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The microstructure and defects of as-grown and annealed ZnO/Si thin films were investigated by high-resolution transmission electron microscopy (HRTEM). The cross-sectional bright-field TEM images showed that the ZnO thin films consisted of columnar grains. The selected-area electron diffraction pattern showed that the ZnO/Si thin film were c-axis oriented and the deviation angle along the ZnO (0001) direction with respect to the growth direction was no more than 5°. The grain boundaries can be classified into three types: low-angle boundaries, boundaries near a 30 deg angle with (1010) facet structures and large-angle boundaries. In addition to grain boundary, the as-grown and annealing processing defects were also investigated by HRTEM. The crystal quality of the ZnO/Si thin films can be improved by annealing at 600 °C. However, at too high an annealing temperature of 800 °C, the newly produced processing defects such as three layer stacking fault and double stacking fault were formed. The research was useful for us to find optimal growth conditions to improve ZnO/Si thin film quality. [ABSTRACT FROM AUTHOR]

Transparent conductive ZnO films doped with 0–6 mol% of Al 3+ (or AZO films) and AZO- rGO (rGO - reduced graphene oxide, ∼0–0.5 g/L) nanocomposite films were deposited on silica glass substrates by sol-gel multilayer spin-coating, with annealing at 250 °C in vacuum. The effects of the processing conditions on the structure, optical and electrical properties of the AZO-rGO films, as well as the AZO thin films for comparison, were investigated by XRD, Raman spectroscopy, TEM and SEM, UV-Vis-NIR spectroscopy, and with the four-point prober and Hall effect measurements. Al 3+ ions and rGO sheets existed in the composite films, and both of more Al 3+ amount and more rGO could result in worse crystallinity of ZnO. More amount of rGO led to more rGO flakers existed in the surface of the AZO-rGO films. Increasing Al-doping amount could not obviously affect the optical transmittances of the AZO-rGO films, but lead to the UV absorption edge of the films slightly blue-shifted. Optical transmittances of the AZO-rGO films decreased obviously with increasing the rGO ratio, but slightly decreased with increasing the annealing time. The minimum sheet resistance R □ could be obtained when Al-doping amount was ∼2 mol% and rGO ∼0.25 g/L: 50.1 kΩ/□ for the AZO film and 15.2 kΩ/□ for the AZO-rGO film. Addition of rGO could improve the electric conductivity of AZO films. Longer time of vacuum-annealing could also improve the electric conductivity of the AZO-rGO films. For the AZO-rGO film doped with 2 mol% Al 3+ and 10 mg rGO after vacuum-annealing for 12 h, Hall mobility was ∼17.7 cm 2 /Vs and the carrier concentration was ∼10.6 × 10 19 /cm 3 . [ABSTRACT FROM AUTHOR]

• BiVO 4 powders with A-site or B-site dopants are fabricated. • Phase transition of BiVO 4 is investigated with high-temperature X-ray diffraction. • Selective sites doping in BiVO 4 shows different transition temperatures. Doping in bismuth vanadate (BiVO 4) is widely used to enhance the efficiency of photoelectrochemical water splitting, but the fundamental mechanism is not fully understood due to its correlation with structure distortion and phase transition. Here, we investigate the selective site doping effect on the phase transition behavior of BiVO 4 using in-situ high-temperature X-ray diffraction. BiVO 4 powders with A-site doping by Gd3+ and B-site doing by Mo6+ are prepared, and transition from monoclinic to tetragonal in these powders is observed in real time with increasing temperature from 30 ℃ to 450 ℃. Both dopants are found to assist the tetragonal structure distortion and lower the transition temperature. The lowest transition temperature of 210 ℃ is observed in Mo-doped BiVO 4 , followed by 220 ℃ in Gd-doped BiVO 4 and 235 ℃ in pristine BiVO 4. This study delivers mechanistic insights into the doping impact on the structural transition in BiVO 4 for efficient photoelectrode design. [ABSTRACT FROM AUTHOR]

Presents a study on the calculation of the critical layer thickness strain in Si1-xGe/Si strained-layer heterostructures. Heterostuctures and superlattices of Si1-Gex/Si; Theoretical model and calculation used to carry out the study; How the critical layer thickness is reduced.

Carbonaceous materials are considered strong candidates as anode materials for sodium‐ion batteries (SIBs), which are expected to play an indispensable role in the carbon‐neutral era. Herein, novel braided porous carbon fibres (BPCFs) are prepared using the chemical vapour deposition (CVD) method. The BPCFs possess interwoven porous structures and abundant vacancies. The growth mechanism of the BPCFs can be attributed to the polycrystalline transformation of the nanoporous copper catalyst in the early stage of CVD process. Density functional theory calculations suggest that the Na+ adsorption energies of the mono‐vacancy edges of the BPCFs (−1.22 and −1.09 eV) are lower than that of an ideal graphene layer (−0.68 eV), clarifying in detail the adsorption‐dominated sodium storage mechanism. Hence, the BPCFs as an anode material present an outstanding discharge capacity of 401 mAh g−1 at 0.1 A g−1 after 500 cycles. Remarkably, this BPCFs anode, under high‐mass‐loading of 5 mg cm−2, shows excellent long‐term cycling ability with a reversible capacity of 201 mAh g−1 at 10 A g−1 over 1000 cycles. This study provided a novel strategy for the development of high‐performance carbonaceous materials for SIBs. [ABSTRACT FROM AUTHOR]

As a third-generation semiconductor material, chemical vapor deposition (CVD) diamond single crystals find crucial applications in electronic devices. While focused ion beam (FIB) milling which is a commonly employed method for processing micro/nano electronic devices, it inevitably results in the implantation of ion source materials and the formation of tens of nanometers of damaged layer, which is typically excessively thick for modern micro/nano electron devices. This study systematically explores the damaged layer induced by Ga ions during FIB diamond processing. The research revealed that damaged layer on the diamond surface measures 43 nm under 30 kV. The structure and electronic properties of the damaged layer were analyzed using high spatial resolution transmission electron microscopy (TEM) and high energy resolution electron energy loss spectroscopy (EELS) techniques. The findings indicate that the damaged layer consists of a double-layer structure, identified as an a-C I layer mainly composed of sp2 hybridized carbon atoms and an a-C II layer primarily composed of sp3 hybridized carbon atoms. Through the integration of results from energy-dispersive X-ray spectroscopy (EDS), EELS, and stopping and range of ions in matter (SRIM) simulations, it was determined that the a-C I layer is predominantly caused by the direct implantation of Ga ions, whereas the a-C II layer is primarily influenced by carbon recoil atoms. Remarkably, a 4.0 eV bandgap was deduced from the EELS spectrum of the a-C II layer. This semiconducting amorphous carbon layer (a-C II) and the diamond substrate together form an all‑carbon heterostructure, suggesting potential applications in field-effect transistors. [Display omitted] • At an accelerating voltage of 30 kV, when the implantation fluence is 5×1017 ions/cm2, the maximum thickness of the damaged layer on the diamond surface is 43.1nm. • The damaged layer is composed of two layers, the formation of a-C II is induced by the carbon recoil atoms alone. • The a-C II layer exhibits semiconducting properties with a bandgap of 4.0 eV. With potential applications in field-effect transistors. [ABSTRACT FROM AUTHOR]

Sm 2 Co 17 -type permanent magnets have important application value due to their advanced magnetic properties, which can be ascribed to their unique cellular structure and element segregation in various phases developed after isothermal aging treatment. In this study, the evolution of the microstructure combined with the microchemistry of Sm 2 Co 17 -type magnets from solid solution precursor to the cellular structure is investigated, and a new insight into the formation of the cellular structure is provided. We report for the first time that a large number of strip-like nanoscale short-range ordered micro-domains are distributed in the disordered matrix of the solution precursor, which serve as the nucleation centers in the formation of the embryos of the cellular structure. Based on atomic scale structural analyses, a new mechanism concerning the ordering transformation from short-range 2:17R microtwins to long-range 2:17R phase is proposed, involving collective glide of three partial dislocations on successive basal planes with the net Burgers vector to be zero. Furthermore, microchemistry analysis reveals that the segregation of Cu and Fe in the early stage of isothermal aging is accelerated substantially during the ordering transformation, indicating that the ordering transformation can act as a new driving force for element segregation in Sm 2 Co 17 -type magnets. These findings provide new considerations for the development of high performance Sm 2 Co 17 -type magnets. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Hierarchical hollow CoP and carbon composites were obtained through a facile synthetic method, where carbonization and phosphorization of the precursor were completed within one single step. The composites are composed of hollow CoP@C spheres, which are further made up of CoP nanoparticles with a thin outer carbon layer. Electrochemical performances of the prepared CoP@C composites as anodes for sodium and potassium storage were evaluated and compared. In situ TEM, in situ synchrotron XRD, and DFT calculations were conducted to study the structural evolution and the interaction between Na/K and CoP during cycling processes. Benefiting from the synergistic effect of conductive carbon layer and hierarchical hollow structure, the as‐prepared CoP@C composites demonstrate superior sodium and potassium storage capability as anode materials for rechargeable batteries. [ABSTRACT FROM AUTHOR]

Hierarchical hollow CoP and carbon composites were obtained through a facile synthetic method, where carbonization and phosphorization of the precursor were completed within one single step. The composites are composed of hollow CoP@C spheres, which are further made up of CoP nanoparticles with a thin outer carbon layer. Electrochemical performances of the prepared CoP@C composites as anodes for sodium and potassium storage were evaluated and compared. In situ TEM, in situ synchrotron XRD, and DFT calculations were conducted to study the structural evolution and the interaction between Na/K and CoP during cycling processes. Benefiting from the synergistic effect of conductive carbon layer and hierarchical hollow structure, the as‐prepared CoP@C composites demonstrate superior sodium and potassium storage capability as anode materials for rechargeable batteries. [ABSTRACT FROM AUTHOR]

In this work, a comparative study of thermally reduced graphite oxide (rGO) materials prepared by thermal exfoliation and reduction of graphite oxide (GO) at the temperature of 300 °C and 600 °C under different atmospheres (air, N2, Ar, vacuum and H2) was investigated through kinds of characterizations. The evaluation of chemical structure and quality of the rGOs by these various atmospheres is of high importance and is attempted side‐by‐side for the first time in this paper. The order of C/O ratio of rGOs obtained at 600 °C is that HH‐rGO>HV‐rGO>HAr‐rGO≈HN‐rGO>HA‐rGO, whereas the effect of atmospheres on the rGOs obtained at 300 °C is not obvious. HH‐rGO possesses better restoration of π‐conjugated structure and the increased average size of sp2 carbon domains compared with other rGOs. rGOs with higher reduction degree result in the aggregation of rGO nanosheets and closer to graphite structure. TGA results proved the order of thermal stability is that HH‐rGO>HV‐rGO>HAr‐rGO≈HN‐rGO>HA‐rGO. Additionally, HH‐rGO could be easily exfoliated to few‐layer nanosheets compared with others according to the AFM measurement. We believe that the findings will deepen our understanding of graphene obtained via thermal exfoliation and reduction method. In this work, the effect of atmospheres and temperature on the chemical structure and quality of the rGOs was investigated. The order of C/O ratio and the order of thermal stability of rGOs were obtained through XPS and TGA results, respectively. The defect level of of rGOs (300 °C) under different atmospheres is similar. The ID/IG value for HH‐rGO (0.90) obviously decreased. Additionally, HH‐rGO could be easily exfoliated to few‐layer nanosheets compared with others according to the AFM measurements. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) interpenetrating network graphene/copper (G/Cu) composites were fabricated by in-situ growth of G on nanoporous Cu followed by rolling and sintering processes. In-situ growth of G network generate an intimate interface between G and Cu matrix, which is not only essential for high load transfer efficiency but also minimize the interfacial resistance. Moreover, the 3D interpenetrating network structure is propitious to fully exert the additional electronic transport pathway and load-bearing of 3D G, as well as helping to generate and store dislocation without initiating cracks. Consequently, the obtained composite exhibits an elegant combination of enhanced tensile strength (354 MPa), extraordinary ductility (16.5% elongation) and robust conductivity (98% IACS). [ABSTRACT FROM AUTHOR]

This study developed a freestanding nanoporous high-entropy alloy foil as a dual-functional electrocatalyst. The ultrahigh HER activity of the catalyst originates from the synergetic effect of optimized hydrogen adsorption in the segregation area and enhanced H 2 O adsorption in the un-segregation area produced by spinodal decomposition. [Display omitted] • A nanoporous NiCoFeMoMn HEA with ultrahigh catalytic activity is synthesized. • Hierarchical porous structure greatly increases the number of active sites. • The synergistic effect of element segregation area and un-segregation area promotes HER. • The electrode can stably deliver 1000 mA cm−2 at only 150 mV for HER. • Overall water splitting runs stably for 375 h at 10 mA cm−2. The development of low-cost non-noble-metal-based electrocatalysts that can work stably at high current densities is crucial to apply a hydrogen evolution reaction (HER) and an oxygen evolution reaction (OER) in electrolyzed water. This study developed a freestanding nanoporous high-entropy alloy foil as a dual-functional electrocatalyst. The proposed electrocatalyst combines dealloying and polarization and shows excellent electrocatalytic activity in an alkaline electrolyte. It has an extremely small overpotential of 150 mV at 1,000 mA cm−2 for the HER and a low Tafel slope of 29 mV dec−1. At the same current density, the overpotential of the OER is only 350 mV. The alkaline electrolyzer using the electrocatalyst as both anode and cathode requires a cell voltage of only 1.47 V to output a stable current density of 10 mA cm−2. This enables it to be an efficient bifunctional electrocatalyst for alkaline overall water splitting and better stability for more than 375 h of continuous hydrogen production while providing substantial material cost savings relative to platinum. Density functional theory calculations indicate that the ultrahigh HER activity of the catalyst originates from the synergetic effect of optimized hydrogen adsorption in the segregation area and enhanced H 2 O adsorption in the un-segregation area produced by spinodal decomposition. [ABSTRACT FROM AUTHOR]

Abstract: The field-emission properties of the ZnO nanotip arrays, nanowire arrays as well as Al-doped ZnO nanowires were investigated in detail. After comparison of the different morphologies, it was found that the morphology of the nanostructure ZnO materials has played a crucial role in their field emission performances, especially the turn-on field and the emission current density. Among them, the ZnO nanotip arrays have the lower turn-on field, higher current density, which is attributed to the small emitter radius on the nanoscale and the well vertical align on the substrates. It can effectively improve the field-emission property to dope aluminium in ZnO nanowires because of the carrier concentration increasing, which results in the increase of the field enhancement factor and the reduction of the work function. The emission stability is very good from the emission persistence measurement. [Copyright &y& Elsevier]

Abstract: A biomimetic film has been found on the surface of the historic stone buildings and monuments. The stone inscriptions under the film are preserved so well that has not been damaged for more than 1000 years. Samples of the crude film have been analyzed by XRD, FTIR, PLM, EDA, SEM and TEM. The results show that it consists mainly of calcium oxalate monohydrate. On the basis of the existence of the organism debris, it is concluded that the film should be a product of biomineralization. According to this hypothesis, a similar film has been prepared on the stone surface through biomimetic synthesis in our laboratory. The preliminary analysis shows that the artificial protective film functions well. [Copyright &y& Elsevier]

Long bundles up to several millimeters of aligned carbon nanofibers (CNFs) have been prepared by pyrolysis of a mixture of acetylene and ferrocene in a vertically installed quartz reactor by floating catalyst method. After a long period of reaction, the product of thick blocks closely adhered on the reactor wall was obtained. Field emission scanning electron microscopy (FESEM) verified that blocks were composed of aligned CNF bundles with a high purity that was attested by the means of X-ray diffraction (XRD) and thermal gravimetric (TG) analysis. The morphology and structure features of the CNFs were checked by transmission electron microscopy (TEM) and Raman spectroscopy, respectively. It was originally reported that aligned CNF bundles were synthesized by vertically floating catalyst method. [Copyright &y& Elsevier]

Highly c-axis oriented LiNbO3 thin film has been deposited on the SiO2/Si substrate by KrF excimer pulsed laser deposition (PLD) technique under optimized conditions of 30-Pa oxygen pressure and 600 °C substrate temperature. The amorphous SiO2 buffer layer was coated on the Si (001) wafer by thermal oxidation in situ. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements confirm that the film shows superior crystalline quality and highly c-axis oriented texture. Neither the Li-enriched LiNbO3 target nor a biased electric field was applied during the deposition. [Copyright &y& Elsevier]

The crystalline GaN films were grown on Si(1 1 1) or using Si3N4 as a buffer layer by hot wall chemical vapor deposition. X-ray diffraction (XRD), photoluminescence (PL) and spreading resistance were sued to characterize the crystalline GaN films with or without a Si3N4 buffer. The XRD indicated that the GaN epilayer was in a wurtzite structure. The PL spectrum at room temperature exhibited a strong emission of the GaN epilayer with a silicon nitride buffer at the wavelength of 365 nm and no yellow luminescence (YL) was present, but the PL spectrum of the GaN directly on silicon was not so strong and yellow luminescence was present. The Si3N4 buffer layer was a high resistivity layer by spreading resistance. This simple but effective technique not only suppressed the YL but also made it possible to grow high-quality GaN on Si substrate. [Copyright &y& Elsevier]

How a heavily charged metal nanocrystal, and further a dual-nanocrystals system behavior with continuous electron charging? This refers to the electric dynamics in charged particles as well as the crystal growth for real metal particles, but it is still opening in experimental observations and interpretations. To this end, we performed an in-situ electron-beam irradiation study using transmission electron microscopy (TEM) on the Au nanocrystals that freely stand on the nitride boron nanotube (BNNT). Au nanocrystalline particles with sizes of 2–4 nm were prepared by a well-controlled sputtering method to stand on the BNNT surface without chemical bonding interactions. Au nanoparticles presented the surface atomic disorder, diffusion phenomena with continuous electron-beam irradiation, and further, the long-range motion that contains mainly the three stages: charging, activation, and adjacence, which are followed by final crystal growth. Firstly, the growth process undergoes the lattice diffusion and subsequently the surface-dominated diffusion mechanism. These abnormal phenomena and observations, which are fundamentally distinct from classic cases and previous reports, are mainly due to the overcharging of Au nanoparticle that produces a surface activation state in terms of high-energy plasma. This work therefore brings about new observations for both a single and dual-nanocrystals system, as well as new insights in understanding the resulting dynamics behaviors. [ABSTRACT FROM AUTHOR]