Table of contents

The splitting of laser-induced plumes into the fast and slow components is usually explained by acceleration of ions by the ambipolar electric field. The kinetic simulations show that the splitting is observed even in neutral plumes due to the snow-plow effect. In plasma plumes, the simulations predict bimodal distributions of plasma emission intensity, where the slow maximum appears due to radiation absorption during the laser pulse, while the fast maximum emerges after the pulse at the plume edge. The snow-plow effect explains why the fast component is observed in a limited range of ambient pressure, exists during a limited time, and is characterized by larger degree of ionization.

Chemical mechanical polishing (CMP) is the most effective technique to obtain global and local planarization of metal and brittle surfaces. Conventionally, CMP slurries contain strong acids, alkalis, or hazardous chemicals, which easily cause widespread environmental pollution and are harmful to the operators. It is a challenge to develop a novel green CMP slurry with eco-friendly and non-toxic compositions. Some substances with special structures contain versatile functional groups and have unique physical and chemical properties, including excellent chelating ability, ionization activity, biocompatibility and biodegradability, which have attracted the interest of CMP processing techniques. Therefore, researchers have begun to explore CMP slurries composed of environmentally friendly compositions. This review discussed the latest developments in the field of green CMP of metals and brittle wafers. The research on green CMP slurries was summarized and the future of the field was discussed.

Sulfur hexafluoride (SF₆), one of the most potent greenhouse gases with a global warming potential of 23 500 and an atmospheric lifetime of 3200 years, has been widely used as an insulating gas. The search for eco-friendly gas insulating medium to replace SF₆ has been a hot topic in the power industry over the past 5 years. The performance evaluation of eco-friendly gas insulating medium concentrates on several dimensions including stability and decomposition characteristics. This review focuses on recent advances in knowledge about the decomposition characteristics of eco-friendly gas insulating medium. The basic theoretical and experimental methods, discharge decomposition, thermal stability and gas–solid interface interaction properties of several potential eco-friendly gas insulating medium are summarized. The existing problems and future research directions are also discussed.

Corrosion poses a significant challenge to many materials, from industrial structures to electrochemical catalysts. Nickel (Ni) is considered one of the most active metal catalysts for electrochemical water oxidation reaction in the alkaline environment. To gain more insight into corroded nickel electrodes in the water oxidation reaction, we employed operando ambient pressure x-ray photoelectron spectroscopy to detect the nickel/electrolyte interface under various potentials. To probe the influence of various halide anions on cycled Ni electrode/electrolyte interfaces undergoing the oxygen evolution reaction, we examined the surface changes in nickel electrodes after repeated electrochemical cycles in the presence of KOH mixed with KBr and KI under various potentials. As the applied potential became more anodic, we detected the formation of surface hydroxide and bromide when Br⁻ was present in the electrolyte, whereas in I⁻ -containing electrolytes, we found only hydroxides. The formation of oxidized Ni species was highly dependent on the type and concentration of halide ions. Br⁻ facilitated the formation of more oxidized Ni species than I⁻ did under the same concentration. In the presence of higher concentrations of potassium halide (100 mM) in the bulk electrolyte, metallic nickel could be completely oxidized at the most anodic potentials with surface hydroxide formation. This work reports the observation of cationic metal ions in the bulk electrolyte and describes in situ observation of degradation at the metal/electrolyte interface.

Ultrathin CdTe solar cell is a promising application of using integrated photovoltaics to act as architectural components and bifacial devices to promote the utilization of sunlight. In the preparation process of the ultrathin CdTe solar cells, the chemical solution etching process before back contact deposition has to be refrained due to the high risk of shunting. Therefore, an alternative strategy to get a clean CdTe surface is required. In this work, plasma etching treatment was conducted on sputtered ultrathin CdTe films to eliminate the residual oxides induced by CdCl₂ treatment. Furthermore, ultrathin bifacial CdTe solar cells with a structure of glass/FTO/SnO₂/CdS/CdTe (∼920 nm)/CuCl/ITO were fabricated to investigate the effect of plasma etching on the device performance. As a result, by employing plasma etching treatment, a bifacial device with a front illuminated efficiency of up to 9.93% and a rear illuminated efficiency of 2.41% was achieved. This work provides important indications for the performance optimization of ultrathin CdTe solar cells.

Clinical transplantation medicine currently faces a significant shortage of organ donors to supply the need of an increasingly aged population. Despite this, organs are still discarded due to graft stress induced by hypoxia or ischemia prior to procurement. Approaches to minimize donor organ discard include appropriate organ preservation and monitoring of organ function. Predominant organ preservation strategies involve hypothermia between 0 °C and 12 °C. In this study, we investigate the effect of temperature alone on tissue microstructural and biochemical parameters during cold preservation of mouse organs. To the best of our knowledge, this is the first study evaluating this cooling effect on multiple tissue parameters such as blood oxygenation, concentrations of blood, methemoglobin, water, lipid, and bile as well as scattering amplitude, Mie scattering power and fraction of Rayleigh scattering. These parameters were extracted by using diffuse reflectance spectroscopy spectral fitting at an extended wavelength range between 450 and 1590 nm and a Monte Carlo look-up table including a wide range of tissue optical properties compared to previous studies. Our findings can be used to understand biological processes undertaking cooling to propose new strategies involving optimized cold storage times and composition of organ preservation solutions for minimized cellular and tissue damage.

Antiferromagnets (AFs) have recently surged as a prominent material platform for next-generation spintronic devices. Here we focus on the dynamics of the domain walls in AFs in the presence of magnetoelasticity. Based on a macroscopic phenomenological model, we demonstrate that magnetoelasticity defines both the equilibrium magnetic structure and dynamical magnetic properties of easy-plane AFs in linear and nonlinear regimes. We employ our model to treat non-homogeneous magnetic textures, namely an AF in a multi-domain state. Calculations of the eigen-modes of collective spin excitations and of the domain walls themselves are reported, even considering different kinds of domains. We also compare the output of our model with experimental results, substantiating the empirical observation, and showing that domain walls majorly affect the optically driven ultrafast nonlinear spin dynamics. Our model and its potential developments can become a general platform to handle a wide set of key concepts and physical regimes pivotal for further bolstering the research area of spintronics.

Carbon monoxide flame band emission (CO + O → CO₂ + hν) in CO₂ microwave plasma is quantified by obtaining absolute calibrated emission spectra at various locations in the plasma afterglow while simultaneously measuring gas temperatures using rotational Raman scattering. Comparison of our results to literature reveals a contribution of O₂ Schumann–Runge UV emission at T > 1500 K. This UV component likely results from the collisional exchange of energy between CO₂(¹B) and O₂. Limiting further analysis to T < 1500 K, we demonstrate the utility of CO flame band emission by analyzing afterglows at different plasma conditions. We show that the highest energy efficiency for CO production coincides with an operating condition where very little heat has been lost to the environment prior to ∼3 cm downstream, while simultaneously, T ends up below the level required to effectively freeze in CO. This observation demonstrates that, in CO₂ plasma conversion, optimizing for energy efficiency does not require a sophisticated downstream cooling method.

The realization of ferromagnetism in d⁰ semiconductors is important for its applications in spintronics and instructive to the understanding of the magnetic behavior in dilute magnetic semiconductors (DMSs), but its origin is still not fully uncovered, due to the limitation of the density functional used in previous studies. Here, using more sophisticated hybrid functional (HSE06), we reexamine the cation-vacancy induced ferromagnetism in a series of Zn chalcogenides, ZnX (X = O, S, Se, Te), and compare it with previous theoretical studies. The HSE06 calculations show that the spontaneous magnetization of Zn vacancy (V_Zn) in ZnX is possible, except for ZnTe, due to the more delocalized nature of Te 5p orbitals than O 2p, S 3p and Se 4p orbitals. The ferromagnetic (FM) ground states can then be realized in these systems because the FM coupling between individual V_Zn could lower energy based on the band-coupling model. Moreover, the HSE06 calculations indicate that the FM coupling gradually increases from ZnO to ZnS and to ZnSe because of the enhanced coupling between the more and more extended defect wavefunctions. The result suggests that it may be more likely to achieve the room-temperature ferromagnetism in ZnS and ZnSe than ZnO, pointing out an alternative way to develop d⁰ DMSs. Experimental test of the theoretical predictions is called for.

As a typical sulfide bimetallic semiconductor material, AgInS₂ has been widely studied for its excellent photoelectrochemical properties. However, due to the large lattice mismatch, it is difficult to obtain AgInS₂ single phase nanocrystals by conventional reaction. Therefore, the ligand and pH were selected and adjusted for the preparation of AgInS₂ single phase nanocrystals. Adding organic molecules containing sulfhydryl groups as ligands could combine with metal ions to form covalent bonds, while OH⁻ could react with transition metal ions to form soluble metal hydroxides, which could protect metal ions from direct reaction with S²⁻. With the help of x-ray powder diffraction, AgInS₂ single phase nanocrystals were successfully prepared by hydrothermal reaction at 180 °C with L-cysteine (L-Cys) or glutathione as the ligand in an alkaline environment. Finally, it was determined that the AgInS₂ single phase nanocrystals obtained when the ligand was L-Cys and the reaction time was locked to 24 h had high catalytic activity as determined by a rhodamine B (RhB) removal experiment. In addition, AgInS₂/TiO₂ (AIS-TO) heterojunction photocatalysts were prepared by an in-situ hydrothermal method to improve the photocatalytic activity of TiO₂. Among them, the 5% AIS-TO sample showed the highest catalytic activity, and the degradation rate of RhB was 2.4 times that of TiO₂. It was also proved that electrons were transported by a Z-type mechanism in the AIS-TO heterojunction photocatalytic system. This work would provide a feasible scheme for the preparation of more sulfide bimetallic semiconductor single phase nanocrystals.

Imitation of tactile perception activities is crucial to the developments of advanced interactive neuromorphic platforms. However, it is a challenge to develop such a platform using a low-cost manufacturing process and with low-power consumption. Here, a low-cost, highly sensitive flexible tactile perceptual interactive platform is proposed, composed of polydimethylsiloxane-based flexible tactile sensors and a flexible chitosan-gated oxide neuromorphic transistor. The flexible tactile sensors made with alkaline textured silicon molds are used as skin receptors that convert pressure signals into electrical signals. The flexible indium-tin-oxide neuromorphic transistor fabricated with a single-step mask process can process electrical signals from the tactile sensor. The neuromorphic transistor exhibits good electrical performances against bending stress. Basic synaptic functions, including excitatory postsynaptic current and paired-pulse facilitation, are demonstrated. Thus, the tactile perceptual platform successfully imitates tactile perception activities in our body. Moreover, when loading a low pressure of ∼1.4 Pa, the flexible tactile perceptual platform demonstrates a high S/N value and sensitivity of ∼4.93 and ∼6.9 dB, respectively. As a proof-of-concept, recognition of Braille codes is demonstrated on the platform by integrating two tactile sensors. The results show the widespread potential of the present interactive platform in wearable flexible cognitive electronics. It has potential applications, including but not limited to human-computer interaction technology and intelligent robot technology.

2D-layered nanostructure-based advanced coatings are the most recent advancement in the field of advanced oxidation processes. Effective charge separation is one of the key parameters in enhancing the photodegradation ability of 2D-layered nanostructures. We report the cost-effective hydrothermal synthesis of MoS₂ thin films on conductive ITO substrates with tunable morphology. Scanning electron microscopy studies manifested the modulation in the morphology of MoS₂ thin films and confirmed the presence of spherical, thread, and sheet-like nanostructures under the evolution of precursor concentration. UV–visible absorption spectroscopy revealed the modulation in the optical absorption and effective bandgap narrowing with the changes in the surface morphology. The estimated bandgap value of MoS₂ thin film samples varies from 1.82 to 1.69 eV. PL spectroscopy and electrochemical studies display the morphology-dependent charge separation behavior and confirm that the lowest recombination rate is attained by thread-like MoS₂ nanostructures. Raman spectroscopy and x-ray photoelectron spectroscopy confirms the 2H phase of MoS₂ thin films. MoS₂ thin films with thread-like structures are found to be the most efficient for sunlight-induced photodegradation activity as compared to other MoS₂ samples. Thread-like MoS₂ structures containing MoS₂ thin film with the highest charge transport properties decompose 85% of 5 µM methylene blue molecules and 90.4% of 5 µM rhodamine B molecule solution in 40 min and 80 min, respectively, under natural sunlight. The prominent charge separation effects on the enhanced photodegradation capabilities of MoS₂ thin films due to distinct variations in morphology, which have not been reported till now, are explored precisely.

In this study, we investigate a Schottky junction based on solution-processed multilayered graphene (MLG). We present a rectifying device obtained with a straightforward approach, that is drop-casting a few microliters of MLG solution simultaneously onto Si, Si–SiO₂ and Si–SiO₂–Cr/Au surface. Monitoring the modulation of Schottky barrier height while operating in reverse bias, we study the behavior of such prepared MLG-Si/junction (MLG-Si/J) when exposed to oxidizing atmosphere, especially to nitrogen oxide (NO₂). We finally compare the sensing behavior of MLG-Si/J at 1 ppm of NO₂ with that of a chemiresistor-based on similarly prepared solution-processed MLG. Our study thus opens the path towards low-cost highly sensitive graphene-based heterojunctions advantageously fabricated without any complexity in the technological process.

The sputtering yield amplification (SYA) is a phenomenon based on doping a sputtering target with atoms of higher atomic mass. This doping changes the depth and the direction of the collision cascade in the target surface promoting a higher ejection of target atoms. In this work, we present a new way of generating the SYA phenomenon without the need of expensive and complex deposition systems. This was accomplished by increasing the working pressure and adding small pieces of W, as dopant element, on the racetrack of a Si target. The physical phenomena necessary to promote the SYA, for our experimental parameters, were analysed in two different deposition chambers and two sizes of sputtering targets. Based on the collisions in the gas phase, a calculation on the number of W atoms returning to the racetrack area was made, considering the number of atoms deposited on the thin films, to determine their effect on the cascade of collisions. In addition, calculations with the simulation of metal transport code were developed to determine the location on the racetrack zone the returning atoms were redeposited. By using reference samples placed on the racetrack of the Si target, we found that the percentage of SYA depends on the number of dopant atoms redeposited as well as the depth distribution these atoms had in the racetrack surface.

Aircraft icing poses a major threat to flight safety, and plasma anti-/de-icing becomes a new approach in the field of anti-/de-icing in recent years. In this paper, a surface dielectric barrier discharge (SDBD) plasma actuator with SiC hydrophobic coating-based quartz glass is designed and fabricated. Actuated by nanosecond high voltage pulse, its de-icing characteristics are explored experimentally and compared with the uncoated actuator. The results show that under the same actuation parameters, the discharge current peaks and the power consumption of SDBD are reduced with hydrophobic coating, which can be further verified by surface temperature distribution. Intensified CCD camera images indicate that after the adding of SiC coating, the discharge propagation process of SDBD does not change significantly. For both coated/uncoated actuators, two discharges occur during the voltage rise and fall phases respectively, while no discharge occurs during the pulse width phase, but the coated actuator exhibits slightly longer plasma dissipation time. Static de-icing results reveal that the instantaneous energy utilization rate of the coated actuator at 60 s of de-icing process is about 54% higher than that of the uncoated actuator, which can be explained by two aspects: one is to weaken the adverse effects of melted water on the discharge plasma to a maximum extent, and the other is to reduce the contact area between the ice accretion and the hydrophobic surface.

In this work, we propose a Y-shaped nanojunction consisting of zigzag silicene nanoribbons (ZSNRs), and study the charge/spin transport based on a tight-binding approach, Landauer formalism and non-equilibrium Green's function method. The topological states with various edge modes, such as quantum spin Hall insulator, quantum Hall insulator and band insulator, can all be engineered by the electric field and photoirradiation in ZSNRs. Through tuning the edge states of the two output terminals, three types of charge/spin router can be achieved in the present nanojunction. The first is a charge current switcher, which switches the charge current from one output terminal to the other. The second is a spin current router, which shunts the spin-up and spin-down current into different output terminals. The last is a spin filter, which filters the spin-polarized current into a specific output terminal. The proposed Y-shaped nanojunction may have potential applications in electronic and spintronic nanodevices in the future.

The synergistic effect of nuclear (S_n) and electronic (S_e) energy loss observed in some ABO₃ perovskites has attracted considerable attention due to the real possibility to modify various near-surface properties, such as the electronic and optical properties, by patterning ion tracks in the defective near-surface regions. In this study, we show that low-energy ion-induced disordering in conjunction with ionizing ion irradiation (18 MeV Si, 21 MeV Ni and 91.6 MeV Xe) is a promising approach for tailoring ion tracks in the near-surface of defective KTaO₃. Experimental characterization and computer simulations reveal that the size of these latent ion tracks increases with S_e and level of pre-existing damage. These results further reveal that the threshold S_e value (S_e^th) for track creation increases with decreasing pre-damage level. The values of S_e^th increase from 5.02 keV nm⁻¹, for a pre-existing fractional disorder of 0.53 in KTaO₃, to 10.81 keV nm⁻¹ for pristine KTaO₃. Above these thresholds, amorphous latent tracks are produced due local melting and rapid quenching. Below a disorder fraction of 0.08 and S_e ⩽ 6.68 keV nm⁻¹, the synergistic effect is not active, and damage accumulation is suppressed due to a competing ionization-induced damage annealing process. These results indicate that, depending on S_e and the amount of pre-existing damage, highly ionizing ions can either enhance or suppress damage accumulation in KTaO₃, thus providing a pathway to tailoring defects states. Comprehending the conflicting roles of highly ionizing ions in defective ABO₃ oxides is vital for understanding and predictive modeling of ion-solid interactions in complex oxides, as well as for achieving control over ion track size in the near-surface of defective KTaO₃.

A dual-band perfect optical absorber based on the graphene/hexagonal boron nitride van der Waals hybrid structure is proposed in the mid-infrared band. According to the results of the finite-difference time-domain method, dual-band perfect absorption peaks are formed at 7103 nm and 7499 nm, respectively, which also can be separately shifted in a wide wavelength region by varying some key structural parameters. Moreover, our proposed structure manifests polarization sensitivity and can maintain good optical absorption performance for wide angles of incidence.

In this paper, a facile method was introduced to fabricate fine conductive patterns by low-temperature selective laser sintering of Cu nanoparticles. By virtue of a nanosecond-pulsed ultraviolet laser source, fine circuits with a thickness of ∼8 μm and a conductivity of 3–6.5 × 10⁶ S m⁻¹ was successfully fabricated from Cu nanoparticle paste with a high metal content >80 wt.% on a flexible substrate at a wide scan rate range of 5–500 mm s⁻¹. The sintered circuits exhibited a special sandwich morphology, with fully melted features in the centre and thermally sintered neck-connected features on the edges. A twofold linear relationship between the width of thermally sintered region and the reciprocal of the laser scan rate was revealed, indicating a heat dissipation mode transition from metal layer dominated dissipation to substrate dominated dissipation with the decrease of the laser scan rate. Finite element simulations were carried out to study the evolutions of temperature field and heat dissipation with changing laser scan rate and power, and the results fitted well with experimental results. On this basis, a relational expression was further proposed to determine the optimal processing window for laser sintering of metal nanoparticle layers. Our method extends the producible thickness and improves the fabrication efficiency of laser-printed circuits with desirable conductivity. The findings of this study can provide a guidance for understanding and controlling the sintering and heat transfer process of printing methods with similar materials and techniques.

We show that an optimized growth of magnetic layer/non-magnetic layer stacks allows for the improvement of the spin-to-charge conversion efficiency. From the analysis of the voltage signal generated in spin pumping experiments due to the inverse spin Hall effect (ISHE) on Y₃Fe₅O₁₂ (YIG)/Bi stacks, we have determined values for the spin Hall angle and the spin-diffusion length in Bi of 0.0068(8) and 17.8(9) nm, respectively. Based on these results, we have also studied the influence of aging on the spin-to-charge conversion efficiency by performing spin pumping experiments on YIG/Bi stacks after exposing the samples to ambient conditions for several days and up to 150 days. We have found that in YIG/Bi samples with Bi thicknesses around or below the spin-diffusion length, the ISHE voltage signal is still above 80% of its initial value after 100 days.

DNA complexes formed with graphene oxide (GO) and riboflavin (RF) have multiple interesting characteristics and unique features owing to specific properties of the DNA. Herein, we develop a fabrication method for GO- and RF-embedded DNA and cetyltrimethyl ammonium chloride-modified DNA (DNA-CTMA) thin films with varying concentrations of GO ([GO]) and fixed [RF] content that uses a simple drop-casting process. The properties of the fabricated thin films were investigated to understand (a) the chemical interactions between GO, RF and DNA (DNA-CTMA) molecules using Fourier transform infrared (FTIR) and Raman, (b) the variation in chemical features and spin states using x-ray photoelectron spectroscopy (XPS), (c) the characteristic wavelengths using UV–Vis absorption, (d) electron transfer between energy states using photoluminescence (PL), and (e) electrical conduction using current measurements. The FTIR, Raman, XPS, and UV–Vis spectra of the GO- and RF-embedded DNA and DNA-CTMA thin films exhibit noticeable changes in peak intensity and experience peak shifts with varying [GO] content. The PL spectra of the thin films show a quenching phenomenon with increasing [GO] content due to decreases in recombination efficiency. The increases in current observed with the addition of GO to the DNA and DNA-CTMA thin films can be attributed to the conducting nature of GO. The optical and electrical properties of the GO- and RF-embedded DNA and DNA-CTMA thin films can easily be tuned by the adjusting the [GO] content. Consequently, our thin films show great promise for application in various types of bio-sensors and bio-photonic devices.

Direct bandgap Al_xIn_1−xP alloys offer an advantage for red and amber light-emitting diode (LED) operation over conventional (Al_xGa_1−x)_0.5In_0.5P alloys due to their higher direct bandgap energies. However, the coupled variation of its bandgap energy and lattice constant present challenges for fabricating quantum well (QW)-based LED devices on GaAs substrates. Here, we present the design and demonstration of Al_xIn_1−xP red and amber LEDs incorporating multiple QW structures. Strain balancing the QW layers and manipulating the Al_xIn_1−xP conduction band energy through control of spontaneous atomic ordering produce structures with higher energetic barriers to electron leakage compared to (Al_xGa_1−x)_0.5In_0.5P LEDs. We also discuss future improvements that must be made to realize high efficiency red and amber LEDs.

A comprehensive study of polycrystalline samples of dual-doped Zn_1-xAl_x/2In_x/2O (x = 0.02, 0.04 and 0.06), Zn_1-xGa_x/2In_x/2O (x = 0.02, 0.04 and 0.06) and triple-doped Zn_1-xAl_x/3Ga_x/3In_x/3O (x = 0.03, 0.06 and 0.09) systems synthesized through the solid-state reaction is presented in the light of structure-property correlations. Rietveld refinement of powder XRD data confirmed the presence of impurity phases on highly doped compositions (x ⩾ 0.4) for Zn_1-xAl_x/2In_x/2O and Zn_1-xAl_x/3Ga_x/3In_x/3O systems and scanning electron microscopy microstructural analyses showed the presence of elongated morphological feature in all the compositions associated with ZnO homologue systems. Raman studies confirmed presence of both impurity phase and ZnO homologue phase. No visible traces of the presence of impurity phase in Zn_1−xGa_x/2In_x/2O causes relatively low electrical resistivity (ρ ∼ 4–5 mΩ cm) in this composition. On the other hand, Zn_1−xAl_x/2In_x/2O and Zn_1-xAl_x/3Ga_x/3In_x/3O systems had electrical resistivity in the range of 10–20 mΩ cm that is one order of magnitude higher than Zn_1−xGa_x/2In_x/2O system. This is arising from the presence of the insulating secondary phases in Zn_1−xAl_x/2In_x/2O and Zn_1−xAl_x/3Ga_x/3In_x/3O systems. Contrary to electrical resistivity, thermal conductivity of Zn_1−xAl_x/2In_x/2O and Zn_1-xAl_x/3Ga_x/3In_x/3O (6–8 Wm⁻¹K⁻¹) systems is one order of magnitude lesser than Zn_1-xGa_x/2In_x/2O (12 Wm⁻¹K⁻¹) systems. The impurity phase present causes phonon–phonon and phonon-interface scattering in Zn_1−xAl_x/2In_x/2O and Zn_1-xAl_x/3Ga_x/3In_x/3O systems which in turn stands beneficial in reducing the total thermal conductivities of the system. Therefore, chemical doping acts as an important parameter for controlling the interdependent electrical and thermal transport properties in ZnO system resulting in relatively superior thermoelectric (TE) performance in Zn_0.94Ga_0.03In_0.03O system. Further, lowering of electrical resistivity and thermal conductivity through doping in Zn_0.94Ga_0.03In_0.03O system causes four times improvement of TE performance in comparison with un-doped ZnO.