Evaluation and control of interface are not easy at present. Solid-solid interface is especially very difficult to control and evaluate. Most problems in this field are solved practically as surface control or surface evaluation. Various methods for the evaluation of interface are summarized as to probe, interaction and signal.
There are two methods for observations of boundary surface of metal, polymer, mineral, and biological tissues under Scanning Electron Microscope or Transmission Electron Microscope. One of them is to observe the block surface which is polished as cut with microsome. The other is to observe the complementary surfaces which are cut out of a block with ultramicrotome. The latter has the advantage of making it possible to observe sections which are cut in thicknesses not only 30-100nm but also 0.5-1μm. That is to say, some specimens can be studied by finding their right boundary surfaces under a light microscope; some under an electron microscope.
Recently, metallic materials have been often used under very severe conditions. Therefore, it has become necessary to investigate surface or interface properties of materials precisely. Surface analyzing tools such as AES, XPS or IMA, have been developed to a remarkable degree. So compositions of surface layers can be relatively easily determined. However, we have to be very careful when we want to analyze interface compositions of metallic materials, because interfaces of materials are not so easily exposed. In this paper, the methods of exposing interfaces with mechanical polishing or fracturing are described.
EXAFS spectroscopy has grown in recent years to routine experiments in the investigation of the local structure for various materials. Therefore, it is desired to perform EXAFS measurements in the laboratory. The laboratory EXAFS facilities are built by using a conventional rotating anode X-ray source in conjunction with a Johansson crystal. In this paper, laboratory EXAFS data are reviewed and some data are compared with results by synchrotron radiation source. It also describes some Fluorescent-EXAFS in laboratory EXAFS measurements.
Recent progress in analyzing AlGaAs-GaAs semiconductor heterointerfaces using optical methods, such as photoluminescent spectroscopy, photo-absorption spectroscopy, photoluminescence-excitation spectroscopy and laser-Raman spectroscopy, is reviewed. Three types of interface disorders are discussed : compositional grading parallel to the growth direction, alloy clustering, and island-like structure formation on the interface (interface roughness). When AlAs-GaAs stacked layers are thin enough to form quantum wells or a superlattice, these interface disorders manifest themselves in the optical spectrum, that is, in a broadening of the line width, and a peak shift and additional sub-peaks or shoulders. These optical methods are sufficiently sensitive that differences in the thickness of the grading of a few Angstrom, the existence of alloy clusters of a few atomic diameter, and differences of the height of interface roughness of one monolayer can be detected. Emphasis is put on the potential of laser-Raman and picosecond time-resolved spectroscopy to investigate the unique properties of superlattice stuctures.
With the present-day high resolution electron microscope, it is possible to observe directly individual atom arrangements in crystals, whereas the analytical electron microscope also enables us to determine local chemical compositions from thin specimens. Thus both the high resolution electron microscopy and the analytical electron microscopy are very useful for studying atomic configurations and chemical compositions on interfaces, grain boundaries and surfaces of ceramics, metals and semiconductors. The present paper reviews the image formation and interpretation of high resolution electron micrographs, and also the quantitative analysis of an energy dispersive X-ray spectroscopy. Some current topics of grain boundary analysis in ceramics obtained by electron microscope are shown.
Principles of AES (Auger Electron Spectroscopy), SAM (Scanning Auger electron Microscope), EPMA (Electron Probe Micro Analyzer), XPS (X-ray Photoelectron Spectroscopy), and UPS (Ultraviolet Photoelectron Spectroscopy) are briefly described. Examples for study of interface using these techniques are also described. Advantages, disadvantages and limitations of these are pointed out.
FAB-SIMS (Fast Atom Bombardment Secondary Ion Mass Spectrometry) and LIMS (Laser Ionization Mass Spectrometry) have been explained. FAB-SIMS is a kind of SIMS in which a fast atom beam is used for the primary beam for sample bombardment. It is useful for insulator samples as sample surface charging caused by charge of the primary beam does not occur. The relative intensity for various elements by FAB-SIMS is similar to that of normal SIMS. LIMS is an analytical device in which pulsively generated ions by pulsed laser radiation on solid state samples are generated from samples through thermal ionization or through LTE process of microplasma produced on laser-heated sample sufaces. LIMS has extremely high sensitivity of 10-1810-20gr.
Metastable-atom de-excitation spectroscopy (MDS) is a powerful technique to study the electronic structures of the outermost atomic layers of solid surfaces. In this paper we give an outline of the mechanism of metastable-atom de-excitation followed by electron emission from surfaces. Some recent results of its application to the study on adsorption and thin film growth are reviewed and a unique role of the MDS method in charaterizing interface structures is discussed.
The secondary ion mass spectrometry (SIMS) is a surface analysis technique in wihch a test specimen is bombarded with accelerated ions and secondary ions are extracted from the sputtered particles with an electric field and analyzed with a mass spectrometer. The basic configuration of the SIMS instrument, the fundamental reaction of the secondary ion formation and applications to various materials are shown. The glow discharge emission spectrometry (GDS) is another surface analysis technique in which a test specimen is sputtered with ions formed by a glow discharge, the sputtered particle is excited within a plasma of the discharge, and the light emitted during the transition from the excited state to the ground state is analyzed spectrometrically. The basic configuration of the GDS instrument, the fundamental reaction of the glow discharge emission and applications are shown.
A scanning acoustic microscope operating in the frequency range 0.11GHz has been developed. To increase the resolution in the depth direction, it uses interference between reflected ultrasonic waves from a lens-water boundary to interfere as reference waves with waves reflected from a specimen. With this method, a high degreed of resolution in the depth direction is obtained. The acoustic micrographs obtained have clearly demonstrated that this device can be used nondestructively to observe hydrogen-ion-doped regions in silicon crystals and spike defects at the edge of the local oxidation of silicon structures in semiconductor devices. In addition, the acoustical effects caused by plastic deformations of metal (Fe-3% Si alloy) are experimentally investigated using this device.
Invention of “man-made superlattice” is considered as the greatest advance in the solid state physics in recent years. This can be regarded as a gene-manipulation in semiconductor engineering. Activities in the semiconductor superlattices have expanded greatly with advances achieved both in scope and in depth recently. This expansion arises partly from the general recognition of the interesting physics and electronic properties underlying the superlattice structures and partly from the wide availability of a commercial system of molecular beam epitaxy (MBE). In this paper, very recent advances in the MBE growth of the semiconductor superlattices are reviewed.
The importance of evaluation and control of the interfaces in ceramics to produce ceramic materials with high performance electronic functions attributed to the grain boundary properties is reviewed. Ceramic interfaces, which here mean grain boundaries, play a decisive role in determining the electronic properties in ceramic materials. A double Schottky-type barrier and an SIS-type barrier, which are likely to form at grain boundaries in semiconducting ceramics, are used to demonstrate how the grain boundary resistivity and capacitance are formulated using parameters such as the height and width of the potential barriers and densities of the donor states and the surface acceptor states. In this review, grain boundary properties in ZnO varistors, semiconducting barium titanate PTCR thermistors and barrier layer capacitors are taken as appropriate ones, with which the relationship between the type of energy band structures and associated grain boundary properties are examined.
This paper surveys general knowledge of the interface characteristics in the system of semiconductor-metal and semiconductor-semiconductor junction. Both the interface structure and electronic states appearing at the interfacial layers in compound semiconductors such as III-V and II-VI materials are highlighted especially. We also describe new results concerning the interface formation encountered in semiconductor superlattice, polytype semiconductors and semiconductor hetero-junctions.
In this review article, possibilities for the control of the interface in polymer composites is discussed from both theoretical and experimental viewpoints. The problem is classified into three cases : 1) Interface in semi-crystalline polymers defined as the interface between crystalline and amorphous parts. 2) Interface in polymer alloys defined as the interface between two incompatible polymer blends or the interface in microphase separated block or graft copolymers. 3) Interface in polymer based composites defined as the interface between polymer and other substances, like carbon black and silica. In each case, how the thickness or the profile of the interface is estimated by statistical mechanical approach is introduced. Several molecular parameters which are influential in determining the thickness of the interface are pointed out and experimental method such as application of pulsed nuclear magnetic resonance (NMR) to detect the interface, is explained for actual systems.
Sufficient transference of stress and no harmful reaction at the interface between the reinforcement and the matrix are simultaneously required in an FRM. Alloying Si, Mg, Cu or Fe in Al is effective in restrain the harmful Al4C3 in a C-Al FRM. Adding 2-3% Li in Al is useful to improve the wettability and also to control the reaction between the Al2O3 fibre and the Al matrix. A B4C or SiC barrier can suppress the AlB2 in B-Al. However neither of the barriers is of any use for a Ti matrix. On the other hand, Al, Mo or V in Ti can lessen the reaction. A metal filament such as W or Mo can only be applied to a superalloy matrix. The filament, however, is easily deteriorated by Ni, Co or Al which is the main composition of the superalloy. The deterioration can be restrained by dispersing ZrO2 in the W filament or by coating a ZrO2 barrier on the filament.
The properties of metallic materials can be improved by controlling the grain boundary segregation of solutes. Basic problems in the segregation control are discussed : addition of the third elemennt can decrease the segregation of harmful impurities and increase that of beneficial solutes. As an example, the effect of carbon on the segregation of phosphorus in iron is discussed. Carbon and phosphorus are considered to compete with each other at the site at grain boundaries. Since carbon has a larger segregation energy than phosphorus, it preferentially segregates to decrease the segregation of phosphorus. With this effect and with its own effect to increase the grain boundary cohesion in iron, carbon prevents the intergranular fracture in steels. Other effects of solute-solute interaction on their segregation are discussed in principle.