Keiji Tamura

Third-order spherical aberration correction using multistage self-aligned quadrupole correction-lens systems

New multistage self-aligned quadrupole correction-lens systems are proposed for correcting the spherical aberration of a rotationally symmetrical lens in a probe-forming system such as electron beam lithography and focused ion beam. These multistage correction-lens systems consist of six- or eight-stage electrostatic quadrupole and aperture electrodes placed between the quadrupoles. An octupole field for the correction of aperture aberration is automatically created and aligned with a quadrupole field by supplying a voltage to the aperture electrode. The optical properties of the self-aligned quadrupole correction-lens systems are precisely simulated using the potential functions approximated from the calculated three-dimensional potential distributions. The lens components of the correction-lens systems are symmetric with respect to the mid-plane of the correction system, and the quadrupole excitations are anti-symmetric to the mid-plane. The simulated optical properties of the six- and eight-stage self-aligned quadrupole correction-lens systems are compared with a four-stage self-aligned quadrupole correction-lens system. Aperture aberration coefficients of the six- or eight-stage quadrupole system under non-excitation of the aperture electrodes become much smaller than those of the four-stage quadrupole system. It is found that the correction of spherical aberration using the six- or eight-stage self-aligned quadrupole correction-lens system can be easily achieved under the condition of considerably lower excitation of lens elements in comparison to the four-stage self-aligned quadrupole correction-lens system.

The development of a new windowless XEDS detector

A new windowless X-ray energy-dispersive spectroscopy (XEDS) detector has been developed for an analytical electron microscope (AEM). Different from the conventional XEDS detectors, the new detector does not contain an ultra-thin window (UTW) and a vacuum gate valve which are the major causes of low X-ray detection sensitivity and vibration problems for AEM imaging, respectively. The performance of the newly designed detector was examined at an AEM column vacuum level of 10⁻⁵ Pa. The X-ray detectability was improved considerably; in particular, the sensitivity for detecting nitrogen characteristic X-ray signal was three times higher than that of the conventional UTW detectors.

Development of Two Steradian EDX System for the HD-2700 FE-STEM Equipped with Dual X-MaxN 100 TLE Large Area Windowless SDDs

The model HD-2700 [1] 200 kV spherical aberration (Cs) corrected dedicated Scanning Transmission Electron Microscope (STEM) has been used for analyzing nanoto subnano-area targets in the fields of nanoscience and nanotechnology with Energy Dispersive X-ray spectrometry (EDX). The Cs corrector [2] enables the formation of sub-nanometer probe size with several hundred to a thousand pico amperes of probe current, but still EDX detectors with much higher sensitivity are desired. Recent adaptation of Silicon Drift Detector (SDD) technology [3] accelerated the counting rate of detection and enhancement of detector active area. These features are suitable to improve analytical sensitivity. Using a windowless high solid angle SDD, high sensitivity elemental analysis can be achieved [4].

High Speed and Sensitive X-ray Analysis System with Automated Aberration Correction Scanning Transmission Electron Microscope

In recent years, the aberration-correction technique has brought a revolution in analytical microscope by making atomic-resolution imaging and analysis routinely achievable in transmission electron microscope (TEM) and scanning transmission electron microscope (STEM). We have developed as a product an electron microscope the performance of which is dramatically increased by inclusion of a sphericalaberration-correction function (Inada et al., 2009a, 2009b). In addition, the application of new aberration-correction techniques, such as atomic-resolution secondary-electron (SE) imaging, is now being investigated (Zhu et al., 2009; Inada et al., 2011a, 2011b; Inada & Zhu, 2014). Scherzer (1947) proved that combinations of rotationally symmetrical electromagnetic lenses had convex lens effects only, and the spherical aberration coefficients were always positive. However, multipole lenses in the aberrationcorrection devices of TEMs and STEMs have resulted in concave lens effects, that is, lenses with negative spherical aberrations, and these are now in wide use for cancelling out the positive spherical aberrations of object lenses (Beck, 1979; Rose, 1981; Crewe, 1982; Rose, 1990; Haider et al., 1998). On the other hand, optics systems using multipole lenses give rise to various types of parasitic aberration due to the heterogeneity of the magnetic properties of the materials, and slight deviations from symmetry during machining. With the aberration-correction devices in previous use, for correcting multiple types of aberration, alignment was a difficult process, and users required considerable experience to be able to make

Development of TEM techniques dedicated for characterization of energy related composites and its application

In this paper, recent progress in the improvement of TEM techniques based on a 40-120 kV high resolution analytical TEM and some application to the catalysts are discussed. The spherical aberration coefficient and TEM image resolution of high resolution objective lens at the accelerating voltage of 120 kV are 1.1 mm and 0.2 nm respectively. The high resolution objective lens pole-piece has been newly designed to accommodate a high solid angle silicon drift detector of an energy dispersive X-ray analyzer. A FIB fabricated apertures with the smallest diameter of 1m are equipped as the field limiting aperture for structural analysis of individual nanometer sized crystalline. The external view of the microscope