VAMAS project was set up at the economic summit at Versailles in 1982. The objective of VAMAS project is to establish the reliability of metrological technologies vital to the development of new materials and processing. The round robins of VAMAS project could clearly indicate the standardization process for surface chemical analysis, and TC 201 was established in ISO in 1991 to make the international standards for surface chemical analysis. At present, the number of P-members of TC 201 is 10 and that of O-members is 20. TC 201 is composed of 8 SC and 1 WG. The objective of SC and WG is to propose the new work items and to establish international standards for their covering surface chemical analysis methods. Until now, 12 international standards have been published. At the same time of the establishment of TC 201, TC 202 was also established in ISO to make the international standards for micro beam analysis. In Japan, we established the domestic committee to support the activities of TC 201 and TC 202.
Charging phenomena that occur during XPS and AES analysis of insulating materials are discussed, with special focus on surface potential change by X-ray or electron beam irradiation. Some typical examples of charging phenomena observed during XPS analysis are introduced together with practical methods for charge compensation and for the estimation of peak shifts by charging. As the practical methods are now under discussion in the frame of ISO activities, the content of relating ISO document (ISO 19318) is also briefly explained. Then charging phenomena observed in AES analysis of insulating materials are discussed in terms of the relation between surface charging and secondary electron emission, for which a new concept of static/dynamic secondary electron yield is explained. Practical methods for charge compensation in AES analysis are also introduced, and experimental results showing the effect of those methods are presented.
ISOTC (Technical Committee) 201 was organized in 1992 to establish the International Standard on surface analysis methods such as Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), Secondary Ion Mass Spectrometry (SIMS), Glow Discharge Optical Emission Spectroscopy (GDOES) and Total Reflection X-ray fluorescence Spectroscopy (TXRF). ISO TC 201 on Surface Chemical Analysis consists of eight Sub-Committees and one Working Group (WG) at present. The activities of Sub-Committee 2 (SC 2) and Sub-Committee 3 (SC 3) are deliberation and establishment of the International Standard on General Procedure, and Data Management and Treatment, respectively. “ISO 14976: Surface chemical analysis—Data transfer format” was enacted as the International Standard in 1998, “ISO 14975: Surface chemical analysis—Information formats” was in 2000. These two standards were discussed in SC 3. Specimen handling, reference materials and reporting data have been on the table in SC 2 but International Standard has not yet been adopted. ISO 14976 and ISO 14975 were translated into Japanese to be adapted in JIS. In this report the two International Standards are explained and the trend of standardization in SC 2 and SC 3 as well as practical use of International Standard is briefly touched.
Standardization of depth profiling using XPS, AES, and SIMS has been discussed and developed by ISO/TC 201/SC 4. So far this committee published one standard and one technical report, and the latter is a generally informative summary of depth profiling and the former is a standard for the optimization of ion sputtering. In this standard, the described most important procedure is the alignment of specimens, incident probes, and analyzers and we should pay attention to the probe diameter and scanning area even for the same analysis technique. It is also important to optimize the depth resolution by adjusting the ion accelerating energy, ion species, incident angle, and so on. The experimental parameters are listed in this report and the reference materials are also shown, which are certified in several countries. The mesh-replica method is introduced, that has been discussed in ISO/TC 201/SC 4 and it is very useful to determine the actual sputtering rate.
International standards of XPS and AES spectrometers have been established. Binding energy scale calibration for XPS spectrometers was standardized as ISO 15472. The calibration of kinetic energy scale for AES spectrometers was standardized as ISO 17973 and 17974. The calibrations for the intensity scale are now discussing. The calibrations for the XPS and AES spectrometers were reviewed. The standard for XPS spectrometers specifies the calibration methods to estimate uncertainty with 95% reliability using repeatability and the linearity of binding energy scale and to correct the binding energy scales. This standard also specifies the method to establish the calibration schedule. Moreover, the standards on AES spectrometers specify the calibrations with high energy resolution for the chemical state analysis and the calibration with the medium energy resolution for elemental analysis.
This article describes the standardization of the surface quantification with Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) on International Standard Organization (ISO). The relative sensitivity factor (RSF) method is widely used for the quantitative surface analysis by AES and by XPS, and proposed as ISO/DIS 18118 : Surface chemical analysis —AES & XPS— Guide to the use of experimentally determined relative sensitivity factors for the quantitative analysis of homogeneous materials. Three types of the RSFs have been used in this standard: elemental relative sensitivity factors (ERSFs), atomic relative sensitivity factors (ARSFs), and average matrix relative sensitivity factors (AMRSFs). The ERSFs are the simplest and easiest to apply. However, they are least accurate be-cause no account is taken of matrix correction factor. The ARSFs are more accurate than the ERSFs because they take account of atomic density correction. The AMRSFs are most reliable RSFs in that there is almost complete correction of matrix effects. Then, it is recommended that the AMRSFs be used for the practical quantitative surface analysis of wide variety of solid materials by AES and XPS.
Quantitative analyses by using reference materials and their standardization are reviewed for secondary ion mass spectrometry (SIMS). The accuracy and precision of SIMS trace analysis is evaluated in terms of the three round robin studies. The repeatability deviation of SIMS measurement itself is estimated to be around 3% when a high ion intensity was available. The repeatability deviation of the quantitative value after calibration using a reference material is around 5% for one laboratory. The reproducibility deviation of the SIMS quantitative values among different laboratories is 10% for a high concentration element, and around 20% for a lower concentration one. However, other factors such as distortion of the extraction field of secondary ions affect the reproducibility, causing a larger deviation for some ion species.
Si(001) vicinal surfaces heated with a sine wave of 104 Hz AC are investigated by using scanning reflection electron microscopy. Surfaces of 1×2 that consist of wide 1×2 terraces (the 1×2 dimer is perpendicular to the direction of the heating current) and narrow 2×1 terraces (the 2×1 dimer is parallel to the direction of the heating current) terraces were obtained at temperatures below 850oC. At temperatures between 850oC and 1100oC, on the other hand, double-domain surfaces where 2×1 and 1×2 terraces are arranged regularly with approximately equal widths were formed. The driving force for growth changes from thermal effect to evaporation effect at about 850oC. At temperatures above 1100oC, the surfaces are composed of mosaic domains due to the evaporation of the atoms.