JPH0618700A - X-ray monochrometer - Google Patents

Abstract

PURPOSE:To increase an angle of X-ray incidence with respect to a sample surface by improving resolutions with a narrowed line width of X-rays. CONSTITUTION:A target 11 is irradiated with an electron beam from an electron gun 12 put on an optical axis and X-rays generated from the target 11 are subjected to a Bragg reflection with a ring-shaped spectroscopic crystal 13 having a narrow width arranged about an optical axis. The X-rays focused once are reflected with a spectroscopic crystal 14 having a paraboloid in a rotation symmetry to other optical axes and then, applied to a sample 15. This allows increase in the angle of incidence of X-rays with respect to a sample surface.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an X-ray monochromator for an electron microscope chemical analyzer (ESCA).

[0002]

2. Description of the Related Art Conventionally, an ESCA for identifying an element of a sample by irradiating a sample with X-rays generated by irradiating a target with an electron beam and irradiating the sample with the wavelength selected, and detecting photoelectrons emitted from the sample Is being developed.

FIG. 2 shows an ESCA monochromator. When an electron beam from an electron gun 12 is irradiated on a target 11 and X-rays generated from the irradiation region are irradiated on a dispersive crystal 20, the dispersive crystal is irradiated. Among the X-rays reflected by the surface, the sample 15 is irradiated with the X-ray having the wavelength λ1 that satisfies the Bragg equation 2d sin θ1 = nλ1 (1). At this time, the photoelectrons generated from the sample 15 pass through the electrostatic lens 17, are dispersed by the analyzer 18, are detected by the detector 19, and the elements of the sample are identified.

As shown in FIG. 3A, the dispersive crystal 20 has a radius of curvature of a radius r1 in a plane including the target and the sample, and as shown in FIG.
And a toroidal surface having a radius of curvature r2 in a plane orthogonal to the line connecting the target and the sample, centered on the midpoint (O) of the sample 15. Normally, a Johan type crystal is used as such a dispersive crystal.
In the in-plane of the curvature r1 of (a), the aberration becomes large when it deviates from the center position of the dispersive crystal plane, and therefore the width W cannot be increased so much, but there is no aberration in the surface of the curvature r2 of FIG. 3 (b).

[0005]

By the way, in order to increase the brightness of X-rays on the surface of the sample, it is sufficient to increase the size of the dispersive crystal surface, but it can be increased because of the aberration on the surface having the curvature r1. In-plane 360 of curvature r2 without aberration
The crystal plane may be used, and as shown in FIG.
It suffices to arrange 0 so that it has a cylindrical shape centered on the midpoint (O) of the target 11 and the sample 15 and has a plane rotationally symmetrical with respect to the optical axis. However, in the X-ray monochromator for ESCA, it is necessary to narrow the line width of the X-ray in order to improve the resolution, and therefore it is necessary to make the angle θ1 in Bragg's equation (1) as wide as possible. As can be seen from FIG. 4, in order to increase θ1, the target and the dispersive crystal 2
It is necessary to shorten the interval between 0s, and as a result, the interval between the dispersive crystal and the sample is also shortened, and the incident angle α of the X-ray with respect to the sample surface becomes small. As a result, the electrostatic lens, analyzer, etc. are arranged. There was a drawback that there was no space to play.

The present invention is intended to solve the above-mentioned problems, and narrows the line width of X-rays to improve the resolution and
An object of the present invention is to provide an X-ray monochromator capable of enlarging the X-ray incident angle with respect to the sample surface and taking a large space for disposing the electrostatic lens and the analyzer.

[0007]

The X-ray monochromator of the present invention comprises an electron gun and a target arranged on the optical axis,
A ring-shaped first dispersive crystal having a toroidal surface that Bragg-reflects X-rays generated from a target by electron beam irradiation from the electron gun, and X-rays focused on the optical axis by being reflected by the first dispersive crystal. A second dispersive crystal having a parabolic surface that is rotationally symmetric with respect to the optical axis to be reflected by the Bragg reflection, and a detection unit that detects photoelectrons generated from the sample by the X-ray irradiation reflected by the second dispersive crystal. It is characterized by having.

[0008]

The present invention irradiates an electron beam to a target from an electron gun placed on the optical axis, and a narrow ring-shaped first dispersive crystal arranged around the optical axis for X-rays generated from the target. Bragg reflection with the X-ray, and once the focused X-ray is reflected by the second dispersive crystal having a parabolic surface rotationally symmetric with respect to the optical axis, the sample is irradiated with the X-ray. Since there is no need to increase the reflection angle, it is possible to increase the angle of incidence of X-rays on the sample surface, which increases the degree of freedom around the sample, making it possible to easily dispose the lens and analyzer, resulting in high resolution. It can be measured with high brightness.

[0009]

1 is a diagram showing the construction of an X-ray monochromator of the present invention. In the figure, 11 is a target, 12 is an electron gun, 13 and 14 are dispersive crystals, 15 is a sample, 16 is a sample surface, 17 is a lens, 18 is an analyzer, and 19 is a detector.

The electron beam from the electron gun 12 is the target 11
The X-ray generated from the irradiation region is irradiated to the ring-shaped dispersive crystal 13 having the curvature of the toroidal surface arranged in a cylindrical shape. As described in FIG. 4, in order to improve the resolution, the incident angle to the dispersive crystal 13 (the dispersive crystal plane and X
It is necessary to increase the angle formed by the line), and therefore the dispersive crystal 13 is arranged at a position close to the target 11. The X-rays Bragg-reflected by the dispersive crystal 13 are once focused at a point P on the optical axis, and then enter the dispersive crystal 14 having a toroidal curvature and a parabolic surface rotationally symmetric with respect to the optical axis. The sample 15 is irradiated with Bragg reflection. Since the dispersive crystal 14 is for reflecting the X-rays once dispersed by the dispersive crystal 13, it is possible to use a dispersive crystal under the condition that θ1 in the Bragg equation (1) is small. By increasing the distance between the sample 14 and the sample 15, the incident angle α of the X-ray with respect to the sample surface 16 perpendicular to the optical axis can be increased.

As described above, since α can be set to be sufficiently large, the degree of freedom around the sample is increased, a sufficient space can be provided for disposing the electrostatic lens and the analyzer, and photoelectrons generated from the sample Through the electrostatic lens 17,
It can be separated by the analyzer 18 and detected by the detector 19. Although the sample is tilted by α with respect to the sample surface perpendicular to the optical axis in the figure, the sample need not be tilted.

An X-ray lens (zone plate, total reflection mirror) having the same function as that of the dispersive crystal having the toroidal surface curvature of the dispersive crystal 14 may be used instead of the dispersive crystal 14.

[0013]

As described above, according to the present invention, after focusing once by the dispersive crystal, the Bragg reflection angle is reduced again by the dispersive crystal to irradiate the sample, so that the X-ray is incident on the sample surface. The angle can be made large, the degree of freedom around the sample is increased, and the electrostatic lens and the analyzer can be easily arranged.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an X-ray monochromator of the present invention.

FIG. 2 is a diagram illustrating a conventional X-ray monochromator.

FIG. 3 is a diagram illustrating a toroidal type dispersive crystal.

FIG. 4 is a diagram showing an X-ray monochromator using a cylindrical dispersive crystal.

Claims (1)

[Claims] 1. An electron gun and a target arranged on the optical axis, and a ring-shaped first dispersive crystal having a toroidal surface for Bragg-reflecting X-rays generated from the target by electron beam irradiation from the electron gun. A second parabolic surface that is rotationally symmetric with respect to the optical axis on which the X-rays reflected by the first dispersive crystal and focused on the optical axis are incident, and are Bragg reflected
An X-ray monochromator comprising: the dispersive crystal and the detection means for detecting photoelectrons generated from the sample by the X-ray irradiation reflected by the second dispersive crystal.