A short review of surface chemical analysis by Auger Electron Spectroscopy is presented. Following a brief ntroduction of the basis of quantification in AES, each of the Auger parameters causing inaccuracies in measurements is discussed. These include both specimen and instrument dependent parameters. A result of a round robin involving relative intensity measurements on high purity samples of copper and gold is referred to. Causes of the spread in the relative intensities are considered. The importance of the instrument dependent parameters is discussed. The need for standards (e.g., calibration methods, operating procedures, and data analysis) is emphasized to ensure that data of known accuracy can be obtained routinely. Recent trends and developments in quantification are given.
Quantitative analysis by electron probe microanalyzer has been well studied and established. Many methods of quantitative analysis are provided. 1. Working curve method, 2. ZAF method and 3. Bence-Albee method are well known and used. But these methods are not suited to some specimens. 4. Convergence method and 5. SEF method are convenient and are suited for all kinds of specimens. A new ZAF method is introduced. This method is very accurate for light elements, such as oxide, nitride, etc., and can be used for some specimens which have an undetectable element. Quantitative analysis methods on thin films, small particles and sintered specimens are presented, too.
X-ray photoelectron spectroscopy (XPS) is one of the effective tools for surface analysis. It has been said that basic principle of XPS is not so complicated, so the quantitativity is better than other methods like AES (Auger electron spectroscopy) or SIMS (secondary ion mass spectrometry). In this report the quantification by XPS and the limitations are briefly described.
Present status of quantitative analysis by means of Secondary Ion Mass Spectrometry, which is a typical technique based on ion bombardment and secondary ion emission, is briefly summarized. Characteristic of this technique is marked dependence of the analytical values on the matrix of specimen and on analytical conditions, such as incident ion energy, its current intensity, beam diameter, and oxygen partial pressure in the sample chamber. Several methods have been developed for obtaining stable analytical value, and they are applied to the quantitative analysis of pure iron and GaAs. It is found that the relative errors are within ±30% and the detection limits of impurity elements in GaAs are 10141015 atoms/cm3.
Basic theories of infrared specular reflection, infrared emission and Raman spectroscopies are outlined in relation to the quantitative determination of species on solid surfaces. Infrared absorption and Raman scattering of species on a solid surface are induced by the electric field at the surface in contrast to the conventional infrared and Raman spectroscopy, where the transition is induced by the field of the incident light. The infrared emission from species on a metal surface shows a remarkable interference effect. The intensity of the signal from surface species observed in these methods shows, therefore, tremendous change in changing experimental conditions. Difficulties in quantitative analysis about the surface enhanced Raman scattering are given.
Surface-analytical techniques and their limitations for a better understanding of characteristics of amorphous alloys are reviewed. Preliminary surface treatments are required to obtain reproducible characteristics due to production of the surface whose composition is close to the bulk alloy composition, and hence mechanical polishing in organic liquids has been carried out. Surface analyses of amorphous alloys have been performed mostly by XPS and AES. Problems accompanying XPS and AES techniques are discussed. Particular attention should be given to avoid erroneous data obtained by faulty application of argon ion etching, such as reduction of cations to metals, ion mixing and formation of new substances. One of the best methods for characterizing the surface is XPS, because it is able to determine nondestructively the valency of surface species and the composition and thickness of the surface film along with the composition of the alloy surface immediately under the surface film. Characteristics of amorphous alloys such as corrosion resistance, electrocatalysis and catalysis are interpreted in terms of surface analytical results.
Surface analysis on superconductors is reviewed in the field of the fabrication of Josephson junction and the preparation of high Tc superconductors. The surface oxide and tunnel barrier of Pb alloys, Nb metal, and Nb compounds (Nb3Sn, Nb3Ge, Nb3Al, and NbN etc.) are characterized by using XPS, UPS, AES, TEM, ellipsometer techniques. Among many surface analysis techniques, XPS is used as the most powerful tool for the surface analysis of superconductors. The mechanism of oxide formation on the Nb surface is interpreted. The oxidation mechanism of Pb alloy and A 15 compounds is explained by selective ionic diffusion due to the difference of contact potential between superconductor and the absorbed oxygen layer on it, and the difference of ionization potential between constituent elements.
Recently many efforts have been devoted to preparing diamond-like carbon films. The obtained films are transparent, insulating and as hard as diamond, but no good characterization method has been available to show they are truly diamond-like films. It is shown in the following that low-energy electron energy loss specroscopy shows promise as a method of characterizing the diamond-like films.
In this review, we discuss the heterointerface properties of AlGaAs-GaAs superlattices. Emphasis is laid on the abruptness, the induced disordering and the impurity trapping of heterointerfaces. Photoluminescence (PL) from single quantum wells clearly reveals the monolayer fluctuation of heterointerfaces. A correlation between impurity diffusion and induced disordering is obtained by secondary ion mass spectrometry (SIMS). Impurity trapping effects at heterointerfaces are discussed from PL and SIMS results.
A review is presented on quantitative analysis of impurities in III-V compounds semiconductors, especially GaAs, by secondary ion mass spectrometry (SIMS). The accuracy of SIMS analysis was investigated in comparison with chemical analysis results in the round robin study which was supported by Japan Society for the Promotion of Science Commitee 145. This study shows that the accuracy of SIMS quantitative analysis is ±10-30%. Highly sensitive and highly accurate quantitative SIMS analysis using chemical preparation is reviewed. This method has the very low detection limits (0.5-5ppb) and very high accuracy (±5-10%). SIMS quantitative analysis of GaAs using LTE model is also described. The accuracy of LTE model was considered to be factor 2.
Tris (1, 10-phenanthroline) Rhodium (III) is incorporated in the interlayer space of clay mineral, which has layered structure, by ion-exchange intercalation. This intercalation compound shows the strong absorption band around the visible region when irradiated with UV-light in the presence of triethanolamine. The spectral change is caused by the photoreduction of organometallic complex ions fixed in the interlayer spaces and the reduced species remain stable after the irradiation. A new type of optical memory can be made with this compound in the form of thin film. X-ray photoelectron spectroscopy proved to be a suitable method to observe a topochemical behavior of the intercalation process as well as to detect the reduced state of interlayer species directly.
Among the ultrafine particles of metals used as catalysts, the surface analyses of suppored metal catalysts are reviewed. The techniques commonly used for the surface analysis, such as AES spectroscopy, are also applied for catalysts, but they give information on bulk as well as surface. It is important to get information on surface layer and, especially, active sites for the surface analysis of catalysts. In this review, the chemical methods such as chemisorption using gases as probes are emphasized to obtain the structural and electrical information on surface sites.