Discrete model for laser driven etching and microstructuring of metallic surfaces

We present a unidimensional discrete solid-on-solid model evolving in time using a kinetic Monte Carlo method to simulate micro-structuring of kerfs on metallic surfaces by means of laser-induced jet-chemical etching. The precise control of the passivation layer achieved by this technique is responsible for the high resolution of the structures. However, within a certain range of experimental parameters, the microstructuring of kerfs on stainless steel surfaces with a solution of $\mathrm{H}_3\mathrm{PO}_4$ shows periodic ripples, which are considered to originate from an intrinsic dynamics. The model mimics a few of the various physical and chemical processes involved and within certain parameter ranges reproduces some morphological aspects of the structures, in particular ripple regimes. We analyze the range of values of laser beam power for the appearance of ripples in both experimental and simulated kerfs. The discrete model is an extension of one that has been used previously in the context of ion sputtering and is related to a noisy version of the Kuramoto-Sivashinsky equation used extensively in the field of pattern formation.Comment: Revised version. Etching probability distribution and new simulations adde

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

Applications on Ultrasonic Wave

This book presents applications on the ultrasonic wave for material characterization and nondestructive evaluations. It could be of interest to the researchers and students who are studying on the fields of ultrasonic waves

Modeling and control of material removal and defectivity in chemical mechanical planarization

Chemical Mechanical Planarization (CMP) is a necessary step in semi conductor manufacturing. Since its introduction it has been able to provide better local and global planarization. CMP has found applications in emerging technologies such as shallow trench isolation, damascene technologies. As device size shrinks CMP has become increasingly prominent. CMP process has been analyzed at different length scales such as particle, feature and wafer scales. Models have been developed for each scale. The models initially have been deterministic, accounting for material removal by a single isolated particle. These models predicted the quality control parameters such as material removal rate and planarization at global scales. Recently, probabilistic models have been developed to describe material removal rate from particle scale. However there do not exist models which capture the interaction between parameters at different length scales. The focus of this thesis is to develop a multi-scale model that considers the interaction between parameters at different length scales. The interaction between macro-scale property pH of the slurry on the micro-scale phenomenon such as particle agglomeration has been studied. Interaction between pad asperity distribution and particle diameter distribution has also been studied. In the existing probabilistic models the effect of asperities on the material removal has been studied assuming that the pad asperities are supported on a rigid base. In this thesis the pad cellular structure under the asperities is considered to predict scratch performance and material removal rate. The effect of pad structure and slurry pH on scratch propensity and wafer scale material removal rate is studied. The model prediction of material removal rate has been validated against experimental data. The predicted linear dependence of material removal rate on pressure has been verified. The underlying cellular structure of the pad has been found to have little impact on the dependence of material removal rate on pressure. Defectivity, as defined by scratch propensity has been studied in this thesis. Scratch performance has been found to be effected mainly by the proximity of slurry pH to the isoelectric point of the slurry particles. The scratch performance has worsened as the pH of the slurry becomes closer to the isoelectric point of particles. A parametric study has been undertaken to study the effect of pad and slurry evolution on scratch propensity and material removal rate. Based on the study, suggestions have been made to improve scratch performance and material removal rate. Aggressive pad conditioning has been found to improve scratch propensity while it also has been found to maintain material removal rate, which decreases if the pad is allowed to evolve. On the other hand, pad evolution has been found to alleviate scratch problem. Based on the insights gained in the parametric study, few suggestions about operating conditions have been made. It has been suggested to keep the slurry pH away from the isoelectric point of particles to alleviate scratch propensity. It is suggested that the pad be conditioned when the wafer surface is away from the target profile and the pad be allowed to evolve when the wafer surface is closer to target profile. This strategy maintains the material removal rate during the beginning of the process while avoiding the killer defects towards the end of the process

Particle resuspension: challenges and perspectives for future models

International audienceUsing what has become a celebrated catchphrase, Philip W. Anderson once wrote that "more is different" (Science, Vol. 177, Issue 4047, pp. 393-396, 1972). First formulated in the context of condensed matter, this statement carries far beyond the sole limits of solid-state physics. It emphasizes that collective behavior can be more than the mere sum of what happens for elementary constituents or the mere collation of the evolution of each degree of freedom. Said otherwise, complex phenomena can arise out of the interplay between multiple sub-phenomena each of which can be relatively simple. The process of particle resuspension, in which discrete particles adhering on a surface are pulled off and carried away by a fluid flow, is another example involving a web of phenomena pertaining to fluid mechanics, particle dynamics and interface chemistry whose crosseffects create an intricate topic. The purpose of this review is to analyze the physics at play in particle resuspension in order to bring insights into the rich complexity of this common but challenging concern. Following the more-is-different vision, this is performed by starting from a range of practical observations and experimental data. We then work our way through the investigation of the key mechanisms which play a role in the overall process. In turn, these mechanisms reveal an array of fundamental interactions, such as particle-fluid, particle-particle and particle-surface, whose combined effects create the tapestry of current applications. At the core of this analysis are descriptions of these physical phenomena and the different ways through which they are intertwined to build up various models used to provide quantitative assessment of particle resuspension. The physics of particle resuspension implies to hold together processes occurring at extremely different space and time scales and models are key in providing a single vehicle to lead us through such multiscale journeys. This raises questions on what makes up a model and one objective of the present work is to clarify the essence of a modeling approach. In spite of its ubiquitous nature, particle resuspension is still at the early stages of developments. Many extensions need to be worked out and revisiting the art of modeling is not a moot point. The need to consider more complex objects than small and spherical particles and, moreover, to come up with unified descriptions of mono-and multilayer resuspension put the emphasis on solid model foundations if we are to go beyond current limits. This is very much modeling in the making and new ideas are proposed to stimulate interest into this everyday but challenging issue in physics

Environmental Compatible Circuit Breaker Technologies

Recent research and development in the field of high-current circuit breaker technology are devoted to meeting two challenges: the environmental compatibility and new demands on electrical grids caused by the increasing use of renewable energies. Electric arcs in gases or a vacuum are the key component in the technology at present and will play a key role also in future concepts, e.g., for hybrid and fast switching required for high-voltage direct-current (HVDC) transmission systems. In addition, the replacement of the environmentally harmful SF6 in gas breakers and gas-insulated switchgear is an actual issue. This Special Issue comprises eight peer-reviewed papers, which address recent studies of switching arcs and electrical insulation at high and medium voltage. Three papers consider issues of the replacement of the environmentally harmful SF6 by CO2 in high-voltage gas circuit breakers. One paper deals with fast switching in air with relevance for hybrid fault current limiters and hybrid HVDC interrupters. The other four papers illustrate actual research on vacuum current breakers as an additional option for environmentally compatible switchgear; fundamental studies of the vacuum arc ignition, as well as concepts for the use of vacuum arcs for DC interruption

Low transport stages by water streams of fine, cohesionless, granular and flakey sediments

Imperial Users onl

The use of Frequency domain Electro-magnetometer for the characterization of permafrost and ice layers.

openSince the industrial revolution human activities caused a record-breaking increase in the Earth’s average temperature due to the extensive use of greenhouse gases. [1] As global temperatures increase; glaciers have undergone a significant retreat in the past few decades.[2] The Ice Memory project aims to preserve ice cores from glaciers worldwide, as a record of Earth's past climate. It involves drilling deep into glaciers, extracting ice cores, and storing them in a dedicated facility in Antarctica. This is to prevent the potential loss of valuable climate archives due to glacier retreat which provides future scientists with valuable information for studying historical climate patterns and understanding the role of human activity in climate change. geophysical investigations are typically required to determine the most suitable drilling positions for ice coring. the most common technique for this purpose is the so-called GPR. (Snow cover of several meters limits the use of ERT and active seismic methods.) While each geophysical technique has certain advantages and limitations, combining them can provide a more detailed picture of changes within rock glaciers. In the present study, electromagnetic prospecting in the frequency domain (FDEM) was performed together with the ground penetration radar (GPR). The former is not a commonly used method for studying glacier environments as FDEM has a lower resolution in the study of glaciers with respect to the GPR. However, as we will see in this study, it is a quick and convenient method to study this type of environment, as it provides a large coverage area in a cost-efficient manner, although with a lower resolution with respect to the GPR. Combining these two techniques provide a more detailed map of the glaciers. comparing the GPR and borehole data with the inverted FDEM datasets (CMD-DUO, GF-Instruments) confirms the effectiveness and applicability of FDEM methodology for investigating glacial bodies in mountainous regions.Since the industrial revolution human activities caused a record-breaking increase in the Earth’s average temperature due to the extensive use of greenhouse gases. [1] As global temperatures increase; glaciers have undergone a significant retreat in the past few decades.[2] The Ice Memory project aims to preserve ice cores from glaciers worldwide, as a record of Earth's past climate. It involves drilling deep into glaciers, extracting ice cores, and storing them in a dedicated facility in Antarctica. This is to prevent the potential loss of valuable climate archives due to glacier retreat which provides future scientists with valuable information for studying historical climate patterns and understanding the role of human activity in climate change. geophysical investigations are typically required to determine the most suitable drilling positions for ice coring. the most common technique for this purpose is the so-called GPR. (Snow cover of several meters limits the use of ERT and active seismic methods.) While each geophysical technique has certain advantages and limitations, combining them can provide a more detailed picture of changes within rock glaciers. In the present study, electromagnetic prospecting in the frequency domain (FDEM) was performed together with the ground penetration radar (GPR). The former is not a commonly used method for studying glacier environments as FDEM has a lower resolution in the study of glaciers with respect to the GPR. However, as we will see in this study, it is a quick and convenient method to study this type of environment, as it provides a large coverage area in a cost-efficient manner, although with a lower resolution with respect to the GPR. Combining these two techniques provide a more detailed map of the glaciers. comparing the GPR and borehole data with the inverted FDEM datasets (CMD-DUO, GF-Instruments) confirms the effectiveness and applicability of FDEM methodology for investigating glacial bodies in mountainous regions