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Nano-Heteroepitaxy: An Investigation of SiGe Nano-Pillars Coalescence
摘要： In this paper, SiGe nano-pillars coalescence was investigated using industrial Reduced Pressure-Chemical Vapour Deposition integration scheme based on diblock copolymer patterning provided nanometer size templates for the selective epitaxy of SiGe 25% nano-pillars. In order to study merging, thicknesses ranging from 20 to 35 nm were grown and samples characterized by AFM, XRD, SSRM and TEM. The evolution in terms of grains shape, size and number was examined, with individual pillars merging into larger grains above 30 nm thickness. High degrees of macroscopic strain relaxation were obtained at the different stages of nano-pillars merging. Defects such as stacking faults and twins were identified as occurring at the early stages of nano-pillar coalescence.
关键词： SSRM,TEM,coalescence,AFM,SiGe nano-pillars,Reduced Pressure-Chemical Vapour Deposition,XRD
更新于2025-11-14 14:32:36
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Assessing Physical Stability of Colloidal Dispersions Using Turbiscan Optical Analyzer
摘要： The physical stability of aqueous colloidal dispersions containing highly concentrated droplets of poorly water-soluble drugs has recently been identified as one of the main considerations in developing amorphous solid dispersions (ASDs). Turbiscan, an instrument based on multiple light scattering technology, was employed for the first time to assess colloidal dispersions with ritonavir as the model compound. The physical instability of ritonavir-rich droplets was monitored directly with and without the presence of candidate polymer additives at different drug concentrations and temperatures. The mechanism of the observed instability was confirmed to be coalescence of liquid droplets, based on the low glass transition temperature of water-saturated amorphous ritonavir determined using a newly developed experimental procedure. Temperature and solvent composition, within the range studied, have little influence on the kinetics of ritonavir coalescence. On the contrary, higher concentration of drug, i.e., more droplets per unit volume, greatly accelerates the coalescence process. In addition, polymers with varying degrees of hydrophobicity resulted in different levels of effectiveness in stabilization which is likely related to the strength of drug-polymer interactions and the corresponding differences in surface adsorption. This work demonstrates that the Turbiscan optical analyzer can be used as a rapid screening tool that provides a first-pass, high-throughput feasibility ranking of different excipients and additives to support the development of ASD formulations.
关键词： nanodroplets,coalescence,glass transition temperature,physical stability,stabilization,amorphous,ritonavir,colloidal dispersions,Turbiscan
更新于2025-09-23 15:22:29
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Horizontal GaN nanowires grown on Si (111) substrate: the effect of catalyst migration and coalescence
摘要： Here, we demonstrate the growth of horizontal GaN NWs on silicon (111) by a surface-directed vapour–liquid–solid (SVLS) growth. The influence of the Au/Ni catalysts migration and coalescence on the growth of the NWs has been systematically studied. A 2-D root-like branched NWs were gown spontaneously through catalyst migration. Furthermore, a novel phenomenon that a catalyst particle is embedded in a horizontal NW was observed and attributed the destruction of growth steady state due to the catalysts coalescence. The transmission electron microscopy (TEM) and photoluminescence (PL), cathodoluminescence (CL) measurement demonstrated that the horizontal NWs exhibit single crystalline structures and good optical properties. Our work sheds light on the horizontal NWs growth and should facilitate the development of highly integrated III?V nanodevices on silicon.
关键词： GaN nanowires,silicon substrate,coalescence,catalyst migration,SVLS growth
更新于2025-09-23 15:21:21
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Molecular dynamics simulation of coalescence kinetics and neck growth in laser additive manufacturing of aluminum alloy nanoparticles
摘要： Laser additive manufacturing emerged as an advanced manufacturing process to fabricate components in a layered fashion by fusing the powder particles. This process is multifaceted and pivotal to understand the underlying physics of the coalescence of powder particles during the process, which impacts the structural and mechanical properties of the build component. In this study, a classical molecular dynamics (MD) model is developed for the coalescence of pre-alloyed aluminum alloy (AlSi10Mg) particles during the laser additive manufacturing process. The model is employed to investigate the neck growth and coalescence kinetics of different pairs of particle size with changing the laser energy density from 7 to 17 J/mm2. The simulation results reveal that the unevenly sized particles undergo complete coalescence as compared with even-sized particles, and the neck growth rate of AlSi10Mg particles increases with an increase in laser energy density. Based on the present investigation, it is established that the coalescence kinetics of the AlSi10Mg nanoparticles are governed by the surface and volume diffusion and the surface energy reduction during the joining of particles. This analysis will act as a guideline to design process parameters and quality control for the printing of new components.
关键词： Molecular dynamics,Laser additive manufacturing,Coalescence,Laser energy density,Powder bed fusion
更新于2025-09-23 15:21:01
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Direct in situ TEM visualization and insight of the facet-dependent sintering behaviours of gold on TiO?
摘要： To prevent sintering of supported nanocatalysts is an important issue in nanocatalysis. A feasible way is to choose a suitable support. However, whether the metal-support interactions promote or prevent the sintering has not been fully identified due to the lack of confirmed evidences. Herein, we report on completely different sintering behaviours of Au nanoparticles on distinct anatase TiO2 surfaces by in situ TEM. The full in situ sintering processes of Au nanoparticles were visualized on TiO2 (101) surface, which coupled the Ostwald ripening and particle migration coalescence. In contrast, no sintering of Au on TiO2 anatase (001) surface was observed under the same conditions. This facet-dependent sintering mechanism is fully explained by the density function theory calculations. Our work not only offers the direct evidence of the important role of supports in the sintering process, but also provides insightful information for the design of sintering-resistant nanocatalysts.
关键词： in situ TEM,particle migration and coalescence (PMC),sintering,metal?support interaction (MSI),Au-TiO2,Ostwald ripening (OR)
更新于2025-09-23 15:21:01
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Direct in situ TEM visualization and insight of the facet-dependent sintering behaviours of gold on TiO?
摘要： To prevent sintering of supported nanocatalysts is an important issue in nanocatalysis. A feasible way is to choose a suitable support. However, whether the metal-support interactions promote or prevent the sintering has not been fully identified due to the lack of confirmed evidences. Herein, we report on completely different sintering behaviours of Au nanoparticles on distinct anatase TiO2 surfaces by in situ TEM. The full in situ sintering processes of Au nanoparticles were visualized on TiO2 (101) surface, which coupled the Ostwald ripening and particle migration coalescence. In contrast, no sintering of Au on TiO2 anatase (001) surface was observed under the same conditions. This facet-dependent sintering mechanism is fully explained by the density function theory calculations. Our work not only offers the direct evidence of the important role of supports in the sintering process, but also provides insightful information for the design of sintering-resistant nanocatalysts.
关键词： in situ TEM,particle migration and coalescence (PMC),sintering,metal?support interaction (MSI),Au-TiO2,Ostwald ripening (OR)
更新于2025-09-23 15:21:01
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Drop fragmentation by laser-pulse impact
摘要： We study the fragmentation of a liquid drop that is hit by a laser pulse. The drop expands into a thin sheet that breaks by the radial expulsion of ligaments from its rim and the nucleation and growth of holes on the sheet. By combining experimental data from two liquid systems with vastly different time and length scales, we show how the early-time laser–matter interaction affects the late-time fragmentation. We identify two Rayleigh–Taylor instabilities of different origins as the prime cause of the fragmentation and derive scaling laws for the characteristic breakup time and wavenumber. The final web of ligaments results from a subtle interplay between these instabilities and deterministic modulations of the local sheet thickness, which originate from the drop deformation dynamics and spatial variations in the laser-beam profile.
关键词： breakup/coalescence
更新于2025-09-23 15:19:57
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Light-Induced Coalescence of Plasmonic Dimers and Clusters
摘要： The properties of nanoplasmonic structures depend strongly on their geometry, creating the need for high-precision control and characterization. Here, by exploiting the low activation energy of gold atoms on nanoparticle surfaces, we show how laser irradiation re-shapes nanoparticle dimers. Time-course dark-field micro-spectroscopy allows this process to be studied in detail for individual nanostructures. Three regimes are identified: facet growth, formation of a conductive bridge between particles, and bridge growth. Electromagnetic simulations confirm the growth dynamics and allow measurement of bridge diameter, found to be highly reproducible and also self-limiting. Correlations in spectral resonances for the initial and final states give insights into the energy barriers for bridge growth. Dark-field microscopy shows that coalescence of multiple gaps in nanoparticle clusters can be digitally triggered, with each gap closing after discrete increases in irradiation power. Such control is important for light-induced nanowire formation or trimming of electronic and optoelectronic devices.
关键词： nanoparticle coalescence,gold nanoparticles,optical spectroscopy,plasmonics,sintering,nanoparticle dimers
更新于2025-09-23 15:19:57
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Correlation functions with single-photon emitters under noisy resonant continuous excitation
摘要： To characterize the statistics and indistinguishability of a source, it is common to measure the correlation functions of the emitted field using various interferometers. Here, we present a theoretical framework for the computation of the correlation functions of a two-level system that is resonantly driven by a realistic noisy cw excitation laser. Analytic expressions of the first- and second-order autocorrelation functions are obtained where the various contributions of the noisy excitation source are correctly taken into account. We predict that, even in the low power regime, the noise source has a strong influence on the two-level system dynamics, which is not anticipated by simpler models. The characterization of photon indistinguishability in the pulsed excitation regime is usually done by measuring the value of the zero-delay intensity correlation obtained with a Hong-Ou-Mandel interferometer. We show that this figure is irrelevant in the cw excitation regime and we introduce the coalescence time window, a figure of merit based on a probabilistic interpretation of the notion of photon indistinguishability. We finally use the coalescence time window to quantify how noisy cw excitation influences photon indistinguishability.
关键词： Hong-Ou-Mandel interferometer,correlation functions,coalescence time window,noisy resonant continuous excitation,single-photon emitters
更新于2025-09-19 17:15:36
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Bandgap engineering of TiO2 nanoparticles through MeV Cu ions irradiation
摘要： The effect of 5 MeV Cu++ ions irradiation on structural and optical properties of Anatase TiO2 nanoparticles (TiO2-NPs) is investigated. For this purpose, TiO2-NPs are irradiated with different Cu++ ions ?uences, ranging from 1 (cid:1) 1015 to 1 (cid:1) 1016 ions/cm2 at room temperature. XRD results con?rm the Ti3O7 phase appear at the dose of 5 (cid:1) 1015 ions/cm2 and peak intensity of Ti3O7 phase gradually increases with an increase of Cu++ ions irradiation dose. At the dose of 1 (cid:1) 1016 ions/cm2 TiO2 Anatase phase were transformed to Rutile phase. Same observations are con?rmed from Raman spectroscopy. High resolution transmission electron microscopy (HRTEM) reveals that morphology converted into wavy shape and crystal structure detrioted with increase Cu ion irradiation dose to form vacancy loops and interstitial loops. Scanning electron microscopy (SEM) shows that TiO2-NPs have been fused to form a cluster of nanoparticles at high Cu ion beam dose, while bandgap of TiO2-NPs reduces from 3.19 eV to 2.96 eV as a function of Cu++ irradiation ?uence. These phase transformations and crystal damage are the responsible for optical bandgap reduction. The mechanism for the currently observed phase transformation of TiO2 and coalescence of TiO2-NPs are discussed in term of thermal spikes model.
关键词： Coalescence of NPs,Bandgap engineering,Cu++ irradiation,Rutile phase,TiO2 nanoparticles
更新于2025-09-10 09:29:36