SK68395A3 - Device for x-ray beam-forming - Google Patents

Abstract

The equipment for X-ray beam conditioning is formed by a compact monochrocollimator consisting of at least three diffractors (51) formed by the walls of the crystal material (11) in the leading channels (4). The arrangement is such that the successive diffraction cones of the diffractors (51) share at least one generator and that for each of the diffractors (51) the angle between the successive generators is just the vertex angle of its diffraction cone.

Description

DEVICE FORΑ FORMING X - RAY BAY

Technical field

The invention relates to an apparatus for forming an X-ray beam, in particular in diffractometry instruments.

BACKGROUND OF THE INVENTION

So far, crystal monochromators or monochrocolimulators have been used in various regions of X-ray diffractometry to achieve high angular resolution, which at their output greatly reduce the angular divergence and wavelength scattering of the X-ray radiation coming from the X-ray generator. This reduction is due to diffraction in one, usually horizontal plane. The angular adjustment for a given wavelength according to the X-ray used and for a given crystal (most often silicon and germanium) is determined by the first approximation of Bragg's law. The beam thus formed impinges on a specimen mounted in a precise goniometer, allowing the measurement of the diffraction curves characterizing the structure of the specimen with high angular resolution.

The so-called non-dispersive arrangement of the sample and the monochromator with one, either symmetric or asymmetric diffraction, significantly improves said X-ray beam parameters from the X-ray generator. This arrangement maintains the high intensity of the X-ray beam, but its considerable disadvantage is the need for an additional monochromator and a lengthy repositioning when switching to another diffraction.

Even more pronounced reductions in angular divergence and wavelength scattering are made possible by successive monochro-collimators with two, three, or four successive diffractions, using a dispersion arrangement.

Currently, high-resolution high-resolution diffractometers utilize three or four symmetric or asymmetric diffraction in a coplanar arrangement for monochromatization and collimation.

The monochrocolimulator with three diffraction uses two independent goniometers. The first is a channel-like monolithic block with two diffractions in a non-dispersive arrangement, the second is a crystal with a third diffraction set dispersely. The monochro-collimator with four diffraction uses also two goniometers. Each has a monolithic block with two diffractors in a non-dispersive arrangement, the two blocks being dispersed with each other. An advantage of this monochro-collimator is also that the X-ray beam emerging therefrom continues in the direction of the beam impinging on the monochro-collimator from the X-ray generator. The disadvantage of these monochro-collimators is the need for two goniometers and the resulting demands for. the size of the device, the accuracy and length of adjustment of both trigonometers, as well as the mechanical and thermal stability, due to the need for very precise adjustment of the relative angular position of the individual diffracting planes.

SUMMARY OF THE INVENTION

The aforementioned drawbacks are largely eliminated by the apparatus for forming the X-ray beam entering and exiting the X-ray beam, in particular in a co-ordinated direction, the essence of which is that the monochro-collimator is compact. It comprises at least three diffractors _t formed by the walls of the crystalline guide channel material. The arrangement is such that successive diffractive conical faces of symmetric diffractors, or deformed conical faces of asymmetric diffractors, have at least one forming line in common. Here, the pairs of successive lines form an apex angle of its conical surface for each diffractor. Alternatively, at least one reflector can be formed on the walls of the crystalline material in the guide channels between the diffractors. The reflective conical surfaces of this reflector have at least one forming line with adjacent diffractors or reflectors in common. In this case, the pairs of successive lines form an apex angle of each conical surface of each conical surface.

The monochrome collimator is monolithic / formed from a single crystal. The alignment of the apex angles of the successive symmetrical or asymmetric diffractors, respectively between the symmetric diffractor and the asymmetric diffractor, can also be ensured by a solid connection of two identical crystalline materials or different crystalline materials. The joint is formed on the bevelled faces of these joining materials.

The main advantage of the monochro-collimator according to the invention is that, due to the design in one compact block, there is no need for two goniometers to adjust the relative position of the two separate blocks, which also allows its miniaturization. This results in higher mechanical and thermomechanical stability of the device, higher measurement accuracy, and at the same time easier handling of the device and shortening of the time needed for preparation of the measurement. When using asymmetric diffractors, both compression and beam expansion in one direction are possible, with reduced intensity loss.

Overview of the figures in the drawing

The invention is explained in more detail in the accompanying drawings, in which:

Fig. 1 shows a monolithic monochro-collimator made of one crystal with four symmetrical diffractors formed; FIG. 2 shows a monolithic monochro collimator, also made of a single crystal with four symmetrical diffractors formed and one reflector of FIG. 3 shows a compact monochro collimator made by combining two different crystalline materials with two symmetric diffractors and one asymmetric diffractor formed

EXAMPLES OF THE INVENTION

An X-ray beam forming device, also called a monochro-collimator, is placed in the X-ray diffractometer either on the goniometer or directly in the X-ray machine. It is exemplified according to FIG. 1 for a wavelength λ = 0.178892 nm. Starting from Bragg's law, a suitable combination of lattice parameter, diffraction vectors and external norms of the active surfaces of the diffractors for the desired angular divergence and the wave dispersion of the output beam of the monochrocolimizer can be selected for a given wavelength.

A single crystal of germanium (? = 0.565745 nm) is used as the crystalline material, and successive diffractions of type (220) and (440) are used.

Since the outer normal of the planes are sI = (- Q, 788: -0.616: 0.000), sll = (0.788: 0.616: 0.000), sIII = (0.999: 0.040: 0.013), sIV = (- 0.999: - According to these parameters, precision guide channels 6 are cut into the single crystal 11, which are surface-treated to a high flatness and defect-freeness.

A primary beam 2 of about 1mm width, with a high angle divergence and a wavelength dispersion, is fed from the generator into the monocrystal wall 11 in the channel 8 at the inlet diffractor 51 and after multiple diffraction at further diffractions 51 3 with significantly reduced angular divergence and dispersion (wavelength) of wavelengths within the line. The secondary beam thus formed impinges on the measured sample (e.g., semiconductor substrates, heterostructures, multilayers, polycrystalline layers) mounted in the goniometer of the diffraction apparatus.

In the example shown in Fig. 2, a single crystal of silicon 12 is used as the crystalline material. The guide channels 4 are formed such that, for example, after the second diffraction on the diffractor 52 in the passage channel 6, the advancing beam 21 of the animal, when impinging on the single crystal wall of silicon 12, has an angle less than critical

-5 (approx. 0.26 °), thereby resulting in total reflection and the resulting deflection of the advancing beam 21, together with other diffractions on the diffractors 52, allows an optimal adjustment of the parameters of the secondary beam 8.

In the example shown in Fig. 3, the monochro-collimator consists of two different monocrystalline materials, namely single crystal of germanium 11 and single crystal of silicon 12, the faces of which are bevelled at precisely defined angles and form a solid bond 7 by mutual bonding. The cutting angles correspond to their apex angles of the diffraction conical surfaces.

The primary beam after two symmetrical diffraction in the passage channel 4 on the walls of the germanium monocrystal 11, impinges on the asymmetric diffractor 53 in the transitional channel 6 on the silicon monocrystal wall 12 and causes its approximately 100 fold compression, so the secondary beam 3 is appropriately formed test sample.

Industrial usability

The monochrocolimizer according to the invention can be advantageously used in high-resolution aifractometers and reflectometers used for x-ray characterization of single crystal and polycrystalline materials and layers, as well as multilayers. It can also be used for neutron radiation and for irradiation, taking into account the respective wavelengths and Bragg conditions.

Claims (4)

PATENT CLAIMS An apparatus for forming an X-ray beam entering and exiting it, in particular in a co-ordinate direction, characterized in that the monochro-collimator is compact and comprises at least three diffractors (51,52,53), comprising: framed by the walls of the crystalline material (11, 12) in the guide channels (4) such that successive diffractive cone faces of symmetric diffractors (51, 52) or deformed conical faces of asymmetric diffractors (53) share one another. the at least one forming line and the pairs of successive forming lines form an apex angle of its conical surface for each diffractor (51,52,53). Device according to claim 1, characterized in that at least one reflector (6) is formed on the walls of the crystalline material (11, 12) in the guide channels (4) between the diffractors (51,52,53) such that the reflective conical surfaces The reflector (6) has at least one generating line with adjacent diffractors (51,52,53) or reflectors (6) _t forming a cone angle of each reflector (6) for each reflector (6). Device according to claim 1 or claims 12, characterized in that the monochro-collimator is monolithic, formed from a single crystal. Apparatus according to claim 1, characterized in that the alignment of the apex angles of the diffractive conical surfaces, the successive symmetric diffractors (51) or the asymmetric diffractors (53), optionally between the symmetric diffractor (51) and the asymmetric diffractor (53) is provided by a fixed joining (7) two identical crystalline materials (11) or different crystalline materials (11, 12) formed on icn tapered faces.