XPS Depth Profiling Research Articles

Thermal Pyrolysis of Ammonium Fluoride Induced Multilayered Protection for Longevity of Lithium Metal Batteries

Utilizing the "Holy Grail" lithium metal anode is crucial for attaining high energy density1. Nevertheless, employing a lithium metal as anode faces practical challenges due to thermodynamic instability and dendrite growth1-2. An artificial stabilization of lithium metal mainly employed to mitigate the electrolyte decomposition, dead lithium metal formation and dendrite growth3. A facile and cost effective gas treatment of lithium metal was carried out using thermal pyrolysis of NH4F salt to generate HF(g) and NH3(g). An exposure of lithium metal to the generated gas induces a spontaneous reaction that forms multilayer protection with multiple solid electrolyte interface (SEI) components, such as LiF, Li3N, Li2NH, LiNH2, and LiH from a single salt. The formation energy (ΔEf) using DFT-D3 calculations coupled with depth profile XPS and XRD measurements proven the formation of these reaction products. An operando optical microscope (Operando OM) observation on plating/stripping phenomena in symmetric cells under conventional carbonate electrolyte (1 M LiPF6 EC/DEC (1:1 v/v)) operated at 3 and 5 mA cm−2 current density demonstrate the advantage of protection layer on suppression of lithium dendrite. Furthermore, the artificial multilayer protection on lithium sustains stable lithium reversibility and overpotential under varied cell configuration both symmetric cell, Li||Li and half-cells, under Li||Cu and Li||MCMB systems. We demonstrate that the desirable protective layer with LiFePO4 (LFP) showed a capacity retention (CR) of 90.6% at 0.5 mA cm−2 after 280 cycles, and LiNi0.5Mn0.3Co0.2O2 (NCM523) showed 58.7% at 3 mAcm−2 after 410 cycles. Formulating the multi-layered protection, with the simultaneous formation of multiple SEI components in a facile and cost-effective approach from NH4F as a single salt, making the system competent. References Taklu, B. W.; Su, W.-N.; Chiou, J.-C.; Chang, C.-Y.; Nikodimos, Y.; Lakshmanan, K.; Hagos, T. M.; Serbessa, G. G.; Desta, G. B.; Tekaligne, T. M.; Ahmed, S. A.; Yang, S.-C.; Wu, S.-H.; Hwang, B. J., Mechanistic Study on Artificial Stabilization of Lithium Metal Anode via Thermal Pyrolysis of Ammonium Fluoride in Lithium Metal Batteries. ACS Applied Materials & Interfaces 2024, 16 (14), 17422-17431.Moon, S.; Park, H.; Yoon, G.; Lee, M. H.; Park, K.-Y.; Kang, K., Simple and effective gas-phase doping for lithium metal protection in lithium metal batteries. Chemistry of Materials 2017, 29 (21), 9182-9191.Taklu, B. W.; Nikodimos, Y.; Bezabh, H. K.; Lakshmanan, K.; Hagos, T. M.; Nigatu, T. A.; Merso, S. K.; Sung, H.-Y.; Yang, S.-C.; Wu, S.-H., Air-stable iodized-oxychloride argyrodite sulfide and anionic swap on the practical potential window for all-solid-state lithium-metal batteries. Nano Energy 2023, 112, 108471. Figure 1. Schematic illustration for the formation of an artificial multilayered protection via gas treatment and its effect on lithium plating. Figure 1

Altering the Solid Electrolyte Interface Through Surface-Modification of Lithium Metal Anode for High-Voltage Lithium Battery

The physical structure and chemical composition of the solid electrolyte interphase (SEI) affect the performance of the lithium metal anode. The tuning of the chemical composition and structure of the SEI through the surface modification of the lithium metal anode has been conducted. A series of dicarboxylic acids, oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid have been utilized to modify the surface of the lithium anode. Physical characterization methods have been employed to study the surface morphology and chemical composition of the SEI. Symmetrical (Li/Li) and asymmetrical (NMC622/Li) cells with pristine lithium and surface modified lithium electrodes have been assembled and tested. NMC622/Li cell with surface modified lithium shows improved performance compared to that of pristine lithium. Malonic acid-treated lithium outperforms all the electrodes by retaining 141 mAh g−1 specific capacity even after 100 cycles of charge-discharge. XPS depth profiling analysis reveals that the SEI on the MA-Li contains evenly distributed organic and inorganic components which are responsible for the performance of MA-Li.

Performance enhancement of MOCVD grown Zn-doped β-Ga2O3 Deep-Ultraviolet photodetectors on silicon substrates via TiN buffer layers

Integrating β-Ga2O3-based devices on silicon substrates faces challenges due to lattice and thermal expansion mismatches, leading to performance-degrading defects. Therefore, this work explores the utilization of a titanium nitride (TiN) buffer layer in order to enhance the performance of MOCVD grown Zn-doped β-Ga2O3-based deep-ultraviolet (DUV) photodetectors (PDs) on silicon substrates with 12, 24, and 36 sccm diethylzinc (DEZn) flow rates. The XPS depth profiles revealed the presence of TiN buffer layer in β-Ga2O3/TiN/Si films, which served as a diffusion barrier during deposition, preserving interface integrity and reducing defect density. Zn-doped β-Ga2O3/TiN/Si based DUV PDs revealed remarkable results. The 12 sccm Zn-doped β-Ga2O3/TiN/Si PDs demonstrated an exceptional maximum responsivity of 31.4 A/W, which is 7 times higher compared to the undoped β-Ga2O3/TiN/Si (4.47 A/W) under a 5 V bias and 240 nm wavelength illumination. This PD exhibited the detectivity of 1.68 × 1013 Jones and EQE of 1.63 × 104 %. This PD possess quick rise time of 6.5 s and fall time of 0.5 s. The energy band diagram for Zn-doped β-Ga2O3/TiN/Si metal–semiconductor-metal type PDs is discussed. This work demonstrates that TiN buffer layers and Zn doping significantly improve the performance and reliability of β-Ga2O3-based DUV photodetectors on silicon substrates.

High-precision silver electrode based on PEN substrate with robust mechanical performance

Wearable electronics are becoming more and more popular, and in order to ensure the safety and accuracy of wearable electronics, the requirements for the refinement and stability of flexible electrodes are getting higher and higher. The reduction of the amount of ink jet and the reduction of surface charge density and electrostatic stress near the nozzle hole can significantly improve the jetting state of the ink. And nozzle voltage is a key factor that affects them. The spreading of ink droplets on the substrate and the formation of a specific pattern is a dynamic process, which is closely related to the properties of the substrate and the state of the ink droplets. In this paper, PEN is used as the substrate to print silver electrode, with its good thermal stability and good mechanical properties. In order to solve these problems and improve the accuracy of the electrode pattern on PEN substrate, a joint control method of ink drop spacing and nozzle voltage is proposed. It is found that the accuracy of the pattern increases with the increase of the drop spacing. At 45 μm, 90.91 % of the pattern accuracy with the ideal pattern can be achieved. As the nozzle voltage decreases, so does the satellite spot. And at 25 V, it can achieve satellite-free spot printing. Because this method avoids the adjustment of ink properties and the regulation of voltage waveform, this advancement provides a simpler solution for patterned high-precision printed silver electrodes based on flexible substrates. In addition, a silver electrode with a resistivity of 3.43 μΩ·cm was obtained at an annealing temperature of 160 °C. The resistivity change of the electrode only 7.58 % under 5000 times of bending. This is very rare in flexible electrodes.The silver film on the PEN substrate exhibited excellent adhesion under the tape test. XPS depth profiling was used to characterize the elemental states of the films at different depths. The results indicated that the coordination bond between the PEN substrate and the Ag film resulted in good bending resistance, which gives a persuasive explanation for the first time. This result is also due to the precise handling of the film, which also results in a homogeneous distribution of the film. It solves the problem of poor adhesion of silver electrodes based on other substrates or other preparation methods. Therefore, silver electrodes based on PEN substrates have a broad application prospect in the field of flexible wearable electronics.

Anion-intercalation pseudocapacitance in oxygen vacancy-rich spinel-perovskite NiFe2O4-LaFeO3 nanocomposite for high energy density asymmetric supercapacitor application

Oxide nanomaterials have attracted significant attention as energy storage materials. The combination of spinel-perovskite oxides as nanocomposites creates dense oxygen vacancies (VO) at the hetero-interface. VO present in the complex oxides are indispensable for energy conversion applications. Herein, we demonstrated the one pot synthesis of spinel-perovskite NiFe2O4-xLaFeO3 nanocomposite and investigated the phase formation using variable temperature powder X-ray diffraction of the gel precursor. The role of oxygen-vacancy mediated tuneable redox transitions in NiFe2O4-xLaFeO3 nanocomposite has been understood. The anion-intercalation-based pseudocapacitance and the oxygen intercalation have been exploited for high-performance electrochemical energy storage. The NiFe2O4–2LaFeO3 exhibited a high specific capacity of 652 C g−1 at a current density of 2 A g−1. The fabricated NiFe2O4–2LaFeO3||NiCo2O4 asymmetric supercapacitor device (ASC) exhibited excellent cyclability over 20,000 cycles with superior capacity retention and high Coulombic efficiency (92 %) and achieved a high energy density of 42.5 Wh kg−1 at a power density of 1500 W kg−1. The presence of VO and the mixed-valence states of Fe2+/3+ were confirmed by XPS-depth profiling. The tuneable redox transition of Fe2+/3+ and VO contribute to the higher pseudocapacitance response.

Multiscale Parametrization Of a Friction Model For Metal Cutting Using Contact Mechanics, Atomistic Simulations, And Experiments

In this study, we developed and parametrized a friction model for finite element (FE) cutting simulations of AISI4140 steel, combining experimental data and numerical simulations at various scales. Given the severe thermomechanical loads during cutting, parametrization of friction models based on analogous experiments has been proven difficult, such that the cutting process itself is often used for calibration. Instead, our model is based on the real area of contact between rough surfaces and the stress required to shear adhesive micro contacts. We utilized microtextured cutting tools and their negative imprint on chips to orient chip and tool surfaces, enabling the determination of a combined surface roughness. This effective roughness was then applied in contact mechanics calculations using a penetration hardness model informed by indentation hardness measurements. Consistent with Bowden and Tabor theory, we observed that the fractional contact area increased linearly with the applied normal load, and the effective roughness remained insensitive to cutting fluid application. Additionally, we calculated the required shear stress as a function of normal load using DFT-based molecular dynamics simulations for a tribofilm formed at the interface, with its composition inferred from ex-situ XPS depth profiling of the cutting tools. Our friction model demonstrated good agreement with experimental results in two-dimensional FE chip forming simulations of orthogonal cutting processes, evaluated by means of cutting force, passive force, and contact length prediction. This work presents a proof of concept for a physics-based approach to calibrate constitutive models in metal cutting, potentially advancing the use of multiscale and multiphysical simulations in machining.Graphical abstract

XPS depth profiling of nano-layers by a novel trial-and-error evaluation procedure

In spite of its superior chemical sensitivity, XPS depth profiling is rarely used because of the alteration introduced by the sputter removal process and the resulting inhomogeneous in-depth concentration distribution. Moreover, the application of XPS becomes increasingly challenging in the case of the analysis of thin layers, if the thickness is in the range of 2–3 inelastic mean free paths (IMFP) of the photoelectrons. In this paper we will show that even in these unfavorable cases the XPS depth profiling is applicable. Herein the XPS depth profiling of a model system tungsten-carbide-rich nano-layer of high hardness and corrosion resistance is presented. We will show that the problems arising because of the relatively high IMFP can be corrected by introducing a layer model for the calculation of the observed XPS intensities, while the alteration, e.g. ion mixing, compound formation and similar artefact, introduced by the sputter removal process can be handled by TRIDYN simulation. The method presented here overcomes the limitation of XPS depth profiling.

Effect of Silicate Addition on ZnO Formation during Zn Discharging Process

Rechargeable zinc batteries have been attracting extensive attention as promising candidates for next-generation energy storage, owing to their intrinsic safety, mature recycling processes, low material cost and high theoretical energy density.[1] Nevertheless, there are still several issues holding back the development of zinc batteries, such as the capacity loss due to Zn passivation and poor cyclability caused by Zn dendrite formation. [2] In the past few years, efforts have been made to improve the performance of zinc batteries, among which electrolyte modification with additives is the most widely used. [3] For further development of zinc batteries towards practical application, it is also essential to deepen the understanding of chemical state changes in a working Zn electrode. In our previous work, Zn dissolution−passivation behavior with ZnO formation during Zn discharging process has been systematically elucidated via in-situ analysis. [4] Herein this work, through comparative studies with silicate addition in the electrolyte, the correlation between ZnO formation and the discharging performance of Zn anodes is further clarified, shedding new insights into further optimization of zinc batteries.Firstly, various electrolyte additives were evaluated during Zn discharging at a current density of 40 mA/cm2. As a result, potassium silicate addition with an optimum concentration of 100 mM effectively enhanced the discharge capacity of Zn anode. Effects of silicate addition on Zn discharging process were then further investigated. After 500 s of discharging, ZnO layer with a thickness around 7 um is formed on Zn anodes, which is attributed to the dehydration of supersaturated zincate ions. [4] It is observed that as-formed ZnO petals turned from sharp to round with silicate addition. Moreover, a porous ZnO layer was formed with silicate addition, while a compact one was obtained without any additives. Accordingly, it is assumed that silicate may form adsorption or coordination with ZnO particles, leading to morphology and porosity changes in ZnO.Further analyses were carried out to verify whether the chemical state of ZnO changes with silicate addition. The TEM-EDS mapping result and XPS depth profile indicate that Si is uniformly distributed within the ZnO layer. Moreover, the presence of Si-O bond is confirmed, along with both Zn 2p 2/3 and O 1s peak shifts towards higher binding energy side. Accordingly, the coordination between silicate and ZnO via the formation of Si-O-Zn bridge is suggested, which is also supported by the DFT calculation result, as a stable existence of silicate on ZnO can be achieved.On the other hand, it is noticed via XRD and HRTEM characterization that the crystallite size of ZnO became smaller with silicate addition. Moreover, ZnO formed with silicate addition presented lower crystallinity with higher defect contents, as evidenced by Raman spectra. Given the above, it is considered that silicate modulates the electronic structure of ZnO molecules via the Si-O-Zn bonding, thereby suppresses ZnO crystal growth and particle aggregation, which eventually contributes to a loose ZnO structure that can maintain the activity of Zn anodes. With the discussion of ZnO formation herein, we hope this work may open a new avenue for developing high-performance zinc batteries.AcknowledgementsThis study was supported by the Research and Development Initiative for Scientific Innovation of New Generation Batteries (RISING) Projects, RISING3 [JPNP21006], commissioned by the New Energy and Industrial Technology Development Organization (NEDO), Japan.[1] P. Ruan et al., Angew. Chem., 2022, 134, e202200598[2] W. Shang et al., Energy Storage Mater., 2020, 31, 44–57[3] S. Guo et al., Energy Storage Mater., 2021, 34, 545–562[4] T. Wang et al., Energy Environ. Mater., 2023, 0, e12481

Coexistence of Kondo effect and Weak anti-localization in Topological insulator/Ferromagnetic heterostructure

The presence of a magnetic impurity in a topological insulator weakens the time-reversal symmetry by creating a limited gap at the Dirac point, and could result in the creation of new quantum states. On the other hand, causing magnetization in a topological insulator through the interlayer proximity effect to a magnetically ordered system is a better choice, as magnetic doping may have negative effects. In this report, the magnetic and magneto-transport properties of FeSe intercalated Bi2Se3 crystals and FeSe/Bi2Se3/FeSe hetero-structure have been investigated. The XPS depth profile was studied to confirm the layered structure of the hetero-structure. The weak anti-localization state in the multilayer system has been seen to coexist with the Kondo effect, which may have caused by the interfacial magnetic domains modifying the electronic characteristics at interfaces. Such magnetic spin-induced inter-layer coupling can be a pathway to room-temperature spintronic applications.

A Dielectric MXene-Induced Self-Built Electric Field in Polymer Electrolyte Triggering Fast Lithium-Ion Transport and High-Voltage Cycling Stability.

Quasi-solid polymer electrolyte (QPE) lithium (Li)-metal battery holds significant promise in the application of high-energy-density batteries, yet it suffers from low ionic conductivity and poor oxidation stability. Herein, a novel self-built electric field (SBEF) strategy is proposed to enhance Li+ transportation and accelerate the degradation dynamics of carbon-fluorine bond cleavage in LiTFSI by optimizing the termination of MXene. Among them, the SBEF induced by dielectric Nb4C3F2 MXene effectively constructs highly conductive LiF-enriched SEI and CEI stable interfaces, moreover, enhances the electrochemical performance of the QPE. The related Li-ion transfer mechanism and dual-reinforced stable interface are thoroughly investigated using ab initio molecular dynamics, COMSOL, XPS depth profiling, and ToF-SIMS. This comprehensive approach results in a high conductivity of 1.34 mS cm-1, leading to a small polarization of approximately 25 mV for Li//Li symmetric cell after 6000 h. Furthermore, it enables a prolonged cycle life at a high voltage of up to 4.6 V. Overall, this work not only broadens the application of MXene for QPE but also inspires the great potential of the self-built electric field in QPE-based high-voltage batteries.

A Dielectric MXene‐Induced Self‐Built Electric Field in Polymer Electrolyte Triggering Fast Lithium‐Ion Transport and High‐Voltage Cycling Stability

AbstractQuasi‐solid polymer electrolyte (QPE) lithium (Li)‐metal battery holds significant promise in the application of high‐energy‐density batteries, yet it suffers from low ionic conductivity and poor oxidation stability. Herein, a novel self‐built electric field (SBEF) strategy is proposed to enhance Li+ transportation and accelerate the degradation dynamics of carbon‐fluorine bond cleavage in LiTFSI by optimizing the termination of MXene. Among them, the SBEF induced by dielectric Nb4C3F2 MXene effectively constructs highly conductive LiF‐enriched SEI and CEI stable interfaces, moreover, enhances the electrochemical performance of the QPE. The related Li‐ion transfer mechanism and dual‐reinforced stable interface are thoroughly investigated using ab initio molecular dynamics, COMSOL, XPS depth profiling, and ToF‐SIMS. This comprehensive approach results in a high conductivity of 1.34 mS cm−1, leading to a small polarization of approximately 25 mV for Li//Li symmetric cell after 6000 h. Furthermore, it enables a prolonged cycle life at a high voltage of up to 4.6 V. Overall, this work not only broadens the application of MXene for QPE but also inspires the great potential of the self‐built electric field in QPE‐based high‐voltage batteries.

Self-assembled layer as an effective way to block copper diffusion into epoxy

The reliability of copper/epoxy bonding is important for power semiconductors. It has been found that copper can diffuse into epoxy and accelerate epoxy decomposition at high temperatures, deteriorating reliability. We proposed a way to inhibit copper diffusion into epoxy by using self-assembled layers. Copper substrates with self-assembled layers on their surface were encapsulated with epoxy and placed at 200 °C for 1000 h. The diffusion of copper into epoxy was evaluated by XPS depth profiling, and the decomposition of epoxy was evaluated by ATR-FTIR. The results showed that self-assembled layers can effectively hinder copper diffusion into epoxy. The possible reason is that the existence of the self-assembled layer greatly reduces the formation of copper ions. Also, we found that the self-assembled layer survived the heating, implying its potential for practical power module applications.

Zinc triggers favorable hydrogenation reaction in double perovskite PrBaCo2O6-δ: Applications in protonic ceramic cells

Protonic ceramic cell is seen as the next-generation energy conversion device designed to efficiently and reversibly convert chemical energy into electricity working at intermediate temperatures. However, their practical application heavily relies on the development of high-performance air electrodes. Mixed proton/electron/oxygen-ion conducting materials have promising potential as superior air electrodes, as they can significantly boost activity by extending active sites to the entire air electrode. Herein, we introduce 5 mol% hydrophilic Zn into PrBaCo2O6-δ resulting in the PrBaCo1.9Zn0.1O6-δ (PBCZn10), which exhibits enhanced proton uptake ability and excellent stability in steam-concentrated atmospheres. The electrochemical characterization results demonstrate that introducing Zn into PBC significantly reduces the polarization resistance by 45 % under 10 % H2O/air at 550 °C. Applying such novel air electrode on real electrochemical devices nearly doubled the out-put performance to 655 mW cm−2 at 650 °C. This confirms that the enhanced proton uptake ability in PBCZn10 facilitates proton interfacial transport and extends the reaction zone. Importantly, our study offers an insightful view into the proton uptake process and the surface evolution of the material before and after proton uptakes, employing high-temperature XRD and depth-profiling XPS. This work provides valuable guidance for developing triple electronic-ionic conducting oxides by shedding light on the proton uptake process on electrode materials.

Changes in chemical composition of TixAl1−xN coatings immersed in oxygen-saturated Lead–Bismuth Eutectic at low and moderate temperatures (250 °C ≤ T ≤ 410 °C)

Lead–Bismuth Eutectic (LBE) will serve as a liquid metal coolant in accelerator-driven systems, posing a corrosive threat to exposed materials. To address this challenge, TixAl1-xN coatings (0.38 ≤ x ≤ 0.58) were applied onto AISI 316 L austenitic stainless steel using the reactive bipolar magnetron sputtering technique. These coated samples underwent immersion in static oxygen-saturated LBE at temperatures of 250 °C and 360 °C for durations of 500 h and 1000 h, and at 410 °C for 500 h. XPS depth profiles revealed minimal oxidation at 250 °C even after 1000 h. However, at 360 °C, a mixed oxide layer of (Ti, Al)Ox was formed on the coating's surface. Exposure to LBE at 410 °C for 500 h led to the creation of an oxide bilayer comprising TiO2 (outer sublayer) and (Ti, Al)Ox depleted of Ti (inner sublayer). A model is proposed to illustrate the oxidation mechanism.

Tribological behavior of sulfonitrided tribofilm generated from non-corrosive dimercaptobenzothiadiazole-based additives as effective boundary lubrication layer

Lubricant additives are essential to protect mechanical devices. Although sulfur (S)-based dialkylpentasulfide (RC2540) exhibits acceptable extreme pressure (EP) performance, a high amount of S causes severe corrosion and poorer anti-wear (AW) performance. Herein, dimercaptobenzothiadiazole-based additives (DMTDs) consist of four and five S atoms, namely 2-(benzyldisulfanyl)-5-(benzylsulfanyl)-1,3,4-thiadiazole (4SBZ), 2-(octyldisulfanyl)-5-(octylsulfanyl)-1,3,4-thiadiazole (4SC8), 2,5-bis(benzyldisulfanyl)-1,3,4-thiadiazole (5SBZ), and 2,5-bis(octyldisulfanyl)-1,3,4-thiadiazole (5SC8) were synthesized. The synthesized DMTDs are non-corrosive (Grade 1a-1b) compared to RC2540 (Grade 4c). The 10 wt% 5SBZ demonstrated exceptional EP and AW performance than RC2540. The 10 wt% 5SBZ has improved weld load and reduced wear scar area by 5.0 folds and 94.1% compared to naphthenic base oil. The exceptional tribological properties of 5SBZ are attributed to the strong non-covalent interaction between the benzene ring and metal surfaces, high S content, and synergistic effect between S and N. Alternatively, the DMTDs exhibit better AW performance compared to RC2540. The XPS depth profiling demonstrated the formation of sulfonitrided tribofilm after lubrication with synthesized DMTDs. This tribofilm contributed to an excellent boundary lubrication layer for wear protection. The lubrication mechanism was discussed and proposed. This work provides promising DMTDs as EP and AW additives for industrial applications.

Origin of near-failure in Au contacts to polycrystalline β-Ga2O3 at high temperatures using interfacial studies

Suitable contacts to gallium oxide are a controversial topic with contact behavior depending heavily on the pre- and post-processing conditions. Especially for the extreme environment applications such as those involving high temperatures, contact chemistry is varied and severely lacks understanding. Herein, we report on conventional pure Au contacts to polycrystalline β-Ga2O3, used as Schottky contacts, and explore the origin of their near-failure at high temperature up to 850 °C. For this purpose, β-Ga2O3 with Au interdigitated electrodes is subjected to high temperature annealing and their interface chemistry is studied and correlated with device performance for solar-blind photodetection. Around the optimized temperature of 450 °C, the performance of the PDs is found to be maximum, whereas it reduces drastically at 850 °C. Physical damage to the electrodes along with the formation of intermetallic gold-gallium alloy is observed via XPS depth profile studies and found to be the reason for the near-failure of device at extreme conditions. Although the alloy formation begins to slightly appear at 650 °C and reduces the performance, still it does not lead to device breakdown. This study proves that unlike its counterparts GaN and GaAs, which have reported alloy formation at lower temperatures, β-Ga2O3 shows a higher resilience to the formation of Au–Ga alloy and can withstand higher temperatures before the actual device failure is reached. The proposed study shows the stability of standard metal contacts to Ga2O3 based devices, which have far-reaching implications for the future commercialization of wideband gap semiconductor based (opto)electronics.

Electrochemical sensor based on hollow Au/Pd/Ag dendrites prepared by galvanic replacement from a choline chloride-ethylene glycol deep eutectic solvent

This study presents a simple approach to fabricating a hollow dendritic Au/Pd/Ag electrode through a galvanic replacement reaction (GRR) in a choline chloride-ethylene glycol deep eutectic solvent. The resulting electrode's morphological, structural, and compositional features were characterized using SEM, TEM, XRD, and XPS techniques, with the XPS depth profile providing insights into metal content ratio variations along the electrode's depth. The results emphasize the significant impact of immersion time on both morphological evolution and composition. Cyclic voltammetry investigations revealed significantly enhanced current density in furaltadone (FTD) detection compared to bimetallic and single metallic electrodes. The proposed electrochemical sensor exhibited a dynamic linear range for FTD spanning 1.67–625 μM, accompanied by a low detection limit of 91.7 nM, as confirmed by differential pulse voltammetry (DPV) quantitative experiments. The selectivity, reproducibility, stability, and recovery of the as-prepared sensors were evaluated, particularly in aquaculture water samples, underscoring the practical applicability of the electrodes for furaltadone sensing. This innovative trimetallic electrode design opens avenues for advanced electrochemical sensors with enhanced performance characteristics.

A facile graft-repair strategy: Subsurface Na2Sx heterostructures in hard carbon anodes for high-capacity and ultrafast sodium-ion storage

Hard carbon (HC) anodes hold great promise for sodium-ion batteries (SIBs), yet they still suffer from insufficient rate capability and low initial coulombic efficiency (ICE). Herein, an innovative approach based on the synergistic graft-repair mechanism is proposed to create the multifunctional Na2Sx heterostructure within the subsurface of HC via a facile ball-milling and calcination method. This structure with specific disulfide bonds enlarges the carbon layer for fast ion transfer, offers extra S active sites to boost capacity, and catalytically reduces electrolytes to form an inorganic-dominated and thinner solid electrolyte interface (∼7.1 nm). The introduced Na+ ions compensate for the irreversible Na uptake at intrinsic defects and oxygen-containing groups. These effects are validated by GITT, EIS, Raman, and depth-profiling XPS measurements. The optimized hard carbon delivers an ultrahigh reversible capacity with superior ICE (514.8 mAh g−1 at 0.05 A g−1 with ICE of 84.1%) and excellent rate capability (87.5 mAh g−1 at 40 A g−1) simultaneously. DFT calculations reveal that the moderate S/Na ratio yields suitable adsorption energy, maintaining the balance of rate performance and ICE. The revealed mechanism of ion transport based on graft-repair effects contributes to boosting the key SIB performance indicators required for practical applications.

Femtosecond laser ablation (fs-LA) XPS – A novel XPS depth profiling technique for thin films, coatings and multi-layered structures

Sputter depth profiling has been employed for XPS/AESdepth profilingsincethe late 1960s. However, for many materials, ion beam induced damage distorts the chemical state information and chemical composition, limiting the value of the analysis. A novelmethodology is presented in which XPS depth profiles are generated using a 160 fs pulse length, 1030 nm peak wavelength femtosecond laser in place of the traditional ion gun. Femtosecond laser ablation (fs-LA) XPS depth profiles are compared with argon monatomic and cluster ion beam depth profilesfor different classes of materials, including ceramics, semiconductors, polymers and metals. In all cases, the XPS spectra recorded following femtosecond laser ablation are fully representative of the original chemical composition and chemical state, with no ablation induced damage. The technique is also shown to be very versatile with ablation rates of <20 nm per pulse being achieved for thin films but profiles to depths of >30 μm are also realisable in practical time scales.fs-LA XPS depth profiling promises to be a very exciting new methodology for the XPS community, complementing sputter depth profiling but avoiding the chemical damage induced by ion beams and offering valuable new depth profiling capabilities.

Precise stepwise recovery of platinum group metals from high-level liquid wastes based on SDB polymer-modified SiO2.

Accurate separation and efficient recovery of platinum group metals (PGMs, mainly Ru, Rh and Pd) from high level liquid waste (HLLW) is a good choice for clean production and sustainable development of nuclear energy. Herein a novel SDB polymer modified silica-based amine-functionalized composite (dNbpy/SiO2-P) was synthesized for the separation and recovery of PGMs. Laser particle size analysis and BET results clarified the regular spherical and highly interconnected mesoporous structure of dNbpy/SiO2-P which is critical for the separation of PGMs. The removal percent of PGMs were over 99% on the optimized conditions. In addition, dNbpy/SiO2-P showed excellent selectivity (SFPd/M > 3805, SFRu/M > 1705, SFRh/M > 336) and repeatability (≥5). Interestingly, based on the different adsorption and desorption kinetics of PGMs, a double-column strategy is designed to solve the challenge of separating and recovering PGMs from HLLW. The enrichment factors of Pd(II), Ru(III) and Rh(III) reached 36.7, 8.2, and 1.2. The adsorption of PGMs was coordination mechanism and required the involvement of NO3- to maintain charge balance. The specific distribution of elements within the adsorbents and the changes in valence state were analyzed using depth-profiling XPS. Both depth-profiling XPS results and slope analysis revealed that the complex of dNbpy and PGMs is a 1 : 1 coordination structure. Overall, this work fills the gap that PGMs cannot be effectively separated and enriched from HLLW.