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GaAsSb semiconductor material, a ternary alloy, has long been recognized as a crucial semiconductor in the near infrared range due to its ability to finely adjust the wavelength through controlling the Sb component. In this work, we report on the pattern of orientation variation in self-catalyzed grown GaAsSb nanowires (NWs). Utilizing solid-source molecular-beam epitaxy (MBE), self-catalyzed GaAs and GaAsSb nanowires (NWs) were grown on Si (111) substrates. The influence of various Sb components on the growth direction of the nanowires in the ternary GaAsSb alloy was examined using scanning electron microscopy (SEM). The inclusion of Sb components was discovered to alter the growth direction of the nanowires, transitioning them from a vertical and inclined orientation to a configuration that encompassed vertical, inclined, and parallel orientations with respect to the Si (111) substrate. As the Sb component in GaAsSb increased, there was an increased likelihood of the nanowires growing parallel to the surface of the Si (111) substrate. A combination of X-ray diffraction (XRD) and Raman spectroscopy validated the presence of Sb components and indicated a high crystalline quality. Additionally, XRD confirmed that the Sb components aligned with the intended structure. These findings establish a solid material foundation for the development of high-performance GaAsSb-based devices. [ABSTRACT FROM AUTHOR]

We report the first study on a GaAs/GaAsSb core–shell (CS)-configured nanowire (NW)-based separate absorption, charge control, and multiplication region avalanche photodiode (APD) operating in the near-infrared (NIR) region. Heterostructure NWs consisted of GaAs and tunable band gap GaAs1–xSbx serving as the multiplication and absorption layers, respectively. A doping compensation of absorber material to boost material absorption, segment-wise annealing to suppress trap-assisted tunneling, and an intrinsic i-type and n-type combination of the hybrid axial core to suppress axial electric field are successfully adopted in this work to realize a room-temperature (RT) avalanche photodetection extending up to 1.3 μm. In an APD device operating at RT with a unity-gain responsivity of 0.2–0.25 A/W at ∼5 V, the peak gain of 160 @ 1064 nm and 18 V reverse bias, gain >50 @ 1.3 μm, are demonstrated. Thus, this work provides a foundation and prospects for exploiting greater freedom in NW photodiode design using hybrid axial and CS heterostructures. [ABSTRACT FROM AUTHOR]

In this experiment, gallium trichloride（GaCl3） was used as the Group Ⅲ precursor, and self-catalyzed growth of GaN nanomaterials were achieved on Si（111） substrates using a self-made halide chemical vapor deposition（HCVD） device. The effects of different factors, including ammonia（NH3） flow, the reaction temperature and gradient temperature growth process on GaN nanomaterials synthesized from GaCl3 were discussed. The samples were characterized by scanning electron microscope（SEM）, energy dispersive spectrometer（EDS）, X-ray diffraction（XRD） and photoluminescence（PL）. The results show that GaN nanostructures were grown in a cluster mode, which followed gas-liquid-solid（VLS） growth mechanism. Under different growth conditions, there were obvious differences in the morphology, crystal quality and luminous properties for GaN. When NH3 flow was 60 sccm and the reaction temperature was at 900 ℃, GaN had a regular hexagonal structure and good crystal quality, and no obvious red luminescence band（about 680 nm） was found in the PL spectrum. Multiple structure for GaN was obtained in a gradient temperature（from 800 to 900 ℃） growth process, and surface-to-volume ratios and near-band edge emission peak intensity of GaN were both improved. [ABSTRACT FROM AUTHOR]

A self‐catalytic monomer of phthalonitrile, 2‐amino‐4,6‐bis[3‐(3,4‐dicyano‐phenoxy)phenoxy] pyrimidine (ACPP), was synthesized by a one‐pot method with resorcinol, 2‐amino‐4,6‐dichloropyrimidine, and 4‐nitrophthalonitrile. The chemical structure of the ACPP monomer was characterized by Fourier transform Infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy. The curing behavior of ACPP monomer was studied by differential scanning calorimetric, which indicated that the ACPP monomer had a low melting point (84 °C) and revealed an autocatalytic reaction and tremendously wide processing window (193 °C). Wide‐angle X‐ray diffraction (WAXD) and FTIR analyses were employed to explore the microstructure of the ACPP polymers. The properties of the three polymers with different curing procedures were investigated, which implied that the ACPP polymers exhibited excellent thermal stability, high modulus, superior glass‐transition temperature (Tg > 400 °C), and low water absorption with the increase in curing extent. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2287–2294 [ABSTRACT FROM AUTHOR]

Abstract We report the first self-catalyzed growth of high-quality GaSb nanowires on InAs stems using metal-organic chemical vapor deposition (MOCVD) on Si (111) substrates. To achieve the growth of vertical InAs/GaSb heterostructure nanowires, the two-step flow rates of the trimethylgallium (TMGa) and trimethylantimony (TMSb) are used. We first use relatively low TMGa and TMSb flow rates to preserve the Ga droplets on the thin InAs stems. Then, the flow rates of TMGa and TMSb are increased to enhance the axial growth rate. Because of the slower radial growth rate of GaSb at higher growth temperature, GaSb nanowires grown at 500 °C exhibit larger diameters than those grown at 520 °C. However, with respect to the axial growth, due to the Gibbs-Thomson effect and the reduction in the droplet supersaturation with increasing growth temperature, GaSb nanowires grown at 500 °C are longer than those grown at 520 °C. Detailed transmission electron microscopy (TEM) analyses reveal that the GaSb nanowires have a perfect zinc-blende (ZB) crystal structure. The growth method presented here may be suitable for other antimonide nanowire growth, and the axial InAs/GaSb heterostructure nanowires may have strong potential for use in the fabrication of novel nanowire-based devices and in the study of fundamental quantum physics.

Graphical abstract Oxygen vacancies-rich ZnFe 2 O 4 obtained by a self-catalyzed fast reaction exhibits superior gas sensing properties towards commercial ZnFe 2 O 4. Highlights • ZnFe 2 O 4 with controllable oxygen vacancies were obtained via a facile one-step self-catalyzed strategy. • Oxygen vacancies-rich ZnFe 2 O 4 showed superior gas sensing properties to commercial ZnFe 2 O 4. • Narrower band gap and more chemical adsorption induced by oxygen vacancies were attributed to enhanced sensing properties. • The as-prepared gas sensor has a short response time (6 s) and short recovery time (4 s). Abstract It is widely accepted that oxygen vacancies play an important role in high-performance gas sensors. Unfortunately, the mechanisms responsible for improved gas sensing performance due to oxygen vacancies are not yet well understood because the formation of oxygen vacancy-rich sensors is always accompanied by other variations, especially changes in chemical composition, particle size, and surface morphology. In this work, ZnFe 2 O 4 with controllable oxygen vacancies was prepared by a facile one-step self-catalyzed treatment, "shake and heat", in which commercial ZnFe 2 O 4 served as the raw material and catalyst for tartaric acid oxidation. Compared to commercial ZnFe 2 O 4 , the as-prepared ZnFe 2 O 4 had a similar crystal structure, particle size and morphology but possessed controllable oxygen vacancies, which was validated by XRD, SEM and XPS. The as-prepared oxygen vacancy-rich ZnFe 2 O 4 showed superior performance in sensing acetone compared to the raw materials, i.e., commercial ZnFe 2 O 4. It is proposed that the sensing properties improved because the oxygen vacancies narrowed the band gap and adsorbed more oxygen. This work proves that oxygen vacancies can indeed improve the sensing properties alone and demonstrate a new facile synthesis strategy for oxygen vacancy-rich sensors. [ABSTRACT FROM AUTHOR]

Abstract Single-crystalline Bi 4 Ti 3 O 12 nanosheets with the exposed {001} facets have been successfully prepared using a novel self-catalyzed reaction route, which involves a fast reaction of Bi 2 O 3 and TiO 2 at 280 °C with the critical assistance of tartaric acid. It is believed that the formation of Bi 4 Ti 3 O 12 nanosheets is driven by the massive heat released during the oxidation of tartaric acid when Bi 2 O 3 and TiO 2 are mixed. With this simplified novel process, the synthesis of high quality Bi 4 Ti 3 O 12 photocatalyst can be accomplished at low temperatures of 280 °C in less than 10 min. The as-obtained optimum nanosheet photocatalyst exhibits high visible light photodegradation of methyl orange, indicated by the 3.92 times higher efficiency than that of the Bi 4 Ti 3 O 12 nanosheets prepared by a widely acknowledged molten salt method. In addition, this Bi 4 Ti 3 O 12 nanosheet photocatalyst presents high recycling ability and storage stability. The X-ray photoelectron spectrometer and electron paramagnetic resonance analyses reveal that oxygen vacancies are produced on the surface of as-prepared Bi 4 Ti 3 O 12 nanosheets after the self-catalyzed reaction, which then extend the valence band width and reduce the band gap of the Bi 4 Ti 3 O 12 photocatalyst. It is therefore concluded that the much enhanced photocatalytic activity of the as-prepared catalyst is the synergistic effects of the valence band widening that increases the separation efficiency of the photo-generated carriers and the band gap narrowing that broadens the absorption edge of light. [ABSTRACT FROM AUTHOR]

Controlled growth of heterostructured nanowires and mechanisms of their formation have been actively studied during the last decades due to perspectives of their implementation. Here, we report on the self-catalyzed growth of axially heterostructured GaPN/GaP nanowires on Si(111) by plasma-assisted molecular beam epitaxy. Nanowire composition and structural properties were examined by means of Raman microspectroscopy and transmission electron microscopy. To study the optical properties of the synthesized nanoheterostructures, the nanowire array was embedded into the silicone rubber membrane and further released from the growth substrate. The reported approach allows us to study the nanowire optical properties avoiding the response from the parasitically grown island layer. Photoluminescence and Raman studies reveal different nitrogen content in nanowires and parasitic island layer. The effect is discussed in terms of the difference in vapor solid and vapor liquid solid growth mechanisms. Photoluminescence studies at low temperature (5K) demonstrate the transition to the quasi-direct gap in the nanowires typical for diluted nitrides with low N-content. The bright room temperature photoluminescent response demonstrates the potential application of nanowire/polymer matrix in flexible optoelectronic devices.

Abstract: A catalyst‐free self‐catalyzed [3+2] cycloaddition reaction of isatin‐derived α‐(trifluoromethyl)imines with vinylpyridines is reported. The reaction offers a straightforward and atom‐economical procedure for the preparation of a series of 5′‐trifluoromethyl‐spiro[pyrrolidin‐3,2′‐oxindoles] in excellent yields and diastereoselectivities. The reaction mechanism has been investigated by control experiments, DFT calculation of pKa values and the kinetic profiles, revealing that this reaction featured the mutual activation between isatin‐derived α‐(trifluoromethyl)imines and vinylpyridine to generate the reactive species. [ABSTRACT FROM AUTHOR]

The bottom-up fabrication of regular nanowire (NW) arrays on a masked substrate is technologically relevant, but the growth dynamic is rather complex due to the superposition of severe shadowing effects that vary with array pitch, NW diameter, NW height, and growth duration. By inserting GaAsP marker layers at a regular time interval during the growth of a self-catalyzed GaP NW array, we are able to retrieve precisely the time evolution of the diameter and height of a single NW. We then propose a simple numerical scheme which fully computes shadowing effects at play in infinite arrays of NWs. By confronting the simulated and experimental results, we infer that re-emission of Ga from the mask is necessary to sustain the NW growth while Ga migration on the mask must be negligible. When compared to random cosine or random uniform re-emission from the mask, the simple case of specular reflection on the mask gives the most accurate account of the Ga balance during the growth. [ABSTRACT FROM AUTHOR]

We report on a growth study of self-catalyzed GaAs nanowires based on time-resolved in situ X-ray structure characterization during molecular-beam-epitaxy in combination with ex situ scanning-electron-microscopy. We reveal the evolution of nanowire radius and polytypism and distinguish radial growth processes responsible for tapering and side-wall growth. We interpret our results using a model for diameter self-stabilization processes during growth of self-catalyzed GaAs nanowires including the shape of the liquid Ga-droplet and its evolution during growth. [ABSTRACT FROM AUTHOR]

In this paper, we report for the first time the growth of GaAsSb/InAs core-shell nanowires (NWs) on Si (111) substrates by molecular-beam epitaxy. We first grow high-quality GaAsSb NWs as cores using self-catalyzed technique, then cover these cores by InAs shells. For the growth of InAs shells, we find that the optimum beam equivalent pressure ratio of As/In is only ∼5.2, but the growth temperature window is larger (from 460 to 540 °C). Also, the thickness of InAs shells increases almost linearly with extending the growth time. Because of the high-quality of GaAsSb cores, the InAs shells are continuous, smooth, and without stacking faults or twins adopted from the cores. Temperature dependent I - V curves measured from the field-effect transistor devices based on these GaAsSb/InAs core-shell NWs indicate that GaAsSb/InAs NWs without any intentional doping are electrically conductive. The growth of GaAsSb/InAs core-shell NWs opens up new possibilities for both fundamental studies and future device applications based on such natural p-n junctions. [ABSTRACT FROM AUTHOR]

Reproducible integration of III–V semiconductors on silicon can open new path toward CMOS compatible optoelectronics and novel design schemes in next generation solar cells. Ordered arrays of nanowires could accomplish this task, provided they are obtained in high yield and uniformity. In this work, we provide understanding on the physical factors affecting size uniformity in ordered GaAs arrays grown on silicon. We show that the length and diameter distributions in the initial stage of growth are not much influenced by the Poissonian fluctuation-induced broadening, but rather are determined by the long incubation stage. We also show that the size distributions are consistent with the double exponential shapes typical for macroscopic nucleation with a large critical length after which the nanowires grow irreversibly. The size uniformity is dramatically improved by increasing the As4 flux, suggesting a new path for obtaining highly uniform arrays of GaAs nanowires on silicon. [ABSTRACT FROM AUTHOR]

We report the first self-catalyzed growth of high-quality GaSb nanowires on InAs stems using metal-organic chemical vapor deposition (MOCVD) on Si (111) substrates. To achieve the growth of vertical InAs/GaSb heterostructure nanowires, the two-step flow rates of the trimethylgallium (TMGa) and trimethylantimony (TMSb) are used. We first use relatively low TMGa and TMSb flow rates to preserve the Ga droplets on the thin InAs stems. Then, the flow rates of TMGa and TMSb are increased to enhance the axial growth rate. Because of the slower radial growth rate of GaSb at higher growth temperature, GaSb nanowires grown at 500 °C exhibit larger diameters than those grown at 520 °C. However, with respect to the axial growth, due to the Gibbs-Thomson effect and the reduction in the droplet supersaturation with increasing growth temperature, GaSb nanowires grown at 500 °C are longer than those grown at 520 °C. Detailed transmission electron microscopy (TEM) analyses reveal that the GaSb nanowires have a perfect zinc-blende (ZB) crystal structure. The growth method presented here may be suitable for other antimonide nanowire growth, and the axial InAs/GaSb heterostructure nanowires may have strong potential for use in the fabrication of novel nanowire-based devices and in the study of fundamental quantum physics. [ABSTRACT FROM AUTHOR]

In this Letter, we demonstrate that a significant improvement of optical performance of InAs nanowires can be achieved by capping the core InAs nanowires with a thin InP shell, which successfully passivates the surface states reducing the rate of nonradiative recombination. The improvements have been confirmed by detailed photoluminescence measurements, which showed up to a 10-fold increase in the intensity of room-temperature photoluminescence from the capped InAs/InP nanowires compared to the sample with core-only InAs nanowires. Moreover, the nanowires exhibit a high stability of total photoluminescence emission strength across temperature range from 10 to 300 K as a result of strong quantum confinement. These findings could be the key to successful implementation of InAs nanowires into optoelectronic devices. [ABSTRACT FROM AUTHOR]

Here we report on the Ga self-catalyzed growth of near full-composition-range energy-gap-tunable GaAs1-xSbx nanowires by molecular-beam epitaxy. GaAs1-xSbx nanowires with different Sb content are systematically grown by tuning the Sb and As fluxes, and the As background. We find that GaAs1-xSbx nanowires with low Sb content can be grown directly on Si(111) substrates (0 ≤ x ≤ 0.60) and GaAs nanowire stems (0 ≤ x ≤ 0.50) by tuning the Sb and As fluxes. To obtain GaAs1-xSbx nanowires with x ranging from 0.60 to 0.93, we grow the GaAs1-xSbx nanowires on GaAs nanowire stems by tuning the As background. Photoluminescence measurements confirm that the emission wavelength of the GaAs1-xSbx nanowires is tunable from 844 nm (GaAs) to 1760 nm (GaAs0.07Sb0.93). High-resolution transmission electron microscopy images show that the grown GaAs1-xSbx nanowires have pure zinc-blende crystal structure. Room-temperature Raman spectra reveal a redshift of the optical phonons in the GaAs1-xSbx nanowires with x increasing from 0 to 0.93. Field-effect transistors based on individual GaAs1-xSbx nanowires are fabricated, and rectifying behavior is observed in devices with low Sb content, which disappears in devices with high Sb content. The successful growth of high-quality GaAs1-xSbx nanowires with near full-range bandgap tuning may speed up the development of high-performance nanowire devices based on such ternaries. [ABSTRACT FROM AUTHOR]

We report on the self-catalyzed growth of InAs nanowires on InP substrate by metal-organic chemical vapor deposition. At a moderate V/III ratio, tapered nanowires are obtained, suggesting a strong surface diffusion effect. Dense twin faults are observed perpendicular to the nanowire growth direction due to the fluctuation of In atoms in the droplet originating from the surface diffusion effect. At a lower V/III ratio, the nanowires exhibit kinking, which is associated with a high adhesion due to a large sticking coefficient of TMIn. The twin faults are dramatically suppressed and even completely eliminated in the NW branch after kinking, which is attributed to a stable In supply with a negligible diffusion effect. This work provides a method for the fabrication of defect-free InAs nanowires. [ABSTRACT FROM AUTHOR]

The hollow carbon nanospheres (HCNs) are synthesized by self-catalyzed method. The amino-functionalized silica nanospheres (NH 2 –SiO 2 ) play the roles of template and catalyst. As a basic group, the amino provides slight alkaline conditions which can catalyze the polymerization of resorcinol-formaldehyde (RF) resin. Additionally, the amino group covering the outer surface of SiO 2 turns to be slight positively charged in the solution, which allows deposition of negatively charged RF on the surface of NH 2 –SiO 2 . The method has an advantage over previous method in terms of environment protection due to the absence of surfactant and ammonia. After carbonization and removal of the SiO 2 templates, the obtained HCNs completely copy the morphology of SiO 2 , exhibiting uniform and monodispersed spherical structures with the diameter of ~290 nm and surface area of 777 m 2 g −1 . The sample exhibits a performance for CO 2 capture with the capacity of 3.65 mmol g −1 at 298 K and 1.0 bar after activation with KOH. [ABSTRACT FROM AUTHOR]

Abstract The nucleation and evolution of InN nanowires in a self-catalyzed growth process have been investigated to probe the microscopic growth mechanism of the self-catalysis and a model is proposed for high pressure growth window at ~760 Torr. In the initial stage of the growth, amorphous InN x microparticles of cone shape in liquid phase form with assistance of an InN x wetting layer on the substrate. InN crystallites form inside the cone and serve as the seeds for one-dimensional growth along the favorable [0001] orientation, resulting in single-crystalline InN nanowire bundles protruding out from the cones. An amorphous InN x sheath around the faucet tip serves as the interface between growing InN nanowires and the incoming vapors of indium and nitrogen and supports continuous growth of InN nanowires in a similar way to the oxide sheath in the oxide-assisted growth of other semiconductor nanowires. Other InN 1D nanostructures, such as belts and tubes, can be obtained by varying the InN crystallites nucleation and initiation process.

Abstract ZnO was grown on sapphire substrate by metal–organic chemical vapor deposition using the diethylzinc (DEZn) and oxygen (O2) as source chemicals at 500 °C. Influences of the chamber pressure and O2/DEZn ratio on the ZnO structural properties were discussed. It was found that the chamber pressure has significant effects on the morphology of ZnO and could result in various structures of ZnO including pyramid-like, worm-like, and columnar grain. When the chamber pressure was kept at 10 Torr, the lowest full width at half-maximum of ZnO (002) of 175 arc second can be obtained. On the other hand, by lowering the DEZn flow rate, the crystal quality of ZnO can be improved. Under high DEZn flow rate, the ZnO nanowall-network structures were found to grow vertically on the sapphire substrate without using any metal catalysts. It suggests that higher DEZn flow rate promotes three-dimensional growth mode resulting in increased surface roughness. Therefore, some tip on the ZnO surface could act as nucleation site. In this work, the growth process of our ZnO nanowall networks is said to follow the self-catalyzed growth mechanism under high-DEZn flow rate.

We introduce droplet-confined alternate pulsed epitaxy for the self-catalyzed growth of GaAs nanowires on Si(111) substrates in the temperature range from 550 °C down to 450 °C. This unconventional growth mode is a modification of the migration-enhanced epitaxy, where alternating pulses of Ga and As4 are employed instead of a continuous supply. The enhancement of the diffusion length of Ga adatoms on the {11̅0} nanowire sidewalls allows for their targeted delivery to the Ga droplets at the top of the nanowires and, thus, for a highly directional growth along the nanowire axis even at temperatures as low as 450 °C. We demonstrate that the axial growth can be simply and abruptly interrupted at any time without the formation of any defects, whereas the growth rate can be controlled with high accuracy down to the monolayer scale, being limited only by the stochastic nature of nucleation. Taking advantage of these unique possibilities, we were able to probe and describe quantitatively the population dynamics of As inside the Ga droplets in specially designed experiments. After all, our growth method combines all necessary elements for precise growth control, in-depth investigation of the growth mechanisms and compatibility with fully processed Si-CMOS substrates. [ABSTRACT FROM AUTHOR]

The growth of III-III-V axial heterostructures in nanowires via the vapor-liquid-solid method is deemed to be unfavorable because of the high solubility of group III elements in the catalyst droplet. In this work, we study the formation by molecular beam epitaxy of self-catalyzed GaAs nanowires with AlxGa1-xAs insertions. The composition profiles are extracted and analyzed with monolayer resolution using high-angle annular dark-field scanning transmission electron microscopy. We test successfully several growth procedures to sharpen the heterointerfaces. For a given nanowire geometry, prefilling the droplet with Al atoms is shown to be the most efficient way to reduce the width of the GaAs/AlxGa1-xAs interface. Using the thermodynamic data available in the literature, we develop numerical and analytical models of the composition profiles, showing very good agreement with experiments. These models suggest that atomically sharp interfaces are attainable for catalyst droplets of small volumes. [ABSTRACT FROM AUTHOR]

The influences of droplet size on the growth of self-catalyzed ternary nanowires (NWs) were studied using GaAsP NWs. The size-induced Gibbs-Thomson (GT) effect makes the smaller catalytic droplets have lower effective supersaturations and hence slower nucleation rates than the larger ones. Large variation in droplet size thus led to the growth of NWs with low uniformity, while a good size uniformity of droplets resulted in the production of highly uniform NWs. Moreover, thinner NWs were observed to be richer in P, indicating that P is more resistant to the GT effect than As because of a higher chemical potential inside Ga droplets. These results provide useful information for understanding the mechanisms of self-catalyzed III-V NW nucleation and growth with the important ternary III-V material systems. [ABSTRACT FROM AUTHOR]

III-V nanowires are candidate building blocks for next generation electronic and optoelectronic platforms. Low bandgap semiconductors such as InAs and InSb are interesting because of their high electron mobility. Fine control of the structure, morphology, and composition are key to the control of their physical properties. In this work, we present how to grow catalyst-free InAs1-xSbx nanowires, which are stacking fault and twin defect-free over several hundreds of nanometers. We evaluate the impact of their crystal phase purity by probing their electrical properties in a transistor-like configuration and by measuring the phonon-plasmon interaction by Raman spectroscopy. We also highlight the importance of high-quality dielectric coating for the reduction of hysteresis in the electrical characteristics of the nanowire transistors. High channel carrier mobilities and reduced hysteresis open the path for high-frequency devices fabricated using InAs1-xSbx nanowires. [ABSTRACT FROM AUTHOR]

The III-V nanowire quantum dots (NWQDs) monolithically grown on silicon substrates, combining the advantages of both one- and zero-dimensional materials, represent one of the most promising technologies for integrating advanced III-V photonic technologies on a silicon microelectronics platform. However, there are great challenges in the fabrication of high-quality III-V NWQDs by a bottom-up approach, that is, growth by the vapor-liquid-solid method, because of the potential contamination caused by external metal catalysts and the various types of interfacial defects introduced by self-catalyzed growth. Here, we report the defect-free self-catalyzed III-V NWQDs, GaAs quantum dots in GaAsP nanowires, on a silicon substrate with pure zinc blende structure for the first time. Well-resolved excitonic emission is observed with a narrow line width. These results pave the way toward on-chip III-V quantum information and photonic devices on silicon platform. [ABSTRACT FROM AUTHOR]

Low Pressure Chemical Vapor Deposition (LPCVD) was applied to grow Silicon Nanowires (SiNWs) without any heteroatom catalyst or special pretreatment of substrates used. Silane (SiH 4 ) as a precursor was pyrolyzed at 500 °C in an oven at molybdenum or iron substrates. NWs were several microns long, about 100 nm thick and possessed a core–jacket structure. The thin core was composed of crystalline silicon oriented in 〈110〉 direction whereas the jacket was formed by amorphous silicon. Unlike other approaches, this method avoids contamination caused by metal heteroatom seeds and/or applying special procedures for substrate pretreatment to initialize/support NW growth. The photocatalytical activity revealed that SiNW layers could be accredited with a relatively high rate of photocatalytical splitting of water into H 2 /O 2 . [ABSTRACT FROM AUTHOR]

The effect of Sb addition on the morphology of self-catalyzed InAsSb nanowires (NWs) has been systematically investigated. InAs NWs were grown by molecular beam epitaxy with and without antimony (Sb) flux. It is demonstrated that trace amounts of Sb flux are capable of tuning the geometry of NWs, i.e., enhancing lateral growth and suppressing axial growth. We attribute this behavior to the surfactant effect of Sb which results in modifications to the kinetic and thermodynamic processes. A thermodynamic mechanism that accounts for Sb segregation in InAsSb NWs is also elucidated. This study opens a new route towards precisely controlled NW geometries by means of Sb addition. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

High yielding amination of ketones and benzaldehyde in acid-less conditions has been conducted on several ketones to achieve amides and nitriles. The reactivity of the selected substrates showed to depend on both oximation and Beckmann rearrangement reaction rates. Oximation allows the in-situ production of hydrochloric acid that enables Beckmann rearrangement of the oxime to form the corresponding amide or nitrile. It is noteworthy that, using this one-pot synthetic approach, N-acetyl-4-aminophenol (acetaminophen drug), can be easily synthesized starting from 4-hydroxy-acetophenone in high yield. Acetanilide and ε-caprolactam can be also efficiently synthesized employing this synthetic procedure. [ABSTRACT FROM AUTHOR]

Phthalonitrile resins with many striking properties have drawn much attention as potential candidates for use in composite matrices, adhesives, films, and electrical conductors for the last 30 years. However, it is common shortcomings for phthalonitrile monomers to have high-temperature melting point and need extreme conditions to develop binary phthalonitrile/additives composition. Here, three kinds of self-catalyzed phthalonitrile compounds with low melting point were synthesized, whose structures were characterized by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance. The different cure behaviors, owing to the different positions of catalyzed group on benzene ring, were investigated by differential scanning calorimetry, and cure kinetics parameters were also calculated. The results showed that the meta and para position monomers possessed better reactivity. Melt-processability study by a rheometer indicated that the ortho one owned the largest processing window. Furthermore, the FTIR spectra demonstrated that the cured monomers contained the same structure with a conventional binary phthalonitrile system. All the cured monomers had excellent thermal stability according to thermogravimetric analysis. Mechanical property was determined by dynamic mechanical analysis, and the results showed that the glass transition temperature (represented by the peak temperature of tanδ) was high up to 550°C for all the three cured monomers. Consequently, these autocatalytic phthalonitrile monomers may be good candidates as matrix for high-performance polymeric materials. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The nucleation and evolution of InN nanowires in a self-catalyzed growth process have been investigated to probe the microscopic growth mechanism of the self-catalysis and a model is proposed for high pressure growth window at ~760 Torr. In the initial stage of the growth, amorphous InN x microparticles of cone shape in liquid phase form with assistance of an InN x wetting layer on the substrate. InN crystallites form inside the cone and serve as the seeds for one-dimensional growth along the favorable [0001] orientation, resulting in single-crystalline InN nanowire bundles protruding out from the cones. An amorphous InN x sheath around the faucet tip serves as the interface between growing InN nanowires and the incoming vapors of indium and nitrogen and supports continuous growth of InN nanowires in a similar way to the oxide sheath in the oxide-assisted growth of other semiconductor nanowires. Other InN 1D nanostructures, such as belts and tubes, can be obtained by varying the InN crystallites nucleation and initiation process. [ABSTRACT FROM AUTHOR]

ZnO was grown on sapphire substrate by metal–organic chemical vapor deposition using the diethylzinc (DEZn) and oxygen (O2) as source chemicals at 500 °C. Influences of the chamber pressure and O2/DEZn ratio on the ZnO structural properties were discussed. It was found that the chamber pressure has significant effects on the morphology of ZnO and could result in various structures of ZnO including pyramid-like, worm-like, and columnar grain. When the chamber pressure was kept at 10 Torr, the lowest full width at half-maximum of ZnO (002) of 175 arc second can be obtained. On the other hand, by lowering the DEZn flow rate, the crystal quality of ZnO can be improved. Under high DEZn flow rate, the ZnO nanowall-network structures were found to grow vertically on the sapphire substrate without using any metal catalysts. It suggests that higher DEZn flow rate promotes three-dimensional growth mode resulting in increased surface roughness. Therefore, some tip on the ZnO surface could act as nucleation site. In this work, the growth process of our ZnO nanowall networks is said to follow the self-catalyzed growth mechanism under high-DEZn flow rate. [ABSTRACT FROM AUTHOR]

Abstract: Metal-plasma ion implanter has been used in this research to insert Cu ions as self-catalyst into the sub-surface of the TaN/FSG/Si assembly for electroless-plated Cu film. Cu ions were first implanted using two dosages of 5.0×1016 and 10×1016 cm−2 at accelerating voltages of 30, 40, and 50kV. The specimens were characterized by field emission scanning electron microscopy, atomic force microscopy, and mechanical pull-up tests. A noticed relationship between the implanted voltage and the nanostructure of the implanted Cu was established. The effects of the implanted nanostructure related to the adhesion strength of the electroless-plated Cu film were discussed. The adhesion strength of the final electroless-plated Cu film followed with the implanted dosage of 10×1016 cm−2 is apparently higher than that with the dosage of 5.0×1016 cm−2 at the same accelerating voltage. The adhesion strength of the Cu films tends to decrease with the increasing accelerating voltages applied for the implantation. An excellent gap-filling capability in a 0.2μm width (aspect ratio 7:1) via was obtained. [Copyright &y& Elsevier]

Controlled growth of heterostructured nanowires and mechanisms of their formation have been actively studied during the last decades due to perspectives of their implementation. Here, we report on the self-catalyzed growth of axially heterostructured GaPN/GaP nanowires on Si(111) by plasma-assisted molecular beam epitaxy. Nanowire composition and structural properties were examined by means of Raman microspectroscopy and transmission electron microscopy. To study the optical properties of the synthesized nanoheterostructures, the nanowire array was embedded into the silicone rubber membrane and further released from the growth substrate. The reported approach allows us to study the nanowire optical properties avoiding the response from the parasitically grown island layer. Photoluminescence and Raman studies reveal different nitrogen content in nanowires and parasitic island layer. The effect is discussed in terms of the difference in vapor solid and vapor liquid solid growth mechanisms. Photoluminescence studies at low temperature (5K) demonstrate the transition to the quasi-direct gap in the nanowires typical for diluted nitrides with low N-content. The bright room temperature photoluminescent response demonstrates the potential application of nanowire/polymer matrix in flexible optoelectronic devices. [ABSTRACT FROM AUTHOR]

4,4-bis[5-(aminomethyl)furan-2-yl]pentanoic acid (BAFP), brand new renewable acid-containing diamines, was first utilized as feedstock for preparing fully biomass-based benzoxazine with self-catalytic characteristic. The resulting acid-containing bio-benzoxazine was prepared through Schiff base strategy. The onset ring-opening polymerization temperature of resulting benzoxazine is 173 °C determined by DSC, much lower than that of analogous bisfurfurylamine-based biobenzoxazine free of carboxylic group. The curing kinetics of as-prepared benzoxazine was probed by non-isothermal DSC method. The curing reaction consisted of three stages with overlapped regions with each other. The first stage was ascribed to initiation reaction triggered by protons of acid, with a activation energy of 116.9 KJ/mol calculated by Flynn-Wall-Ozawa method; the second stage was named combination-catalyzed stage for the fact that acid proton and phenolic proton was co-catalyzed the chain propagation, with a activation energy of 118.0 KJ/mol; The third stage was diffusion-controlled curing reaction with a activation energy of 137.3 KJ/mol. More interesting, the calculated apparent activation energy of three reactions decreased with the increase of monomer conversion. Unlabelled Image • Novel acid-functionalized bio-diamine taken as feedstock for preparing monomer. • Bio-based benzoxazine with acid-functionality shows low onset curing temperature of 166.3 °C. • Curing reaction was divided into three reaction to probe the curing details. [ABSTRACT FROM AUTHOR]

The distinguishable physicochemical properties of MXenes render them attractive in electrochemical energy storage. However, the strong tendency to self-restack owing to the van der Waals interactions between the MXene layers incurs a massive decrease in surface area and blocking of ions transfer and electrolytes penetration. Here, in situ generated Ti 3 C 2 T x MXene-carbon nanotubes (Ti 3 C 2 T x -CNTs) hybrids are reported via low-temperature self-catalyzing growth of CNTs on Ti 3 C 2 T x nanosheets without the addition of any catalyst precursors. With combined spectroscopic studies and theoretical calculation results, it is certified that the intralayered Ostwald ripening-induced Ti 3 C 2 T x nanomesh structure contributes to the uniform precipitation of ultrafine metal Ti catalysts on Ti 3 C 2 T x , thus giving rise to the in situ CNTs formation on the surface of Ti 3 C 2 T x with high integrity. Taking advantages of intimate electrolyte penetration, unobstructed 3D Li + /e transport, and rich electroactive sites, the Ti 3 C 2 T x -CNTs hybrids are confirmed to be ideal 3D scaffolds for accommodating sulfur and regulating the polysulfides conversion for high-loaded lithium-sulfur batteries., (© 2021 Wiley-VCH GmbH.)