Real-time X-ray Topography Research Articles

Characteristics of a New High-Sensitivity X-Ray Imaging Tube for Video Topography

A new type of high-sensitivity X-ray imaging tube having an amorphous selenium photoconductive layer with a thickness of 8 µm has been fabricated. Signal charges induced by X-ray photons can be avalanche-multiplied in the photoconductive layer under a large electric field. The sensitivity of the tube reaches the level of individual X-ray photon detection. For the detection of such a small number of X-ray photons, a new kind of noise is generated due to the fluctuation of absorption depth in the photoconductive layer under the operation conditions of avalanche multiplication. Signal-to-noise ratio can be improved by the accumulation of signal charges in the photocon-ductive layer. An example of real-time X-ray topography by weak X-rays using this experimental tube is demonstrated.

In situ observations by synchrotron white beam X-ray topography of the planar, cellular and dendritic growths of a binary alloy

Real-time X-ray topography using white beam synchrotron radiation has been applied to a study of the planar, cellular and dendritic growths of an Al 0.73 wt.% Cu alloy. In situ observations have revealed two different destabilization modes of the solidification front and have provided information on the microstructures obtained by cellular and dendritic growth.

A Study of Behavior of Lattice Defects by means of HVEM <I>In Situ</I> Experiments and Real-Time X-ray Topography

A Study of Behavior of Lattice Defects by means of HVEM <I>In Situ</I> Experiments and Real-Time X-ray Topography

超高圧電顕その場実験法と実時間Ｘ線回折顕微法による格子欠陥の挙動の研究

超高圧電顕その場実験法と実時間Ｘ線回折顕微法による格子欠陥の挙動の研究

Observational Study on the Dendritie Growth of Al–Mg Single Crystals by Real-Time X-Ray Topography

Real-time X-ray topography has been applied to a study of dendritic growth. Unidirectional melting and solidification processes of Al–Mg single crystals containing 0.5, 2.0 and 4.0 at%Mg were observed by real-time X-ray topography. Observations have been made on the following subjects: (1) sequential growth and morphology of dendrite arms during solidification as a function of the growth rate; (2) morphological changes of dendrite arms as a function of the Mg content; (3) morphological changes and solute redistribution during cooling and isothermal annealing after solidification; and, (4) observation of the melting process of a previously grown dendrite. Some valuable information which cannot be obtained by the conventional “ex post fact” method has been obtained by real-time X-ray topography.

Study of the formation mechanism of dislocations during the growth process of aluminium and gallium single crystals from the melt by real time x-ray topography

The formation mechanism of dislocations in metallic crystals during the growth from the melt has been studied by real time X-ray topographic observations of the growth process of aluminium and gallium single crystals. A region without dislocations was observed in aluminium near the solid-liquid interface during growth. Similarly, no dislocations were observed in a gallium single crystal which was grown from a highly perfect seed under a relatively slow growth rate (3 μm/s). These observations support the vacancy condensation mechanism of dislocation formation during the growth from the melt. Some formation mechanism of dislocations are discussed.

Real-time x-ray topography on the growth of an Al crystal from melt

Aluminium crystals grown from melt in an ultrahigh vacuum chamber have been observed in situ and in real time by using white synchrotron radiation [experiments were performed at the Laboratoire pour l’Utilisation du Rayonnement Electromagnétique (L. U. R. E.), Bâtiment 209c, 91405 Orsay, France]. The shape of the solid-liquid interface is determined by the thermal conditions. The defects are generated by strains extraneous to the fusion-crystallization process. The interfacial area is free from growth dislocations. The dislocations and subboundaries have a tendency to be parallel to the growth axis. Simple 1/2 <011>-type dislocations impinge upon the interfacial plane, proving their stability up to the melting point.

Dynamical observations of dendritic growth of aluminum–magnesium alloy single crystals by real time X-ray topography

Dynamical observations of dendritic growth of aluminum–magnesium alloy single crystals by real time X-ray topography

Real-Time X-Ray Topographic Observation of Crystal Growth of Gallium from Melt

The growth of gallium single crystal of 99.9999% purity from the melt was observed by real-time X-ray topography. At the solid-liquid interface, (010), (011), (101) and (111) facets were observed. Dislocations, which intersected the facets and propagated into a newly grown crystal, did not influence the faceted growth. The growth mechanism of the faceted growth of gallium is deduced from continuous observation of the growth process.

Real-time x-ray topography: Applications to bulk HgCdTe materials

Commercially available portable image x-ray intensifiers have found their usefulness with all existing x-ray topographic techniques. Real-time x-ray topography can be employed to align the diffraction images rapidly before recording them on high resolution film. As a quality control procedure, real-time Berg–Barrett x-ray topography can be used to assess macrostructural quality of HgCdTe with approximately 100 μm spatial resolution. As a x-ray screening technique prepared samples of HgCdTe can be assessed in real time before undergoing unnecessary costly processing on poor material. The advantages and disadvantages of the three basic types of x-ray topographic system will be discussed. The usefulness of real-time x-ray intensification as a support tool to Berg–Barrett, Lang, and ACT topography techniques is evaluated. Also, instrument characteristics of the x-ray intensifiers which are useful in real-time x-ray topography applications will be presented.

Instrumentation for real-time x-ray topography

Real-time topography has become important and accessible for investigating the dynamic behavior of materials, their phase transformations, and their defects in materials, because highly brilliant sources, such as rotating-anode X-ray generators and synchrotrons, have now become available. This paper describes instrumentation for real-time topography which we have developed. Our system includes a sample stage, magnifying optics, and an image-processing unit. The sample stage permits applying tensile force and high temperature (up to 1200°C) ambients on the sample. The optical system, containing a special luminescent screen, provides magnification. The image-processing unit can be used for digital image-integration and image-subtraction. The real-time topographic study of motion of dislocation in silicon will be shown as an example. The spatial resolution is better than 10 μm. Although our experiments have been carried out with a rotating-anode X-ray generator, our sample stage and detection system can also be used with a synchrotron source.

High-resolution real-time X-ray topography of dislocation generation in silicon

Abstract Generation of screw and 60° dislocation half-loops in silicon single crystals have been continuously observed, for the first time, with a high-resolution live X-ray topographic arrangement. A videotape has been made of the creation as well as of the motion of the dislocations. The spatial resolution achieved is about 8–10 μm. The real-time images are comparable in quality to the high-resolution topographic images recorded on conventional emulsion plates.

Real-time X-ray topography: Defect dynamics and crystal growth

Real-time X-ray topography is a novel tool to study directly the dynamics of defects and strain fields in solids under various external influences, such as temperature or strain. We describe first the equipment, starting with the rotating anode source up to the video detection system with digital image processing. We present several examples of application to experiments: (a) creation of misfit dislocations during the vapor phase epitaxial growth of Ge on GaAs; (b) dislocation creation and motion in Si; (c) annealing of stresses at the Si/SiO 2 interface; and (d) movement of ferromagnetic domain walls in Fe:Si crystals. An outlook concerning anticipated trends and possible progress in the field of topography (including synchroton sources) concludes this talk.

Real-time x-ray topography studies of the viscoelastic behavior of SiO2 in the system Si/SiO2

The viscoelastic behavior of SiO2 in the system Si/SiO2 during isothermal heat treatment is studied by directly imaging the x-ray topography contrast due to lattice strains at oxide edges of test structures. We measure the relaxation time of those strains, e.g., the time to reach zero x-ray contrast, at different temperatures above 900 °C, the minimum temperature for plastic deformation of SiO2. An Arrhenius plot of the relaxation time yields activation energies for viscous flow of 4.3 for normal- and 2.3 eV for high-pressure thermal SiO2. For small rectangular oxide windows we find the relaxation time proportional to the square root of the window area.

High-temperature real-time studies of lattice strains induced by localized oxidation of silicon

Mechanical strains along oxide edges of semiconductor devices with oxide isolation were studied by real-time x-ray topography in the temperature range from 20 to 1100°C. Due to the different thermal expansion coefficients of silicon and oxide, the strain at these edges decreases continuously with increasing temperature. The strength of the strain pattern corresponds to the structure size. The strain depends also on the thickness of the Si3N4 layer though the nitride was removed before the experiment. During the first heat treatment the contrast splits up into two lines at about 780°C.

Direct synchrotron x-ray topography of moving domain walls in Fe : Si single crystals

A real-time x-ray topography study of moving magnetic domain walls in an Fe : Si single crystal has been performed with double-crystal setting at the synchrotron radiation laboratory LURE. The domain walls were driven by a low-frequency magnetic field and viewed directly by means of a television detector system. Wall locking as well as wall bowing, the latter implying charged walls, have been observed.