Natsuo Fukumoto

X-ray photoelectron spectroscopy and grazing incidence X-ray reflectivity study of silicon nitride thin films

Abstract Silicon nitride thin films were deposited by rf magnetron sputtering with various gas flow conditions (N 2 /Ar). The effect of gas flow conditions on the structure and compositions of the films was investigated. X-ray photoelectron spectroscopy indicated that the binding energy of the Si 2p state successively shifted to higher energy while the binding energy of the N 1s state showed no change with the increase of the N 2 /Ar ratio. The films deposited under conditions of N 2 /Ar ratio below 0.5 were silicon-rich while the films formed with the N 2 /Ar ratio more than 0.5 were nitrogen-rich. Nearly stoichiometric Si 3 N 4 films can be obtained at the N 2 /Ar ratio of 0.5. Grazing incidence X-ray reflectivity showed that the nearly stoichiometric Si 3 N 4 film had a higher density (3.17 g/cm 3 ) while the silicon-rich or nitrogen-rich resulted in a decrease in film density. The surface roughness of these films lies almost in the same level.

X–ray fluorescent spectroscopy with a focused X–ray beam collimated by a glass capillary guide tube and element mapping of biological samples

Abstract Several research groups developed X–ray fluorescent spectroscopic microanalysis systems using focused X–ray beams. Typical examples are reviewed for these systems using conventional and synchrotron radiation light source. Details of the system developed by the present authors are additionally shown. Applications for biological samples done by the present authors are also shown. Focused X–ray beam by a glass capillary guide tube method is useful for non–destructive real–time monitoring of elemental distribution of plants.

STM and AES study of the relation between ion sputter induced roughness and depth resolution

Abstract Scanning tunneling microscopy has been applied to characterize the enhancement of surface roughness by ion sputtering. A certified Ni/Cr multilayer film was employed as a target. It was found that the roughness induced by ion sputtering increased with the increase of sputtered depth, and that this increase in roughness accounted for most of the reduction in depth resolution in Auger depth profiling.

Application of spectrum synthesis method to depth profile analysis

Abstract A spectrum synthesis method based on non-linear least-squares fitting has been applied to the depth analysis of the SiO 2 thin layer on Si. The present treatment was required because the Auger spectra overlapped between the oxide and the metal species both in Si LVV and in Si KLL regions, and the Auger peak energies shifted to the higher energy side with a decrease in the thickness of the oxide layer. The calculation with appropriate constraining conditions yielded the detailed depth profiles which could distinguish the two chemically different species. A non-uniform distribution in the depth of metal species was observed by the profiles derived from LVV and KLL peaks because of the difference in their electron escape depths.

A study on the utilization of the Youden plot to evaluate proficiency test results

Methods of utilizing the Youden plot obtained from interlaboratory comparison tests are proposed. The Youden plot is a powerful tool for visually evaluating between- or within-laboratory errors. However, there are no generally applicable methods to indicate the anomalies in the between- and the within-laboratory errors in qualitative terms. An evaluation frame was therefore developed in this study as an indication method. Moreover, the Youden plot is considered to be useful for visually assessing the comprehensive performance of laboratories using two types of results. Although the confidence ellipse has been proposed in ISO 13528:2005 for this purpose, robust determination of the parameters has not yet been implemented. In the present study, robust determination of one of the parameters, the correlation coefficient, was developed. Our proposals were analytically validated using two types of statistical models. In addition, the properties were evaluated through computational simulations. From the results obtained, it can be concluded that our proposals are practically applicable to actual interlaboratory comparison tests.

TEM, XPS and SIMS Analyzes on Grain Boundary of Lanthanum Chromites

The morphological characteristics, chromium valence state, and cation transport in the vicinity of grain boundary in La1-xCaxCrO3 were investigated by using TEM/EDS, XPS and SIMS techniques. The width of grain boundary was around 1 nm where anomalous enrichment of calcium was observed. Higher valence state of chromium such as Cr6+(d0) was detected in the grain boundaries whereas Cr3+(d3) and Cr4+(d2) were dominant in the bulk. Very fast interdiffusion of alkaline earths was observed in the Sr2+-La0.75Ca0.25CrO3 system. All observed phenomena were correlated by assuming the A-site vacancy which may be induced by the formation of Cr6+ at grain boundaries.

Non-Destructive Determination of Manganese State in Rice Leaf by X-Ray Absorption Spectrometry

Abstract One of the authors analyzed the brown spot symptoms developed on plant leaves caused by nutritional disorders using an X-ray Micro-Analyser (Sasaki et al. 1980). The use of an X-ray Fluorescence Element Mapping Spectrometer (XEMS) revealed that external and internal stresses such as X-ray irradiation and manganese excess induced the transport of manganese, and excess of manganese concentration as cationic Mn2+ was related to the formation of the abnormal brown spots (Watanabe and Kobayashi 1986; Watanabe et al. 1988). Since, the mechanism of the transport of manganese remains to be elucidated the analysis of the chemical state of manganese in plant is important. Since the valency of manganese readily changes depending on the redox potential, non-destructiye analysis may be effective. In fact, few studies have been carried out on the non-destructive determination of the manganese state in plant tissues. We studied the state of manganese in rice leaf in performing Extended X-ray Absorption Fine Str...

Least squares curve fitting in Mo3d X-ray photoelectron spectra for determination of oxidation states of supported molybdenum catalysts.

石炭液化油の水素化改質触媒として用いられる金属酸化物上に担持された硫化モリブデンについて,担体及び前処理条件の異なる各種の試料のX線光電子分光(XPS)スペクトルを最小二乗法を用いてカーブフィット処理し,価数別定量を試みた.XPSスペクトルにおいてモリブデンの四価,五価,六価の3dピークは各々,化学シフトが半値幅と同程度なので各成分別の存在比を求めるにはピーク分離が必要である.最小二乗法によるピーク分離を行うと先の3種の価電子状態のピークに分離されるが個々のスペクトルについて,3d5/2と3d3/2の(1)強度比は3:2,(2)半値幅は等しい,(3)分裂間隔は3.0eV,という拘束条件をつけ,(4)五価の半値幅は四価のそれと等しい,ということを仮定して単独に処理した場合には価電子状態が同じでも結合エネルギーがずれるなど,合理的な結果は得られなかった.このため,(5)各状態の結合エネルギー,半値幅は同一担体上ではそれぞれ等しい,という仮定を追加したところ,電子スピン共鳴法を用いた五価のモリブデンによる信号強度とよく対応する結果が得られた.本研究の結果,前処理条件が同じであっても担体の種類によりモリブデンの状態別存在量,特に五価の増減挙動は大きく異なることが示された.