1. Field of the Invention
The present invention relates to an X-ray diffraction apparatus for irradiating a sample with X-rays and detecting the X-rays diffracted by the sample, and a method of measuring X-ray diffraction.
2. Description of the Related Art
As one of devices which analyze crystallinity and a crystal structure of a sample, an X-ray diffraction apparatus is known. The X-ray diffraction apparatus irradiates a sample with X-rays generated from an X-ray source, detects diffracted X-rays, and measures the intensity of the X-rays.
FIG. 27 is a schematic diagram illustrating a constitutional example of a measurement optical system of a conventional X-ray diffraction apparatus.
In FIG. 27, in a radiation direction of X-rays generated from an X-ray source 1, a paraboloidal multilayer mirror 2, a selection slit 3, an incidence soller slit 4, a length limiting slit 5, and an incidence slit 6 are disposed. An optical incidence system is constituted by these elements, for making X-rays be incident on a sample S set on a sample stage 7. The paraboloidal multilayer mirror 2 is installed in the optical incidence system as needed.
Meanwhile, in an emission direction of diffracted X-rays generated when the X-rays are made incident on the sample S of the sample stage 7, a front optical receiving slit 8, a Kβ filter 9, a parallel slit analyzer 10a, an optical receiving soller slit 10b, a rear optical receiving slit 11, an attenuator 12, and a detector 13 are disposed. An optical receiving system is constituted by these elements, for making the detector 13 receive the diffracted X-rays emitted from the sample S on the sample stage 7. The parallel slit analyzer 10a is installed in the optical receiving system as needed.
Relative positional relationship between the optical incidence system, the sample stage 7 and the optical receiving system is changeable by a goniometer not shown in the figure. The goniometer changes the relative positional relationship by rotating the optical incidence system and the optical receiving system by a prescribed angle each with an incident position of the X-rays made incident on a surface of the sample S set on the sample stage 7 as a rotation center.
The goniometer rotates the optical incidence system and the optical receiving system around a common rotation axis. In this case, when the optical incidence system is rotated in one direction, the optical receiving system is rotated reversely at the same angle. At the time, relative positions of the rotating directions of the optical incidence system and the optical receiving system are generally controlled such that relationship between an incidence angle of the X-rays made incident on the sample surface and a diffraction angle of the X-rays diffracted by the sample surface satisfies relationship of θ and 2θ.
In the X-ray diffraction apparatus including the measurement optical system composed of the above-described configuration, while synchronously rotating the optical incidence system and the optical receiving system by driving the goniometer, following measurement is performed in a predetermined scan angle range. Namely, the X-rays emitted from the X-ray source 1 to the sample stage 7 are fetched through the paraboloidal multilayer mirror 2 and the selection slit 3 to the incidence soller slit 4. The X-rays which have passed through the incidence soller slit 4 are radiated through the length limiting slit 5 and the incidence slit 6 to the surface of the sample S on the sample stage 7.
Meanwhile, the diffracted X-rays emitted from the surface of the sample S by the irradiation of the X-rays are fetched through the front optical receiving slit 8 and the Kβ filter 9 to the parallel slit analyzer 10a and the optical receiving soller slit 10b. The diffracted X-rays which have passed through the optical receiving soller slit 10b pass through the rear optical receiving slit 11 and the attenuator 12 and reach the detector 13, and the intensity of incident X-rays is detected.
In the conventional X-ray diffraction apparatus, when limiting a dose of the X-rays incident on the detector 13 in the rear optical receiving slit 11, a resolution of measurement (hereinafter, called “measurement resolution”) varies depending on how much slit width is used for limiting the dose. Namely, when the slit width of the rear optical receiving slit 11 is relatively narrow as illustrated in FIG. 28(A), since a fetch angle of the X-rays in the view from the center of the goniometer becomes narrow, the measurement resolution when detecting the X-rays using the detector 13 becomes relatively high. Meanwhile, when the slit width of the rear optical receiving slit 11 is relatively wide as illustrated in FIG. 28(B), since the fetch angle of the X-rays in the view from the center of the goniometer becomes wide, the measurement resolution when detecting the X-rays using the detector 13 becomes relatively low.
Accordingly, when the measurement resolution is desired to be changed, the slit width of the rear optical receiving slit 11 needs to be changed. There are mainly two methods of changing the slit width of the rear optical receiving slit 11. One is a method in which the rear optical receiving slit 11 is configured to be attachable and detachable by a manual insertion method and the slit width is changed by exchanging the slit by manual insertion. The other one is a method in which the rear optical receiving slit 11 includes an opening/closing mechanism for opening and closing the rear optical receiving slit 11 and the slit width of the rear optical receiving slit 11 is changed by the opening/closing mechanism (for instance, see Patent Document 1, Japanese Patent Laid-Open No. 2007-10486).
Conventionally, a user who uses the X-ray diffraction apparatus sets the slit width of the rear optical receiving slit 11 by the slit exchange or the opening/closing mechanism, and by operating the X-ray diffraction apparatus under the set condition, X-ray diffraction is measured by a desired measurement resolution. Also, conventionally, an X-ray diffraction apparatus is known which adopts a strip type sensor configuration in which thin and long sensors are arranged adjacently to each other as a configuration of a detector provided in the X-ray diffraction apparatus and allows a user to select which of the adjacent sensors is to be used to perform measurement.
The detector used in the X-ray diffraction apparatus is divided into, for instance, a zero-dimensional detector and a one-dimensional detector depending on whether or not the resolution of a position (hereinafter, called “position resolution”) is provided on the detection surface. The zero-dimensional detector is the detector not having the position resolution on the detection surface, and the one-dimensional detector is the detector having the position resolution in one direction on the detection surface. In the X-ray diffraction apparatus using the detectors, by changing the slit width of the rear optical receiving slit 11 as described above, the measurement resolution can be changed.
In a type of exchanging the slit by the manual insertion method, it is necessary to exchange the slit in order to change the measurement resolution. However, the slit is frequently exchanged so as to be suited to a desired measurement condition when adjusting an optical system or a sample position or when actually performing measurement. Therefore, there is a problem that it takes time and labor to change the measurement resolution by slit exchange.
Meanwhile, in a type including the opening/closing mechanism of the slit, since the slit width can be changed by the opening/closing operation of the slit, the time and labor accompanying the slit exchange can be saved. However, since the opening/closing mechanism of the slit is expensive compared to the type of exchanging the slit by the manual insertion method, there is a problem that it causes cost increase of the X-ray diffraction apparatus. Also, when disposing a monochromator crystal or an analyzer crystal in an optical path of the X-rays from the sample S on the sample stage 7 to the detector 13 to detect the X-rays by a higher measurement resolution, the cost is increased further. The reason is as follows.
Namely, in the measurement optical system illustrated in FIG. 29(A), the X-rays are incident on the detector 13 through the rear optical receiving slit 11 and the attenuator 12. In this case, in order to increase the measurement resolution without changing the slit width of the rear optical receiving slit 11, it is effective to remove an unneeded element by installing two monochromator crystals 14a and 14b at a front portion before the rear optical receiving slit 11 and reflecting the X-rays by the respective monochromator crystals 14a and 14b as illustrated in FIG. 29(B). However, in that case, before and after installing the monochromator crystals 14a and 14b, a position of the X-rays incident on the detection surface of the detector 13 is shifted by L. Therefore, in the type including the opening/closing mechanism of the slit, a moving mechanism is separately required for shifting an opening/closing center position of the rear optical receiving slit 11 by mechanically moving a slit position of the rear optical receiving slit 11 according to a shift amount L of the incident position of the X-rays, thus resulting in a further cost increase.
The main object of the present invention is to provide an X-ray diffraction apparatus and an X-ray diffraction method capable of changing the measurement resolution without using the rear optical receiving slit and flexibly coping with the change of the measurement resolution that cannot be realized when using the rear optical receiving slit.