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Tailoring metal film texture by use of high atomic mobility at metal-semiconductor interfaces
摘要： The difference in the microstructural and texture evolution of Al films grown on amorphous SiO2 (a-SiO2) and amorphous Ge (a-Ge) substrates have been investigated. Surprisingly, the a-Ge substrate was found to change the preferred orientation of Al grains from the conventional (1 1 1) to the unconventional (1 1 0). The effect of the high mobility of Ge atoms at the metal-semiconductor interface on the microstructural and texture evolution of the metal thin film was studied. The diffusion of the Al adatoms on the a-Ge substrate was suppressed owing to the segregation of Ge atoms at the film surface. The mobility of Al grain boundaries was also suppressed because of grain-boundary wetting by the Ge atoms. It is concluded that the a-Ge substrate could tailor the Al grain orientation from (1 1 1) to (1 1 0) owing to the change in the film-growth mode from three-dimensional to two-dimensional nucleation. The concept of interaction-induced island-growth model, which is based on the Volmer–Weber growth model, is also discussed here. This work thus demonstrates how the atomic mobility at the interface of the metal thin film and the semiconductor substrate controls the film microstructure and texture during deposition.
关键词： Substrate,Microstructure,Surface diffusion,Texture,Metal thin film,Grain-boundary wetting
更新于2025-09-23 15:23:52
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A study of surface diffusion of ternary (Cu-Ag-Zr) adatoms clusters for applications in thin film formation
摘要： This study presents the diffusion of heterogeneous ternary (Cu‐Ag‐Zr) adatoms clusters on Ag(111) using molecular dynamics techniques which could be important for the surface phenomena's and helpful for the ternary cluster's growth and formation of ternary alloy‐based thin films. The mechanism of nanoscale surface diffusion is investigated for 1Cu‐1Ag‐1Zr, 2Cu‐2Ag‐2Zr, 3Cu‐3Ag‐3Zr, and 4Cu‐4Ag‐4Zr clusters at temperatures 300, 500, and 700 K. The diffusion mechanism displays that the diffusion of trimer cluster exhibits hopping, sliding, and shearing at 300 K, whereas for hexamer, nonamer, and decamer, the diffusion rate is low; however, breathing, anchoring, and concentrated motion dominates. At 500 K, trimer and hexamer show the process of atomic exchange; however, the atomic exchange is not observed in the case of nonamer and decamer diffusion. The atomic exchange mechanism of Cu and Zr adatoms dominates at 700 K for all size clusters, except Ag adatoms, where Zr adatoms show a relatively more tendency. Separation and rejoining of the one and two adatoms (likely Zr adatom) are also witnessed at high temperature. The pop‐up of Ag adatoms also occurs in very short intervals over the remaining adatoms of clusters. Interestingly, during trimer diffusion, the adsorption of the Zr‐ or Cu‐adatom among the trimer cluster into the substitutional site is found. At 700 K, vacancy generation, filling of vacancies, and migration of vacancy, in the neighborhood of the adatoms cluster, also observed. Moreover, the rate of diffusion decreases with the size increase of the clusters and increases with the increase in temperature.
关键词： molecular dynamics,adatoms clusters,vacancy diffusion,surface diffusion
更新于2025-09-23 15:22:29
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Dependence of h-BN film thickness as grown on nickel single crystal substrates of different orientation
摘要： Chemical vapor deposition of 2D materials has been an active area of research in recent years because it is a scalable process for obtaining thin films that can be used to fabricate devices. The growth mechanism for hexagonal boron nitride (h-BN) on metal catalyst substrates has been described to be either surface energy driven or diffusion driven. In this work, h-BN is grown in a CVD system on Ni single crystal substrates as a function of Ni crystallographic orientation to clarify the competing forces acting on the growth mechanism. We observed that the thickness of the h-BN film depends on the Ni substrate orientation, with the growth rate increasing from the (100) surface to the (111) surface, and the highest on the (110) surface. We associate the observed results with surface reactivity and diffusivity differences for different Ni orientations. Boron and nitrogen diffuse and precipitate from the Ni bulk to form thin multilayer h-BN. Our results serve to clarify the h-BN CVD growth mechanism which has been previously ascribed to a surface energy-driven growth mechanism.
关键词： surface diffusion,electron backscatter diffraction,growth mechanism,hexagonal boron nitride
更新于2025-09-23 15:21:01
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Mechanisms of GaN quantum dot formation during nitridation of Ga droplets
摘要： We have examined the formation mechanisms of GaN quantum dots (QDs) via annealing of Ga droplets in a nitrogen ?ux. We consider the temperature- and substrate-dependence of the size distributions of droplets and QDs, as well as the relative roles of Ga/N diffusivity and GaN nucleation rates on QD formation. We report on two competing mechanisms mediated by Ga surface diffusion, namely, QD formation at or away from pre-existing Ga droplets. We discuss the relative roles of nucleation- and coarsening-dominant growth, as well as zincblende vs wurtzite polytype selection, on various substrates. These insights provide an opportunity for tailoring QD size distributions and polytype selection for a wide range of III-N semiconductor QDs.
关键词： polytype selection,surface diffusion,GaN quantum dots,nitridation,Ga droplets
更新于2025-09-23 15:19:57
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Self‐Assembly of Nanoparticle‐Spiked Pillar Arrays for Plasmonic Biosensing
摘要： Plasmonic biosensors have demonstrated superior performance in detecting various biomolecules with high sensitivity through simple assays. Scaled-up, reproducible chip production with a high density of hotspots in a large area has been technically challenging, limiting the commercialization and clinical translation of these biosensors. A new fabrication method for 3D plasmonic nanostructures with a high density, large volume of hotspots and therefore inherently improved detection capabilities is developed. Specifically, Au nanoparticle-spiked Au nanopillar arrays are prepared by utilizing enhanced surface diffusion of adsorbed Au atoms on a slippery Au nanopillar arrays through a simple vacuum process. This process enables the direct formation of a high density of spherical Au nanoparticles on the 1 nm-thick dielectric coated Au nanopillar arrays without high-temperature annealing, which results in multiple plasmonic coupling, and thereby large effective volume of hotspots in 3D spaces. The plasmonic nanostructures show signal enhancements over 8.3 × 108-fold for surface-enhanced Raman spectroscopy and over 2.7 × 102-fold for plasmon-enhanced fluorescence. The 3D plasmonic chip is used to detect avian influenza-associated antibodies at 100 times higher sensitivity compared with unstructured Au substrates for plasmon-enhanced fluorescence detection. Such a simple and scalable fabrication of highly sensitive 3D plasmonic nanostructures provides new opportunities to broaden plasmon-enhanced sensing applications.
关键词： surface diffusion,plasmonic biosensors,spherical metal nanoparticles,3D nanostructures,surface energy
更新于2025-09-19 17:13:59
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The merging mechanisms of poly(3-hexylthiophene) domains revealed through scanning tunneling microscopy and molecular dynamics simulations
摘要： Herein, we in situ track the merging processes of poly(3-hexylthiophene) (P3HT) domains physisorbed onto graphite while keeping the domain structures clearly resolved through scanning tunneling microscopy (STM). The domain shape-fixed, amoeba/worm-like and bridge-mediated merging mechanisms are revealed. In the domain shape-fixed diffusion, the moving domains obey the principle of the non-continuous random walks. Both diffusive and ballistic-like dynamics are disclosed. Additionally, the asymmetrical domains may show anisotropic movements. In the amoeba-like style, the pseudopodia are formed and changed stochastically while in the worm-like style two permanent parts (head and body) of the domains are formed prior movement and kept fixed in the motions. Finally, the integration of two domains is called a bridge-mediated one, if a small domain is bound to a bigger one directly through a dynamic bridge. The molecular dynamics simulations support the experimental findings of P3HT domain movements and rotations on the graphite surface.
关键词： Surface diffusion,Poly(3-hexylthiophene),Scanning tunneling microscopy
更新于2025-09-19 17:13:59
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Controlled growth of single-crystalline metal nanowires via thermomigration across a nanoscale junction
摘要： Mass transport driven by temperature gradient is commonly seen in fluids. However, here we demonstrate that when drawing a cold nano-tip off a hot solid substrate, thermomigration can be so rampant that it can be exploited for producing single-crystalline aluminum, copper, silver and tin nanowires. This demonstrates that in nanoscale objects, solids can mimic liquids in rapid morphological changes, by virtue of fast surface diffusion across short distances. During uniform growth, a thin neck-shaped ligament containing a grain boundary (GB) usually forms between the hot and the cold ends, sustaining an extremely high temperature gradient that should have driven even larger mass flux, if not counteracted by the relative sluggishness of plating into the GB and the resulting back stress. This GB-containing ligament is quite robust and can adapt to varying drawing directions and velocities, imparting good controllability to the nanowire growth in a manner akin to Czochralski crystal growth.
关键词： single-crystalline,surface diffusion,nanowires,grain boundary,thermomigration
更新于2025-09-16 10:30:52
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Titanium coverage for plasma-induced uniform HfSiON film from Hf nanoscale islands on SiO <sub/>2</sub> /Si
摘要： Signi?cant improvement of the in-plane uniformity of an HfSiON ?lm is enabled by a Ti coverage over Hf islands on an SiO2/Si substrate. Surface diffusion of Hf during an HfSiON ?lm growth from Hf (island)/SiO2/Si structure induced by a nitrogen inductively coupled plasma (ICP) exposure is effectively suppressed by the Ti coverage. The nitrogen ICP exposure to the Ti/Hf (island)/SiO2/Si surface forms a TiN layer, which suppresses the surface diffusion of Hf by lowering the surface energy. Even a small Ti coverage of 5% is effective for the uniform Hf concentration in the HfSiON ?lm. The uniformity of the ?lm is monitored by an in vacuo noncontact AFM and a cross-sectional SEM imaging. An ex situ XPS analysis indicates that the TiN layer is sputtered by the ion bombardment and the Ti content in the ?lm decreases less than 1%. The intermixing of Si with Hf and the subsequent nitridation of the ?lm is successfully performed even the surface is covered with TiN. The mercury probe measurement revealed that the improved uniformity by the Ti coverage increases the capacitance and reduces the leakage current of the high-k dielectric ?lm.
关键词： uniform film,capacitance,HfSiON,Ti coverage,leakage current,nitrogen ICP,surface diffusion,plasma-induced,TiN layer
更新于2025-09-09 09:28:46
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Thermal Reshaping Dynamics of Gold Nanorods: Influence of Size, Shape, and Local Environment
摘要： The thermal reshaping of gold nanorods in a polymer matrix is an important phenomenon for many potential applications. However, a fundamental understanding of the various mechanisms that govern the nanorod reshaping dynamics is still lacking. Here we provide evidence for a phenomenological model of the gold nanorod shape transformation based on the measurements and detailed analysis of the time-resolved thermal reshaping for a variety of gold nanorods having different geometries (aspect ratio, volume, diameter) in a crosslinked epoxy matrix at application relevant temperatures (120 ? 220 ?C). Our analysis suggests that a) the nanorod reshaping dynamics consist of two temporal regimes that are governed by different phenomena, and b) the ultimate amount of reshaping at a given temperature depends strongly on the initial particle geometry and the mechanical stiffness of its surroundings. At short times the shape transformation is dominated by a curvature-induced surface diffusion process in which the activation energy for diffusion depends on curvature. At long times, however, the surrounding environment plays a key role in slowing the diffusion and stabilizing the nanorod shape. We show that the long time behavior can be well described using a modified surface diffusion model that takes into account the slowing of atomic diffusivity as a result of external forces arising from mechanical constraints. The ability to tune both the final shape and the reshaping dynamics in nanocomposites opens up new possibilities in tailoring the optical properties of these materials.
关键词： Polymer Nanocomposites,Surface Diffusion,Temperature Sensing,Plasmonics,Thermal Reshaping,Gold Nanorods
更新于2025-09-09 09:28:46
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Modeling of metastable phase formation for sputtered Ti1-xAlxN thin films
摘要： Metastable titanium aluminum nitride coatings are widely applied in cutting and forming applications. Although it is generally accepted that the phase formation of metastable TiAlN is governed by kinetic factors, modeling attempts today are based solely on energetics. In this work, the metastable phase formation of TiAlN is predicted based on one combinatorial magnetron sputtering experiment, the activation energy for surface diffusion, the critical diffusion distance, as well as thermodynamic calculations. The phase formation data obtained from further combinatorial growth experiments varying chemical composition, deposition temperature, and deposition rate are in good agreement with the model. Furthermore, it is demonstrated that a significant extension of the predicted critical solubility range is enabled by taking kinetic factors into account. Explicit consideration of kinetics extends the Al solubility limit to lower values, previously unobtainable by energetics, but accessible experimentally.
关键词： Surface diffusion,TiAlN,Metastable phase,Combinatorial magnetron sputtering
更新于2025-09-04 15:30:14