Kenichi Obori

Monte Carlo simulation of x‐ray spectra in electron probe microanalysis: Comparison of continuum with experiment

A Monte Carlo simulation code has been developed to describe the x‐ray generation in a specimen for electron probe microanalysis (EPMA), enabling x‐ray spectra observed by EPMA to be reproduced theoretically. The Monte Carlo simulation is based on the use of the Mott cross section and Bethe stopping power equation in describing elastic and inelastic scattering processes, respectively. With respect to x‐ray generation the Sommerfeld theory for bremsstrahlung radiation was described by equations of Kirkpatrick–Wiedmann and of Statham for bremsstrahlung cross section. The up‐to‐date compilation of mass absorption coefficient by Henke, Gullikson, and Davis [At. Data Nucl. Data Tables 54, 181 (1993)] is used to evaluate attenuation of x‐ray intensity. To verify the present Monte Carlo simulation measurements of x‐ray spectra for Cu and Rh targets have been performed for primary electron energies of 10–30 keV by energy‐dispersive x‐ray spectrometry of an electron probe microanalyzer. Excellent agreement between...

Multiple-scanning-probe tunneling microscope with nanoscale positional recognition function

Over the past decade, multiple-scanning-probe microscope systems with independently controlled probes have been developed for nanoscale electrical measurements. We developed a quadruple-scanning-probe tunneling microscope (QSPTM) that can determine and control the probe position through scanning-probe imaging. The difficulty of operating multiple probes with submicrometer precision drastically increases with the number of probes. To solve problems such as determining the relative positions of the probes and avoiding of contact between the probes, we adopted sample-scanning methods to obtain four images simultaneously and developed an original control system for QSPTM operation with a function of automatic positional recognition. These improvements make the QSPTM a more practical and useful instrument since four images can now be reliably produced, and consequently the positioning of the four probes becomes easier owing to the reduced chance of accidental contact between the probes.

Continuum X-Ray Generation from W Film on Cu Substrate

The dependence of the continuum X-ray generation from a W film on the primary energy (15 to 30 keV) and film thickness (0.1 to 0.7 µm) have been investigated by experiment and Monte Carlo (MC) simulation in order to develop a high-power rotor-type X-ray source of high efficiency. The continuum X-ray spectra obtained by MC simulation show excellent agreement with the experimental data, confirming the fact that the present MC simulation is applicable for a systematic study to optimize the construction of an X-ray source. The dependence of the continuum X-ray generation on the thickness of the W film has revealed that the continuum X-ray spectra from the W film of thickness ~0.7 µm are almost similar to those of the bulk W in the investigated range of primary energies. This indicates that the thickness of the W film of ~0.5 µm is sufficient for the rotor-type X-ray source, although a commercial-type source is of the order of hundreds µm with the primary energy of ~50 keV.

Monte Carlo Study of X-ray Generation from Film/Substrate Structure by Electron Impact

The Monte Carlo (MC) simulation of X-ray emission from film/substrate structures induced by electron impact was investigated. The developed MC simulation enables the calculation of the absolute X-ray spectrum consisting of continuous, characteristic K-line and fluorescent X-rays without any fitting parameters. The samples used were 40- and 78-nm-thick Ti films on Al, Cu and Zr substrates. These samples have atomic number combinations of Zfilm Zsub. An excellent agreement between the simulation and experimental X-ray spectra was observed for the wide range of the primary energy of electrons from the threshold energy of the K-shell ionization of each element to ~30 keV.

Monte Carlo Modeling of Generation of Characteristic, Continuous and Fluorescent X-rays by Electron Impact

A Monte Carlo (MC) simulation to calculate the absolute intensity of an X-ray spectrum generated by electron impact was developed. The X-ray spectrum consists of continuous and characteristic X-rays excited by primary electron, and fluorescent X-rays due to the absorption of the continuous and characteristic X-rays. The comparison of the simulated X-ray spectra with the experimental ones showed excellent agreement for bulk Al, Sc, Ge and Zr. The quantitative investigations of the simulated intensity of the characteristic K peak and the effect of the fluorescent X-ray were performed. It was confirmed that the developed MC simulation is applicable not only for optimizing the design of the rotor-type X-ray source to develop a high-brightness wavelength-tunable X-ray source, but also for quantitative electron probe microanalysis.

Quantitative microanalysis of individual particulates. I. Electron probe microanalysis of NBS‐glass particulates

The applicability of the Monte Carlo calculation technique for quantitative analysis of particulate samples with an electron probe microanalyzer was verified through comparison between theoretical and experimental results for an NBS K‐411 series of glass particulates. Good agreement between theory and experiment suggests that the Monte Carlo calculation technique will be a useful tool for performing quantitative electron probe microanalysis of individual particulate samples.

Monte Carlo Simulation of Generations of Continuous and Characteristic X-Rays by Electron Impact

A new Monte Carlo (MC) simulation code has been developed to describe the spectra of not only continuous X-rays but also characteristic X-rays. The simulation code is developed using the Kirkpatrick-Wiedmann-Statham equation and the formulae derived by Casnati and Gryzinski to describe generations of continuous X-rays and characteristic X-rays, respectively. The results indicate that a series of experimental X-ray spectra from W films of different thickness on Cu substrates have been reproduced by the present MC simulation with considerable success. A practical application for designing the optimum construction of a rotor-type X-ray source is also presented.

Development of Monte Carlo Simulation of Generation of Continuous and Characteristic X-Rays by Electron Impact

A new Monte Carlo simulation code has been developed to describe an X-ray spectrum excited by an electron impact. The simulated spectrum consists of the continuous X-ray and characteristic X-ray emitted after ionization by an electron and the absorption of the continuous and characteristic X-rays. The simulated spectra from bulk Cu, W and W film on a Cu substrate were compared with the experimental spectra. The results reveal that a significant degree of agreement can be obtained without any fitting parameters.