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Ultraviolet (UV) photodetectors have gained much attention due to their numerous important applications ranging from environmental monitoring to space communication. To date, most p‐NiO/n‐Si heterojunction photodetectors (HPDs) exhibit poor UV responsivity and slow response. This is mainly due to a small valence band offset (ΔEV) at the NiO/Si interface and a high density of dangling bonds at the silicon surface. Herein, an UV HPD consisting of NiO/Al2O3/n‐Si is fabricated using magnetron sputtering technique. The HPD has a large rectification ratio of 2.4 × 105. It also exhibits excellent UV responsivity (R) of 15.8 A/W at −5 V and and detectivity (D*) of 1.14 × 1013 Jones at −4 V, respectively. The excellent performance of the HPD can be attributed to the defect passivation at the interfaces of the heterojunction and the efficient separation of photogenerated carriers by the Al2O3 nanolayer. The external quantum efficiency (EQE) of the HPD as high as 5.4 × 103%, hence implying a large optical gain due to carrier proliferation resulting from impact ionization. Furthermore, the ultrafast response speed with a rise time of 80 µs and a decay time of 184 µs are obtained. [ABSTRACT FROM AUTHOR]

This study employs a regression discontinuity design to systematically examine the governance effect of bike-sharing on urban traffic congestion, utilizing city-level data from Beijing, Shanghai, and Wuhan in China between 2016 and 2018. We discover that the introduction of bike-sharing services significantly mitigates traffic congestion in the short term. Our heterogeneity analysis reveals that the initial deployment of shared bicycles primarily alleviates urban congestion, while additional deployments have a limited impact. Further, mechanism test analysis demonstrates that bike-sharing leads to increased metro ridership in these cities, effectively explaining the reduction in road congestion. This study underscores the pivotal role of bike-sharing services in easing urban traffic congestion and provides vital policy insights for enhancing traffic management strategies in Chinese cities. [ABSTRACT FROM AUTHOR]

In this study, we examine the green innovation effect of investor preference on Chinese listed companies from 2008 to 2020. We observe that investors with environmental protection preferences can significantly increase enterprise green innovation. The baseline conclusions remain robust after we conduct multiple sensitivity tests, such as establishing a shift-share instrumental variable (Bartik IV), using the Heckman's two-step method, changing the regression methods, substituting the core variables, adopting the DID method, and considering investors' ownership. Our analysis shows that the green innovation effect of environmental investors is highly pronounced in companies with a high level of indebtedness and low managerial ability. We verify that environmental investors can improve the green innovation level of enterprises through two potential mechanisms, namely, easing corporate financing constraints and incentivising managers. In addition, political and public attention can strengthen the positive relationship between environmental investors and green innovation. [ABSTRACT FROM AUTHOR]

Natural birnessite‐like minerals are commonly enriched in various transition metals, such as iron (Fe). Though the fates of metals associated with birnessites during mineral transformation in aqueous conditions are thoroughly studied, we determined the Fe behaviors in Fe‐doped hexagonal turbostratic birnessites during mineral evolution in dry state at room temperature for 8 years and upon thermal treatments at temperatures ranging from 323 to 773 K, covering the temperatures in extreme environments such as wildfires. These Fe‐containing birnessites were very stable upon aging in the dry state. Upon thermal treatment, the birnessite sample with a small amount of Fe (≤2.8 wt.%) was transformed to cryptomelane at 573–673 K, while for the sample with ∼5.6 wt.% Fe, the transformation temperature increased to 673–773 K. This indicated that Fe adsorption enhanced the birnessite's thermal stability. Further, there was a linear relationship between the fraction of edge‐sharing Fe–Fe(Mn) pairs and temperature over 298–473 K. This implied the migration of Fe adsorbed on vacancies into birnessite layers and/or increased edge‐sharing of Fe around vacancies from adjacent layers during heating. The average manganese (Mn) valences in the Mn dioxides were almost constant with the increase in temperature when the layer structure was kept, but greatly increased when the tectomanganate was formed. These results provided deep insights into the mechanisms of Mn dioxide mineral transformation and the fates of associated metals under extreme conditions in terrestrial environments. Core Ideas: Birnessite structure remained stable during 8 years of dry aging.Iron (Fe) adsorption enhanced birnessite thermal stability.Heating at 298–473 K promoted the formation of edge‐sharing Fe–Fe(Mn) pairs in the birnessite structure.Fe‐doped birnessite was converted to cryptomelane after heating at 673–773 K.Average manganese valences were almost constant in birnessites but were greatly increased for cryptomelanes. [ABSTRACT FROM AUTHOR]

Lead sulfide colloidal quantum dots (PbS CQDs) are promising optoelectronic materials due to their unique properties, such as tunable band gap and strong absorption, which are of immense interest for application in photodetectors and solar cells. However, the tunable band gap of PbS CQDs would only cover visible short-wave infrared; the ability to detect longer wavelengths, such as mid- and long-wave infrared, is limited because they are restricted by the band gap of the bulk material. In this paper, a novel photodetector based on the synergistic effect of PbS CQDs and bismuth telluride (Bi2Te3) was developed for the detection of a mid-wave infrared band at room temperature. The device demonstrated good performance in the visible-near infrared band (i.e., between 660 and 850 nm) with detectivity of 1.6 × 1010 Jones at room temperature. It also exhibited photoelectric response in the mid-wave infrared band (i.e., between 4.6 and 5.1 μm). The facile fabrication process and excellent performance (with a response of up to 5.1 μm) of the hybrid Bi2Te3/PbS CQDS photodetector are highly attractive for many important applications that require high sensitivity and broadband light detection. [ABSTRACT FROM AUTHOR]

Quantum dots have found significant applications in photoelectric detectors due to their unique electronic and optical properties, such as tunable bandgap. Recently, colloidal quantum dots (CQDs) have attracted much interest because of the ease of controlling the dot size and low production cost. In this paper, a high-performance ZnO/PbS heterojunction photodetector was fabricated by spin-coating PbS CQDs onto the surface of a hydrothermally grown vertical array of ZnO nanowires (NWs) on an indium tin oxide (ITO) substrate. Under 940 nm near-infrared light illumination, the device demonstrated a responsivity and detectivity of ~3.9 × 104 A/W and ~9.4 × 1013 Jones, respectively. The excellent performances and low cost of this nanocomposite-based photodetector show that it has the potential for widespread applications ranging from medical diagnosis to environmental monitoring. [ABSTRACT FROM AUTHOR]

Heteroatom doped atomically dispersed Fe1‐NC catalysts have been found to show excellent activity toward oxygen reduction reaction (ORR). However, the origin of the enhanced activity is still controversial because the structure‐function relationship governing the enhancement remains elusive. Herein, sulfur(S)‐doped Fe1‐NC catalyst was obtained as a model, which displays a superior activity for ORR towards the traditional Fe‐NC materials. 57Fe Mössbauer spectroscopy and electron paramagnetic resonance spectroscopy revealed that incorporation of S in the second coordination sphere of Fe1‐NC can induce the transition of spin polarization configuration. Operando 57Fe Mössbauer spectra definitively identified the low spin single‐Fe3+‐atom of C‐FeN4‐S moiety as the active site for ORR. Moreover, DFT calculations unveiled that lower spin state of the Fe center after the S doping promotes OH* desorption process. This work elucidates the underlying mechanisms towards S doping for enhancing ORR activity, and paves a way to investigate the function of broader heteroatom doped Fe1‐NC catalysts to offer a general guideline for spin‐state‐determined ORR. [ABSTRACT FROM AUTHOR]

Rationale: Continuously downscaling integrated circuit devices requires fabrication of shallower p‐n junctions. The ion implantation approach at low energy is subject to low beam current due to the Coulomb repulsion. To overcome this problem cluster ions can be used for implantation. In comparison with single ions, cluster ions possess lower energy per atom and reduced Coulomb repulsion resulting in high equivalent current. Methods: In this study to carry out low‐energy implantation into single crystalline silicon and 4H‐SiC samples we employ Aln− (n = 1–5) clusters with energy in the range of 5–20 keV. The Al clusters are obtained by Cs sputtering of Al rod. Time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS; IONTOF TOF.SIMS‐5) is used to study aluminum and oxygen sputter depth profiles for different cluster sizes and implantation energies before and after annealing treatment. Results: A distinguishable effect of the energy per atom in the cluster on reduction of the projected range Rp is revealed. The lowest Rp of 3 ± 1 nm has been achieved in SiC samples at the energy per atom of 1.66 keV. After annealing of Si samples, a considerable change in the Al profiles due to redistribution of Al atoms during motion of the front of recrystallization is observed. The influence of the number of atoms in the cluster at the same energy per atom within the experimental uncertainty is not observed. Conclusions: The transient effects of the sputtering by the primary ion beam distort the shape of the Al profiles in Si samples. In the case of SiC, due to its relatively lower surface chemical activity, more informative TOF‐SIMS depth profiling of the shallow cluster implantation is feasible. [ABSTRACT FROM AUTHOR]

We have developed a solid electrolyte ion source (SEIS) with CsAg 4 Br 2.68 I 2.32 film deposited on a silver tip. In the paper, Ag+ ion emission was significantly enhanced and the ion current of 1.6 μA was obtained at 168 °C temperature and 20 kV accelerating voltage. I-T and I-U characteristics were well described by the field evaporation (FEV) model, and the surface potential barrier was estimated to be 0.19 eV. Experimental investigations of the Ag+ ion emission mechanisms revealed that the solid electrolyte film plays an important role of ion-transport system, and the emitted Ag+ ions were compensated by the ions diffusing from the silver reservoir (Ag-tip). The developed SEIS was exploited for the synthesis of Ag nanoparticles on Si surface. The average size of these nanoparticles was estimated 15.5 ± 0.3 nm, and the projected range R p of the low-energy high-dose Ag+ ions implanted Si sample was found to be less than 5 nm using TOF-SIMS depth profiling. The future application of SEISs in ion propulsion systems of miniature spacecraft with limited on-board payloads was discussed, and the thrust was estimated within μN range. • Ion emitter with superionic conductor CsAg 4 Br 2.68 I 2.32 film was fabricated. • Intense Ag+ ion beams were obtained. • Characteristics and mechanisms of Ag+ ion-beam generation were established. • Synthesis of Ag nanoparticles was achieved via Ag+ ion beam from the emitter. [ABSTRACT FROM AUTHOR]

Highlights • A unique velocity mode helped to distinguish the sublattices (tetrahedral A-site and octahedral B-site) in greigite. • The discrepancy of dynamics of A and B sub-lattices in Fe 3 S 4 was revealed by 57Fe Mӧssbauer spectroscopy. • Debye temperature θ D were estimated: 805 ± 10 K and 760 ± 10 K for tetrahedral and octahedral sites, respectively. • The Lamb–Mӧssbauer factor ratio f B / f A was found to be 0.98 at room temperature. Abstract 57Fe Mӧssbauer spectroscopy studies on chemically synthesized greigite Fe 3 S 4 have been conducted with a unique velocity mode, known as constant velocity with slope, which allows detection of subtle changes and in-depth details of sextets in the spectra. Accurate determination of the overlapped sub-spectra corresponding to tetrahedral Fe3+ (A) and octahedral Fe2.5+ (B) sub-lattices has been made based on the special velocity mode. Estimation of Debye temperature θ D from the temperature dependent central shift (CS) values gives the values: 805 ± 10 K and 760 ± 10 K for A- and B-sites, respectively. The discrepancy of two θ D values reveals different lattice vibration between A- and B-sites. The Lamb-Mӧssbauer factor ratio f B / f A is found to be 0.98 at room temperature. The different low-temperature behaviors of hyperfine magnetic field for tetrahedral A- and octahedral B-sites are observed. [ABSTRACT FROM AUTHOR]

A novel ion-extraction method named side extraction, i.e., extracting ions from the direction perpendicular to that of plasma expansion, is proposed in this paper, which can be used to filter ions or macro-particles for vacuum arc ion sources. Particle-in-cell simulations were performed to study filtering effects of side extraction on ions with different mass, different charges, and different initial kinetic energies. The results indicate that side extraction can separate ions by their charge states or initial kinetic energies and the extracting efficiency for different ion species is identical. Influences of extraction voltages, extraction interval, and the aspect ratio of the extraction aperture on ion filtering effects were also studied, which suggests that lower extraction voltages and longer extraction interval are beneficial for ion filtering and a high-aspect-ratio aperture contributes to the increase in the ratio of lighter ions in extracted beams. A theoretical analysis on the deflected distance of beams in the y direction was made and shows good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

Ion beam technology has shown itself worth to be an efficient method to produce nanoparticles embedded in dielectrics for photoelectronic devices. However, direct ion-beam deposition of nanoparticles (NPs) on the surface of dielectrics is rarely reported because the conventional metal ion source runs into difficulties to generate low energy (<10 keV) ion-beams. Herein, Ag NPs are directly deposited on the surface of Si substrates using the recently developed solid electrolyte ion source (SEIS), which possesses advantages of compactness, simple working conditions, and ability of emitting ion-beam at an energy of few keV. The composition, morphology and size of the synthesized Ag NPs are studied. Precise control of the NPs size including in-plane diameter and height is achieved by a modulation of the ion implantation dose. Localized maskless deposition of metal films on semiconductor surface is also expected using the SEIS device. • A direct ion-beam deposition technology based on solid electrolyte was produced. • Spherical Ag NPs was obtained and randomly distributed on the entire Si surface. • The Ag NPs size including in-plane diameter and height were modulated by ion dose. [ABSTRACT FROM AUTHOR]

To develop the hard and self-lubricating coatings applied for the industrial dry-cutting and die-casting machining tool fields, a series of MoTiAlN/MoN/Mo multilayered coatings were deposited on Si substrates under low substrate rotation by cathodic multi-arc ion plating. XRD, SEM, TEM, RBS, nanoindentation, and tribology tester were used to monitor the phase structure, morphology, component, nanohardness, and friction coefficient of the coatings. It was found that the coatings deposited at various substrate rotations comprised paramount cubic B1 structure TiAlN and Mo2N phases. The micrographs confirmed that the mean modulation period and total physical thickness of multilayered TiAlN/Mo2N coatings with a sharp interface fabricated at 2 revolutions per minute (rpm) were 26 nm and 1.15 μm. The mean nanohardness and friction coefficient were ca. 30 GPa and 0.4, respectively. RBS results along with the SIMNRA code allowed to estimate the total atomic concentrations and the physical thickness of individual sublayer as well as the modulation period of multilayered coatings, which demonstrated an efficiency of this approach for characterization of nano-multilayered structures. [ABSTRACT FROM AUTHOR]

We present a study on structure and ion emission behavior of copper ion-conducting solid electrolyte Rb 4 Cu 16 I 7 Cl 13 prepared via mechano-chemical ball milling. The powder samples with varying milling time and rotation rate was studied. The room temperature ionic conductivity of Rb 4 Cu 16 I 7 Cl 13 was approximately with σ rt ∼ 0.213 S/cm. The SEM morphology of this solid electrolyte was studied, and the larger particle sizes was estimated to be 1.3 μm. The thermal property was examined by differential scanning calorimetry, revealing a melting temperature of 229.7 °C. In addition, the ability to generate Cu+ ion beams was also tested, and an ion current of 0.82 μA was obtained at 197 °C and 20 kV. It was observed that copper ions increase significantly with temperature and acceleration voltage. There is a good linear correlation between log(current) and the square root of the voltage, indicating that the emission current of copper ion from the tip of solid electrolyte abides by the Schottky model. A silicon sample was irradiated by the ion beam and copper nanoparticle were detected on the surface. • Solid electrolyte Rb 4 Cu 16 I 7 Cl 13 was synthesized by high-energy ball milling. • Ion emitter with superionic conductor Rb 4 Cu 16 I 7 Cl 13 film was fabricated. • The ion emission technique using the sharp Cu + conductive solid electrolyte film is presented. • Characteristics and mechanism of Cu + ion-beam generation were studied. • Synthesis of Cu nanoparticles was achieved via Cu + ion beam from the emitter. [ABSTRACT FROM AUTHOR]

Ar 1000 cluster ion beam was used to fabricate irregular structures of a micrometer scale on the surface of pressed Si powder of 60 nm nanoparticles (NPs). The average density of the target material played an important role in the surface features formation. The samples with lower average density, i.e. with larger distance between adjacent NPs demonstrated more developed surface morphology, which implied an importance of the degree of freedom of NP and its beam induced mobility in formation of the surface features. At higher average density a process of particle erosion was accompanied by the debris formation, which filled the gaps between the NPs, blocked the particle mobility, and, eventually, resulted in conventional smoothing effect. • Ar cluster beam is used to fabricate structures on the surface of pressed Si powder. • Density of the target plays an important role in the surface features formation. • At lower density well developed surface features of a micron size are formed. • At higher density conventional surface smoothing effect is observed. [ABSTRACT FROM AUTHOR]

Ar 2900 clusters with energy in the range of 10.4–69 keV were used to bombard the surface of pressed Si nanopowder targets. High nonmonotonic sputtering yield is observed within the energy range of 10.4–34.5 keV, which is considered as enhanced by the finite size effect of the target particles. The cluster bombardment results in the sputtering of Si nanoparticles with a mean size of ca. 12 nm. The number of the sputtered nanoparticles is correlated with the sputtering yield within the energy range of 10.4–34.5 keV. Hence, their formation is associated with the finite size effect. Scanning electron microscopy revealed the formation of debris on the target surface starting at the cluster energy of 15.3 keV, which results in reducing the finite size effect and consequently the sputtering yield. Individual impacts of the argon clusters are observed as craters of 3–6 nm in diameter on the Si particles surface. The crater formation is considered to be responsible for the sputtering at the cluster energy in the range of 15.3–69 keV. • Cluster ion bombardment of pressed Si nanopowder targets is studied. • High nonmonotonic sputtering yield of the silicon nanopowder is observed. • The sputtering is considered as enhanced by the finite size effect. • The debris formation during cluster bombardment results in the smoothing effect. • Particles sputtered by the cluster bombardment from the target are studied. [ABSTRACT FROM AUTHOR]

Functional nanomaterials offer an attractive strategy to mimic the catalysis of natural enzymes, which are collectively called nanozymes. Although the development of nanozymes shows a trend of diversification of materials with enzyme-like activity, most nanozymes have been discovered via trial-and-error methods, largely due to the lack of predictive descriptors. To fill this gap, this work identified e g occupancy as an effective descriptor for spinel oxides with peroxidase-like activity and successfully predicted that the e g value of spinel oxide nanozymes with the highest activity is close to 0.6. The LiCo 2 O 4 with the highest activity, which is finally predicted, has achieved more than an order of magnitude improvement in activity. Density functional theory provides a rationale for the reaction path. This work contributes to the rational design of high performance nanozymes by using activity descriptors and provides a methodology to identify other descriptors for nanozymes.

Oxygen evolution reaction (OER) is an obstacle to the electrocatalytic water splitting due to its unique four-proton-and-electron-transfer reaction process. Many methods, such as engineering heterostructure and introducing oxygen vacancy, have been used to improve the catalytic performance of electrocatalysts for OER. Herein, the above two kinds of regulation are simultaneously realized in a catalyst by using unique ion irradiation technology. A nanosheet structured NiO/NiFe 2 O 4 heterostructure with rich oxygen vacancies converted from nickel-iron layered double hydroxides by Ar + ions irradiation shows significant enhancement in both OER and hydrogen evolution reaction performance. Density functional theory (DFT) calculations reveal that the construction of NiO/NiFe 2 O 4 can optimize the free energy of O * to OOH * process during OER reaction. The oxygen vacancy-rich NiO/NiFe 2 O 4 nanosheets have an overpotential of 279 mV at 10 mA cm -2 and a low Tafel slope of 42 mV dec -1 . Moreover, this NiO/NiFe 2 O 4 electrode shows an excellent long-term stability at 100 mA cm -2 for 450 h. The synergetic effects between NiO and NiFe 2 O 4 make NiO/NiFe 2 O 4 heterostructure have high conductivity and fast charge transfer, abundant active sites, and high catalytic reactivity, contributing to its excellent performance., (© 2021 Wiley-VCH GmbH.)

In the present study Ar + cluster ions accelerated by voltages in the range of 5-10 kV are used to irradiate single crystal ZnO substrates and nanorods to fabricate self-assembled surface nanoripple arrays. The ripple formation is observed when the incidence angle of the cluster beam is in the range of 30-70°. The influence of incidence angle, accelerating voltage, and fluence on the ripple formation is studied. Wavelength and height of the nanoripples increase with increasing accelerating voltage and fluence for both targets. The nanoripples formed on the flat substrates remind of aeolian sand ripples. The ripples formed at high ion fluences on the nanorod facets resemble well-ordered parallel steps or ribs. The more ordered ripple formation on nanorods can be associated with the confinement of the nanorod facets in comparison with the quasi-infinite surface of the flat substrates., (Copyright © 2020, Zeng et al.; licensee Beilstein-Institut.)

Ternary oxide Zn 2 GeO 4 with a wide bandgap of 4.84 eV, as a candidate for fourth generation semiconductors, has attracted a great deal of attention for deep ultraviolet (DUV) photodetector applications, because it is expected to be blind to the UV-A/B band (290-400 nm) and only responsive to the UV-C band (200-290 nm). Here, we report on the synthesis of Zn 2 GeO 4 nanowire (NW) networks by lower pressure chemical vapor deposition and investigate their corresponding DUV detection properties. We find that pure Zn 2 GeO 4 NWs could be obtained at a growth pressure of 1 kPa. The DUV detection tests reveal that growth pressure exerts a significant effect on DUV detection performance. The Zn 2 GeO 4 NW networks produced under 1 kPa show an excellent solar-blind photoresponsivity with fast rise and decay times ( t rise ≈ 0.17 s and t decay ≈ 0.14 s)., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In this work an Ar + cluster ion beam with energy in the range of 10-70 keV and dose of 7.2 × 10 14 -2.3 × 10 16 cluster/cm 2 was used to irradiate pressed Si nanopowder targets consisting of particles with a mean diameter of 60 nm. The influence of the target density and the cluster ion beam parameters (energy and dose) on the sputtering depth and sputtering yield was studied. The sputtering yield was found to decrease with increasing dose and target density. The energy dependence demonstrated an unusual non-monotonic behavior. At 17.3 keV a maximum of the sputtering yield was observed, which was more than forty times higher than that of the bulk Si. The surface roughness at low energy demonstrates a similar energy dependence with a maximum near 17 keV. The dose and energy dependence of the sputtering yield was explained by the competition of the finite size effect and the effect of debris formation.

Transition metal dichalcogenide materials have been considered as promising anode materials for rechargeable sodium-ion batteries because of their high specific capacity and low cost. Here, we demonstrate an iron sulfide Fe 3 S 4 as a new anode material for a rechargeable sodium-ion battery. The involved conversion mechanism has been proved when the as-prepared Fe 3 S 4 was used as the host material for sodium storage. Remarkably, a compound FeS x with quantum size generated by conversion reaction overcame the kinetic and thermodynamic constraints of chemical conversion to achieve superior cycling and rate capability. As a result, the as-prepared Fe 3 S 4 electrode delivers a high reversible specific capacity of 548 mA h g -1 at 0.2 A g -1 , together with an excellent cycling stability of 275 mA h g -1 after 3500 cycles at 20 A g -1 .