Growth Process Research Articles

Epitaxial Growth of Monolayer SnP3 with High Mobility and Chiral Boundary Junctions.

Two-dimensional materials with layered structures, appropriate band gaps, and high carrier mobility have attracted tremendous interest for their potential applications. Here we report the growth of monolayer SnP3 on Au(111) surfaces by molecular beam epitaxy. The kinetic processes for the growth and the crystalline properties are studied by scanning tunneling microscopy. The weak interaction between SnP3 and its Au(111) substrate is signified by the random crystal orientation distributions of SnP3 nanosheets. The electronic structures exhibit a band gap of ∼0.25 eV and high charge carrier mobility comparable to that of black phosphorus engineered by compressive strain. Additionally, domain boundary junctions with opposite chirality are observed, resulting from the strained film in the epitaxial growth process. Our work provides a method to fabricate high-quality monolayer SnP3 and suggests that the monolayer SnP3 is a promising candidate for applications in nanoelectronics and optoelectronics.

Barriers to social enterprise growth in developing countries: proposition of a multilevel approach

Purpose The purpose of this study is to investigate the hybridity of social enterprises (SEs) by examining the barriers to growth they face at the individual, organizational and institutional levels. Through this investigation, the study aims to contribute to our understanding of hybrid SEs and advance knowledge in the field. Design/methodology/approach This exploratory study uses Gioia’s grounded theory method to analyze qualitative data from 16 interviews conducted with established SEs, dissolved SEs and consulting centers in Vietnam. Findings SEs do have barriers to growth that distinguish them from traditional enterprises. Hybrids face barriers to growth at individual, organizational and institutional levels. This study offers a theoretical framework and provides the process model of SE barriers to growth. The SE growth process demonstrates the complex and dynamic interplay of specific components within two groups: organizational capacities and the SE ecosystem elements. This highlights the roles of various actors and institutions within the ecosystem in enhancing organizational capabilities and removing barriers to SE growth, extending knowledge of the SE, barriers to growth and the ecosystem literature. Research limitations/implications This paper has two main limitations. First, it is an empirical research conducted in a specific context, so the results may not be universally applicable. Second, it has a qualitative approach, which has limitations in comparing differences among different groups, such as hybrids versus traditional enterprises. However, these limitations also open numerous possibilities for further research directions. For instance, future research could apply this theoretical framework to conduct surveys in diverse contexts and use quantitative analysis to further examine the model of hybrid constraints. Originality/value The findings of this paper contribute to a more holistic understanding of barriers to growth facing SEs, which is an under-researched topic in the Vietnamese context. This paper offers a theoretical framework of barriers and the process of growth, providing potential recommendations for practitioners seeking to support SEs in addressing their unique challenges, and suggests avenues for further research in this area.

Impact of oxygen vacancy on luminescence properties of dysprosium-doped zinc oxide thin films

Pristine and dysprosium-doped ZnO thin films, highly c-axis oriented, were grown on a c-Al2O3 substrate using the pulsed laser deposition technique. During the deposition process, the growth was impacted by changes in the oxygen partial pressure. The structural, optical, and compositional properties of the pristine and dysprosium-doped ZnO thin films were systematically characterized using various state-of-the-art experimental techniques. The crystallinity associated with these films was observed to be highly dependent on the oxygen partial pressure maintained during the growth process. An average optical transparency of more than ∼90% in the visible spectral range (i.e., 400–800 nm) was observed for all specimens. For doped specimens, expected intra-4fn emissions of (dysprosium) Dy3+ ions that emanated from the 4F9/2 energy state were observed in room-temperature photoluminescence spectra under direct excitation. The Jacobian-transformed wavelength-to-energy plot for Dy-doped ZnO thin films in the UV-Visible region revealed intriguing findings. Specifically, it depicted a prominent peak at 2.82 eV, indicative of the energy state of Dy3+ ions, alongside intense band-edge emission and various defect-related emissions. The intensity of these transitions was observed to depend on the oxygen partial pressure kept during deposition. An x-ray photoelectron spectroscopy analysis of the doped specimen confirmed the +3 oxidation state of dysprosium into the ZnO matrix. These results provide a promising approach for controlling the doping and growth strategy of Dy-doped ZnO thin films, thereby opening up a wide range of applications and enhancement for next-generation optoelectronic devices.

Global Change in a Material World.

The biological structures that fill the environment around us are derived from materials produced by organisms. These biological materials are key to the mechanical function of organisms. The pathways and growth processes that produce biological materials can influence the mechanical properties of the materials, which can in turn shape the higher-level function of the system into which the materials are incorporated. Characterizing a biological system requires thorough knowledge of the underlying materials, including their mechanical function, diversity, evolution, and sensitivity to the environment. Anthropogenic activity is driving rapid and widespread changes to the natural environment and global climate, which are influencing organismal growth and physiology in myriad ways. Here, we briefly introduce a collection of articles that focus on the intersection of anthropogenic activity and the mechanical function of biological materials, as part of the "Global Change in a Material World" bundle for Integrative and Comparative Biology. In addition, we provide an analysis of the current scientific literature in this field, highlighting an urgent need to better understand how changes to our world, driven by human activity, are influencing the fundamental architecture and mechanical performance of organisms across the globe.

Digital Twin System of Pest Management Driven by Data and Model Fusion

Protecting crops from pests is a major issue in the current agricultural production system. The agricultural digital twin system, as an emerging product of modern agricultural development, can effectively achieve intelligent control of pest management systems. In response to the current problems of heavy use of pesticides in pest management and over-reliance on managers’ personal experience with pepper plants, this paper proposes a digital twin system that monitors changes in aphid populations, enabling timely and effective pest control interventions. The digital twin system is developed for pest management driven by data and model fusion. First, a digital twin framework is presented to manage insect pests in the whole process of crop growth. Then, a digital twin model is established to predict the number of pests based on the random forest algorithm optimized by the genetic algorithm; a pest control intervention based on a twin data search strategy is designed and the decision optimization of pest management is conducted. Finally, a case study is carried out to verify the feasibility of the system for the growth state of pepper and pepper pests. The experimental results show that the virtual and real interactive feedback of the pepper aphid management system is achieved. It can obtain prediction accuracy of 88.01% with the training set and prediction accuracy of 85.73% with the test set. The application of the prediction model to the decision-making objective function can improve economic efficiency by more than 20%. In addition, the proposed approach is superior to the manual regulatory method in pest management. This system prioritizes detecting population trends over precise species identification, providing a practical tool for integrated pest management (IPM).

Role of nuclear protein Akirin in the modulation of female reproduction in Nilaparvata lugens (Hemiptera: Delphacidae)

Introduction: Akirin as a highly conserved transcription factor, exerts a profound influence on the growth, development, immune response, and reproductive processes in animals. The brown planthopper (BPH), Nilaparvata lugens, a major pest in rice production in Asia, possesses high reproductive capacity, a critical factor contributing to reduced rice yields. The aims of this study were to demonstrate the regulatory role of Akirin in the reproduction of BPH.Methods: In this study, quantitative PCR (qPCR) was used to detect the mRNA expression of genes. RNA interference (RNAi) was used to downregulate the expression of Akirin gene, and RNA sequencing (RNA-seq) was used to screen for differentially expressed genes caused by Akirin downregulation. Hormone contents were measured with the enzyme linked immunosorbent assay (ELISA), and protein content was evaluated with the bicinchoninic acid (BCA) method.Results: Using BPH genome data, we screened for an Akirin gene (NlAkirin). An analysis of tissue-specific expressions showed that NlAkirin was expressed in all tissues tested in female BPH, but its expression level was highest in the ovary. After inhibiting the mRNA expression of NlAkirin in BPH females, the number of eggs laid, hatching rate, and number of ovarioles decreased. Transcriptome sequencing was performed, following a NlAkirin double-stranded RNA treatment. Compared with the genes of the control, which was injected with GFP double-stranded RNA, there were 438 upregulated genes and 1012 downregulated genes; the expression of vitellogenin (Vg) and vitellogenin receptor (VgR) genes as well as the mRNA expression of genes related to the target of rapamycin (TOR), juvenile hormone (JH), and insulin pathways involved in Vg synthesis was significantly downregulated. As a result of NlAkirin knockdown, the titers of JH III and Ecdysone (Ecd) were downregulated in unmated females but returned to normal levels in mated females. The ovarian protein contents in both unmated and mated females were downregulated.Discussion and conclusion: Our results suggest that NlAkirin affects female BPH reproduction by regulating the mRNA expression of genes related to the Vg, VgR, TOR, JH, and insulin signaling pathways, in addition to the titers of JH III and Ecd. The findings of this research provide novel insights into the regulatory role of Akirin in insect reproductive capacity.

Efficiency of zinc in alleviating cadmium toxicity in hydroponically grown lettuce (Lactuca sativa L. cv. Ferdos)

BackgroundA study on photosynthetic and enzyme activity changes and mineral content in lettuce under cadmium stress has been conducted in a greenhouse, utilizing the modulated effect of zinc (Zn) application in the nutrient solution on lettuce. Zn is a micronutrient that plays an essential role in various critical plant processes. Accordingly, three concentrations of Zn (0.022, 5, and 10 mg L− 1) were applied to hydroponically grown lettuce (Lactuca sativa L. cv. Ferdos) under three concentrations of Cd toxicity (0, 2.5, and 5 mg L− 1).ResultsThe results showed that along with increasing concentrations of zinc in the nutrient solution, growth traits such as plant performance, chlorophyll index (SPAD), minimum fluorescence (F0), leaf zinc content (Zn), leaf and root iron (Fe) content, manganese (Mn), copper (Cu), and cadmium increased as well. The maximum amounts of chlorophyll a (33.9 mg g− 1FW), chlorophyll b (17.3 mg g− 1FW), carotenoids (10.7 mg g− 1FW), maximum fluorescence (Fm) (7.1), and variable fluorescence (Fv) (3.47) were observed in the treatment with Zn without Cd. Along with an increase in Cd concentration in the nutrient solution, the maximum amounts of leaf proline (5.93 mmol g− 1FW), malondialdehyde (MDA) (0.96 μm g− 1FW), hydrogen peroxide (H2O2) (22.1 μm g− 1FW), and superoxide dismutase (SOD) (90.3 Unit mg− 1 protein) were recorded in lettuce treated with 5 mg L− 1 of Cd without Zn. Additionally, the maximum activity of leaf guaiacol peroxidase (6.46 Unit mg− 1 protein) was obtained with the application of Cd at a 5 mg L− 1 concentration.ConclusionsIn general, an increase in Zn concentration in the nutrient solution decreased the absorption and toxicity of Cd in lettuce leaves, as demonstrated in most of the measured traits. These findings suggest that supplementing hydroponic nutrient solutions with zinc can mitigate the detrimental effects of cadmium toxicity on lettuce growth and physiological processes, offering a promising strategy to enhance crop productivity and food safety in cadmium-contaminated environments.

Women and Urbanisation in the Federal Capital Territory, Abuja, Nigeria

This study examines women's role in the urbanisation of the Federal Capital Territory (FCT), Abuja. From the standpoint of feminist theory, urbanisation is believed to create expanded opportunities for the general populace as well as for women, who typically face discrimination in rural economies. However, the initial FCT master plan ended up being distorted by the dynamics and complexities of Abuja's urbanisation and growth process over time, which is driven by political and economic realities. There are drawbacks to urbanisation in civilisations with strong sociocultural norms and values, such as the fact that women must endure various forms of gender inequality, discrimination, and exclusion, particularly in the political sphere, which present significant difficulties. This study makes use of secondary data to demonstrate how the FCT's 2003 reconstruction to its original Master Plan provided chances for active participation in which women were included for both native people and newcomers. In a similar vein, the Federal Capital Development Authority's (FCDA) and other local council offices, which hired indigenous people for their departments and agencies, significantly altered the way of life for women from being rural farmers to empowered workers. In order to address the issues facing women in the FCT, empowerment must be a multifaceted process that transforms the economic, political, social, psychological, and legal conditions of the weak (women). It must also aim to demolish cultural, traditional, and social norms that devalue, disempower, and dispossess women, with a primary goal of meeting their needs.

Interpreting the Initial Growth Process of Surface Peeling: Microstructural Evolutions of Soil Deterioration on Archaeological Sites

ABSTRACT Few previous studies have investigated the mechanism of surface peeling from the perspective of soil microstructure. This study investigated surface peeling patterns and their growth feature in a large-size archaeological site, and SEM-EDS observed microstructure characteristics towards soil samples collected at different stages. Muddy Peeling (MP) irregular crusts with curling edges and Peeling with Salt Efflorescence (PSE) triggered by salt accumulation and formation of flakes in different shapes and thicknesses were the two main surface peeling patterns on the site. The average particle size of MP and PSE decreased from 6.0 μm to about 3.1 μm and 2.5 μm, respectively. Average pore size (4.5 μm) in unweathered soil decreased to 2.21 μm (MP) and 2.36 μm (PSE), and then rose to 4.86 μm (MP) and 5.74 μm (PSE), respectively. Micro-observation showed that the formation of flocculated calcium secondary minerals in MP and CaSO4 in PSE triggered by different water impacts caused different surface peeling patterns. This is the first study to reveal the differences lying in the initial growth process of archaeological site’s surface peeling in depth.

Phytotoxicity, cytogenotoxicity and antimicrobial potential of extracts with gold-silver bimetallic nanoparticles obtained from pteridophyte spores

Investigating the toxicity of naturally occurring or synthesized nanoparticles for various applications is absolutely necessary for environmental protection and safety use. The aim of these research was to investigated the phytotoxicity, cytogenotoxicity and antibacterial potential of the extracts with gold-silver bimetallic nanoparticles (Au-Ag NPs) obtained from green synthesis in Asplenium scolopendrium L. and Dryopteris filix-mas (L.) Schott spores extracts. To our knowledge, this is the first report of the Au-Ag NPs phytosynthesis based on extracts obtained from fern spores. UV-Vis spectroscopy analysis of the samples revealed the maximum absorbance, characteristic of samples with bimetallic nanoparticles, which varied depending on the Au:Ag ratio. Energy-dispersive X-ray spectroscopy confirmed the presence and distribution of Au, Ag and other chemical elements. The presence of specific secondary metabolites in the extracts that helped in NPs biosynthesis stimulated growth processes. Good results were recorded for some Dryopteris filix-mas samples, correlated with a significantly increased mitotic index. Cell viability decreased significantly in three of the nanoformulations. Only extracts with Au-Ag NPs showed antimicrobial effect against Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633 and Escherichia coli ATCC 8739. The testing of the antibacterial potential of these extracts must be extended to other bacterial strains and other microorganisms, the search of new antimicrobial resources being an urgent necessity nowadays.

Role of bacteria on bio-induced calcium carbonate formation: insights from droplet microfluidic experiments

Microbially induced calcium carbonate precipitation (MICP) has emerged as a promising solution for geotechnical issues. However, the role of bacteria in the formation of calcium carbonate (CaCO3) remains incompletely comprehended. In this study, a droplet microfluidic chip was developed to observe the growth process of CaCO3 and bacterial behavior during the MICP process under various bacterial density conditions at the monocrystal-scale. Scanning electron microscope (SEM) was then utilized to analyze the CaCO3 morphology, and Raman spectroscopy was employed to identify CaCO3 polymorphs. Nucleation within microspaces showed a stochastic nature. Within the droplets where crystals formed, all crystals manifested as cubic calcite. Higher bacterial density led to the formation of larger and more irregularly shaped crystals, with crystal size showing a significant correlation with urease activity. In droplets where no crystals formed, higher bacterial density and urease activity resulted in the precipitation of amorphous calcium carbonate (ACC) on the bacterial surface. However, this precipitation pattern differed from the formation of monocrystalline CaCO3. Our results demonstrate that bacteria act primarily as urease secretors to regulate crystal growth during the MICP process, while their role as nucleation sites for crystals remains controversial. This study provides a novel insight into understanding the bio-induced CaCO3 formation mechanism.

MC-ShuffleNetV2: A lightweight model for maize disease recognition

Maize has a long history of cultivation and is renowned for its high yield, superior quality, and adaptability. Currently, maize holds a significant position in grain cultivation and occupies a significant place in the agricultural structure. However, maize is susceptible to various diseases during its growth process, which can have a significant impact on the quality and yield. Traditional machine learning is heavily reliant on feature extraction, whereas deep learning has demonstrated notable success in image recognition for computer vision.The use of bloated models and the resulting wastage of computational resources represent significant challenges. The paper proposes a lightweight model, MC-ShuffleNetV2 (Mish + Convolutional Block Attention Module + ShuffleNetV2), to meet the practical needs of convolutional neural networks in maize disease image recognition. The model has designed with a focus on network lightweighting and accurate feature extraction. The model was constructed upon the foundation of the high-performance ShuffleNetV2 1 × network. The Convolutional Block Attention Module was integrated into the network architecture to enhance the model’s adaptive expressiveness. The depthwise separable convolution kernel of the depth-separable module was modified from a 3 × 3 kernel to a 5 × 5 kernel. This modification was implemented with the objective of expanding the image receptive field and extracting more detailed features of the image. It was necessary to modify the activation function in each stage for Mish. The model was compressed through the application of pruning operations. In the maize disease dataset test, the accuracy of the test set recognition accuracy of the network model constructed in this paper reaches 99.86 %, the model parameters are only 873,936, and the FLOPs (Floating-point Operations) are only 1,751,286. Compared with LeNet, AlexNet, MobileNetV2, and EfficientNetV2 models, the MC-ShufflenetV2 model’s recognition ability and size have obvious advantages, and it is more conducive to the actual deployment of the agricultural mobile terminal.

Disentangling Competitive and Synergistic Chemical Reactivities During the Seeded Growth of High-Entropy Alloys on High-Entropy Metal Sulfide Nanoparticles.

The seeded growth of one type of nanoparticle on the surface of another is foundational to synthesizing many multifunctional nanostructures. High-entropy nanoparticles that randomly incorporate five or more elements offer enhanced properties due to synergistic interactions. Incorporating high-entropy nanoparticles into seeded growth platforms is essential for merging their unique properties with the functional enhancements that arise from particle-particle interactions. However, the complex compositions of high-entropy materials complicate the seeded growth process due to competing particle growth and chemical reactivity pathways. Here, we design and synthesize a 36-member nanoparticle library to identify and disentangle these competitive interactions, ultimately defining chemical characteristics that underpin the seeded growth of high-entropy alloys on high-entropy metal sulfide nanoparticles. As a model system, we focus on (Cu,Zn,Co,In,Ga)S-SnPdPtRhIr, which combines a high-entropy metal sulfide semiconductor with a high-entropy alloy catalyst. We study the seeded growth of all possible pairwise combinations of Sn, Pd, Pt, Rh, Ir, and SnPdPtRhIr on the metal sulfides Cu1.8S, ZnS, Co9S8, CuInS2, CuGaS2, and (Cu,Zn,Co,In,Ga)S, which have comparable morphologies and sizes. Through these studies, we uncover unexpected chemical reactivities, including cation exchange, redox reactions, and diffusion. Reaction temperature, threshold reduction potentials, metal/sulfide chemical reactivity, and the relative strengths of the various bonds that could be formed during particle growth emerge as the primary factors that underpin seeded growth. Finally, we disentangle these competitive and synergistic chemical reactivities to generate a reactivity map that provides practical guidelines for achieving seeded growth in compositionally complex systems.

Influence of Different Ions on Pulse Electrodeposition of CaCO3 Scales in the Simulated Seawater.

In the circulating water system of coastal power plants, various kinds of ions have a great influence on the formation and growth of CaCO3 scales. This paper focuses on investigating the influence of existing ions on the pulse electrodeposition behaviors of CaCO3 scales. Different concentrations of ions, such as Fe3+, Mg2+, PO43- and SiO32-, are introduced to simulate the actual seawater environment, and their influence on the CaCO3 scale deposition behaviors is assessed by linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy tests. The surface coverage of the CaCO3 scale layer is evaluated through the residual current density and polarization resistance values, while the crystal structure and surface compactness of the layer are confirmed by the scanning electron microscope and X-ray diffractometer tests. Results indicate that high concentrations of Mg2+, Fe3+, and PO43- ions have the most significant inhibitory effect on the pulse electrodeposition of CaCO3 scales, among which the inhibition effect of Mg2+ ions is mainly reflected in the change of crystal morphology of CaCO3, that is, the crystallization growth process is inhibited. The inhibition effect of PO43- ions is mainly reflected in the gradually reduced coverage and density of CaCO3 crystals on the electrode surface, suggesting that the crystallization nucleation process is inhibited, while Fe3+ ions have a certain inhibition effect on both the crystallization nucleation and growth processes. Furthermore, lower concentrations of SiO32- ions also display a significant inhibition effect on the crystallization nucleation and growth process, and the inhibition effect weakens with increased concentration. This study provides a theoretical basis for exploring the removal of ions in the industrial water softening field.

Interactive effects of ammonium sulfate and lead on alfalfa in rare earth tailings: Physiological responses and toxicity thresholds

Ion-adsorption rare earth ore contains significant levels of leaching agents and heavy metals, leading to substantial co-contamination. This presents significant challenges for ecological rehabilitation, yet there is limited understanding of the toxicity thresholds associated with the co-contamination of ammonium sulfate (AS) and lead (Pb) on pioneer plants. Here, we investigated the toxicity thresholds of various aspects of alfalfa, including growth, ultrastructural changes, metabolism, antioxidant system response, and Pb accumulation. The results indicated that the co-contamination of AS-Pb decreased the dry weight of shoot and root by 26 %–77 % and 18 %–92 %, respectively, leading to irregular root cell morphology and nucleus disintegration. The high concentration and combined exposures to AS and Pb induced oxidative stress on alfalfa, which stimulated the defense of the antioxidative system and resulted in an increase in proline levels and a decrease in soluble sugars. Structural equation modeling analysis and integrated biomarker response elucidated that the soluble sugars, proline, and POD were the key physiological indicators of alfalfa under stresses and indicated that co-exposure induced more severe oxidative stress in alfalfa. The toxicity thresholds under single exposure were 496 (EC5), 566 (EC10), 719 (EC25), 940 (EC50) mg kg−1 for AS and 505 (EC5), 539 (EC10), 605 (EC25), 678 (EC50) mg kg−1 for Pb. This study showed that AS-Pb pollution notably influenced plant growth performance and had negative impacts on the growth processes, metabolite levels, and the antioxidant system in plants. Our findings contribute to a theoretical foundation and research necessity for evaluating ecological risks in mining areas and assessing the suitability of ecological restoration strategies.

Nitrate pollution deterioration in winter driven by surface ozone increase

Recently, nitrate (NO3–) levels in winter pollution in eastern China have been increasing yearly and have become the main component of PM2.5. The factors contributing to this rise in surface NO3– concentrations remain unclear, complicating the development of targeted pollution control measures. This study utilizes observational data from Shanghai during the winter 2019, alongside box model simulations, to recreate the NO3− pollution event and identify the key factors in the growth process. The analysis demonstrated that a rise in winter ozone levels significantly promotes NO3– production by facilitating NOx conversion via gas-phase and heterogeneous reactions. These findings could explain the correlation between the synchronous increase of surface ozone and NO3− in recent years. Furthermore, simulation of control strategies for NOx and volatile organic compounds (VOCs) identified an approach centered on ozone reduction as notably effective in mitigating winter NO3– pollution in the Yangtze River Delta.

Doped SnO2 thin films fabricated at low temperature by atomic layer deposition with a precise incorporation of niobium atoms

Nb-doped SnO2 (NTO) thin films were synthesized by atomic layer deposition technique at low temperature (100 °C). For an efficient incorporation of the Nb atoms, i.e. fine control of their amount and distribution, various supercycle ratios and precursor pulse sequences were explored. The thin film growth process studied by in-situ QCM revealed that the Nb incorporation is highly impacted by the surface nature as well as the amount of species available at the surface. This was confirmed by the actual concentration of the Nb atom incorporated inside the thin film as determined by XPS. Highly transparent thin films which transmit more than 95% of the AM1.5 global solar irradiance over a wide spectral range (300–1000 nm) were obtained. In addition, the Nb atoms influenced the optical band gap, conduction band, and valence band levels. While SnO2 thin film were too resistive, films tuned to conductive nature upon Nb incorporation with controlled concentration. Optimal incorporation level was found to be ⩽1 at.% of Nb, and carrier concentration reached up 2.5 × 1018 cm−3 for the as-deposited thin films. As a result, the high optical transparency accompanied with tuned electrical property of NTO thin films fabricated by ALD at low temperature paves the way for their integration into temperature-sensitive, nanostructured optoelectrical devices.

Nucleation of InP on Si under Micro-Crucibles at Ultra-High Vacuum using a Two-Step VLS Process

Abstract We reported nucleation mechanisms of InP directly on Si (8% lattice mismatch) under confined structures, called micro-crucibles, at ultra-high vacuum (UHV) by chemical beam epitaxy (CBE). These micro-crucibles are used to induce lateral growth in the presence of a micro-scale Au catalyst. It is found that at this UHV condition, the kinetics is dictated predominantly by adatom surface diffusion. Using a two-step growth process ((1) In-only exposure, then, (2) simultaneous In and P exposures), InP islands have been successfully nucleated on Si substrates under micro-crucible structures. The nucleation of these InP islands strongly depends on the metal catalyst location relative to the micro-crucible opening with metal catalysts residing closer to the opening having a higher chance to get incorporated with In and P atoms. Importantly, we found that using smaller micro-crucibles with double openings can increase the possibility of having metal catalysts reside near either opening and nucleate InP under micro-crucibles.

Adsorption Mechanism and Characteristic Temperatures of the Monolayer Adsorption of CO2 on Graphite: The Role of Graphene Dimensions.

Although simulation results for gaseous adsorption on a surface of infinite extent, modeled with periodic conditions at the boundaries of the simulation box, agree with experimental data at high temperatures, simulated isotherms at temperatures below the triple point temperature show unphysical substeps because of the compromise of interactions within the box and interactions between the box and its mirror image boxes. This has been alleviated with surfaces of finite dimensions (Loi, Q. K.; Colloids Surf., A 2021, 622, 126690 and Castaño Plaza, O.; Langmuir 2023, 39 (21), 7456-7468) to account for free boundaries at the adsorbate patch on the surface, and the critical parameter of this model substrate is the size of the finite surface. If it is too small, the adsorbate patch does not model the physical reality; however, if it is too large, the computation time is excessive, making the simulation impractical. In this study, we used carbon dioxide/graphite as the model system to explore the effects of finite dimensions on the description of experimental data of Terlain, A.; Larher, Y. Surf. Sci. 1983, 125 (1), 304-311, especially for temperatures below the bulk triple point temperature. With the appropriate choice of graphene size, we derived the 2D triple point and 2D critical point temperatures of the monolayer, and most importantly, for temperatures below the 2D critical point temperature, the adsorption mechanism for the formation of the monolayer is due to the interplay between the boundary growth process and the vacancy filling. The extent of this interplay is found to depend on the fractional coverage of the surface.

Fabrication of tips for scanning probe magnetometry by diamond growth

The use of quantum sensors is promising detailed insights into physical phenomena such as magnetism or superconductivity. One example of such quantum sensors is a microscopic diamond tip containing nitrogen vacancy (NV) centers, which is capable of producing correlated measurements of vectorial magnetic fields and the sample topography on the nanoscale. In this study, we present a chemical vapor deposition (CVD) process to produce diamond tips with NV centers by overgrowing microstructured diamond substrates. The resulting diamond tips exhibit a radius of curvature of approximately 10 nm, suitable for use as a probe in an atomic force microscope. The magnetic sensitivity of the CVD-grown diamond tips is characterized with pulsed measurements of the optically detected magnetic resonance, which yield a minimum magnetic sensitivity of 60 µT Hz−1 . The growth of the diamond microstructures is observed to differ from the commonly used geometric model predicting CVD growth of bulk diamond crystals. We identify an empirical model for the growth behavior of the microstructures by taking into account processes described in the step flow growth model for crystals. Additionally, we demonstrate the applicability of the developed CVD growth process to membrane substrates required for the preparation of magnetometry-capable diamond tips.