Topography Simulation Research Articles

Conductive-AFM topography and current maps simulator for the study of polycrystalline high-k dielectrics

In this work, a simulator of conductive atomic force microscopy (C-AFM) was developed to reproduce topography and current maps. In order to test the results, the authors used the simulator to investigate the influence of the C-AFM tip on topography measurements of polycrystalline high-k dielectrics, and compared the results with experimental data. The results show that this tool can produce topography images with the same morphological characteristics as the experimental samples under study. Additionally, the current at each location of the dielectric stack was calculated. The quantum mechanical transmission coefficient and tunneling current were obtained from the band diagram by applying the Airy wavefunction approach. Good agreement between experimental and simulation results indicates that the tool can be very useful for evaluating how the experimental parameters influence C-AFM measurements.

Modelling and simulation of the surface topography generation with engineered grinding wheel

This paper establishes the kinematics model, elastic deformation model and plastic accumulation model of the engineered grinding wheel and makes the numerical simulation of the surface topography of the engineered grinding wheel with quenching 45 steel as the research subject. The results show that when the axial grains of the grinding wheel are the most densely arranged and the offset distance of the grains is greater than 0 and less than 25% of the average diameter of the grains, the good surface roughness can be obtained after grinding. Compared with the arrangement schemes in which the offset distance of the grain is 0 and 50% of the average diameter of the grains, the scheme in which the offset distance of the grain is 25% of the average diameter of the grains can get the best surface topography, surface profile curve and surface roughness of the workpiece.

Analysis of Second Harmonic Generation of a KDP crystal based on multi-scale topography simulation

The surface topography of the supporting frame of a KDP crystal is studied, as well as its influence on the deformation and stress of the KDP crystal, together with the Second Harmonic Generation (SHG). A comprehensive model incorporating principles of multi-scale surface analysis, mechanics, and optics is proposed, and it is applied to investigate the surface topography of the supporting frame, the deformation and stress of the KDP crystal, as well as the SHG efficiency. The surface topography is analyzed using fractural theory, and then classified according to its multi-scale specifics. Based on the surface analysis results, the mounting configuration of the KDP crystal is modeled and analyzed in global and local modes, respectively, using the Finite Element Method (FEM). Moreover, deformation and stress of the KDP crystal that is induced by the mechanical mounting is studied using the FEM, together with the effects of the surface topography on them. Furthermore, the change of the refractive index that induced by the deformation and stress are calculated, respectively, the results of which is applied to studied the phase mismatch, and the SHG efficiency considering the phase mismatch is eventually obtained. The numerical results demonstrate that the frame surface with multi-scale dimensions has diverse influences on the distortion and stress, as well as the SHG efficiency.

The Impact of Finite-Amplitude Bottom Topography on Internal Wave Generation in the Southern Ocean

Abstract Direct observations in the Southern Ocean report enhanced internal wave activity and turbulence in a kilometer-thick layer above rough bottom topography collocated with the deep-reaching fronts of the Antarctic Circumpolar Current. Linear theory, corrected for finite-amplitude topography based on idealized, two-dimensional numerical simulations, has been recently used to estimate the global distribution of internal wave generation by oceanic currents and eddies. The global estimate shows that the topographic wave generation is a significant sink of energy for geostrophic flows and a source of energy for turbulent mixing in the deep ocean. However, comparison with recent observations from the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean shows that the linear theory predictions and idealized two-dimensional simulations grossly overestimate the observed levels of turbulent energy dissipation. This study presents two- and three-dimensional, realistic topography simulations of internal lee-wave generation from a steady flow interacting with topography with parameters typical of Drake Passage. The results demonstrate that internal wave generation at three-dimensional, finite bottom topography is reduced compared to the two-dimensional case. The reduction is primarily associated with finite-amplitude bottom topography effects that suppress vertical motions and thus reduce the amplitude of the internal waves radiated from topography. The implication of these results for the global lee-wave generation is discussed.

Modeling and on-line simulation of surface topography considering tool wear in multi-axis milling process

The understanding and prediction of the generated surface topography are very important in milling process. This paper presents a surface topography model and an on-line simulation method of surface topography considering tool wear in a multi-axis milling process. First, the cutting edge equation is established by dividing the cutting edge into a series of cutting edge elements considering tool wear influence and tilt angle of tool axis on each discrete cutting edge element, and an algorithm is proposed to determine the range of divided position angle. Then, the sculptured surface workpiece is divided into a series of elements along the feed direction with the same or less than discrete precision of cutting edge. The intersection points between the discrete cutting edge elements and the planes of both sides of each divided element on workpiece can be obtained based on the established cutting edge equation in the cutting process. The left cutting trajectory points on workpiece are got by reserving the points with the minimum coordinate value in the Z-axis direction under the same coordinate value in the X-axis and Y-axis direction among the intersection points and points on workpiece. Thus, surface topography model can be constructed based on the established cutting edge equation, the determined range of position angle, discrete cutting edge elements, and divided element on workpiece surface. Finally, an on-line simulation algorithm is proposed to simulate the generation process of surface topography in multi-axis milling operation. Experimental work and validation of the established model are performed on a five-axis milling center by using stainless steel 0Cr17Ni12Mo2 and cemented carbides milling cutter. The results about the topography generation of the constructed B-spline surface show that the predictions of the established surface topography model correlate well with the experimental results.

Meteo–geographical data input tools used with ATD Demokritos code

Geographical and meteorological data input tools used with the Demokritos atmospheric transport dispersion code system are specifically designed for dispersion computations over complex terrain. The code initialisation depends mainly on the topography simulator (DELTA), which provides detailed information with respect to orography, land–cover, roughness and inclination, orientation and area of the individual ground surfaces, simulating the real topography. The meteorological input data can be provided by regional simulation codes and/or meteorological stations. In both above–mentioned cases, meteorological pre–processing (FILMAKER) is vital for improving the performance of the dispersion model. For each point of interest, the existing meteorological measurements are taken into account with region characterisation based on meteorological coherence. A hierarchical treatment is then established by treating first calculation points belonging to one of the above regions using local 'significant' meteorological measurements and taking into account the time of the year and day. A standard 1/rn interpolation scheme is then used for the remaining calculation points. The method has been successfully tested against real field experimental data.

An investigation on surface finishing in ultra-precision raster milling of aluminum alloy 6061

The technology of ultra-precision machining with single crystal diamond tool produces advanced components with a higher dimensional accuracy and a better surface quality. This article develops a three-dimensional surface topography simulation model for ultra-precision raster milling process by considering the effect of cutting parameters, tool geometry and tool interference as well as the tool–workpiece relative movement on surface generation. Based on the developed surface topography simulation model, a prediction model for the surface roughness in ultra-precision raster milling is built. The effects of depth of cut and surface topography on the cutting-induced heat generation in ultra-precision milling of aluminum alloy 6061 are investigated. Experiment is conducted to verify the developed surface topography simulation model by raster milling of aluminum alloy 6061 under different feed rates and depths of cut. The experimental results show that the surface topography simulation model can properly simulate the surface profile in the raster milling process and the predicted surface roughness agrees well with the measured results of the machined workpiece. Heat generation in horizontal cutting is less than that in vertical cutting and a larger depth of cut generates more heat on the machined workpiece. The cutting-induced heat generates precipitate on the machined aluminum alloy 6061 which results in a worse surface finish in ultra-precision raster milling.

Rejuvenation of Appalachian topography caused by subsidence-induced differential erosion

Topographic relief continued to develop in the Appalachian Mountains, eastern USA, long after the tectonic forces that created the range had become inactive. Numerical modelling and reconstructions of sediment deposition in the Gulf of Mexico suggest that the topographic relief was rejuvenated by subsidence-induced differential erosion caused by sinking of the subducted Farallon slab in the underlying mantle. In ancient orogens, such as the Appalachian Mountains in the eastern United States, the difference between the high and low points—topographic relief—can continue to increase long after the tectonic forces that created the range have become inactive. Climatic forcing1 and mantle-induced dynamic uplift2,3 could drive formation of relief, but clear evidence is lacking in the Appalachian Mountains. Here I use a numerical simulation of dynamic topography in North America, combined with reconstructions of the sedimentation history from the Gulf of Mexico4, to show that rejuvenation of topographic relief in the Appalachian Mountains since the Palaeogene period could have been caused by mantle-induced dynamic subsidence associated with sinking of the subducted Farallon slab. Specifically, I show that patterns of continental erosion and the eastward migration of sediment deposition centres in the Gulf of Mexico closely follow the locus of predicted dynamic subsidence. Furthermore, pulses of rapid sediment deposition in the Gulf of Mexico4 and western Atlantic5 correlate with enhanced erosion in the Appalachian Mountains during the Miocene epoch, caused by dynamic tilting of the continent. The model predicts that such subsidence-induced differential erosion caused flexural-isostatic adjustments of Appalachian topography that led to the development of 400 m of relief and more than 200 m of elevation. I propose that dynamically induced continental tilting may provide a mechanism for topographic rejuvenation in ancient orogens.

Realistic simulation of surface defects in five-axis milling using the measured geometry of the tool

Managing macro- and micro-geometry of surfaces during manufacturing processes is a key factor for their following uses. Indeed, micro-geometry and surface topography are directly linked to the performances of functions (contact, friction, lubrication, etc.) by texture parameters to ensure the desired local geometry. Common models for simulation of surface topography are based on ideal geometry of the machining tool and cannot represent surface defects. The actual prediction and simulation of defects are one step forward in a competitive context. In this paper, the realistic model proposed aims to simulate and predict as finely as possible local defects of machined surfaces taking into account the actual edge geometry of the cutting tool. The combined use of the machining kinematics and of the measured geometry of the cutting edges leads to the representation of the geometrical envelope of the surface using a Zbuffer technique. Simulation assessment is carried out by the analysis of 3D surface topography parameters such as surface complexity and relative area and by a comparison of simulation results to an experimental case of study.

Modeling the Growth of Tin Dioxide Using Spray Pyrolysis Deposition for Gas Sensor Applications

In order for the gas sensor devices to enjoy the miniaturization trend that has consumed much of the electronic device industry, major research in the field is undertaken. The bulky sensor devices of previous generations can not easily be incorporated into a CMOS processing sequence, because of their bulky nature and potential higher cost of production. More recently, materials such as zinc oxide and tin dioxide have shown powerful gas sensing capabilities. Among many potential deposition methods, spray pyrolysis has become a popular approach because of its ease of use and cost effectiveness. A model for spray pyrolysis deposition is developed and implemented within the level set framework. The implementation allows for a smooth integration of multiple processing steps for the manufacture of smart gas sensor devices. From the observations, it was noted that spray pyrolysis deposition, when performed with a gas pressure nozzle, results in good step coverage, analogous to a CVD process. This is mainly due to the atomizing nozzle being placed at a reasonable distance away from the wafer surface and reducing the droplets volume and mass in order to ensure they fully evaporate prior to contact with the substrate surface. A topography simulator for this deposition methodology is presented.

Establishment of Surface Topography Simulation Model with Considering Vibration and Wear of Ball-end Milling

Focusing on the influence of various factors of cutter and work-piece in milling process, such as force, wear and vibration, using discrete method to compute the trajectory of each points, and get the coordinates values of discrete points on the cutting edge at any time. A new method has been proposed to obtain the dynamic response of discrete points by transforming deformation of those values into work-piece coordinate system. At the same time, a new policy of retention has been proposed to avoid inadequate statistics and large number of statistics. Retaining coordinates which can effectively influence the formation of surface topography, the prediction model of surface topography can be established with the consideration of force, wear and dynamic response on the ball-end mill. This prediction model of surface topography has been proved to be effective and practicable by an experiment.

Characterization of Threading Dislocations in PVT-Grown AlN Substrates via x-Ray Topography and Ray Tracing Simulation

Threading dislocations in aluminum nitride boules grown by physical vapor transport method were systematically studied via synchrotron x-ray topography (white beam and monochromatic) in conjunction with ray tracing simulations. Two major types of threading dislocations were observed in the c-axis-grown boules: threading screw dislocations (TSDs) and threading edge dislocations (TEDs) with Burgers vectors along the [0001] and \(\langle 11\bar{2}0 \rangle \) directions, respectively. TSDs were typically observed in the middle of the boule while TEDs were commonly observed to aggregate into arrays along the \( \langle 1\bar{1}00 \rangle \) and \( \langle 11\bar{2}0 \rangle \) directions in various parts of the boule on basal plane oriented wafers. By comparison with ray tracing simulations, the absolute Burgers vectors of both TSDs and TEDs in the arrays could be unambiguously determined. TEDs comprise over 90 % of all threading dislocations observed. The relationships between TED arrays and low angle grain boundaries and their possible formation mechanisms are discussed.

Fabrication of a side aligned optical fibre interferometer by focused ion beam machining

Focused ion beam (FIB) machining is a promising technique for the fabrication of micro-optical components with high quality surface finishes. In this work, a prototype of a side aligned optical fibre interferometer was successfully fabricated by the three-dimensional deterministic FIB machining technique. A highly accurate 45° reflective mirror with surface roughness (Ra) of 10 nm has been successfully fabricated at the centre of the fibre to direct the core guided light to the side of the fibre. A surface topography simulation method was developed to simulate the ion beam polishing process. According to the simulation result, a 0.5° offset on the ion beam polishing direction is necessary to maintain the machining accuracy. In the fabrication process, it was also found that for structures requiring a high aspect ratio the existence of an open edge can mitigate against the material redeposition on the sidewalls and therefore increase the overall material removal rate. The fibre has been tested optically and the interference signals have been successfully observed, demonstrating the alignment accuracy of the fabrication method.

Research on the Simulation of Friction Material Surface Topography

Through analysis and research on the surface topography of reinforced copper matrix composite materials, taking advantage of fractal statistical method to discuss distribution law about characteristics parameter which symbolizes the asperity, combining Monte-Carlo method with fractal theory to set up mathematics model of characteristics parameter which symbolizes size of asperity , talking about the construction of iterated function system in fractal interpolated theory, a easy realizable friction materials surface topography simulation algorithm was put forward.

Comparing Idealized and Complex Topographies in Quasigeostrophic Simulations of an Antarctic Circumpolar Current

AbstractThe circumpolar transport of a wind-driven quasigeostrophic Antarctic Circumpolar Current is considered. Simple theory suggests transport in a strongly forced regime—the focus of this study—is largely determined by a partitioning of the southward Sverdrup flux into Drake Passage latitudes: some streamlines feed a “basin contribution” to the circumpolar transport and others feed a large-scale recirculation gyre. Simulations assuming an idealized Scotia Ridge topography are considered to test for sensitivity to resolution. Considerable sensitivity to both vertical and horizontal resolution is found, and associated with this is a tight stationary eddy trapped on the western flank of the ridge. That is, this eddy is sensitive to resolution and exerts an influence that acts to reduce the circumpolar transport. Simulations using the Scotia Ridge–like topography are also compared to others using more realistic topography. In the idealized (ridge) topography experiments, there is only a single ridge against which topographic form drag can act to remove eastward momentum from the system; in the complex topography experiments, there are many. It is found that the experiments assuming realistic topography do not develop an analog to the single topographically trapped eddy prevalent in the Scotia Ridge topography simulations. Additionally, circumpolar transport in these simulations agrees better with the theory. Whether this agreement is simply fortuitous, however, is unclear. To address this, a series of simulations assumes topography that varies smoothly between the idealized ridge and realistic configurations.

A novel fast and flexible technique of radical kinetic behaviour investigation based on pallet for plasma evaluation structure and numerical analysis

This paper describes a new, fast, and case-independent technique for sticking coefficient (SC) estimation based on pallet for plasma evaluation (PAPE) structure and numerical analysis. Our approach does not require complicated structure, apparatus, or time-consuming measurements but offers high reliability of data and high flexibility. Thermal analysis is also possible. This technique has been successfully applied to estimation of very low value of SC of hydrogen radicals on chemically amplified ArF 193 nm photoresist (the main goal of this study). Upper bound of our technique has been determined by investigation of SC of fluorine radical on polysilicon (in elevated temperature). Sources of estimation error and ways of its reduction have been also discussed. Results of this study give an insight into the process kinetics, and not only they are helpful in better process understanding but additionally they may serve as parameters in a phenomenological model development for predictive modelling of etching for ultimate CMOS topography simulation.

A method for simulating Atomic Force Microscope nanolithography in the Level Set framework

During the last decades it has been shown that the Atomic Force Microscope (AFM) can be used in non-contact mode as an efficient lithographic technique capable of manufacturing nanometer sized devices on the surface of a silicon wafer. The AFM nanooxidation approach is based on generating a potential difference between a cantilever needle tip and a silicon wafer. A water meniscus builds up between the tip and the wafer, resulting in a medium for oxyions to move due to the high electric field in the region. A simulator for nanooxidation with a non-contact AFM, implemented in a Level Set environment, was developed. The presented simulator implements the growth of thicker oxides by analyzing the potential, electric field, and ion concentrations at the ambient/oxide and oxide/silicon interfaces, while the growth of thin oxides assumes a single liquid/silicon interface, which is modeled as an infinitely long conducting plane. The nanodot shapes have been shown to follow the electric field and hence the surface charge distribution shape; therefore, a Monte Carlo particle distribution for the surface charge density is generated for two-dimensional and three-dimensional topography simulations in a Level Set framework.

Simulation and assessment of diamond mill grinding wheel topography

The topography of grinding wheel has a remarkable effect on grinding process. In this paper, the topographies of two mill grinding wheels with different grain sizes were measured by using an Olympus confocal scanning laser microscope. Kolmogorov–Smirnov normality tests were carried out to obtain distribution characteristics of abrasive grains. The test results indicate that the surface of grind wheel is of non-Gaussian nature. Consequently, a non-Gaussian statistical model was proposed to simulate the mill grinding wheel topography. Simultaneously, some parameters of “Birmingham 14” were introduced to assess the grinding wheel surface quantitatively. Simulated profile of the grinding wheel is found to correspond well in appearance with that of the actual grinding wheel.

Fabrication of periodic nanostructures by single-point diamond turning with focused ion beam built tool tips

Periodic nanostructures have been widely used on emerging nano-products such as plasmonic solar cell and nano-optics. However, lack of cost-effective fabrication techniques has become the bottleneck for commercialization of these nano-products. In this work, we develop a scale up approach to fabricate high-precision nanostructures in large area. In this method, a nano-scale single crystal diamond (SCD) tool is produced by focused ion beam (FIB) machining. The nano SCD tool is then further applied to cut periodic nanostructures using single-point diamond turning (SPDT). A divergence compensation method and surface topography generation model forms a deterministic FIB fabrication approach. It has been used to generate four periods of the required periodic nano-grating structures (with a minimal dimension of 150 nm) on a normal SCD tool tip and achieves 10 nm form accuracy. The contribution of the beam tail effect has also been evaluated by using the surface topography simulation method. The fabricated diamond tool is then applied to obtain nano-grating on an electroless nickel substrate in a total area of 5 × 2 mm2 through SPDT. The whole SPDT machine process only takes 2 min (with a material removal rate up to 1.8 × 104 μm3 s−1). Due to the elastic recovery that occurred upon the workpiece material, the practical cutting width is 13 nm smaller than the tool tip. The machining trial shows it is very promising to apply this scale up nanofabrication approach for commercialization of nano-products which possess period nanostructures.

Surface topography and roughness in hole-making by helical milling

Helical milling is used to generate holes with a cutting tool traveling on a helical path into the workpiece in which the diameter of the hole can be adjusted through that of the helical path. Based on an improved Z-map model, a 3D surface topography simulation model is established to simulate the surface finish profile generated after a helical milling operation using a cylindrical end mill. The surface topography simulation model incorporates the effects of the relative motion between the cutting tool and the workpiece, in which the effect of the insert runout error of the cutting tool is considered. Furthermore, the roughness parameters are deduced from simulations of the 3D surface topography. The experimental result shows that the proposed simulation algorithm can predict well the surface roughness in a helical milling operation. The surface topography simulation model is used to study the effects of cutting conditions such as the tangential feedrate, the diameter of the cutting tool and the hole, the insert runout error of the cutting tool, as well as the revolution of the cutting tool around the axis of the hole on the surface finish profile. It is found that the surface quality can be improved by optimization of the cutting conditions. As a result, the proposed model will be helpful in determining the cutting conditions to meet surface finish requirements in helical milling operation.