Evolution Of Surface Morphology Research Articles

Formation of partially embedded Au nanostructures: Ion beam irradiation on thin film.

The Au partially embedded nanostructure (PEN) is synthesized by ion irradiation on an Au thin film deposited on a glass substrate using a 50 keV Ar ion. Scanning electron microscopy results show ion beam-induced restructuring from irregularly shaped nanostructures (NSs) to spherical Au NSs, and further ion irradiation leads to the formation of well-separated spherical nanoparticles. Higuchi's algorithm of surface analysis is utilized to find the evolution of surface morphology with ion irradiation in terms of the Hurst exponent and fractal dimension. The Au PEN is evidenced by Rutherford backscattering spectrometry and optical studies. Also, the depth of the mechanism behind synthesized PEN is explained on the basis of theoretical simulations, namely, a unified thermal spike and a Monte Carlo simulation consisting of dynamic compositional changes (TRIDYN). Another set of plasmonic NSs was formed on the surface by thermal annealing of the Au film on the substrate. Glucose sensing has been studied on the two types of plasmonic layers: nanoparticles on the surface and PEN. The results reveal the sensing responses of both types of plasmonic layers. However, PEN retains its plasmonic behavior as the NSs are still present after washing with water, which demonstrates the potential for reusability. RESEARCH HIGHLIGHTS: Synthesis of PENs by ion irradiation Utilization of Higuchi's algorithm to explore the surface morphology. Unified thermal spike and TRIDYN simulations being used to explain the results. Glucose is only used as a test case for reusability of substrate.

Morphology evolution and non-uniformity removal mechanism analysis of diamond nanocone arrays by reactive ion etching

Microstructures of diamond can be fabricated by reactive ion etching and during this process the evolution of surface morphology can affect the electric field near the microstructure. These changes in the electric field will alter the trajectory of ions, thereby affecting the number of ion bombardments on the surface regions of the microstructure. Consequently, this will affect the removal rate of the material on the microstructure surface and consequently affects the evolution of microstructure morphology. In order to understand the morphology evolution process of diamond during etching. H2 and Ar were used as the reactive gases to etch the nanocrystalline diamond (NCD) films with masks. The electric field near the microstructure and the trajectories of reactive ions was stimulated. The number of H+ and Ar+ bombardments at various regions on the diamond microstructure surface has been recorded and analyzed. By observing the cross-sectional morphology of the microstructure at different periods, the etching process of nanocones was analyzed. The study found that the microstructure of the diamond surface would gradually be etched into convex shaped and waist drum shaped and cone. By stimulating the electric field near the microstructure, it was found that the electric field distorted near the microstructure, causing the electric field lines initially perpendicular to the diamond surface to be diverted. As a result, the trajectory of the particles originally arrived perpendicularly to the diamond surface was distorted and hence they bombarded against the sidewall of the diamond microstructures. The angle between the ion trajectory and the electric field line also increased gradually.

Modeling the coverage of MoS2 and WS2 thin films using in-situ spectroscopic ellipsometry

In-situ spectroscopic ellipsometry (SE) was used to analyze monolayer and few-layer samples of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. MoS2 and WS2 film growth times ranged from 5 – 40 min to achieve a range of film coalescence and surface coverage from less than a monolayer to considerable bilayer and additional layers. Post-growth measurements using atomic force microscopy, photoluminescence and Raman spectroscopy were used to assess the evolution of surface morphology and film properties with growth time to determine the areal coverage of monolayer, bilayer, multilayer and void regions. The room temperature SE spectra were modeled using an effective medium approximation to obtain the monolayer and bilayer dielectric functions of MoS2 and WS2. Using these distinct dielectric functions, changes in ellipsometry parameters associated with partial to full coverage of monolayers and bilayers were simulated. Such simulations will enable improved control of the layer-by-layer deposition of MoS2 and WS2 by monitoring in-situ spectroscopic ellipsometry.

Surface roughness evolution and heterogeneous plastic deformation of austenitic stainless steel during micro deep drawing: Modeling and experiment

The present work involves the numerical simulation and experimental study on the surface roughness evolution and heterogeneous plastic deformation (strain localization and concomitant surface morphology evolution) in grain scale of micro deep drawn parts of austenitic stainless steel (ASS) 304 foils. A three-dimensional modeling framework was used to simulate the micro deep drawing (MDD) process. The simulation involved the development of a Voronoi-based polycrystalline geometry model (VPGM), a multi-stress-strain response model, and a crystal plasticity finite element methods (CPFEM) model. The results indicate that CPFEM model exhibits higher accuracy in the localized stress and strain, thickness distribution fluctuation and surface roughness evolution of the fabricated parts compared to multi-stress-strain response model. Therefore, the plastic deformation heterogeneity in MDD is in-depth discussed based on CPFEM model. The results show that the coarse-grained foils correspond to the intense strain localization, which is the main cause of surface roughening. Considering the average grain size is close to the thickness of ASS foils, mounding features on the rough surface may readily develop further into potentially fractured sites during deformation. On the other hand, crystal orientation influence plastic deformation by affecting the slip behavior of materials. The effect of crystal orientations including {011} 〈211〉 (Brass), {011} 〈100〉 (Goss), and {112} 〈110〉 components on deformation is discussed. The results indicate a strong correlation between the magnitude of the Schmid's factor and the ease of deformation. Additionally, variations in Schmid's factor across different directions result in differences in deformation accumulation, which affects the thickness distribution along the radial direction and the distribution of earrings and wrinkles along the circumferential direction of the fabricated micro parts.

Linear vs. Non-linear Behaviour in Ion Irradiation Nanostructuring of Nickel and Silicon Surfaces

Spontaneous nanometre-scale quasi-periodic ripple-like structures are formed at the surface of polycrystalline Ni films and Si(111) single crystal wafers by irradiation with a broad Ar+ ion beam at room temperature and studied with Atomic Force Microscopy as a function of fluence. The development of these structures can be reproduced by numerical solution of a continuum equation describing the evolution of surface morphology under ion irradiation, using realistic coefficients derived from material properties. In particular, we demonstrate that differences observed in pattern formation on the two surfaces under the conditions studied, such as wavelength stability and exponential growth of interface width for the Ni surfaces compared with wavelength coarsening and interface width saturation on Si(111), can be understood in terms of a cross-over between linear and non-linear behaviours.

The Study on Corrosion Resistance of Ti-6Al-4V ELI Alloy with Varying Surface Roughness in Hydrofluoric Acid Solution

The corrosion resistance of titanium alloy poses a crucial challenge, significantly affecting its prospect for service and application. The present study aimed to investigate the corrosion resistance of Ti-6Al-4V ELI alloys with varying surface roughness in hydrofluoric acid solution, in order to assess the influence of roughness on their corrosion resistance performance. The weight loss percentage, surface morphology evolution, and roughness variation of Ti-6Al-4V ELI alloys before and after exposure to hydrofluoric acid corrosion were characterized. While the weight loss and weight loss percentage of the Ti-6Al-4V ELI alloy increased with prolonged corrosion, the overall weight loss rate decreased. The accumulation of TiF3 phases and depletion of the Ti-6Al-4V ELI matrix mutually led to the alterations of the surface roughness. Due to the inability to prevent fluoride ions from contacting with the Ti-6Al-4V ELI alloy, continuous corrosion occurred in hydrofluoric acid. Based on these experimental results and analysis, the corrosion mechanism of the Ti-6Al-4V ELI alloy corroded by hydrofluoric acid solution was elucidated. Furthermore, an analysis was conducted to explore the influence of corrosion time on mechanical properties by analyzing the decay in compressive properties of the Ti-6Al-4V ELI titanium alloy after hydrofluoric acid corrosion treatment. The bearing capacity of the Ti-6Al-4V ELI alloy deteriorated over the corrosion time.

Investigating the Dynamic Mechanical Properties and Strengthening Mechanisms of Ti-6Al-4V Alloy by Using the Ultrasonic Surface Rolling Process.

The demand for titanium alloy has been increasing in various industries, including aerospace, marine, and biomedical fields, as they fulfilled the need for lightweight, high-strength, and corrosion-resistant material for modern manufacturing. However, titanium alloy has relatively low hardness, poor wear performance, and fatigue properties, which limits its popularization and application. These disadvantages could be efficiently overcome by surface strengthening technology, such as the ultrasonic surface rolling process (USRP). In this study, the true thermo-mechanical deformation behavior of Ti-6Al-4V was obtained by dynamic mechanical experiment using a Hopkinson pressure bar. Moreover, USRP was applied on the Ti-6Al-4V workpiece with different parameters of static forces to investigate the evolution in surface morphology, surface roughness, microstructure, hardness, residual stress, and fatigue performance. The strain rate and temperature during the USRP of Ti-6Al-4V under the corresponding conditions were about 3000 s-1 and 200 °C, respectively, which were derived from the numerical simulation. The correlation between the true thermo-mechanical behavior of Ti-6Al-4V alloy and the USRP parameters of the Ti-6Al-4V workpiece was established, which could provide a theoretical contribution to the optimization of the USRP parameters. After USRP, the cross-sectional hardness distribution of the workpiece was shown to initially rise, followed by a subsequent decrease, ultimately to matrix hardness. The cross-sectional residual compressive stress distribution of the workpiece showed a tendency to initially reduce, then increase, and finally decrease to zero. The fatigue performance of the workpiece was greatly enhanced after USRP due to the effect of grain refinement, work hardening, and beneficial residual compressive stress, thereby inhibiting the propagation of the fatigue crack. However, it could be noted that the excessive static force parameter of USRP could induce the decline in surface finish and compressive residual stress of the workpiece, which eliminated the beneficial effect of the USRP treatment. This indicated that the choice of the optimal USRP parameters was highly crucial. This work would be conducive to achieving high-efficiency and low-damage USRP machining, which could be used to effectively guide the development of high-end equipment manufacturing.

Influence of deposition pressure on the microstructure and mechanical properties of sputter-deposited MoNbTaW refractory multi-principal element alloy thin films

A systematic investigation into the effects of deposition pressure on the microstructure and mechanical properties of MoNbTaW refractory multi-principal element alloy (RMPEA) films deposited on Silicon (100) substrates using direct current magnetron sputtering (DCMS) is presented. The deposition pressure was varied from 3 Pa to 0.3 Pa at a homologous temperature (T/Tm) ≤ 0.1. The crystal structure, surface morphology, cross-sectional microstructure and mechanical properties were studied using X-ray diffraction, scanning and transmission electron microscopy and nanoindentation. X-ray diffraction findings indicate a single-phase BCC structure throughout the pressure range. An evolution in surface morphology was observed, coupled with a transition from a void-rich to a densified microstructure as the deposition pressure decreased, in line with the structure zone model. Additionally, variations in crystallographic orientations were detected, with changes in I(110)/(211) suggesting an interplay between film growth dynamics and crystallographic orientation shifts with the deposition pressure. The mechanical properties have shown significant improvement, with hardness and modulus values increasing from 7GPa to 12 GPa and 135 GPa to 243 GPa, with a decrease in deposition pressure. The study provides insights into the deposition mechanism, highlighting that microstructural changes and variations in crystallographic orientations are influenced by deposition pressure-induced alterations in adatom energy and surface mobility, thus affecting the films' mechanical properties.

Millisecond X-ray reflectometry and neural network analysis: unveiling fast processes in spin coating.

X-ray reflectometry (XRR) is a powerful tool for probing the structural characteristics of nanoscale films and layered structures, which is an important field of nanotechnology and is often used in semiconductor and optics manufacturing. This study introduces a novel approach for conducting quantitative high-resolution millisecond monochromatic XRR measurements. This is an order of magnitude faster than in previously published work. Quick XRR (qXRR) enables real time and in situ monitoring of nanoscale processes such as thin film formation during spin coating. A record qXRR acquisition time of 1.4 ms is demonstrated for a static gold thin film on a silicon sample. As a second example of this novel approach, dynamic in situ measurements are performed during PMMA spin coating onto silicon wafers and fast fitting of XRR curves using machine learning is demonstrated. This investigation primarily focuses on the evolution of film structure and surface morphology, resolving for the first time with qXRR the initial film thinning via mass transport and also shedding light on later thinning via solvent evaporation. This innovative millisecond qXRR technique is of significance for in situ studies of thin film deposition. It addresses the challenge of following intrinsically fast processes, such as thin film growth of high deposition rate or spin coating. Beyond thin film growth processes, millisecond XRR has implications for resolving fast structural changes such as photostriction or diffusion processes.

Controllable release of Cu ions contributes to the enhanced environmentally-friendly performance of antifouling Cu-bearing stainless steel coating prepared using high-velocity air fuel

Organic antifouling coatings represent an economical and efficient solution for addressing the marine biofouling. However, their application is constrained by issues of durability and toxicity. Therefore, this study has developed a metal-based antifouling coating by utilizing pre-alloyed copper-bearing stainless steel (Cu-bearing SS) powder in conjunction with high-velocity air fuel (HVAF) technology, aiming to achieve an environmentally-friendly and long-lasting antifouling coating. Compared to the self-polishing copolymer (SPC) coating, the adhesion strength of Cu-bearing SS coating increased to 69.0 MPa, which is approximately a 33-fold increase. The coating also exhibited enhanced wear resistance, the width and depth of the wear track for the Cu-bearing SS coating decreased 42.9 % and 81.0 %, respectively. Furthermore, the coating still demonstrated strong inhibitory effects on typical fouling microorganisms and algae adhesion due to Cu ions release process environmentally-friendly. The electrochemical techniques coupling with surface morphology observations were used to elucidate the antifouling mechanism. The variation trend of coating corrosion current was consistent with the release process of Cu ions, which was directly related to the evolution of the coating surface morphology. The three-stage change in the surface morphology of the 304 L-Cu SS coating contributes to the formation of a cyclic variation trend process of Cu ions. The evolution of surface morphology, accompanied by the controlled release process of Cu ions, had become a distinctive feature of antifouling properties for a metal-based coating.

20 μm Copper Micro-Bump Bonding Through a Silver Metallization for Advanced Packaging Under a Low Pressure Condition

In this work, we proposed a copper (Cu) microbump bonding strategy by using a silver (Ag) metallization layer as an interconnect bridge. Si chips with 20 μm Cu-Ag bumps were bonded under a low pressure (0.4 MPa) and atmospheric conditions at 250 °C. By investigating the surface morphology evolution of the Cu-Ag bump, it is found that severe surface deformation caused by Ag abnormal grain growth and hillock generation plays a critical role in the Cu-Ag bump bonding, which facilitates the approach and bonding of top and bottom Ag surface of the bump structure. Moreover, this bonding strategy is expected to be particularly advantageous for finepitch interconnect applications. It not only mitigates the severe bonding condition requirements that are used in thermal compression bonding and hybrid bonding, but also provides higher quality bonding structures for advanced packaging.

Surface topography and microstructure changes of ultrafine-grained graphite prepared from filler of onion-like carbon spheres by Xe ions irradiation

Onion-like carbon spheres (OLC) were doped into the traditional graphite raw material system to decrease the pore diameter to ∼400 nm, with potential for use in molten salt reactors. The obtained graphite (OLCG) prepared from OLC was subjected to 7 MeV Xe26+ irradiation in this work, and a systematic investigation was conducted to verify its irradiation behavior. The surface morphology and microstructural evolution in graphite samples under different irradiation conditions were studied with different characterization methods. The surface roughness of OLCG increased and the hill appeared at lower irradiation doses, which was similar to that of IG-110, but the filler particles of OLCG gradually become spherical at 2.5 dpa. The analysis by X-ray diffraction reveals that OLCG's graphitization degree is approaching but slightly worse compared to IG-110. Raman studies indicate that the irradiation causes an increase in defect density and in-plane disorder both in graphite. The OLC filler exhibits a greater sensitivity to radiation, leading to OLCG being slightly sensitive to radiation as compared to IG-110. Neutron irradiation of the resulting graphite should be continued as OLCG showed good irradiation resistance at low irradiation doses and had a much smaller pore diameter.

A Flexible Wearable Sensor Based on Laser-Induced Graphene for High-Precision Fine Motion Capture for Pilots.

There has been a significant shift in research focus in recent years toward laser-induced graphene (LIG), which is a high-performance material with immense potential for use in energy storage, ultrahydrophobic water applications, and electronic devices. In particular, LIG has demonstrated considerable potential in the field of high-precision human motion posture capture using flexible sensing materials. In this study, we investigated the surface morphology evolution and performance of LIG formed by varying the laser energy accumulation times. Further, to capture human motion posture, we evaluated the performance of highly accurate flexible wearable sensors based on LIG. The experimental results showed that the sensors prepared using LIG exhibited exceptional flexibility and mechanical performance when the laser energy accumulation was optimized three times. They exhibited remarkable attributes, such as high sensitivity (~41.4), a low detection limit (0.05%), a rapid time response (response time of ~150 ms; relaxation time of ~100 ms), and excellent response stability even after 2000 s at a strain of 1.0% or 8.0%. These findings unequivocally show that flexible wearable sensors based on LIG have significant potential for capturing human motion posture, wrist pulse rates, and eye blinking patterns. Moreover, the sensors can capture various physiological signals for pilots to provide real-time capturing.

Digital twin-driven graph domain adaptation neural network for remaining useful life prediction of rolling bearing

Remaining useful life (RUL) prediction is significant for the healthy operation of machinery. In order to accurately identify the bearing degeneration states, it is necessary to collect massive full lifecycle data. However, the bearing lifecycle data is insufficient for effectively training a RUL prediction model in engineering practice. In this paper, a digital twin-driven graph domain adaptation method is proposed. First, a full lifecycle dynamic twin model of bearings is constructed to generate abundant twin data, in which the surface morphology evolution and roller relative slip at different stages are simulated to generate vibration responses. Second, a novel multi-layered cross-domain gated graph convolutional network (MGGCN) is developed, in which a new graph domain adaptation model is designed to solve the problem that traditional domain adaptation methods are not effective in processing the non-Euclidean data. The spatial and temporal features are extracted by multiple nonlinear transformations and previous time-step hidden state incorporation, respectively. In addition, a graph Laplacian regularized maximum mean discrepancy (GLMMD) is designed and applied in the training of model to enhance the capability of discerning graph domain differences. The experimental results confirm that the proposed method can achieve effective performance even in scenarios with limited actual data.

Numerical simulation for the evolution in surface morphology of titanium alloy by nanosecond pulsed laser ablation

Lack of effective methods to investigate the evolution mechanism of crater and stripe morphology formed on the surface of titanium alloy by nanosecond pulsed laser. In this paper, the evolution of the surface morphology of titanium alloy during laser ablation was elucidated by numerically simulating the temperature and flow fields of multiple nanosecond pulsed lasers. With 8.75 J/cm2 and 35 J/cm2, uniform crater morphology and stripes shape were formed respectively, but the surface roughness increased. In the former case, the surface of the melt pool was depressed by the vaporization pressure, and the rapid solidification caused the edge of the supercooled crater to increase, forming crater morphology. In the latter case, the difference is related to the formation of multiple relatively independent melt pools at lower energy input, where the heat accumulation caused multiple molten pools to merge into a large-scale molten pool. The flow velocity increased, the molten pool duration was prolonged and the size of the molten pool increased, resulting in a triangular-trapezoidal-tower trend of the pit edge. The size of the pit edge decreased or even “disappeared”, eventually forming stripes shape.

Kinetic Monte Carlo study on the effect of growth conditions on the epitaxial growth of 3C–SiC (0001) vicinal surface

Due to the lack of research on the microscopic evolution process and the formation of step growth patterns for SiC crystals, it is of great importance to deepen the understanding of the epitaxial growth of a SiC vicinal surface from a microscopic point of view. In this study, a three-dimensional lattice kinetic Monte Carlo algorithm was used to study the step flow growth characteristics of SiC crystals. The microscopic evolution of the step flow growth patterns for SiC vicinal surfaces was shown. C and Si were treated as the basic particles, and the net deposition and diffusion of atoms were considered in this model. The periodic boundary conditions were applied along the step edge and the helical boundary conditions were applied in the direction perpendicular to the step. The surface morphology evolution of SiC crystals grown on step substrates was simulated at different growth temperatures, partial deposition fluxes, and terrace widths. The results indicated that the growth patterns of the SiC vicinal surface could be transformed from a step flow growth to a nucleation growth pattern by decreasing the growth temperature, increasing the deposition flux, and increasing the terrace width.

Stress-driven recrystallization of pentacene films via diffusion-induced ingress of MOF nanocrystals into the grain boundaries

Metal-organic frameworks (MOFs) have been identified as versatile candidates for producing functional materials for various applications. However, the growth of MOF thin film becomes challenging due to non-availability of a proper solvent that restricts the use of the materials in electronic sensor fabrication. The receptor molecules in sensors are often used to functionalize the semiconducting channel. However, integrating such molecules degrade the crystallinity of channel materials, leading to poor sensor performance. In this work, we report the growth of a MOF (CPO-27-Ni) thin film and the recrystallization of semiconducting pentacene thin films due to diffusion of the crystallites into the grain boundaries. MOF films were successfully spin coated at various revolutions per minute (rpm) on pentacene surfaces. The growth of MOF films was studied using statistical analysis of rough surfaces by utilizing scaling theory to capture the evolution of surface morphologies. The x-ray reflectivity study unveiled the diffusion-induced ingress of the MOF through the grain boundaries of pentacene films that imparts compressive stress within the grains leading to subsequent rearrangement of pentacene molecules in the thin-film phase and recrystallizes the bulk crystallographic phase, which in a way will enhance the device performance.

Surface morphology evolution mechanisms of pulse laser polishing mold steel

In this study, high-frequency nanosecond pulse laser was conducted on mold steel surfaces for solving surface defects during polishing processes. The influence of different single-pulse energy densities on surface roughness was carefully investigated through technical experiments, with the lowest roughness obtained at 2.5 J/cm2. A computational fluid dynamics (CFD) model was developed to simulate the evolution of surface morphology at different energy densities. The applicability of the model was successfully verified by comparative experiments and simulative results. The evaporation threshold for nanosecond pulse laser polishing was found to be between 2.5 and 3.0 J/cm2. The introduction of evaporation and increased temperature gradients accelerate the flow of the melt pool, thereby leading to a shift in the driving force for fluid velocity. The short pulse cycle can create a continuous melt pool that moves with the laser beam, resulting in surface flattening along the scanning path. Under a large number of overlapping pulses, the surface over melting (SOM) mechanism dominated the morphology evolution of the molten pool. Significant findings demonstrated that pulse laser-induced heat accumulated to melt the peaks and valleys of the initial surface, while convective flow reduced the height difference of the melt pool. It can provide a new insight into surface roughness improvement of metals through nanosecond pulse laser polishing.

X‐ray imaging for structural evolution and phase transformation dynamics of battery electrodes

AbstractThe impending energy crisis entails sustainable battery technologies with improved energy density, reliability, safety and lifetime. Hence, it is essential to gain detailed insights into the surface reactions, ionic diffusion, structural and morphological evolution, and degradation mechanisms of battery electrodes. Recently, X‐ray techniques emerged as revolutionary tools to reveal an in‐depth understanding of the battery during operations. This review provides an overview of the use of in situ/operando X‐ray techniques to understand the different functionalities of electrode materials inside the battery. It will focus on the phase transformation, structural evolution and dynamic properties of the battery electrodes, and discuss the relationship between battery failure and electro‐chemo‐mechanical failure in the electrode. Finally, the limitations of these methods are also discussed with the prospects for effective use of these techniques in the development of advanced battery technologies.

Surface Morphology Evolution of AlGaN Microhoneycomb Structures during Epitaxial Overgrowth

The surface morphological development during epitaxial overgrowth of AlGaN on microhoneycomb (μ‐HC) patterned relaxed AlGaN/AlN/sapphire templates is studied. Optimization of μ‐pattern design and influence of various growth parameters are carried out in search for conditions resulting in coalescence of μ‐HC structures into planar layers or ordered arrays of V‐pits with well‐defined crystallographic facets. It is found that in a wide range of growth conditions, formation of V‐pits with semipolar facets occurs where their crystallographic orientation is defined by the geometry of the initial μ‐HC patterns and growth conditions. High‐temperature and high V/III ratio conditions are found to favor c‐plane expansion and allow recovery of planarity on the patterned templates. Systematic study of surface morphology evolution in conditions favoring 1) semipolar facets formation and 2) coalescence is carried out and possible mechanisms underpinning the observed behaviors have been proposed.