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The synthesis of controllable pure and p-type in situ Ta-doped monolayer MoS2 with different doping concentrations via a one-step salt-assisted chemical vapor deposition (CVD) method with systematic characterization studies is reported.

We report a hybrid strategy to improve the responsivity and reduce the response time of a n-Si/p-GaTe heterojunction simultaneously through AlOx interface passivation and thermal oxidation.

This meta-analysis aimed to explore the diagnostic value of diffusion kurtosis imaging (DKI) compared to mono-exponential diffusion weighted imaging (DWI) in the diagnosis of breast cancer.A systematic electronic literature search (up to September 2020) was conducted for published English-language studies comparing the diagnostic values of DKI and DWI for the detection of breast cancer. The data of mean kurtosis (MK), mean diffusivity (MD), and apparent diffusion coefficient (ADC) were extracted to construct 2 × 2 contingency tables. The pooled sensitivities, specificities, and areas under the receiver operating characteristic curve (AUCs) were compared between DKI and DWI in the diagnosis of breast cancer.Eight studies were finally included, with a total of 771 patients in the same population. Pooled sensitivities were 82.0% [95% confidence interval (95% CI), 78.2-85.3%] for ADC, 87.3% (95% CI, 83.9-90.1%) for MK, and 83.9% (95% CI, 80.2-87.1%) for MD. Pooled specificities were 81.1% (95% CI, 76.7-84.9%) for ADC, 85.1% (95% CI, 81.1-88.5%) for MK, and 83.2% (95% CI, 79.0-86.8%) for MD. According to the summary receiver operator characteristic curve analyses, the AUCwas 0.901 for ADC, 0.930 for MK, and 0.918 for MD (ADC vs MK, P = .353; ADC vs MD, P = .611). No notable publication bias was found, while significant heterogeneity was observed.Although DKI is feasible for identifying breast cancer, MD and MK offer similar diagnostic performance to ADC values. Thus, we recommend that DKI should not be included in the routine evaluation of breast lesions now.

Two-dimensional van der Waals heterostructures provide an amazing platform to study the fundamental physical properties and build optoelectronic devices because of their abundant band structures and clean interface. In this paper, a MoS2/GeSe2 vertical heterostructure is built with type I band alignment, and the hysteresis voltage reaches 94 V under the scan range of ±80 V. The large hysteresis is attributed to the charge transfer between the MoS2 and GeSe2 layers according to a series of investigations, which is beneficial for its application in memory devices. The understanding of the mechanism will be helpful to improve the device performance and develop other new van der Waals heterostructure devices.

Molybdenum disulfide (MoS2) with excellent properties has been widely reported in recent years. However, it is a great challenge to achieve p-type conductivity in MoS2 because of its native stubborn n-type conductivity. Substitutional transition metal doping has been proved to be an effective approach to tune their intrinsic properties and enhance device performance. Herein, we report the growth of Nb-doping large-area monolayer MoS2 by a one-step salt-assisted chemical vapor deposition method. Electrical measurements indicate that Nb doping suppresses n-type conductivity in MoS2 and shows an ambipolar transport behavior after annealing under the sulfur atmosphere, which highlights the p-type doping effect via Nb, corresponding to the density functional theory calculations with Fermi-level shifting to valence band maximum. This work provides a promising approach of two-dimensional materials in electronic and optoelectronic applications.

Few-layer black phosphorus generally shows p-type or hole dominated ambipolar transfer characteristics with electron mobility being equal to or nearly zero, and tends to degenerate very quickly under ambient conditions. Herein, we demonstrate an effective surface charge transfer doping and passivation scheme on few-layer black phosphorus through in situ encapsulation by thin layer hexagonal boron nitride and surface modification by HfO2 or MgO. Both HfO2 and MgO can provide an electron doping effect on black phosphorus, resulting in an increase in electron mobility over one order of magnitude up to 65 cm2 V−1 s−1 modified by HfO2 and 305 cm2 V−1 s−1 modified by MgO, respectively. The highest electron mobility achieved approaches the record value in the literature, and the hole mobility of the same sample is also as high as 1150 cm2 V−1 s−1. Thin layer hexagonal boron nitride not only isolates black phosphorus from ambient conditions, but also protects it from destruction by metal oxides' deposition. Our work provides an effective technique to simultaneously realize electron doping and passivation on black phosphorus field effect transistors.

As a promising layered material for electronic, optical and thermoelectric applications, black phosphorus nanoribbons have attracted much attention. Herein, single crystal black phosphorus nanoribbons have been successfully grown by chemical vapor transport. The microstructure characterization results clearly reveal that the zigzag direction is the preferential growth direction of the nanoribbons. The performance of FETs shows the good electrical properties of black phosphorus. Our research provides an economical method for growing high quality BPNRs, offering more possibilities for experimental research and their applications.

Surface functionalization of layered transition metal dichalcogenides is of fundamental significance to a wide range of electronic and optoelectronic applications. Here, using density functional theory calculations, the n-type surface functionalization of a MoS2 monolayer using Arg and Lys amino acids was successfully predicted. Air stability and effective electron doping of the system have been demonstrated using Raman spectroscopy, photoluminescence spectroscopy, and the performance of field-effect transistors based on the MoS2 monolayer. The long-term stability in air and reversibly controllable doping properties make Arg and Lys amino acids an attractive option for modulating electronic and optoelectronic devices using a simple and effective route.

Two-dimensional molybdenum disulfide (MoS2) shows a great potential for optoelectronic devices due to its unique electronic, optical, photo-catalytic properties. While the bi-layer MoS2 via direct grown or mechanical exfoliation shows poor photoelectric effect due to its indirect band gap. In this work, we build bi-layer MoS2 via two-step PMMA transfer method, which shows the monolayer Raman characteristics. More importantly, the PL intensity of the built bi-layer MoS2 area shows four-to eight-fold increase compared that of the monolayer MoS2 area, indicating that the bottom monolayer MoS2 plays a role as a substrate and effectively separates the impurities of the SiO2 substrate from the upper monolayer MoS2. We believe that the residue PMMA between monolayers prevents the formation of interlayer coupling and results in the upper monolayer MoS2 suspending in some areas of the twisted bi-layer area. Our results provide a method to enhance the photoluminescence of the monolayer MoS2 by constructing the homogeneous MoS2 structure.

Phosphorus has drawn much attention for energy storage applications due to its high theoretical capacity while its surface is prone to oxidization, causing alterations of its physicochemical properties. Herein, we report a previously overlooked Li storage mechanism in the oxidized 2D black phosphorus/graphene oxide (BP/GO) heterostructure, where Li+ ions transport at an ultralow diffusion barrier of 80 meV and an ultrafast diffusion kinetics of 2.5 × 10–6 cm2 s–1 according to the ab initio molecular dynamics simulations. Furthermore, significant synergy arises when the 2D BP sheets chemically bind with GO layers, giving rise to an exceptional mechanical strength and flexibility of the BP/GO paper. The BP/GO composite anode sustains 500 stable cycles with Coulombic efficiencies as high as 99.6% in a Li ion half-cell. A quasi-solid-state, bendable Li-ion full-cell battery is assembled for the first time by using the BP/GO anode, a V2O5/CNT cathode, and a gel polymer electrolyte. It delivers simultaneously h...

The low-cost synthesis of high-quality black phosphorus (BP) has always been a challenge. Herein, we selected different mineralizers to synthesize high-crystallinity BP by the chemical vapor transport (CVT) method and demonstrated that the use of Pb instead of Sn can lead to higher purity BP. Residual Sn in Sn-BP was confirmed by X-ray photoelectron spectroscopy (XPS), but no mineralizer impurity was observed in Pb-BP. The performance of FET devices showed that the hole mobility of Pb-BP was significantly higher than that of Sn-BP. On the other hand, the Pb-BP devices exhibited good bipolarity with the highest hole mobility of 523 cm2 V-1 s-1 at room temperature and electron mobility of up to 28 cm2 V-1 s-1.

Molybdenum disulfide (MoS

We introduce a metal-assisted exfoliation method to produce few-layer black phosphorus with the lateral size larger than 50 μm and the area 100 times larger than those exfoliated using the normal “scotch-tape” technique. Using a field effect transistor it was found the hole mobility is 68.6 cm2 V−1 s−1 and the current on/off ratio can reach about 2 × 105.

Understanding the local electronic properties of individual defects and dopants in black phosphorus (BP) is of great importance for both fundamental research and technological applications. Here, we employ low-temperature scanning tunnelling microscope (LT-STM) to probe the local electronic structures of single acceptors in BP. We demonstrate that the charge state of individual acceptors can be reversibly switched by controlling the tip-induced band bending. In addition, acceptor-related resonance features in the tunnelling spectra can be attributed to the formation of Rydberg-like bound hole states. The spatial mapping of the quantum bound states shows two distinct shapes evolving from an extended ellipse shape for the 1s ground state to a dumbbell shape for the 2px excited state. The wave functions of bound hole states can be well-described using the hydrogen-like model with anisotropic effective mass, corroborated by our theoretical calculations. Our findings not only provide new insight into the many-...

Resistive random access memory (RRAM) is considered to be one of the important candidates for the next generation of memory devices. Zinc oxide resistive memory has also been studied for many years, but there are still some controversial topics and problems. Herein, an unusual resistance state has been observed in devices following the measurement and analysis of ZnO resistive memories with different thicknesses, a middle resistance state was speculated to explain the instability of ZnO RRAM. According to this speculation, a two-layer structure ZnO RRAM has been designed to significantly increase the device performance with the introduction of an HfO2 layer and the enhancement has also been explained based on the results of first-principles calculations.

Enhanced on/off ratio, obvious threshold voltage left shift, newly emerging bipolar field effect performance and most importantly, excellent stability in ambient condition have been reported for the HfO

In this article, black phosphorus quantum dots (BP QDs) were prepared and spin-coated on the surface of monolayer MoS2 to fabricate hybrid BP QD/MoS2 photodetectors. The conductivity of the monolayer MoS2 was significantly improved by the decoration of BP QDs. The dark current at V = 4 V was increased by two orders of magnitude. Moreover, the hybrid structure of BP QD/MoS2 showed a maximum photodetection responsivity of 2.87 × 104 A/W at a power density of 8 × 10−6 μW cm−2. The photoelectronic response of BP QD/MoS2 structures may pave the way for applications in phototransistors and photodetectors.

Heterojunction integrated by two-dimensional/three-dimensional materials has shown great potential applications in optoelectronic devices because of its fast response speed, high specific detectivity and broad spectral response. In this work, the vertical n-Si/p-GaTe heterojunction has been designed and fabricated, which shows a high responsivity up to 5.73 A W−1 and a fast response time of 20 μs at zero bias benifitting from the high efficiency of light absorption, internal photocurrent gain and strong built-in electrical field. A specific detectivity of 1012 Jones and a broad spectral response ranging from 300 to 1100 nm can also be achieved. This work provides an alternative strategy for high-performance self-powered optoelectronic devices.

Silicon hollow nanostructure has been considered as one of the most promising material for commercial application in lithium-ion batteries due to its significant improvement of cycling stability. The fabricated hybrid structures, carbon-coated silicon nanotube arrays on carbon cloth substrate, with a high surface area and short electron collection pathway have been directly used as anode electrodes without any additional binder. The electrodes exhibit high capacity, excellent rate capability and good cycling stability. The discharge capacity of the hybrid electrode (the deposition time of silicon shell: 5 min) keeps stable, and after 100 cycles, the discharge capacities still remain 3654 mAh g−1 at the rate of 0.5 C.

Black phosphorus, a promising two-dimensional material to be widely used in many areas of electronics and optoelectronics, can be prepared traditionally by high pressure or fast low-pressure transport routes. However, there lacks a general understanding of the growth mechanism, and it often suffers from poor yield and high cost. In this paper, we report a facile method to synthesize large-scale black phosphorus microribbons, significantly decreasing its cost and increasing its yield, and then it can commercially produce black phosphorus. The growth process of black phosphorus microribbons has been investigated systematically, and its growth mechanism has been speculated, which opens up the possible opportunity to directly grow black phosphorus microbelts and even few-layered nanobelts by adjusting the growth conditions. In addition, ribbon-like few-layered black phosphorus with large areas can be easily exfoliated from the grown microribbons because of their smooth and large area of the cleavage plane. Th...

The growth of high-quality black phosphorus crystals is very important to further study the physical properties of two-dimensional black phosphorus exfoliated from bulk crystals. Herein, we designed a series of experiments to fully understand the growth of black phosphorus crystals and then explore the roles of metals (or alloys) and I elements in its growth process. Finally, we developed a general approach to grow black phosphorus in high yield with high quality and low cost. The work introduced here sheds light on the growth mechanism of black phosphorus crystals and opens up the possibility of the growth of black phosphorus thin film.

Recently, two-dimensional materials have shown great potential in the application of memories due to their atomic thickness and excellent electrical properties. Furthermore, van der Waals heterostructures consisting a variety of two-dimensional materials provide more possibilities for memory research. Here, we design a simple memory device based on the molybdenum disulfide/germanium diselenide (MoS2/GeSe2) van der Waals heterostructure, which exhibits a large memory window of about 10 V in the gate range of ±10 V. Its ratio of program/erase current reaches over 102 and remains after more than 2 × 103 s and 103 cycles, showing good stability and reliability. Compared to conventional floating gate memory, the device based on this structure provides promising advantages in the reduction of the device size and simplification of manufacturing.

Black phosphorus has many potential applications in optoelectronic devices because of its unique properties. Adjusting its performance by doping is an important issue of research. In this paper, we synthesized high-quality Te-doped crystals by the chemical vapor transport method. Tellurium doping with an atomic ratio of 0.1% was confirmed by X-ray photoelectron spectroscopy, X-ray diffraction, and energy dispersive X-ray analysis. The performance of field effect transistors devices shows that the hole mobility of Te-doped black phosphorous (BP) is significantly improved compared with that of undoped-BP. The highest hole mobility at room temperature is 719 cm2 V-1 s-1, and the electron mobility is 63 cm2 V-1 s-1. Te-doped BP field effect transistors show an obvious bipolar behavior.

Two-dimensional layered SnS2 is attracting more and more attention due to its good electronic and optoelectronic properties. Herein, high yield and high quality SnS2 single crystals have been grown by chemical vapor transport method using muffle furnace instead of the traditional tube furnace. In addition, we report a modified mechanical exfoliation method, which is based on strong adhesion between gold decorated substrate and bulk SnS2, to produce high yield few-layered SnS2 with typical area size of nearly thousands of square microns. The electrical properties of FETs based on few-layered SnS2 further confirm the high quality of layered SnS2 with the carrier mobility of 2.8 cm2V−1s−1 and the current on/off ratio up to 105. It suggests that the exfoliation method introduced here provides an effective way to produce large-area, high-quality few-layered S n S 2 materials for future application.

A technique to fabricate nanogaps with controllably variable gap width in silver (Ag) nanowires (NWs) by photothermal-induced stress utilizing a focused continuous-wave laser (532 nm) is presented. For the case of an Ag NW on gold thin film, a gap width starting from ∼20 nm is achieved with a critical minimum power (CMP) of about 160 mW, whereas in the case of an Ag NW placed on top of a zinc oxide NW, the attained gap width is as small as a few nm (

Silicon has been considered as one of the most promising anode materials for the next generation lithium-ion battery due to its high theoretical capacity, but large volume changes during the electrochemical cycling limit its commercial application. In this study, we report the synthesis of silicon carbide @ silicon core–shell nanowires on carbon paper and their application in lithium-ion batteries. The hybrid nano-structures are fabricated via a two-step chemical vapor deposition method and directly used as the working electrode without any additional binder, exhibiting high specific capacity, high coulombic efficiency and good cycling stability. After 50 cycles, the discharge capacities still remain 2837 and 1809 mAh g −1 at the rates of 0.1C and 0.5C, respectively. Furthermore, we also study the influence of the growth time of SiC NWs and the thickness of Si film on the lithium-ion batteries' performance, and propose the possible method to further improve the battery performance.

A two-dimensional layered Ti3C2/carbon nanotubes (CNTs) hybrid thin film was prepared. Owing to the excellent conductivity of the CNTs, this unique layered structure provides a rapid charge transfer path during the electrochemical reaction, as a lithium ion battery anode, which exhibits higher capacitance and better cycling stability (a reversible capacity of 428.1 mA h g(-1) at 0.5 C after 300 cycles) compared with 96.2 mA h g(-1) of pure Ti3C2 nanosheets, as well as superior rate capability.

Silicon carbide (SiC) nanowires (NWs) are grown on flexible carbon fabric by chemical vapor deposition (CVD) method and Ni(OH) 2 are deposited on the surface of SiC NWs by electrochemical cathodic deposition. The capacitive performance of the as-prepared electrode was calculated based on pure Ni(OH) 2 and a very-high rate capability is achieved. A high specific capacitance of 1724 F g −1 is got at 2 A g −1 and the electrode still has a specific capacitance of 1412 F g −1 at an ultrahigh charging/discharging current density of 100 A g −1 . The excellent rate capability means great power characteristics of the supercapacitor electrode. With the charge/discharge rate of 100 A g −1 , a high power density of 27.5 kW kg −1 is achieved and the energy density still holds 59.4 Wh kg −1 . Solid-state supercapacitor based on SiC NWs@Ni(OH) 2 on carbon fabric is also made and shows good flexible and cycling properties.

A novel ternary tungsten disulfide (WS2)/copper oxide (CuO)/single-wall carbon nanotubes (SWCNT) porous laminated hybrids are fabricated with the aid of electrostatic interaction and vacuum filtration. In which, the layered WS2 sheets are spaced by high electrochemical active CuO nanosheets and conductive SWCNT and form a unique sandwich-like porous structures. When used as a lithium ion batteries anode, it demonstrates high reversible specific capacity of 962.4 mA h g−1 at 0.1 A g−1 after 100 cycles and excellent rate capability, a reversible specific capacity of 418.1 mA h g−1 even at a high rate current density of 2 A g−1. The unique assembled WS2/CuO/SWCNT porous hybrids not only show the improved electrical conductivity, but also provide efficient charge transport channels for electrolyte penetration and sustain for the volume variation during the lithiation and delithiation. These synergistic effects significantly improve the electrochemical performances. The synthesis approach presented here would be extended to the other layered-based composites for energy applications.

We study the epitaxial growth of Ag nanoislands on the surface of silicon nanowires (SiNWs) in ambient air by annealing SiNWs fabricated by metal-assisted chemical etching using Ag particles as the catalysts. We demonstrate that the nucleation of Ag on the surface of SiNWs is realized either by the direct decomposition of Ag m O or by the reaction between Ag m O and Si depending on the annealing temperature; Ag m O is an adspecies with a lower effective detachment barrier, commonly introduced in oxygen-induced Ag surface migration systems. Along with the formation of Ag nanoislands, a thin layer of SiO x is formed on the outside surface of Ag nanoislands. The ambient-air epitaxial growth of Ag islands on the surface of SiNWs offers great flexibility in designing ideal metal contacts and Schottky barrier formation, and studying the electronic, magnetic and optical properties of the Si/Ag system. We also believe that SiNWs decorated by Ag nanoislands have many potential applications in plasmonic photovoltaic cells, surface-enhanced Raman spectroscopy detection and electronic devices.

It is well known that the nanocomponents with opposite charges can be easily assembled into hybrid composites via electrostatic interaction, but it is difficult for like-charged nanomaterials. Here, we developed a general method to directly assemble lamellar composite paper composed of both negative-charged WS 2 and graphene oxide (GO) nanosheets from their aqueous dispersion through filtration process. After hydrothermal reduction, the flexible lamellar WS 2 /reduced-graphene oxide (rGO) paper was evaluated as binder-free anodes for Li-ion batteries, which presented a reversible capacity of 697.7 mA h g −1 after 100 cycles, 8 times higher than 88.5 mA h g −1 of pure WS 2 nanosheets and 60.2 mA h g −1 of rGO, excellent cyclic stability and good rate capacity. In the uniformly alternated lamellar structures, rGO nanosheets efficiently prevent the restacking of WS 2 sheets, increase the conductivity of the electrode, and sustain the volume expansion during Li + insertion/extraction, which significantly improved the electrochemical performances. This simple filtration assembling method provides a general and efficient way to synthesize functional composite films from like-charged colloid solutions.

The response current of Ni foam in alkaline solutions can be reduced significantly by high-temperature annealing, making it more suitable for current collectors, and a porous NiO(OH) film deposited on the passivated 3D Ni foam by anodic electrodeposition shows an ultrahigh specific capacitance of 2302 F g−1 at 1 A g−1.

Usually the bi-layer MoS2 grown directly by chemical vapor deposition or exfoliated by mechanical method has an indirect band gap, which leads to poor optical property. In this work, we design and build the sandwich structure by stacking a bi-layer MoS2 with Au nanoparticles embedded in the adjacent layers. This structure shows a 45-fold enhancement in photoluminescence (PL) compared with the direct grown bi-layer MoS2. More importantly, the as-built bi-layer MoS2 area shows much stronger in the PL intensity than that of the monolayer MoS2 area. This work presents the optimized PL enhancement of this homogeneous MoS2 structure by the surface plasmon resonance (SPR) effect of the Au nanoparticles and the effect of direct bandgap bi-layer MoS2 structures via tuning the interlayer distance between the adjacent MoS2 layers.

Enhanced on/off ratio, obvious threshold voltage left shift, newly emerging bipolar field effect performance and most importantly, excellent stability in ambient condition have been reported for the HfO2-passivated black phosphorus field effect transistors . Both Raman spectra and x-ray photoelectron spectroscopy (XPS) show a thickness reduction effect after HfO2 passivation, XPS further demonstrates that the formation of P-Hf and P-O chemical bonds contributes to the thinning of layered black phosphorus (BP), in which P-Hf bonds also provide chemical protection for BP flakes from degradation. Atomic force microscopy measures the thickness of the passivation layer and also verifies the stability of the passivated BP flakes.

In this paper, we report the supercapacitor electrodes with excellent cycle stability, which are made of silicon carbide nanowires (SiC NWs) grown on flexible carbon fabric. A high areal capacitance of 23 mF cm−2 is achieved at a scan rate of 50 mV s−1 at room temperature and capacitances increase with the rise of the working temperature. Owing to the excellent thermal stability of SiC NWs and carbon fabric, no observable decrease of capacitance occurs at room temperature (20 °C) after 105 cycles, which satisfies the demands of the commercial applications. Further increasing the measurement temperature to 60 °C, 90% of the initial capacitance is still retained after 105 cycles. This study shows that silicon carbide nanowires on carbon fabric are a promising electrode material for high temperature and stable micro-supercapacitors.

Flexible free-standing CuO nanosheets (NSs)/reduced graphene oxide (r-GO) hybrid lamellar paper was fabricated through vacuum filtration and hydrothermal reduction processes. A unique three-dimensional nanoporous network was achieved with CuO NSs homogeneously embedded within the r-GO layers. This hybrid lamellar composite paper was examined as a binder-free anode for lithium ion batteries, and demonstrated excellent cyclic retention with the specific capacity of 736.8 mA h g(-1) after 50 cycles. This is much higher than 219.1 mA h g(-1) of the pristine CuO NSs and 60.2 mA h g(-1) of r-GO film at the same current density of 67 mA g(-1). The high capacitance and excellent cycling performance were generated from the integrated nanoporous structure compose of CuO NSs spaced r-GO layers, which offered an efficient electrically conducting channels, favored electrolyte penetration, and buffered to the volume variations during the lithiation and delithiation process. These outstanding electrochemical capabilities of CuO NSs/r-GO paper holds great promise for flexible binder-free anode for lithium ion batteries.

Monolayer molybdenum disulfide (MoS2), consisting of covalently bonded S-Mo-S sandwiched layers, has high carrier mobility and a direct bandgap of 1.8 eV, offering properties for electronic and optoelectronic devices with high performance. Usually, it is essential to modulate the carrier concentrations and conductivities of monolayer MoS2 for practical applications. In this paper, black phosphorus (BP) quantum dots (QDs) were synthesized by a liquid exfoliation method successfully, and have a diameter of ~5 nm as confirmed with a transmission electron microscope (TEM). BP QDs were utilized to decorate monolayer MoS2 grown by chemical vapor deposition (CVD). The Raman and PL spectra of the BP QD/MoS2 hybrid structure clearly indicate that BP QDs are an effective n-type doping scheme for monolayer MoS2. Back-gated monolayer MoS2 transistors were fabricated and show an improved source–drain current after BP QD modifications. A high electron concentration of ~5.39 × 1012 cm−2 in monolayer MoS2 was achieved, which is beneficial for designing FETs and photodetector devices with novel functions.

We report on the feasible control of the threshold voltage (V th) in ultra-thin ZnO nanobelt FETs by using substoichiometric molybdenum trioxide (MoO x , x < 3) either as a modification layer on the surface of ZnO nanobelts or as electrodes instead of the widely used Ti/Au. ZnO nanobelt FETs using Ti/Au as the electrodes usually exhibit a negative threshold voltage, indicating n-channel depletion mode behavior, whereas ZnO FETs with MoO x /Au electrodes instead of Ti/Au show a positive shift of threshold voltage, exhibiting an n-channel type enhancement mode, which can be explained by a high Schottky barrier created at the interface of MoO x and the ZnO channel. In contrast, the decoration on the surface of ZnO channel by MoO x significantly increases the zero-bias conductivity and electron carrier concentration, and then negatively shifts the threshold voltage. We propose that MoO x thin film may play a passivation effect role, much more so than the doping effect role, due to the large amount of adsorbed species on as-grown ZnO nanobelts, especially oxygen species.

SnO2 nanoparticles (NPs)@carbon nanofibers as anode materials for lithium-ion battery are synthesized by a novel facile route using the commercial filter paper and tin dichloride dehydrate (SnCl2·2H2O). The weight ratio between carbon nanofibers and SnO2 NPs, which seriously affects the battery performance, has been demonstrated to be easily tuned by adjusting the sintering temperature. The electrochemical investigations show that the SnO2 NPs@carbon nanofibers with 9 wt% carbon have the best performance with the highest capacity of 383 mAh g−1 after 30 cycles at a current density of 100 mA g−1. The method introduced in this study provides an easy strategy for the controlled introduction of carbon to optimize the performance of lithium-ion battery using SnO2 NPs@carbon nanofibers as anode materials.

A simple and cost-effective chemical method was introduced to assemble gold (Au) nanoparticles on smooth silver (Ag) spheres for realizing surface-enhanced Raman scattering (SERS) enhancement by the replacement reaction between chloroauric acid and Ag spheres. In addition, the Ag-Au core-shell spheres were fabricated when a certain amount of chloroauric acid was used in the reaction solution. We found that the Ag particles decorated with small Au nanoparticles demonstrated the strongest SERS enhancement, while Ag-Au core-shell spheres showed the weakest enhancement.

The fabrication of vertical-oriented, high aspect ratio silicon nanowires (SiNWs) with controllable density and length is of interest for the development of nanowire-based electronics and photovoltaic devices. Here we reported a both simple and economical method for synthesizing large-area epitaxial-oriented SiNW arrays, which was achieved on the Si (111) substrates by Au catalyzed vapor-liquid-solid mechanism using the conventional chemical vapor deposition furnace system. Their morphologies and microstructures were investigated with scanning electron microscopy and transmission electron microscopy, respectively. The results showed that most of nanowires were vertically grown on substrates, their density and length can be well controlled. As-grown SiNW is composed of a single crystalline silicon core and a thin amorphous silicon oxide coating layer. Furthermore, their growth kinetics was discussed in detail. It indicates that there are both the substrate-nanowire Si adatom surface diffusion and the slight radial growth during the upgrowth of nanowire, and besides, the migration of Au on the sidewall of nanowire was also found for such epitaxial-oriental SiNWs.