities and Activation Energy of Diffusion in Amorphous Ge0.8Si0.2

Amorphous Ge-Si solid solutions are an interesting class of materials from the fundamental as well as the technological point of view. Self-diffusion of the constituents is an important process because of the inherent metastability. While self-diffusion was already examined in crystalline GexSi1-x (0 < x <1) this is not the case for the amorphous counterparts. This work reports on Ge self-diffusivities obtained from insitu neutron reflectometry measurements during isothermal annealing of ion-beam sputter-deposited amorphous Ge0.8Si0.2 films. The diffusivities are modified peculiarly fast with annealing time by a maximum factor of two due to structural relaxation. The diffusivities in the relaxed state are lower (higher) than in amorphous germanium (silicon). They follow the Arrhenius law and show an activation energy of (2.06 ± 0.1) eV, which equals that of amorphous germanium, but differs from that of amorphous silicon. Thus, it is concluded that the diffusion mechanism of Ge in amorphous Ge0.8Si0.2 and Ge are similar, despite of the presence of dispersed 20 at.% of Si.

Utilisation of corn starch in production of ‘eco friendly’ polymer electrolytes for proton battery applications

Proton conducting solid polymer electrolyte [SPE] based on Cornstarch [CS] and Polyvinylpyrrolidone [PVP] with ammonium acetate are prepared by solution casting technique. The structure and Functional group of the prepared biopolymer electrolytes are confirmed by X-Ray diffraction analysis and FTIR. Conductivity, dielectric of this proton conducting SPE can be ascertained by AC impedance techniques. Sample AA-60 shows higher conductivity of 1.09 × 10−6 S/cm at ambient temperature with 0.403 eV of activation energy. Higher conducting SPE follows the overlapping large polaron tunnelling (OLPT) conduction mechanism. From the transference number analysis, 60 wt% sample shows the maximum transference number (∼0.99). The diffusion coefficient (D) and mobility of the cation is higher than the anion. The recorded CV curve lies in an applied potential window from - 0.2 to 0.7 V. The fabricated proton battery has reached an open circuit voltage of 0.89 V and discharge time of 63 h.

Radiative and Magnetically Stimulated Evolution of Nanostructured Complexes in Silicon Surface Layers.

The effect of a weak magnetic field (B = 0.17 T) and X-irradiation (D < 520 Gy) on the rearrangement of the defective structure of near-surface p-type silicon layers was studied. It was established that the effect of these external fields increases the positive accumulated charge in the region of spatial charge (RSC) and in the SiO2 dielectric layer. This can be caused by both defects in the near-surface layer of the semiconductor and impurities contained in the dielectric layer, which can generate charge carriers. It was found that the near-surface layers of the barrier structures contain only one deep level in the silicon band gap, with an activation energy of Ev + 0.38 eV. This energy level corresponds to a complex of silicon interstitial atoms SiI+SiI. When X-irradiated with a dose of 520 Gy, a new level with the energy of Ev + 0.45 eV was observed. This level corresponds to a point boron radiation defect in the interstitial site (BI). These two types of defect are effective in obtaining charge carriers, and cause deterioration of the rectifier properties of the silicon barrier structures. It was established that the silicon surface is quite active, and adsorbs organic atoms and molecules from the atmosphere, forming bonds. It was shown that the effect of a magnetic field causes the decay of adsorbed complexes at the Si–SiO2 interface. The released hydrogen is captured by acceptor levels and, as a result, the concentration of more complex Si–H3 complexes increases that of O3–Si–H.

Effect of Zn2+ co-doping on the luminescence of Sm3+ doped SrMoO4 phosphor

In this paper, we report the result of Zn2+ co-doping on the photoluminescence and structural properties of Sm3+ doped SrMoO4 phosphors which are synthesized by a lucrative auto combustion method. The structural study ascertains the improvement in crystallinity of the Sm3+ doped SrMoO4 phosphor by Zn2+ co-doping. Photoluminescence excitation analysis evinces that the intensity of 404 nm peak (6H5/2 → 4F7/2) is enhanced by 93.5% after 1% Zn2+ co-doping in the 4% Sm3+ doped SrMoO4 phosphor. Emission study manifests that the intensity of Sm3+ doped SrMoO4 phosphors increases up to 4% doping concentration of Sm3+ ion, and its peaks located at 562 nm, 597 nm, 645 nm, and 705 nm are ascribed to 4G5/2 to 6HJ/2 (J = 5, 7, 9, and 11) electronic transitions of Sm3+ ions, respectively. The overall emission of Sm3+ doped SrMoO4 phosphors lies in the reddish-orange region. The emission intensity of 4% Sm3+ doped SrMoO4 is further increased by 87.80% after 1% Zn2+ co-doping. The lifetime of the 4G5/2 level of the Sm3+ ions has also increased on doping 1% Zn2+ ions. The temperature-dependent emission spectra reveal good thermal stability of the phosphor with 0.17eV activation energy. The prepared Zn2+ co-doped SrMoO4:4Sm3+ phosphor has near-UV excitation and reddish-orange emission and thus can be used as a potential red phosphor in lighting devices.

Dislocation Dynamics in Monocrystalline Si near the Melting Point Studied in Situ by X‐Ray Bragg Diffraction Imaging

To study dislocation dynamics in a model sample, an intrinsic float zone (FZ) Si wafer is chosen as seed to initiate directional solidification. During the temperature ramp, a Von Laue diffraction spot is recorded by a camera. It provides time‐resolved information on the evolution of silicon crystalline quality and on the defect nucleation locations and dynamics. With increasing temperature, dislocations are observed to propagate through the seed starting mainly from the sample edges. The effective thermomechanical local stress is estimated as low as (1.2 ± 0.4) × 105 Pa in a thermal gradient of (1.8 ± 0.2) × 102 K m−1. The latter is sufficient to allow dislocation nucleation and motion at temperatures beyond (1523 ± 9) K. Dislocation velocity increases with temperature and reaches a maximum velocity of (3.0 ± 0.5) × 10−4 m s−1 close to the silicon melting point. From the dislocation velocity measurements as a function of temperature, an activation energy of (3.1 ± 0.6) eV is estimated and this value is discussed, along with dynamical interactions between defects and dislocations.

Synthesis and spectroscopic analysis of Eu3+-doped tungsten bronze Sr5YTi3Nb7O30 phosphors for w-LED and visualization of latent fingerprint

A series of novel Sr5YTi3Nb7O30: x Eu 3+ ( x = 0.05–0.40) red-emitting phosphors were firstly synthesized using the high-temperature solid-state method. The X-ray diffraction (XRD) patterns demonstrate that the phosphors are pure phase with the space group P 4 bm of tetragonal system. Under the 395 nm excitation wavelength, the red emission of Sr5YTi3Nb7O30:Eu 3+ phosphor is considered to be dominated by the 5 D 0 → 7 F 2 transition at 613 nm. The asymmetry ratios (R/O) of Sr5YTi3Nb7O30: x Eu 3+ ( x = 0.05–0.40) phosphors are identified as 2.64–2.78, which contribute to the high color purity (99.5%–99.8%). The phosphor has good thermal stability with 0.17 eV of activation energy. The Commission International de L'Eclairage (CIE) coordinates of the w-LED nearly overlap with the standard white light (0.333, 0.333), the R a is as high as 90. Meanwhile, the features of fingerprint are simultaneously distinguished at three levels on aluminum foil by Sr5YTi3Nb7O30:0.30Eu 3+ phosphor. In addition, the latent fingerprint on various nonporous substrates (stainless steel, glass, and plastic surfaces) were identified. In summary, the phosphor is feasible to apply in the w-LEDs and latent fingerprint detection.

Effects of Eu3+ doping on the luminescence properties of novel Sr2CaLa(VO4)3 from partial substitution of Sr2+ by Ca2+ in Sr3La(VO4)3

Eu 3+ -activated Sr 3 −x Ca x La(VO 4 ) 3 phosphors were fabricated via citric-acid-assisted sol combustion. Characterization of the Sr 3 −x Ca x La(VO 4 ) 3 :Eu 3+ samples with different concentrations of Ca 2+ revealed a hexagonal crystal structure belonging to the R -3 m space group. The amount of Ca 2+ added ( x ) was controlled within 0 ≤ x ≤ 2 to yield high-purity phosphors. Scanning electron microscopy results showed that an increase in Ca 2+ concentration resulted in a decrease in the particle size of Sr 3 −x Ca x La(VO 4 ) 3 :Eu 3+ , with the shape gradually changing from nearly equiaxed to lath-shaped. The Sr 2 CaLa(VO 4 ) 3 :Eu 3+ phosphor (denoted as SCLVO:Eu 3+ ) exhibited the strongest photoluminescence (PL) intensity at 618 nm among the samples under excitation of 394-nm near-UV (NUV) light. The study of Eu 3+ doping concentration confirmed that Eu 3+ could enter the lattice of the SCLVO matrix without altering its crystal structure. SCLVO:Eu 3+ was found to strongly absorb 394 nm NUV light and 464 nm blue light. The optimal concentration of the Eu 3+ dopant in the SCLVO host was 0.11, which resulted in the phosphor achieving an excellent PL intensity and a color purity of 98.68%. Tunable luminescence from the orange area (0.5280, 0.4522) of Commission Internationale de l'éclairage (CIE) to the red area (0.6313, 0.3650) was achieved by adjusting the concentration of Eu 3+ . Under 394 nm excitation, SCLVO:0.11Eu 3+ phosphor has a quantum yield (QY) of 28.2% and excellent thermal stability with 0.383 eV activation energy. Consequently, White-light-emitting diode (WLED) based on SCLVO:0.11Eu 3+ phosphor yielded a high color rendering index (CRI), low correlated color temperature (CCT), and CIE coordinates of 91.8, 5196 K, and (0.3407, 0.3612), respectively, under the 20 mA driven current. These results indicated the tremendous potential of SCLVO:0.11Eu 3+ phosphors for application in WLEDs excited by NUV or blue light.

A growth diagram for chemical beam epitaxy of GaP1−xNx alloys on nominally (001)-oriented GaP-on-Si substrates

The compound GaP1−xNx is highly attractive to pseudomorphically integrate red-light emitting devices and photovoltaic cells with the standard Si technology because it is lattice matched to Si with a direct bandgap energy of ≈1.96 eV for x = 0.021. Here, we report on the chemical beam epitaxy of GaP1−xNx alloys on nominally (001)-oriented GaP-on-Si substrates. The incorporation of N into GaP1−xNx was systematically investigated as a function of growth temperature and the fluxes of the N and P precursors, 1,1-dimethylhydrazine (DMHy) and tertiarybutylphosphine (TBP), respectively. We found that the N mole fraction exhibits an Arrhenius behavior characterized by an activation energy of (0.79 ± 0.05) eV. With respect to the fluxes, we determined that the N mole fraction is linearly proportional to the flux of DMHy and inversely proportional to the one of TBP. All results are summarized in a universal equation that describes the dependence of x on the growth temperature and the fluxes of the group-V precursors. The results are further illustrated in a growth diagram that visualizes the variation of x as the growth temperature and the flux of DMHy are varied. This diagram also shows how to obtain single-phase and flat GaP1−xNx layers, as certain growth conditions result in chemically phase-separated layers with rough surface morphologies. Finally, our results demonstrate the feasibility of chemical beam epitaxy to obtain single-phase and flat GaP1−xNx layers with x up to about 0.04, a value well above the one required for the lattice-matched integration of GaP1−xNx-based devices on Si.

Si-Based Infrared Detector Using Organic Nano-Dot Array

Silicon-based infrared photodetector is proposed using an organic nano-dot array covered with an Au thin film. The nano-dots were self-assembled structures composed of crystalline CuPc and PTCDA organic semiconductors, and they enhanced the absorption of the incident infrared light. The annealing process at the CuPc and PTCDA deposition formed these semiconductor materials to be a nano-dot array shape. The Au-coated nano-dots presented broadband reflectance decrease in the near- to mid-infrared region. The Arrhenius plot investigation revealed that the proposed photodetector had 0.4-0.43 eV activation energy, a sub-Si-bandgap energy barrier. The photodetection experiments in the near-infrared region presented the proposed photodetector discriminated on and off of 2.07- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> -long super continuum light. In addition, band-pass filtered emission from a black body cavity with a wavelength of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.05~\mu \text{m}$ </tex-math></inline-formula> could be measured. Since the derivation of the activation energy and the cut-off wavelength showed a good agreement, the organic semiconductor generated a carrier at the photodetection. A possible detection mechanism was thus attributed to carrier excitations at an interface between organic semiconductors, CuPc and PTCDA. The proposed structure contributes to fabricate mid-infrared silicon-based photodetectors with high light absorption performance.

Enhanced Performance of Li6.4La3Zr1.4Ta0.6O12 Solid Electrolyte by the Regulation of Grain and Grain Boundary Phases.

The application of Li-ion conducting garnet electrolytes is challenged by their large interfacial resistance with the metallic lithium anode and the relative small critical current density at which the lithium dendrites short-circuit the battery. Both of these challenges are closely related to the morphology and the structure of the garnet membranes. Here, we prepared four polycrystalline garnet Li6.4La3Zr1.4Ta0.6O12 (LLZTO) pellets with different particle sizes (nano/micro) and grain boundary additive (with/without Al2O3) to investigate the influence of grain size, the composition of the grain boundary, and the mechanical strength of the pellet on the total Li-ion conduction of the pellet, Li/garnet interfacial transfer, and lithium dendrite growth in all-solid-state Li-metal cells. The results showed that the garnet pellets prepared with nanoparticles and LiAlO2-related grain boundary phase had decreased total Li-ion conductivity because of the increased resistance of the grain boundary; however, these pellets showed higher mechanical strength and improved capability to suppress lithium dendrite growth at high current densities. By controlling the grain size and optimizing the grain boundary with Al2O3 sintering additive, the hot-pressing sintered LLZTO solid electrolytes can reach up to 1.01 × 10-3 S cm-1 in Li+ conductivity and 0.29 eV in activation energy. LLZTO with nanosized grain and LiAlO2-modified grain boundary showed the highest critical current density, which is 0.6 mA cm-2 at room temperature and 1.7 mA cm-2 at 60 °C. This study offers a useful guideline for preparing a high-performance LLZTO solid electrolyte.

Experimental investigation of buffer traps physical mechanisms on the gate charge of GaN-on-Si devices under various substrate biases

The gate charge change (ΔQg) of GaN-on-Si power devices subjected to different substrate biases has been investigated. On-wafer pulse-mode voltage stress measurement is examined to probe the physical insight of different trap mechanisms into Qg characteristics. Distinct injected electrons interacting with the buffer traps lead to a significant decrease (increase) in Qg under negative (positive) substrate bias. Different levels of degradation on ΔQgd to ΔQgs after stress under negative and positive substrate biases indicate uneven distribution of acceptor-like traps and uniform distribution of donor-like traps in the GaN buffer level. Using Arrhenius plots associated with the ΔQg shift, three dominant buffer traps with activation energies of EV + 0.542 eV, EC −0.604 eV, and EC −0.608 eV are extracted.

Impact of defects on the electrical properties of BiFeO3 thin films

The impact of defects on the electrical properties of bismuth ferrite thin films has been studied. Secondary phases and oxygen vacancies were the main defects considered. Thin films with secondary phases show higher conductivities than single-phase films. Monophasic films annealed in oxygen atmosphere shows lower conductivity than the non-annealed film. For selected thin film with secondary phase, the relaxation in the grain boundary was predominant with activation energy eV, suggesting the first ionization oxygen vacancies as the relaxation mechanism in the studied films. The electric field effect on relaxation processes was similarly to Arrhenius thermally activated process.