Initial Growth Behavior Research Articles

Interfacial Microenvironment-Regulated Coordinate Structures Dictate the Metal-Organic Framework Facet Orientation toward Efficient CO2 Cycloaddition.

The preparation of high-quality highly oriented metal-organic framework (MOF) thin films is desirable for developing advanced functional devices. However, the pathways for controlling the oriented growth of MOFs are largely unknown, and determining their microcosmic evolution at the complex solid-liquid interface remains a challenge. Herein, we investigate the critical early growth stage of typical HKUST-1 on the COOH-functionalized Au substrate utilizing a combination of in situ surface-enhanced infrared spectroscopy, X-ray photoelectron spectroscopy, and photoinduced force microscopy. Detailed molecular level information indicates that it is not only the COOH-terminated SAM itself but also the distinct interfacial structures of the first metal coordinate layer and second ligand coordinate layer, which can be regulated in aprotic and protic solvents, that dominate the initial growth behavior of MOF and thus lead to the [111], [100], and polycrystal facet-oriented growth of HKUST-1. Moreover, the prepared HKUST-1 films exhibit a crystal facet-dependent catalytic rate in the chemical fixation of CO2 into cyclic carbonate. Our observations provide a reasonable guide for designing MOF-based anisotropic functional equipment.

Ultrathin Metal Films with Low Resistivity via Atomic Layer Deposition: Process Pressure Effect on Initial Growth Behavior of Ru Films

Ultrathin Metal Films with Low Resistivity via Atomic Layer Deposition: Process Pressure Effect on Initial Growth Behavior of Ru Films

Nucleation and Layer Closure Behavior of Iridium Films Grown Using Atomic Layer Deposition.

Understanding the initial growth process during atomic layer deposition (ALD) is essential for various applications employing ultrathin films. This study investigated the initial growth of ALD Ir films using tricarbonyl-(1,2,3-η)-1,2,3-tri(tert-butyl)-cyclopropenyl-iridium and O2. Isolated Ir nanoparticles were formed on the oxide surfaces during the initial growth stage, and their density and size were significantly influenced by the growth temperature and substrate surface, which strongly affected the precursor adsorption and surface diffusion of the adatoms. Higher-density and smaller nanoparticles were formed at high temperatures and on the Al2O3 surface, forming a continuous Ir film with a smaller thickness, resulting in a very smooth surface. These findings suggest that the initial growth behavior of the Ir films affects their surface roughness and continuity and that a comprehensive understanding of this behavior is necessary for the formation of continuous ultrathin metal films.

Impact of contact heterogeneity on initial growth behavior of an epidemic: Complex network-based approach

The initial growth behavior of the scalar susceptible-infected-recovered (SIR) epidemic model is fully determined by the basic reproduction number. However, increasing individuals’ contact heterogeneity may invalidate the classical results and cause complex dynamics. Thus, we first consider the SIR model in annealed networks with bimodal degree distribution and derive some sufficient or necessary conditions that determine the monotonicity of densities of infected individuals in each degree class around the initial time t=0. Then, we consider the SIR model in annealed networks with arbitrary degree distribution and analyze the initial growth behavior of it. Interestingly, if we assume that initial densities of infected individuals in each degree class are proportional to the right eigenvector of a specified non-negative and irreducible matrix, then the initial growth behavior of infected individuals in each degree class is completely determined by the basic reproduction number. However, this is not the case for any initial condition, and the initial growth behavior may be very complex. Numerical simulations are performed to verify our analytical results and further investigate the effect of contact heterogeneity on disease behavior.

Primary Growth Behavior of Sulfur Particles through the Throttle Valve in the Transmission System of High Sulfur Content Natural Gas

The deposition of sulfur particles in gathering and transportation pipeline system can cause serious safety problems and economic losses. When the high sulfur content natural gas (HSCNG) flows through the throttle valve of the gathering and transportation system, it will cause the supersaturation of elemental sulfur in the gas phase, and then the sulfur crystal nuclei and sulfur particles will appear in the pipeline system. Studying the initial growth behavior of sulfur crystal nuclei and sulfur particles can lay a necessary prerequisite for the accurate prediction of sulfur particle deposition in high sulfur content natural gas gathering and transportation (HSCNGGT) pipelines. Based on the homogeneous nucleation theory in crystallization kinetics, a mathematical model of elemental sulfur nucleation was established. Taking the throttling condition in the process of HSCNGGT as an example, the effects of temperature, pressure and H2S concentration in HSCNG on the critical nucleation radius and nucleation rate of elemental sulfur were explored. The results show that: (1) after the supersaturation of elemental sulfur, sulfur crystal nuclei with nanoscale radius will be precipitated. The temperature and pressure after throttling have great influence on the nucleation radius, and the influence of H2S concentration on the nucleation radius is more complex. (2) The temperature, pressure and H2S concentration after throttling also have great influence on the nucleation rate. By solving the growth kinetics model of sulfur particles based on Brownian condensation, it is found that the nano-sized sulfur crystal nuclei can grow into micron-sized sulfur particles in a very short time.

Initial Growth Behavior in Catalyst-Free-Grown Vertical ZnO Nanorods on c-Al2O3, as Observed Using Synchrotron Radiation X-ray Scattering

In this study, synchrotron radiation X-ray diffraction analysis is used to investigate the initial growth dynamics of metal–organic vapor-phase epitaxy-grown ZnO nanorods on c-Al2O3 substrates. A two-dimensional area detector with a grazing-incidence geometry enables projected reciprocal space mapping (RSM) using coordinate transformation of diffraction images. The projected RSM reveals multiple heteroepitaxial relationships between ZnO and Al2O3, including the dominant relationship of ZnO(101̅0)∥Al2O3(21̅1̅0). Evolution of internal strain is revealed by an additional study on diffraction images and θ–2θ scans. Surface topology from atomic force microscopy estimates the growth rate, supported by the Scherrer equation analysis of the θ–2θ diffraction.

Direct evidence of the non-uniform electrodeposition of zinc at the early stage

Aqueous zinc-ion batteries (ZIBs) are regarded as one of the most promising electrical energy-storage systems for their eco-friendliness, low cost and high-safety. Although there have been a lot of studies recently on the Zn metal anode, little attention has been paid to its initial nucleation and growth behavior, which is critical to the understanding of fundamental mechanisms of the Zn plating. Herein, the digital holographic surface imaging (DHSI) method, combined synchronously with electrochemical tests, is employed to in-situ observe the non-uniform concentration changes on the surface of the copper substrate caused by the Zn nucleation and growth at the early stage. It is the first time to observe the early uneven depositions from a perspective of solution concentration changes in a symmetrical battery system. Results show that the later dendritic growth of Zn is closely related to the nucleation and earlier deposition process. Based on the phase maps obtained with in-situ DHSI technique, the nucleation and growth during the Zn electrodeposition can be closely investigated and vividly demonstrated, offering a promising avenue towards the understanding of the interfacial electrochemistry in all aqueous metal-ion batteries.

Interior defect-induced crack initiation mechanism and initial growth behavior for Ti6Al4V alloy fabricated using laser powder bed fusion

The interior defect-induced crack initiation mechanism and early growth behavior of Ti6Al4V alloy fabricated by laser powder bed fusion (LPBF) has been investigated in very high cycle fatigue (VHCF) regime. P–S–N curves under 10% and 90% failure probabilities are obtained in VHCF regime. The cracks inside the early stages of fine granular area (FGA) formation are driven by the maximum shear stress and propagate as Mode II + III mixed cracks. It can be found that the FGA region is composed of many discontinuous nanograins for Ti6Al4V alloys manufactured by LPBF, which are responsible for grain refinement. Grain refinement is associated with dislocation movement within the martensite laths. Dislocation pileup and rearrangement in martensitic laths form dislocation cells, which further develop into nanograins and low angle boundaries. Besides, both the fatigue loading process and the LPBF process form their respective microvoids, which merge and aggregate with each other, thus accelerating the microcrack extension.

Effects of Stepped Heating on the Initial Growth of Oxide Scales on NiCrAlHf Bond Coat Alloy under Air and Water Vapor Atmospheres.

Temperature and atmosphere have a significant effect on the oxidation of MCrAlY (M = Ni, Co) bond coating. The initial growth behavior of the NiCrAlHf bond coat alloy was investigated at 1100 °C under different atmospheric conditions and using heating methods. A thick Al2O3 oxide layer and large HfO2 particles were observed, perhaps due to metastable oxide growth at low temperatures when using stepped heating. However, in air and water vapor atmospheres, the oxide scale was thinner and the HfO2 precipitates were smaller in stepped heating than in constant heating. The size and distribution of the HfO2 particles might have induced different microstructures, particularly voids within the oxide scale.

Initial growth behavior of bismuth on Ag(111) and Au(111)

The Rashba effect of surface alloys of semimetallic bismuth (Bi) is strongly related to its specific structural properties. The initial growth behaviors of Bi atoms on Ag(111) substrate and Au(111) substrate are systematically investigated by combining scanning tunneling microscopy (STM) and density flooding theory (DFT) in this paper. Continuous Ag<sub>2</sub>Bi alloy films are formed preferentially at the step edge on Ag(111) held at room temperature; Bi atoms replace step edge atoms with low coordination number and are randomly distributed from single atoms to the forming of long-range ordered Ag<sub>2</sub>Bi alloy phase as the coverage increases to 0.33 ML on Ag(111) held at 570 K. With the coverage increasing, Ag<sub>2</sub>Bi is converted into Bi films with a <inline-formula><tex-math id="M3">\begin{document}$ p\times \sqrt{3} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20211360_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20211360_M3.png"/></alternatives></inline-formula> structure by the dealloying process. In contrary to Ag(111), Bi growth behavior on Au(111) held at room temperature and at 570 K are consistent: Bi atoms are adsorbed preferentially on Au atom pairs with coordination 5 and are dispersed as single atoms and clusters in the densely packed region and the corners of the herringbone reconstruction when coverage level is below 0.40 ML; as the coverage level increases to 0.60 ML, the disordered Bi atoms gradually transform into the long-range ordered (<inline-formula><tex-math id="M4">\begin{document}$ \sqrt{37}\times \sqrt{37} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20211360_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20211360_M4.png"/></alternatives></inline-formula>) phase. Moreover, the adsorption of Bi atoms leads the Au(111) surface strain to gradually release. The different growth behaviors of Bi atoms on Ag(111) substrate and Au(111) substrate suggest that the interaction between Bi atoms and the substrate plays a key role. Bi atoms are adsorbed preferentially around atoms with low surface coordination number under low coverage.

Investigation of the initial growth behavior of bismuth on Ag(111) and Au(111)

Investigation of the initial growth behavior of bismuth on Ag(111) and Au(111)

In Situ Synchrotron X-ray Diffraction Reciprocal Space Mapping Measurements in the RF-MBE Growth of GaInN on GaN and InN

In this work, in situ synchrotron X-ray diffraction reciprocal space mapping (RSM) measurements were carried out for the radio-frequency plasma-assisted molecular beam epitaxy (RF-MBE) growth of GaInN on GaN and InN layers, which were also grown by RF-MBE on commercialized GaN/c-sapphire templates. In situ XRD RSM measurements were performed using an MBE apparatus directly coupled to an X-ray diffractometer at the beamline of the synchrotron radiation facility SPring-8. It was observed in situ that both lattice relaxation and compositional pulling occurred during the initial growth stage, reducing the strain of GaInN on GaN and InN. Different initial growth behaviors of GaInN on GaN and InN were also observed from the results of the evolution of GaInN integrated peak intensities.

Graphene on Group-IV Elementary Semiconductors: The Direct Growth Approach and Its Applications.

Since the first development of large-area graphene synthesis by the chemical vapor deposition (CVD) method in 2009, CVD-graphene has been considered to be a key material in the future electronics, energy, and display industries, which require transparent, flexible, and stretchable characteristics. Although many graphene-based prototype applications have been demonstrated, several important issues must be addressed in order for them to be compatible with current complementary metal-oxide-semiconductor (CMOS)-based manufacturing processes. In particular, metal contamination and mechanical damage, caused by the metal catalyst for graphene growth, are known to cause severe and irreversible deterioration in the performance of devices. The most effective way to solve the problems is to grow the graphene directly on the semiconductor substrate. Herein, recent advances in the direct growth of graphene on group-IV semiconductors are reviewed, focusing mainly on the growth mechanism and initial growth behavior when graphene is synthesized on Si and Ge. Furthermore, recent progress in the device applications of graphene with Si and Ge are presented. Finally, perspectives for future research in graphene with a semiconductor are discussed.

硅基重构表面上金属初期生长行为研究

硅基重构表面上金属初期生长行为研究

Formation of spherical-shaped GaN and InN quantum dots on curved SiN/Si surface

This paper reports the formation of GaN and InN quantum dots (QDs) with symmetric spherical shapes, grown on SiN/Si(111). Spherical QDs are grown by modulating initial growth behavior via gallium and indium droplets functioning as nucleation sites for QDs. Field-emission scanning electron microscope (FE-SEM) images show that GaN and InN QDs are formed on curved SiN/Si(111) instead of on a flat surface similar to balls on a latex mattress. This is considerably different from the structural properties of In(Ga)As QDs grown on GaAs or InP. In addition, considering the shape of the other III–V semiconductor QDs, the QDs in this study are very close to the ideal shape of zero-dimensional nanostructures. Transmission-electron microscope images show the formation of symmetric GaN and InN QDs with a round shape, agreeing well with the FE-SEM results. Compared to other III–V semiconductor QDs, the unique structural properties of Si-based GaN and InN QDs are strongly related to the modulation in the initial nucleation characteristics due to the presence of droplets, the degree of lattice mismatch between GaN or InN and SiN/Si(111), and the melt-back etching phenomenon.

Effects of monolayer Bi on the self-assembly of DBBA on Au(111)

The initial growth behaviors of nonplanar 10,10′-dibromo-9,9′-bianthryl (DBBA) molecules on the Au(111) substrates, which is either pristine or Bi-3 × √3-Au(111), at low deposition rates have been systematically investigated using low temperature scanning tunneling microscopy (LT-STM) and density functional theories (DFT) calculations. The effects of such substrates on the subsequent graphene nanoribbons (GNRs) formation are addressed. On clean Au(111), DBBA molecules self-assemble into highly ordered commensurate single-molecule chains along <112¯>Au at a coverage of 0.8 monolayer (ML), and collectively transit into long-range ordered commensurate double-molecule chains along <11¯0>Au but with many single-molecule vacancies at a coverage of 1.2 ML, revealing the delicate competing between intermolecular interactions and molecule-substrate interfacial interactions. The interfacial interactions are further tuned by introducing bismuth to form a Bi-3 × √3-Au(111)surface, where DBBA molecules self-assemble into an unique hexamer phase due to the enhanced intermolecular interactions via CH…π and halogen bonds. DFT calculations confirm the proposed molecular configuration change of single DBBA molecule when adsorbed on different substrates. The calculated difference in CBr bond gives further insight into why no GNRs formed on Bi-3 × √3-Au(111).

Adsorption of Phenacenes on a Metallic Substrate: Revisited

Phenacenes represent a class of simple hydrocarbons with appealing physical properties ranging from high charge mobility to superconductivity in combination with chemical robustness that are easily modified to serve as versatile building blocks for tailored structures. As a promising candidate for applications in organic devices, phenacenes are the focus of recent investigations. Thereby, the initial growth behavior starting from a single molecule is controversial. Here, we address the growth of [7]phenacene and [9]phenacene on a Ag(111) surface, studying the details of the initial stage of growth by scanning tunneling microscopy. According to our results, a previously introduced model involving a coverage-dependent phase change with the out-of-plane rotation of molecules in the initial growth stage can be disregarded. Instead, we find evidence for the formation of a new phase on top of an in-plane wetting layer during the initial stage of growth.

4点曲げ応力下における摩擦攪拌接合A6063合金の疲労き裂発生および初期進展挙動

4点曲げ応力下における摩擦攪拌接合A6063合金の疲労き裂発生および初期進展挙動

Plant Growth Responses of Apple and Pear Trees to Doses of Glyphosate

ABSTRACT Glyphosate is commonly used for intra-row weed management in perennial plantations, where unintended crop exposure to this herbicide can cause growth reduction. The objective of this research was to analyze the initial plant growth behavior of young apple and pear plants exposed to glyphosate. Glyphosate was sprayed on 2-year-old 'Gala' apple and 'Abbè Fetel' pear plants at doses from 18 to 720 g per hectare of acid equivalent (a.e.). The plant height of neither species was not significantly reduced (less than 1%) by any glyphosate dose at 240 days after spraying, whereas the stem diameter and the dry mass of stem and leaves were reduced by 720 g a.e. ha-1. The glyphosate dose required to reduce the aboveground dry mass by 50% was 162 and 148 g a.e. ha-1 for apple and pear, respectively. Aboveground dry mass was reduced 2% and 6% for apple and pear plants, respectively, at 720 g a.e. ha-1. Hormesis was not observed in either species at doses down to 18 g a.e. ha-1. Both species showed low susceptibility to glyphosate; however apple was less susceptible than pear.

Analysis of the Spiral Step Structure and the Initial Solution Growth Behavior of SiC by Real-Time Observation of the Growth Interface

Microscopic real-time observation of the solution growth interface of SiC using Fe–Si solvent at 1673 K was successfully performed to understand the interface morphology at the initial stage of solution growth. The growth interface was composed of a number of domains with step–terrace structures originating from either spiral growth of 4H-SiC or two-dimensional island growth of other polytypes. The validity of the measurements of the step structures by bright-field and interference images was confirmed by ex-situ atomic force microscopy. In addition, the encounter between a spiral growth domain and steps from another spiral growth domain was observed, and it was found that a certain step height is needed to stop spiral growth by covering the spiral center.