Volume 26(1) - Winter 2010

X-ray diffraction intensities from a thin film deposited on a substrate can be relatively weak in comparing to the enormous X-ray diffraction and background intensities from its substrate. The in-plane XRD technique with a grazing incident X-ray beam has been used successfully to enhance the thin-film intensities and to minimize the substrate intensities in the analysis a thin-film.

Three-dimensional thin-film structure, such as preferred orientation (or texture), orientational relationship and lattice distortion between an epitaxial film and its substrate, crystallite-size anisotropy, etc, can be obtained from both in-plane and out-of-plane XRD measurements (see the second review of this series). It is well known that the crystalline structure of a thin film can affect the device characteristics.

In this article, the in-plane XRD technique used for the characterizations of extremely thin films as well as the crystallinity and orientational relationships in complex heteroepitaxial systems is explained.
 

There is growing demand for high precision and sensitivity micro-spot elemental analysis of microelectronic components. EPMA (electron probe micro analyzer) and EDXRF (energy-dispersive X-ray fluorescence) are commonly used for this purpose. However, two of the drawbacks for EPMA and EDXRF are their relatively low sensitivities, and spectral resolutions.

A wavelength dispersive X-ray fluorescence (WDXRF) spectrometer equipped with a high-energytype polycapillary lens has recently been developed by Rigaku. This WDXRF spectrometer can be used for a 100-μm spot-size measurement and has high precision as well as sensitivity even for light elements. In this article, the newly developed Rigaku WDXRF spectrometer equipped with a polycapillary lens is briefly described and examples on its applications to micro-spot analysis are given~
 

The International Confederation for Thermal Analysis and Calorimetry (ICTAC) defines thermomechanical analysis (TMA) as a method of thermal analysis in which the temperature of a sample is being subjected to a defined temperature program, allowing changes, while a non-oscillatory load is being applied and that the deformation of the sample is being measured as a function of temperature or time. It is a technique that measures the dimensional changes of a sample due to heating or cooling.

The measurement results are plotted in a TMA curve where the temperature or time is plotted on the horizontal-axis, while the change in length (i.e., rate of change or expansion ratio) is plotted on the vertical-axis.  In a TMA curve, an increase in the TMA measurement data represents expansion while a decrease denotes contraction.

The TMA curve can be divided into three regions. In the temperature range from 30 to 290°C, the glass expands linearly with increasing temperature. The expansion increases drastically from 290 to 310°C because of a glass transition. For temperature increases beyond 310°C, contraction is seen rapidly due to softening.

Using TMA, the expansion ratio and the coefficient of thermal expansion of the sample, as well as the softening temperature and glass transition temperature can be measured. The coefficient of thermal expansion (CTE) is defined as the expansion ratio per unit temperature of a calculated temperature range. The expansion ratio and the coefficient of thermal expansion of the glass at 30 to 250°C calculated from the TMA curve shown are 0.3% and 1.23105K1, respectively. Other TMA measurements include the determination of the sintering temperature and the volumetric contraction ratio caused by sintering of ceramic samples.

This paper summarizes effective techniques for common cases in performing TMA measurements.  The overview of this paper include types of TMA measurements; differential thermal expansion principle and single expansion principle; sample preparation and sampling; sample setting; calibration and correction of measurement results; and high- accuracy measurement module.
 

In X-ray powder diffraction analysis, obtaining high resolution and high intensity diffraction data leads to the improved accuracy of analyses based on that data, such as qualitative and quantitative analysis of minor phases, crystallite size and strain analysis, lattice constants refinement and so on. Powder structure analysis has received a lot of attention in recent years. Powder structure analysis requires high-resolution, highintensity data: accurate diffraction angles are needed for the determination of lattice parameters and accurate integrated intensity for each diffraction peak needs to be evaluated for the structure determination.

However, there is always a trade-off between resolution and intensity. Using older optical systems, it has generally taken quite a long time to collect high resolution, high intensity measurement data.

CALSA (Crystal Array on Logarithmic Spiral Analyzer), the high resolution spiral analyzer introduced here, is able to obtain very high resolution data using the Cu Kα₁ emission line, and gets an intensity ten times higher than conventional optics with the same angular resolution.

X-ray powder diffraction (XPD) analysis has been widely used in the field of materials science, such as materials development or quality control for over fifty years. However, many scientists and engineers may not be aware of exactly how much information XPD can provide on a sample. Using previous generations of software, high degrees of background knowledge and practical experience have been required to successfully obtain useful analysis results.

In the last five years, both diffractometer and dataanalysis software have made significantly advances. New developments of high-speed position sensitive detectors make possible a rapid collection of high-resolution and high-intensity diffraction data. Improvements in PC processing speed make easy the use of an entire experimental pattern, known as “whole-pattern analysis”, for a rapid and precise structure analysis of a material. The whole-pattern analysis method is becoming more popular than the conventional analysis methods, which use only certain diffraction peaks to obtain information on specific topics of materials science.

Ab-initio crystal-structure analysis of unknown samples is also gaining popularity in XPD analysis.  Many users used to consider this type of XRD analysis difficult because 3-dimensional diffraction data is “flattened” into one- or two-dimensions. There is a misconception that whole-pattern analysis, such as the Rietveld analysis or ab-initio crystal structure analysis, is difficult to perform and requires advanced know-how and technical understanding. With this in mind, Rigaku Corporation has developed PDXL, a new application software package created to enable the user who is not familiar with whole pattern analysis to easily perform Rietveld or ab-initio crystal-structure analysis with just a few clicks.

Many kinds of information can be obtained from XPD data. PDXL allows the user to perform many types of analysis using a single platform, making it possible to obtain a diverse array of analysis results from one single XPD pattern. The following sections describe how to use PDXL, and several new features in PDXL are also introduced.
 

Recently, various thin film and multilayer materials are being developed and produced for use as functional devices. The characteristics of such a device are often influenced by layer parameters such as film thickness, film density and surface/interface roughness. X-ray reflectivity (XRR) is one of the techniques widely used to evaluate these parameters quantitatively.

XRR has various advantages over other characterization techniques: there is no need to treat the sample before measurement or measure reference samples, it is non-destructive, and it can be used with multi-layer systems and opaque materials.

XRR analysis is preceded by a pattern fitting process between the measured and the calculated XRR pattern.  During pattern fitting, layer structure parameters are refined, commonly by using the least square method.  However, it is very hard to find the best-fit model using only this method when the initial values of the structural parameter are quite different from the real ones.  Therefore, practitioners of XRR analysis were often required to have a specialist’s understanding of material science as well as enough experience to construct appropriate structure models.

GlobalFit (Reflectivity Analysis), the newly released XRR analysis software from Rigaku Corp., overcomes these difficulties with the use of two powerful tools for data analysis and automatic profile fitting.

On October 9th, 2009 three scientists were awarded the Nobel Prize in Chemistry “for studies of the structure and function of the ribosome”. The awardees were Venkatraman Ramakrishnan of the MRC Laboratory of Molecular Biology, Thomas Steitz of Yale University and Ada Yonath of the Weizmann Institute of Science. The first Nobel Prize in Physics was awarded to Wilhelm Conrad Röntgen for the discovery of X-rays.  Since then many Nobel Prizes have been awarded to X-ray crystallographers. The first Nobel in Chemistry that was awarded to an X-ray crystallographer was to Linus Pauling, “for his research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances” in 1954. The penultimate Chemistry prize was awarded to Roger Kornberg “for his studies of the molecular basis of eukaryotic transcription” in 2006.