Narrow Results

A microbeam analysis system has been developed at Tohoku University for biological applications. Spatial resolution of less than 1 μm has been achieved with a beam current of ~40 pA. In microbeam analysis of biological specimens, simultaneous measurement of structural and elemental properties is very important. Our system is applicable to simultaneous in-air/vacuum PIXE, RBS and STIM analyses. Typical results of biological application are shown.

A microbeam analysis system at Tohoku University has been improved in detection efficiency for application to single cell analysis. The system is applicable to STIM analysis and to simultaneous PIXE and RBS analysis. Sample preparation methods suitable for non-adhesive single cell analysis were developed and first results with the improved analysis system are shown.

A microbeam system has been developed for the analysis of single aerosol particles. Combination of PIXE, RBS and off-axis STIM methods enabled simultaneous analysis for hydrogen to metal elements. Aerosol particles were collected on thin polycarbonate film (~0.3 μm) resulting in good signal-to-noise ratio. Quantitative elemental correlation was measured for single aerosol particles. A total of 270 particles were analyzed and clustered into 4 groups. The analysis system reveals the chemical composition of aerosol particles and is a powerful tool for source identification.

We have developed an in-air on/off axis STIM for simultaneous density mapping with PIXE and RBS, which will be useful for damage-monitoring in cell analysis and for yield correction based on the thickness distribution of X-ray self-absorption in samples. The in-air on/off axis STIM system provides a mass concentration map in the cell analysis. In the system, a thin scattering foil is placed downstream of the sample and scattered protons are detected by a Si-PIN photodiode set at 30 degrees with respect to the beam axis. These components are set in a He-gas-filled chamber to reduce energy loss, scattering and sample damage. Using this system, areal density mapping is carried out for RBL-2H3 cells simultaneously with PIXE and RBS. Correction for self-absorption is performed and areal density map of elements is converted into a mass-concentration map using the measured matrix density. The areal density distribution of P corresponds to that of matrix and mass concentration of P is uniform in the cell region. On the other hand, Br is concentrated in the nucleus, even in the mass concentration map. The Br accumulation in the nucleus is first confirmed in mass concentration using the on/off axis STIM and PIXE system. The in-air on/off STIM system will be effective for monitoring changes in cell density during beam irradiation.

Wall thinning of piping made of carbon steel when exposed to high temperature water flow and va-por is a common problem in all types of these plants. Oxide layer formation and dissolution should be related to the mechanism of corrosion. In order to understand the mechanism of corrosion, characterization of oxide layer including elemental concentration in the localized area is indispensable. In this study, simultaneous μ-PIXE/RBS/SEM analysis system was developed to obtain elemental characterization on oxide layer in localized area as well as to obtaining surface condition. Carbon steel samples were oxidized dynamically for 1100 hours and analyzed by the system. The oxide layer is not uniform even in the localized area of 30 × 30 μm². In the chromium content of 0.003 wt%, oxide layer thickness varied from 0.71 to 1.2 mg/cm². While accumulation of chromium is seen in the map, accumulation is not related to the iron distribution. Chromium and iron ratio in the accumulated region is more than five times higher than that of the other area. The higher chromium and iron ratio indicates that chromium migrate from substrate to oxide layer. In the chromium content of 1.01 wt%, oxide layer thickness varies from 1.4 to 3.9 mg/cm². Oxide layer is thicker than that in the chromium content of 1.01 wt%, which is opposite to the result in the static condition. Large variation of X-ray yield of iron indicates that dissolution of the oxide layer might occur during long exposure to the water flow. These results of this experiment obviously show the simultaneous μ-PIXE/RBS and SEM analysis system to be useful for better understanding of the corrosion mechanism.

Nine gold-plated costume jewelries bought in the street market of Porto Alegre and from Chinese websites were investigated through Particle-Induced X-ray Emission (PIXE) and Rutherford Backscattering Spectrometry (RBS) in order to verify their elemental composition and distribution. The analyzed costume jewelries were made of Cu-based alloys with Ni, Zn, Sn and Al. Elements such as Ag, Al, Bi, Cd, Co and Fe were found in minor amounts in some particular samples. Through RBS, it was possible to distinguish the bulk from the gold-plated layer. Toxic elements as Ni and Cd were found in at least one sample. The high concentration of Ni comes from the bulk Cu-alloy below the Au layer. In this case, the Au acts as a protective layer separating the Ni from the user’s skin.

Natural FeTiO₃ (illuminate) and synthesized FeTiO₃, single crystals were characterized by Rutherford backscattering spectroscopy combined with channeling technique and particle-induced x-ray emission (RBS-C and PIXE). The results obtained by the ion beam analysis were supplemented by the x-ray diffraction analysis to identify the crystallographic phase. Oriented single crystals of synthesized FeTiO₃ were grown under the pressure control of CO₂ and H₂ mixture gas using a single-crystal floating zone technique. The crystal quality of synthesized FeTiO₃ single crystals could be improved by the thermal treatment but the exact pressure control is needed to avoid the precipitation of Fe₂O₃ even during the annealing procedure. Natural FeTiO₃ contains several kinds of impurities such as Mn, Mg, Na and Si. The synthesized samples contain Al, Si and Na which are around 100 ppm level as impurities. The PBS-C results of the natural sample imply that Mn impurities occupy the Fe sublattice in FeTiO₃ or in mixed phase between ilmenite and hematite.

Ti and C ions extracted from a metal vapor vacuum arc ion source (MEVVA) were implanted into H13 steel using a masking procedure to ensure reproducible conditions for testing and subsequent analysis. An optical interference microscope and pin-on-disc apparatus investigated the wear and friction characteristics of the steel. The Ti concentration depth profile from Rutherford backscattering spectroscopy was compared with that calculated by a TRIDYN code. It was observed by grazing-angle X-ray diffraction and transmission electron microscopy that carbide of Ti appeared in the doped region. The concentration depth profile and microstructure analysis can serve to illuminate the wear resistance improvement mechanisms of the Ti-implanted steel.

The aim of our investigation is focused on studying the effect of dopant dose loss during annealing treatments on heavily doped surface layers, obtained by recoil implantation of antimony in silicon. We are interested particularly by the increase of sheet resistance consequently to the shallow junctions obtained at the surface of substrate and the contribution of the dopant dose loss phenomenon following the high concentration of impurities at the surface. In this work, we report some quantitative data concerning the dopant loss at the surface of silicon implanted and its dependence with annealing treatments. Electrical measurements associated with Rutherford backscattering (RBS) technical analysis showed interesting values of sheet resistance compared with classical ion implantation and despite dopant dose loss phenomenon.

The processes in the synthesis of a thin layer of hexagonal YSi_2-x phase on a single-crystal Si(111) substrate by implantation of 195 keV Y ions with a dose of 2 × 10¹⁷Y⁺/cm² at 300°C followed by annealing in an N₂ atmosphere at different temperatures for 1 h are investigated. The characterization of the as-implanted and annealed samples is performed using Rutherford backscattering spectrometry (RBS) and X-ray diffraction (XRD) pole figures. Scanning electron microscopy (SEM) was used to view the surface topography. The results show that the orientation relationship between the YSi_2-x layer and Si substrate is YSi_2-x(0001)//Si(111) and YSi_2-x[11–20]//Si[110].

This paper analyzes the effect of 100keV silicon negative ion implantation in semi-insulating gallium arsenide sample for the fluences varying between $1\times 10^{15}$ and $2\times 10^{17}$ioncm${}^{-2}$ using Raman spectroscopy, Rutherford backscattering spectroscopy and Electron spin resonance spectroscopy. The gallium arsenide sample implanted with silicon negative ion for different fluences showed shift in the TO peak position with respect to unimplanted gallium arsenide sample. Increase in the broadening of TO peak was observed in the as-implanted samples, indicating development of stress and phonon confinement due to the incorporation of silicon in gallium arsenide crystal lattice. Annealing of as-implanted samples showed stress relaxation. Increase in RBS backscattering yield was observed in the as-implanted samples. Annealing of as-implanted (with high fluence) sample showed flat RBS yield response. ESR measurement study revealed restructuring of defects in the gallium arsenide sample implanted with fluence of $1\times 10^{17}$ioncm${}^{-2}$ after annealing to the temperature of $300^{\circ }$C.

Analysis using MeV ion beams is a thin film characterisation technique invented some 50 years ago which has recently had the benefit of a number of important advances. This review will cover damage profiling in crystals including studies of defects in semiconductors, surface studies, and depth profiling with sputtering. But it will concentrate on thin film depth profiling using Rutherford backscattering, particle induced X-ray emission and related techniques in the deliberately synergistic way that has only recently become possible. In this review of these new developments, we will show how this integrated approach, which we might call "total IBA", has given the technique great analytical power.

Analysis using MeV ion beams is a thin film characterisation technique invented some 50 years ago which has recently had the benefit of a number of important advances. This review will cover damage profiling in crystals including studies of defects in semiconductors, surface studies, and depth profiling with sputtering. But it will concentrate on thin film depth profiling using Rutherford backscattering, particle induced X-ray emission and related techniques in the deliberately synergistic way that has only recently become possible. In this review of these new developments, we will show how this integrated approach, which we might call “total IBA”, has given the technique great analytical power.