Cover Page

Reliability of Multiphysical Systems Set

coordinated by

Abdelkhalak El Hami

Volume 2

Nanometer-scale Defect Detection Using Polarized Light

Pierre Richard Dahoo

Philippe Pougnet

Abdelkhalak El Hami

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Preface

The various actions decided on at a global level to stimulate sustainable development and to respond to climate issues bring forth increasingly stringent regulations in terms of greenhouse gas emissions and hazardous substances. In the automotive sector these regulations drive industrial companies to develop new mechatronic systems using electricity to replace the various mechanical functions of vehicles. International competition and constant pressure to improve the performance of innovative products compel the companies supplying embedded mechatronic devices to innovate in increasingly shorter lead times to remain competitive.

To improve the performance of embedded systems in terms of volume or mass reduction, or to reduce energy losses, the mechatronic industry implements new packaging methods (such as those based on multimaterials) or incorporates new materials (for instance, carbon nanotubes). Modeling and simulation are used to limit cost, increase durability and reduce lead time to market. The Physics of failure provides the knowledge to predict and reduce potential failures in application and optimize design before activating serial production. In this respect, Reliability Based Design Optimization (RBDO) is a numerical tool used to optimize design and reduce industrial fabrication risks. This approach can only be applied efficiently when the underlying physical phenomena are thoroughly understood and when the models used accurately represent the conditions under which the device operates.

To model a dynamic system consisting of interacting sub-parts, a simplified system behavior model based on realistic hypotheses and key parameters is first used. Dynamic behavior is controlled by Partial Differential Equations (PDE) based on the characteristics of the system. By incorporating elements or parameters that were initially not included and by improving the PDE (for instance by taking into account non linearities or novel coupling schemes …) this model is extended and improved leading to an increasingly precise simulation of the real functioning behavior, as used in the process like approach.

Theoretical models are usually built following an analysis of the complex system which leads to equations based on fundamental laws from the bottom-up. Consequences are deduced from realistic hypotheses and known physical laws. Either analytical or digital methods are applied to solve the equations. Whenever possible, experiments are conducted to compare expected results and real data. A top-down approach can also be applied using experimental methods. This approach is based on data obtained by applying specific stresses or external constraints, and from the study of the system response. Data from these tests are compared to simulation results from theoretical or empirical models. Both bottom-up and top-down approaches can lead to some uncertainties in data analysis. This can be evaluated through statistical analysis which provides predictions and margins of error. The objective is to reduce the margin of error in order to obtain realistic predictions and to better understand the properties of active materials.

This book describes experimental and theoretical methods which are developed in fundamental research to better understand the physical chemistry and physical processes in complex systems and which, on the nanometric scale, are the root cause of the outstanding properties of the materials used in innovative technological devices. It presents optical techniques based on polarized light which can be applied to detect material or interface defects which have an impact on their performance. It also describes how to measure the mechanical properties of nanomaterials and how to analyze experimental data taking into account the range of uncertainties using theoretical models.

This book is written for students at Master and Doctoral levels, teaching academics and researchers in Materials Science and Experimental Studies, as well as engineers and technical staff from industrial sectors involved in systems where embedded electronics, mechatronics and electronic and optical materials are employed.

Chapter 1 describes various approaches which take into account uncertainties and are applied to analyze the static and dynamic behavior of systems and structures. Chapter 2 presents an approach to optimizing the design of a system which matches design cost with the guarantee of functioning without failure in the planned use conditions. This approach is based on taking into account uncertainties and on simultaneously solving two problems: optimizing the production cost of the structures performing the expected functions and ensuring an acceptable probability to fulfill its function. Chapters 3 and 4 give an overview of the classical and quantum theories of light as well as the various methods established to describe the polarization state of light.

Chapter 5 reviews theories on the interaction of light and matter and various condensed phase materials used in industrial applications. The notion of incomplete information about a quantum system is presented using the density matrix to take into account the problem of the interaction of the quantum system with the environment. Chapter 6 describes lasers, sources of polarized light and the experimental methods based on lasers to study either bulk materials using Laser Induced Fluorescence and IR-IR Double Resonance techniques, or the surface of materials using techniques to analyze the reflexion of a probe over the ultrasonic waves created by a pump laser. These methods make it possible to discriminate the different paths through which energy dissipates in materials when defects are present. This approach is used to build theoretical models to understand and analyze the thermal effects in composite materials.

Chapter 7 describes how to apply these methods to model systems before describing the apparatus used to prepare the systems composed of molecules which are trapped at low temperature in a solid matrix (rare gases or nitrogen). The various lasers and infrared detectors used in Laser Induced Fluorescence and Double Resonance techniques are presented. The results obtained on O3-GR, CO2-GR, and N2O-GR systems are analyzed using theoretical models developed to determine the energy relaxation rate constants according to the various paths through which a system may transfer energy. Predictions and extrapolations applying the results of the highlighted transfer mechanisms to other sytems are proposed.

Chapter 8 describes the study of the interfaces of assembled materials using the IR spectroscopic ellipsometry technique. This technique is summarized as well as the necessary equipment and the analysis process, which is based on an inverse method applied to the models describing the interaction of light and matter through optimization algorithms. The results obtained on various types of interfaces found in the assembly of mechatronic power devices are presented and discussed. The ellipsometry technique is used to determine the possible modifications that occur in the properties of the materials when they come into contact as a result of physical or physical-chemical processes, as well as to follow the evolution of interfaces as a function of temperature in a dry or humid atmosphere.

Chapter 9 describes how to determine the properties of carbon nanotubes by applying the RBDO approach which correlates theoretical models and statistical methods to characterization and fabrication methods.

Pierre Richard DAHOO
Philippe POUGNET
Abdelkhalak EL HAMI
June 2016