JP-7855243-B2 - Imaging dielectric spectroscopy method and apparatus thereof

Inventors

• 岩崎 洋

Assignees

• 国立研究開発法人理化学研究所

Dates

Publication Date

20260508

Application Date

20220315

Priority Date

20210317

Claims (19)

1. An imaging dielectric spectroscopy method using an electron microscope equipped with an interferometric electron optical system, By periodically stimulating the sample in the electron microscope with a repetition period T, and repeatedly exposing it on the imaging device for 1/M time of the period T, synchronized with the period T, the interference image formed by the interference electron optical system is captured stroboscopically, interference images with different exposure delay times relative to the stimulation are obtained, and a reconstructed image is obtained from each of the interference images, thereby obtaining the frequency dependence of the complex dielectric constant. An imaging dielectric spectroscopy method characterized by the following:
2. The imaging dielectric spectroscopy method according to claim 1, The aforementioned delay time is varied in N ways to obtain N interference images with different time delays, a reconstructed image of each interference image is obtained, the electromagnetic field is determined, and the dynamic response of the electromagnetic field of the sample during the period T is observed as a series of N frame images. An imaging dielectric spectroscopy method characterized by the following:
3. The imaging dielectric spectroscopy method according to claim 1, The electron microscope has a deflection device for deflecting the electron beam from the electron source, A pulse is applied to the deflection device to turn on the irradiation of the electron beam. An imaging dielectric spectroscopy method characterized by the following:
4. The imaging dielectric spectroscopy method according to claim 1, A pulsed electron source is used as the electron source for the aforementioned electron microscope. An imaging dielectric spectroscopy method characterized by the following:
5. The imaging dielectric spectroscopy method according to claim 1, The aforementioned M is M > 50. An imaging dielectric spectroscopy method characterized by the following:
6. An imaging dielectric spectrometer using an electron microscope equipped with an interferometric electron optical system, An imaging device that periodically applies stimulation to a sample in the electron microscope at a repeating period, and repeatedly exposes it for 1/M time of the period, synchronized with the period, thereby stroboscopically capturing the interference image formed by the interference electron optical system, and obtaining interference images with different exposure time delays in response to the stimulation, The system includes a signal processing device that obtains a reconstructed image from the interference image captured by the aforementioned imaging device, thereby obtaining the frequency dependence of the complex dielectric constant. An imaging dielectric spectrometer characterized by the following features.
7. The imaging dielectric spectrometer according to claim 6, The electron microscope has a shutter mechanism that is synchronized with the period and accumulates repeated exposures on the camera for a time of 1/M of the period. An imaging dielectric spectrometer characterized by the following features.
8. An imaging dielectric spectrometer according to claim 7, The shutter mechanism has parallel plate electrodes, An imaging dielectric spectrometer characterized by the following features.
9. An imaging dielectric spectrometer according to claim 7, The system includes a signal generator that provides the aforementioned stimulus, and applies the generated signal to the sample via a current measuring device. An imaging dielectric spectrometer characterized by the following features.
10. The imaging dielectric spectrometer according to claim 6, The electron microscope is equipped with a pulsed electron source. An imaging dielectric spectrometer characterized by the following features.
11. The imaging dielectric spectrometer according to claim 6, The aforementioned M is M > 50. An imaging dielectric spectrometer characterized by the following features.
12. The imaging dielectric spectrometer according to claim 8, An exposure pulse with a duration τ2 can be supplied to the parallel plate electrode from a pulse generator, and a deflection potential can be applied to interrupt the exposure for a time shorter than τ2, τ1 , during the duration of this pulse τ2 . An imaging dielectric spectrometer characterized by the following features.
13. The imaging dielectric spectrometer according to claim 8, The shutter mechanism is configured using two stages of electrostatic deflectors, each consisting of parallel plate electrodes. An imaging dielectric spectrometer characterized by the following features.
14. An imaging dielectric spectrometer according to claim 13, Long pulses and short pulses are supplied to separate stages of the two-stage electrostatic deflector, which consists of parallel plate electrodes. An imaging dielectric spectrometer characterized by the following features.
15. The imaging dielectric spectrometer according to claim 8, The shutter mechanism is equipped with two stages of deflectors using parallel plate electrodes, Since the two stages of the deflector are held on a common support base, the two stages of the deflector can be introduced through a single opening provided in the vacuum chamber of the electron microscope. An imaging dielectric spectrometer characterized by the following features.
16. The imaging dielectric spectrometer according to claim 8, The deflector, consisting of the parallel plate electrodes, is held on a common support base with the electron beam aperture. An imaging dielectric spectrometer characterized by the following features.
17. The imaging dielectric spectrometer according to claim 6, An imaging dielectric spectrometer comprising a switching element, wherein a voltage is applied to the sample from an external circuit via the switching element, and the response of the sample to the applied voltage is observed by an electron microscope image including the interference image.
18. An imaging dielectric spectrometer according to claim 17, An imaging dielectric spectrometer characterized in that the switching element is formed on a sample support by microfabrication using a focused ion beam or the like.
19. An imaging dielectric spectrometer according to claim 17, The sample support that supports the sample has a capacitance connected in parallel with the sample, and a voltage from the external circuit is applied to the sample and the capacitance via the switching element. An imaging dielectric spectrometer characterized by the following features.

Description

This invention relates to a material analysis technique using electron holography, and more particularly to an imaging dielectric spectroscopy technique for obtaining a mapping of dielectric properties in a sample. Electron holography has applications such as observing the potential created by the ion distribution in solid electrolyte samples, as described in Non-Patent Document 1. However, this involved observing the potential in a steady state reached after applying a voltage to the sample. While technical studies on high-speed imaging using electron holography have progressed, the actual application of time-resolved electron holography to material samples has been slow (see Non-Patent Document 2). Analytical methods for investigating the dynamic response of a sample to an external electric field are called dielectric spectroscopy or impedance spectroscopy. In recent years, their applications have expanded to include the evaluation of cells flowing through microchannels between microelectrodes. However, dielectric spectroscopy measures the response of the entire volume between electrodes and has not been able to image the internal structure of the sample (see Non-Patent Literature 3). Scanning probe microscopes (SPMs) can measure not only the surface topography of a sample but also electrical properties such as dielectric constant. Therefore, they require scanning with a probe-shaped microelectrode. However, a microscopic technique capable of mapping dielectric constant has been developed (Patent Document 1). Patent No. 5295066 Tsukasa Hirayama, Yuka Aizawa, Takeshi Sato, Craig A. J. Fischer, Tatsumi Yoshida, Kazuo Yamamoto, Eiichi Murata, "In situ observation of potential changes in solid electrolytes by electron beam holography," Microscope 52, 4-7 (2017).A. Arbouet, G. Caruso, F. Houdellier, “Ultrafast Transmission Electron Microscopy: Historical Development, Instrumentation, and Applications” Advances in Imaging and Electron Physics, 207, 1-72 (2018).Yoichi Katsumoto, "Application of Dielectric Spectroscopy to Microanalysis of DNA and Cells," Kyoto University Doctoral Dissertation (2010). A diagram showing an example configuration of an imaging dielectric spectrometer according to Example 1.A figure showing a modified example of the imaging dielectric spectrometer according to Example 1.A schematic diagram showing the deflection device of the imaging dielectric spectrometer according to Example 1.A diagram showing a specific configuration of the deflection device according to Example 1.A diagram showing interference fringes captured by the apparatus according to Example 1.A diagram showing the clarity of interference fringes captured with the apparatus according to Example 1.A diagram showing a circuit for connecting an impedance matching device to the deflection device according to Example 1.A diagram showing one configuration example for increasing the speed of electrostatic deflection according to Example 1.This figure shows another configuration example for increasing the speed of electrostatic deflection according to Example 1.A diagram illustrating the principle of differential blanking electrostatic deflection according to Example 1.A diagram showing one example configuration of a differential blanking electrostatic deflector according to Example 1.A schematic diagram illustrating still images of the dynamic response of the electromagnetic field according to Example 1.A diagram showing an example configuration for monitoring the current flowing through a sample according to Example 1, and an example of discrete modeling of the sample.This figure shows three configuration examples for measuring the current flowing through the sample according to Example 1.A schematic diagram of a two-stage electron beam deflector installed along the electron beam path according to Example 2.This figure shows a reconstructed image of a fluctuating electric field captured by stroboscopic exposure according to Example 2.This figure shows a phase-reconstructed image from a still image hologram captured by continuous exposure according to Example 2.A schematic diagram of a device in which two electron beam deflectors according to Example 2 are mounted on a common support mechanism.A schematic diagram of a device in which a converging electron diaphragm and an electron beam deflector according to Example 2 are mounted on a common support mechanism.A diagram showing a comparison between Example 3 and the conventional method.A diagram showing a configuration in which a voltage is applied to a sample via a switching element, according to Example 3.This figure shows a cross-sectional view of the switching element fabricated on a sample support according to Example 3.A diagram showing a planar configuration in which capacitances are arranged in parallel with the sample according to Example 3.A diagram illustrating the operation using the equivalent circuit according to Example 3. Hereinafter, embodiments for carrying out t