X Ray Scattering

During the last 20 years interest in high-resolution x-ray diffractometry and reflectivity has grown as a result of the development of the semiconductor industry and the increasing interest in material research of thin layers of magnetic, organic, and other materials. For example, optoelectronics requires a subsequent epitaxy of thin layers of different semiconductor materials. Here, the individuallayer thicknesses are scaled down to a few atomic layers in order to exploit quantum effects. For reasons of electronic and optical confinement, these thin layers are embedded within much thicker cladding layers or stacks of multilayers of slightly different chemical composition. It is evident that the interface quality of those quantum weHs is quite important for the function of devices. Thin metallic layers often show magnetic properties which do not ap pear for thick layers or in bulk material. The investigation of the mutual interaction of magnetic and non-magnetic layers leads to the discovery of colossal magnetoresistance, for example. This property is strongly related to the thickness and interface roughness of covered layers.

X-ray scattering is used extensively to provide detailed structural information about materials. Semiconductors have benefited from X-ray scattering techniques as an essential feedback method for crystal growth, including compositional and thickness determination of thin layers. The methods have been developed to reveal very detailed structural information concerning material quality, interface structure, relaxation, defects, surface damage, and more.

This manual is a useful ready-reference guide to the analytical power of modern X-ray scattering in the field of soft matter. The author describes simple tools that can elucidate the mechanisms of structure evolution in the studied materials, and follows this up with a step-by-step guide to more advanced methods. Data analysis based on clear, unequivocal results is rendered simple and straightforward – with a stress on careful planning of experiments and adequate recording of all required data.

With contributions by Paul F. Fewster and Christoph Genzel While X-ray diffraction investigation of powders and polycrystalline matter was at the forefront of materials science in the 1960s and 70s, high-tech applications at the beginning of the 21st century are driven by the materials science of thin films. Very much an interdisciplinary field, chemists, biochemists, materials scientists, physicists and engineers all have a common interest in thin films and their manifold uses and applications. Grain size, porosity, density, preferred orientation and other properties are important to know: whether thin films fulfill their intended function depends crucially on their structure and morphology once a chemical composition has been chosen. Although their backgrounds differ greatly, all the involved specialists a profound understanding of how structural properties may be determined in order to perform their respective tasks in search of new and modern materials, coatings and functions. The author undertakes this in-depth introduction to the field of thin film X-ray characterization in a clear and precise manner.

The properties of soft-matter thin films (e.g. liquid films, polymer coatings, Langmuir-Blodgett multilayers) nowadays play an important role in materials science. They are also very exciting with respect to fundamental questions: In thin films, liquids and polymers may be considered as trapped in a quasi-two-dimensional geometry. This confined geometry is expected to alter the properties and structures of these materials considerably. This volume is dedicated to the scattering of x-rays by soft-matter interfaces. X-ray scattering under grazing angles is the only tool to investigating these materials on atomic and mesoscopic length scales. A review of the field is presented with many examples.

X-ray diffraction crystallography for powder samples is a well-established and widely used method. It is applied to materials characterization to reveal the atomic scale structure of various substances in a variety of states. The book deals with fundamental properties of X-rays, geometry analysis of crystals, X-ray scattering and diffraction in polycrystalline samples and its application to the determination of the crystal structure. The reciprocal lattice and integrated diffraction intensity from crystals and symmetry analysis of crystals are explained. To learn the method of X-ray diffraction crystallography well and to be able to cope with the given subject, a certain number of exercises is presented in the book to calculate specific values for typical examples. This is particularly important for beginners in X-ray diffraction crystallography. One aim of this book is to offer guidance to solving the problems of 90 typical substances. For further convenience, 100 supplementary exercises are also provided with solutions. Some essential points with basic equations are summarized in each chapter, together with some relevant physical constants and the atomic scattering factors of the elements.

Small-angle scattering of X rays and neutrons is a widely used diffraction method for studying the structure of matter. This method of elastic scattering is used in various branches of science and technology, includ ing condensed matter physics, molecular biology and biophysics, polymer science, and metallurgy. Many small-angle scattering studies are of value for pure science and practical applications. It is well known that the most general and informative method for investigating the spatial structure of matter is based on wave-diffraction phenomena. In diffraction experiments a primary beam of radiation influences a studied object, and the scattering pattern is analyzed. In principle, this analysis allows one to obtain information on the structure of a substance with a spatial resolution determined by the wavelength of the radiation. Diffraction methods are used for studying matter on all scales, from elementary particles to macro-objects. The use of X rays, neutrons, and electron beams, with wavelengths of about 1 A, permits the study of the condensed state of matter, solids and liquids, down to atomic resolution. Determination of the atomic structure of crystals, i.e., the arrangement of atoms in a unit cell, is an important example of this line of investigation.

X-ray scattering techniques are a family of nondestructive analytical techniques. Using these techniques, scientists obtain information about the crystal structure and chemical and physical properties of materials. Nowadays, different techniques are based on observing the scattered intensity of an X-ray beam hitting a sample as a function of incident and scattered angle, polarization, and wavelength. This book is intended to give overviews of the relevant X-ray scattering techniques, particularly about inelastic X-ray scattering, elastic scattering, grazing-incidence small-angle X-ray scattering, small-angle X-ray scattering, and high-resolution X-ray diffraction, and, finally, applications of X-ray spectroscopy to study different biological systems.