With the introduction of the Fourier-Transform technique in the mid-seventies, infrared spectroscopy has become one of the most important tools for the characterization of the chemical and physical nature of polymers. Apart from the increasing availability of a broad range of special sampling devices and detection techniques (attenuated total reflection, photoacoustic and microspectroscopy) in the course of the years, the following development of the step-scan technique and the extension from the mid- to the near-infrared (NIR) region have had the most significant impact on the applicability of IR-spectroscopy for time-resolved polymer analysis and process control In the following contribution the principles and experimental details of the new techniques will be discussed and selected applications from various fields of polymer research shall demonstrate their potential.
This paper presents a review of the principles, experimental details and applications of four wave mixing. The principles of four wave mixing are discussed using models of both nonlinear optical interaction and transient grating. Various physical mechanisms contributing to four wave mixing are discussed. The contributions of purely electronic coherent term as well as of the population dependent and time delayed incoherent terms are discussed. Applications illustrated here cover the determination of third-order optical nonlinearity; study of excited state dynamics; evaluation of acoustic properties and elastic moduli; and application to high density holographic data storage using photorefractivity.
The "Mossbauer effect" is the recoil-free nuclear resonance absorption. The phenomenon was discovered in 1958 by the German physicist Rudolf L. Mossbauer, who was awarded the nobel prize for this work1. Mossbauer discovered the recoilffee absorption with the heavy nucleus 193 Ir. Resonance absorption is the absorption of a quantum of energy which is equal to the difference between 2 energy states of a system. It has long been known in connection with electronic transitions. The energy states of an atomic nucleus are similarly quantized discrete values. Therefore it was expected that the ground state of a nucleus might be able to absorb the y-radiation emitted by activated nuclei of the same species. However the experimental demonstration of this nuclear resonance absorption turned out to be difficult because of the kinetic energy change of the emitting nucleus, which is called the recoil energy.
Ultraviolet-Visible (UV-Vis) spectroscopy comprises electromagnetic radiation of relatively high energy, with the wavelength ranges of 200 to 400 ran, called ‘ultraviolet spectroscopy’, and 400 to 800 nm, ‘visible spectroscopy’. Both are useful for investigating the electronic structures of unsaturated molecules and for measuring the extent of their conjugation. Spectroscopic techniques always complement to each other in elucidating the structure of investigated molecules in solid, liquid or gaseous form. UV-Vis spectroscopy is one of the important analytical tools in the armory of a scientist for the characterization of polymers.
Laser atomic fluorescence (LAF) is a powerful spectroscopic tool in analytical applications when it is necessary to measure extremely low concentrations of atoms. The main purpose of this method is to determine the presence and absolute concentrations of different elements in materials. In this paper we will describe the basic principles of the method and how advances in lasers, fiberoptics and detectors allow for significant improvement and simplification of the LAF spectrometer.
The dielectric method provides application data essential for the use of insulating and semi-insulating materials in electrical and electronic systems. At the microscopic level, measurements on polymers at radio frequencies and below can yield valuable information regarding dipole-driven modes of molecular and segmental motion, particularly when considered in conjunction with complementary data provided by other techniques.
Representative observations are presented for commercial homopolymers and blends to illustrate the utility of the dielectric method as an analytical technique for polymers. Its sensitivity ensures that dielectric spectroscopy is appropriate for the investigation of phase morphology and miscibility and for the characterization of changes induced by irradiation or the presence of additives.
The scanning electron microscope (SEM) can be used to study and characterize a wide variety of materials used in photonic applications. These range from highly conductive samples to insulating materials. Several different techniques make use of this versatile tool. These include secondary electron imaging, backscattered electron imaging, X-ray analysis (both qualitative and quantitative), electron channeling patterns for studying crystalline materials, charge collection techniques for semiconductor samples and cathodoluminescence. These techniques will be described here with examples of applications. In addition, electron-matter interactions as well as the basic operation principles of the scanning electron microscope will be discussed.
In this paper, a review of Transmission Electron Microscopy (TEM) for the characterization of materials is presented. TEM is a technique which allow the crystallographic and chemical characterization of materials with high spatial resolution. Now, TEM allows the visualization of rows of atoms as well as defects like dislocations or staking faults. Chemical and crystallographic information in areas smaller than 1 nm can now be achieved with a Field Emission Gun Transmission Electron Microscope (FEGTEM). In this paper, a special emphasis is directed toward the characterization of electronic and magnetic materials. After an introduction of Transmission Electron Microscopy, all the Signals which are generated when an electron beam strike a thin foil in the TEM will be presented. This will allow to present all the techniques available in a TEM to perform materials characterization. All these techniques will be presented in the context of what they can do for materials characterization and their advantages as well as their limitations will be covered. The techniques which are covered are electron diffraction, the relation between image contrast and electron diffraction conditions in the context of defects characterization, Convergent Beam Electron Diffraction (CBED), x-ray microanalysis, Electron Energy Loss Spectroscopy (EELS), High-Resolution Transmission Electron Microscopy images (HRTEM) and the Z contrast. Specific examples of material characterization are presented for all these techniques. A description of the different electron sources is presented because they affect the spatial resolution of TEM.
High energy ion scattering spectrometry (HEIS) is a materials analysis technique which can provide absolute concentrations of several elements at once as a function of depth, without the use of standards. Rutherford backscattering spectrometry (RBS) can detect elements heavier than the probing ion, while elastic recoil detection analysis (ERDA) yields concentrations of lighter elements in a matrix of heavier atoms. Sensitivity as well as depth, lateral and mass resolution can be adapted to particular analytical requirements by varying parameters such as incident ion mass and energy, angles of the incident and exiting probe ions, detection geometry, beam focusing, and by the addition of subsidiary energy analysis. Although elemental concentration profiles are absolute with these techniques, they provide no information about chemical bonds, and are thus complementary to other depth profiling methods such as Auger electron spectrometry (AES), secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectrometry (XPS). The techniques are described in general, sources of more detailed information are referenced, and some examples are provided which illustrate their application to various (including optical) materials.
Auger electron spectroscopy is one of the most commonly used techniques for surface analysis. It has evolved from its first common use for solid surfaces in the late 1960s to become a tool for routine analysis of materials. This article provides a concise review of the use of Auger electron spectroscopy, with emphasis on its use for optical materials. The fundamentals of the technique are reviewed, along with a discussion of data analysis and the equipment commonly used to perform the technique. Several examples of the use of AES for optical materials are discussed.
Scanning probe microscopy is reviewed, including some of the abilities of scanning tunneling microscopy and spectroscopy. The technology of atomic force microscopy is discussed, including tip and cantilever fabrication and preparation, as well as a variety of detection schemes to measure cantilever deflection. Several atomic force microscopy techniques, including constant force imaging, interleaved imaging, resonantly-enhanced imaging, adhesion force microscopy and friction force microscopy are also reviewed. Finally, two important applications of scanning probe microscopy, magnetic force and scanning capacitance microscopy, are discussed.
Recording of optical information is requesting development of new materials which will permit high packing density of information per unit area. The demand of new optical materials with characteristics such as high resolution, better energy sensitivity, broad wavelength sensitivity , simpler processing procedure and erasability arises due to the increase in optical applications. Those materials need to be characterize form the point of view of their potential applications. Holographic characterization is offering a good way to evaluate some so those potentials materials.
Photothermal sensing techniques are widely used in materials characterization and are particularly useful for noninvasive inspection of thin film coatings. The specific applications include measuring optical absorption, characterizing thermal conductivity, detecting local defects, as well as monitoring laser-interaction dynamics and determining laser modification thresholds as well as thermal/acoustic impedance at boundaries of multilayers. This paper introduces the basic concepts and principles of photothermal sensing techniques, the various detection methods, and the progress made during the last a few years in applying these techniques to characterization of thin film coatings, particularly those for high power laser applications. The further potential and limitations of these techniques will also be discussed, with emphasis on spectroscopic studies and in-situ investigations.
This is a review of the applications that various core level spectroscopies have in surface analysis. Three methods are highlighted, i.e., photoelectron spectroscopy of core level shifts (XPS or ESCA), absorption spectroscopy, and soft X-ray fluorescence. These techniques provide not only elemental analysis at surfaces, but also the chemical state of atoms and molecules in the outermost atomic layers, such as oxidation state, hybridization, and nearest neighbor bonding information. The probing depth can be adjusted in non-destructive fashion from 3 A to 300 A by detecting electrons or photons of variable energies. Advances in detectors and light sources, such as synchrotron radiation, are breaking ground for new applications, such as chemically-resolved microscopy.
Point defects are known to limit the performance of many nonlinear optical materials. For example, gray tracks form along the beam path in some KTP crystals when they are subjected to lasers operating at high peak powers. Transient absorption bands in the visible and ultraviolet can be induced in KDP and BBO crystals by intense pulsed laser beams. Chalcopyrite crystals such as ZnGeP2 and AgGaS2 can have unwanted absorption bands which overlap their desirable 2-μm OPO pump region. All of these device-limiting extrinsic absorption bands are associated with point defects in the bulk of the crystals. Among the responsible defects are transition-metal-ion impurities, other nonmagnetic impurities, cation vacancies, anion vacancies, and antisites. In some materials, the point defects present in the as-grown crystals may already exhibit absorption bands, while in other cases, the existing point defects may need to trap an electron or hole during device operation before the absorption band is activated. Eliminating the optically active point defects during crystal growth will lead to materials with higher damage thresholds. With this as a goal, numerous investigators have used electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) to identify and characterize point defects which give rise to the unwanted absorption bands. EPR can detect concentrations of defects at levels as low as tens of parts per billion. Furthermore, each defect has a unique g-value signature which allows a variety of defects to be monitored simultaneously. Superhyperfine interactions with surrounding nuclei permits a "mapping" of the wave function for each defect and this results in a detailed model of the defect. The following review provides examples of how EPR and ENDOR are used to characterize commercially available nonlinear optical materials.
A brief historical background of ellipsometry is given, followed by a detailed assessment of its current status and future development. Spectroscopic ellipsometry in the near UV-VIS is now a well-established characterization technique, and its extension to the IR range is quickly reaching a mature state. Other important developments in both theory and instrumentation in the last decade are leading to better and faster in situ, real-time and imaging ellipsometry. Selected works from recent literature are presented to illustrate not only new development trends in the field but also other well-known applications of ellipsometry as a characterization technique.
A Critical Review is given on the use of the SIMS technique. The basic concepts of sputtering process and secondary ion production as well as quantification problems are briefly reviewed. A description of the possible operational modes and instrumental aspects are presented. Particular attention is devoted to the specific analysis of insulating samples. SIMS has been applied to the characterization of LiNbCO3 passive and active optical waveguides obtained by thermal diffusion of metals from thin film and by proton ion-exchange. Results obtained by SIMS on the study of the chemical interaction in ion-implanted silica glass are presented. The technique has also been used to measure in-depth concentration profiles of metals in soda-lime glass planar waveguides obtained by metal ion-exchange process and to correlate compositional modifications with the optical properties. The need of complementary techniques for quantification of the obtained data has been underlined.
Integrated optics are powerful and versatile methods for determining the structural properties of polymeric thin films. By complete analyses of the modal structure of the optical fields within the guiding film, the thickness, indices of refraction (including any anisotropy) and the attenuation of the propagating wave can all be calculated. The decrease in the optical field with distance can be caused by absorption or Rayleigh scattering, that is, surface and bulk scattering. Because each mode has a distinct profile across a film, laminar structures through a film or a multilayered film are probed. The intense optical field within the waveguide makes possible fluorescence or Raman scattering with good signal strength. To reduce interference coming from fluorescence, frequently found in commercial polymers, Fourier transform waveguide Raman in the infrared allows one to observe the Raman spectrum without exciting any fluorescence. Finally, the high sensitivity of optical waveguides to structural or chemical changes has led to a number of sensor and nonlinear optical applications.
Electric field induced second harmonic generation technique is described and its application for molecular first hyperpolarizability β(-2ω, ω,ω) determination is reviewed. Limits of the applicability as well as possible artefacts connected with its utilization are also discussed.
We review Z-scan and related techniques for the measurement of the nonlinear optical properties of materials. The Z-scan is a simple technique for measuring the change in phase induced on a laser beam upon propagation through a nonlinear material it gives both the sign and magnitude of this phase change, ΔΦ, which is simply related to the change in index of refraction, An. Additionally, a Z-scan can also separately determine the change in transmission caused by nonlinear absorption that is related to the change in the absorption coefficient, Aa. Importantly, the determination of the nonlinear refraction from Δn is independent of the determination of the nonlinear absorption from Δα, within a quite broad range of these parameters. Thus, for third-order nonlinear responses the real and imaginary parts of the third-order nonlinear susceptibility, χ(3) can be measured. However, Z-scan is sensitive to any nonlinear processes which result in Δα or Δn, so that great care must be taken in interpreting data taken with this or any other nonlinear materials characterization technique.
This paper describes the application of the analytical ultracentrifuge for the characterization of polymers and colloidal particles. The aim of this review is describing the basic principles and giving an overview over the wide field of possible applications rather than providing an exhaustive theoretical background. After an introduction of the experimental setup, the four basic experiment types: sedimentation velocity experiment, sedimentation equilibrium run, density gradient run and synthetic boundary experiment are introduced. It is explained which kind of information can be derived from which type of experiment. Examples are given for the fractionation of polymers/particles due to their molar mass/particle size in a sedimentation velocity experiment and the fractionation due to the structure achieved in a density gradient run. It is shown that sedimentation equilibrium experiments do not only deliver molar masses but are furthermore very useful for the quantitative characterization of interactions between polymers. Some new trends in analytical ultracentrifugation are outlined as well as some special applications of the analytical ultracentrifuge showing that it is a universal technique for analysis of polymer solutions and dispersions.