Chiaki Morita

Measurement of electric field distribution using a conventional transmission electron microscope

A simple and quick method to measure the electric field distribution near a specimen using a conventional transmission electron microscope has been developed. The electric field distribution around a field emitter needle was measured to evaluate the performance of the method. It was found that this method allows us to measure the 2D distribution of electric field quantitatively with error of <10% with submicron spatial resolution. The dedicated aperture and software to construct an automated analysis system have been developed.

Convergent-beam electron diffraction in the high-voltage electron microscope with continuously variable reference voltage for lenses and alignments

Abstract A device which provides a continuously variable reference voltage for lenses and alignments is developed for the high-voltage scanning transmission electron microscope H-1250ST. When continuously varying the operating voltage, compensation for all lenses and alignments is easily performed by the adoption of the device. The device is especially useful for forming the convergent-beam electron diffraction (CBED) patterns at any accelerating voltage. The performance of the device is demonstrated by observing the CBED patterns. Large-angle CBED patterns are taken for Si- and Y-based high- T c superconductors at various voltages. Systematic critical voltages of Y-based high- T c superconductors are measured for the 400 and 220 reflections.

Mapping of minority carrier lifetime distributions in multicrystalline silicon using transient electron-beam-induced current.

We have used transient electron-beam-induced current (EBIC) to map minority carrier lifetime distributions in multicrystalline Silicon (mc-Si). In this technique, the electron beam from a scanning transmission electron microscope was on-off modulated while the sample was scanned. The resulting transient EBIC was analyzed to form a lifetime map. An analytical function was introduced as part of the analysis in determining this map. We have verified this approach using numerical simulations and have reproduced a lifetime map for an mc-Si wafer.

Optimization of the operating condition of the accelerating tube for the high voltage electron microscope equipped with the field emission gun

Abstract Numerical calculations have been conducted on the electron optical characteristics of the accelerating tube (AT) for the high voltage electron microscope (HVEM) equipped with the field emission gun (FEG). The emitted electrons are firstly accelerated to V0 by the FEG and finally to Va by the AT which consists of 34 stages of accelerating electrodes with an inner diameter of 33 mm and has an overall length of 1423 mm. The AT is treated as a thick electrostatic accelerating lens. Several electron optical problems arising from a combination of the AT with the FEG are studied. In order to reduce an unfavorable aberration effect of the AT-lens, the beam crossover must be brought to a position near the entrance plane of the AT. This can be done by a transfer lens which is placed between the FEG and the AT. The introduction of a partial retarding field in the AT is also very effective for a flexible operation of the FEG system without serious aberration effects of the AT-lens.

Computer simulation of electron optical characteristics of accelerating tube for high-voltage electron microscope

Numerical calculations were conducted on the electron optical characteristics of the accelerating tube (AT) for the high voltage electron microscope. The emitted electrons are firstly accelerated to V0 by the TE gun or the FE gun and finally to Va by the AT which consists of 34 electrodes with the inner diameter of 33 mm and has the overall length of 1423 mm. The AT is treated as a thick electrostatic accelerating lens. Several electron optical problems arising from a combination of the AT with a thermionic emission (TE) gun or a field emission (FE) gun are studied. For the TE gun the aberration effect of the AT lens is found to be safely neglected for any combination of Va and V0. In the case of the FE gun, on the other hand, the aberration effect of the AT lens can not be neglected and deteriorates the brightness of the beam. This situation can be overcome by placing an electron lens between the FE gun and the AT.