JPS598025B2 - electronic microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron microscope suitable for observing magnetic domains by applying an alternating magnetic field to a magnetic sample.

Recently, a lot of knowledge about the magnetic domain structure has been obtained by observing a magnetic sample subjected to a magnetic field using an electron microscope.

However, in all conventional methods, the magnetic field applied to the sample is a static magnetic field, and an electron microscope is used to observe how the magnetic domains of the sample move when an alternatingly changing magnetic field is applied to the sample. None existed, and the emergence of such an electron microscope was awaited.

The present invention has been made in response to these demands, and involves applying a magnetic field whose intensity changes periodically to a sample, and applying an electron beam that passes through an objective lens in synchronization with a specific phase of the periodic magnetic field. The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram for explaining one embodiment of the present invention. In the drawing, 1 is an electron gun, and an electron beam 2 generated from the electron gun enters a converging lens 3 and becomes a parallel beam. and enters the magnetic sample 5 along the optical axis 4.

6 is a coil for applying a magnetic field to the sample 5;
The coil 6vc is supplied with a sine wave current of, for example, several KH as shown in FIG.

Therefore, the magnetic field applying coil 6 applies to the sample 5 a magnetic field whose magnetic field strength changes sinusoidally as shown in FIG. 2bK.

The electron beam transmitted through the sample 5 is influenced by the magnetic field created by the magnetic field applying coil 6.

That is, the electron beam is deflected in proportion to the amplitude of the magnetic field strength shown in FIG. 2b.

Therefore, in order to cancel such deflection, the correction magnetic field applied force I
] A stage 1 is provided after the magnetic field applying coil 6.

The correction magnetic field application port 1 consists of first and second correction coils 9a and 9b to which the current from the current amplifier 7 is supplied.

The first and second correction coils 9a and 9b are connected in the opposite direction and the same direction as the connection direction of the magnetic field applying coil, respectively.

Therefore, the first correction coil 9a generates a magnetic field with an opposite phase to the magnetic field strength waveform shown in FIG.
b generates a correction magnetic field having the same phase as that in FIG. 2b.

Therefore, for example, the magnetic field application port coil 6
An electron beam that is deflected to the right at a certain moment as shown by A in the figure is deflected to the left by the first correction coil 9a as shown by the mouth in the figure, and then directed to the optical axis by the second correction coil 9b. deflected to proceed along.

For example, an electron beam that is deflected to the left by the magnetic field application port coil 6 at a certain moment as shown by the dotted line C in FIG. The beam is deflected by the second correction coil 9b so as to proceed along the optical axis.

In this way, the electron beam, which is made to always travel along the optical axis 4 by the correction magnetic field application means, is transmitted to the objective lens 1.
0.

A channel plate 11 is arranged after the objective lens 10.

The channel plate 11 is composed of a bundle 12 of a large number of secondary electron multiplier tubes and a bundle 13 of optical fibers, and has the function of multiplying an electron beam image, converting it into an optical image, and taking it out of the vacuum housing. do.

A high voltage generation circuit 1 is installed at both ends of the bundle 12 of secondary electron multiplier tubes.
4 is applied, and only the electron beam image during the period when the high voltage is applied is multiplied and converted into an optical image.

15 is supplied with a signal from the sine wave generating circuit 20,
The high voltage generating circuit 14 is a synchronizing signal generating circuit that generates a trigger signal at the moment when the signal reaches a specific phase, and the high voltage generating circuit 14 generates a high voltage based on the trigger signal.

Reference numeral 16 denotes an optical lens, and the optical image guided by the fiber bundle 13 is formed by the lens 16 onto an image orthicon 17, and the image taken by the image orthicon 17 is captured by a cathode ray tube. 18.

Of course, other imaging lenses may be arranged after the objective lens 10.

In this configuration, a magnetic field whose intensity varies sinusoidally as shown in FIG. 2b is applied to the sample by the magnetic field application port coil 6.

Furthermore, at this time, a trigger signal synchronized with the specific phase of the applied magnetic field shown in FIG. 2B as shown in FIG. 2C is supplied from the synchronization signal generation circuit 15 to the high voltage generation circuit 14.

Since the secondary electron multiplier tube multiplies the incident electrons only at the moment when the high voltage is marked 71[], the electron beam image formed by the electron beam transmitted through the sample 5 and the objective lens 10 at this moment is After being converted into an optical image by the channel plate 11, the image orthicon 17 is converted by the optical lens 16.
imaged on top.

Therefore, the sample image at the moment when the trigger signal is generated is periodically displayed on the cathode ray tube 18, and due to the action of the fluorescent surface of the cathode ray tube 18, the operator of the cathode ray tube 18 can make a specific image synchronized with the phase. A static image of the sample under a strong magnetic field can be observed, and the state of the magnetic domains of the sample can be observed from this image.

By setting the generation timing of the trigger signal generated by the synchronization signal generation circuit 15 to a different phase, it is possible to observe a sample image using the cathode ray tube 18 in a state where a magnetic field with an intensity corresponding to the phase is applied to the sample. .

In the above-mentioned embodiment, a channel plate, an image orthicon, and a cathode ray tube were used to select and display only the image at a specific phase of the periodic magnetic field applied to the sample. For example, a fluorescent plate is used as the display means, and a deflection electrode or a deflection electrode is provided on the electron beam path from the electron gun to the fluorescent plate to direct the electron beam toward the fluorescent plate only at the moment when the sinusoidal magnetic field reaches a specific phase. A control electrode may also be provided.

Alternatively, the electron beam may be detected over all phases, and when displayed, only signals at a specific phase may be selected and displayed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIG.
Figures a, b, and c are diagrams showing the current waveforms supplied to the coil of the embodiment device shown in Figure 1, the magnetic field generated by the coil, and the trigger signal of the synchronization signal generation circuit, respectively. . DESCRIPTION OF SYMBOLS 1... Electron gun, 2... Electron beam, 3... Converging lens, 4... Optical axis, 5... Sample, 6... Magnetic field application coil, 7... Current amplifier, l... Correction magnetic field applying means, 9a... 1st (7) correction = r ill, 9b... 2nd
correction coil, 10... objective lens, 11... channel plate, 12... bundle of secondary electron multiplier tubes, 13
... bundle of optical fibers, 14 ... high voltage generation circuit, 15 ... synchronization signal generation circuit, 16 ... optical lens, 17 ... image orthicon, 18 ...
Cathode ray tube, 20...Sine wave generation. circuit.

Claims (1)

[Claims] 1. An electron gun, a converging lens for focusing the electron beam generated from the electron gun onto a sample, means for applying a periodic magnetic field to the sample, and correcting the deflection of the electron beam by the means. an objective lens into which the electron beam corrected by the correction means enters; and means for selecting and displaying only images at a specific phase of the periodic magnetic field. electron microscope.