DE4127778C2 - Device for total reflection X-ray fluorescence analysis - Google Patents

Description

The invention relates to a device for total reflection X-ray Gene fluorescence analysis (TRFA) according to the preamble of claim 1.

To carry out surface-selective and surface-sensitive Investigations on solid surfaces require probes from shallow penetration or penetration depth. Shallow depths of penetration have, for example, low-energy electrons and ions because of their intense interaction with matter. This intense Interaction with matter also leads to these probes  interact with the atmosphere in which the sample surface che is located. Therefore, these probes and thus the Pro can only be used analytically in ultra-high vacuum chambers. Probes with relatively little interaction with matter, such as. B. X-ray photons and neutrons are subject to these restrictions not enough. X-ray photons and neutrons have large ones Penetration and penetration depths. The great depths of penetration However, ger probes can be used in the area of surfaces and Selectively reduce interfaces to a few nm if the Probes fall onto the sample surface so that they are external total experience reflection.

External total reflection occurs when radiation goes in flat on smooth surfaces of solid or liquid, organic shear or inorganic, amorphous, polycrystalline or crystal stalliner samples falls and for this radiation the refractive index dex of the matter in question is smaller than that of the surrounding one Vacuum or the surrounding atmosphere. For X-ray photons and there is no significant sub-index for neutrons in the refractive index differentiated between air and vacuum. In the following, therefore, without Restriction of vacuum also by air or another gas atmosphere sphere to be replaced.

The refractive index n of X-ray photons (ν) and neutrons (n) in vacuum:

n _ν = 1 (1)
n _n = 1 (2)

and in matter:

n _ν = 1 - δ _ν - iβ _ν (3)
n _n = 1 - δ _n - iβ _n (4)

With:

In the above formulas, δ is the dispersive decrement of the refractive index, β is the absorptive decrement of the refractive index, and b _{ν , n is} the coherent scattering length for X-ray photons (ν) and neutrons (n). The absorptive decrement β can be neglected in the calculation of the total reflection limit angle, since δ <β for X-ray photons (ν) as well as for neutrons (n).

The following applies to the coherent scattering length of X-ray photons:

b _ν = r _e Z (7)

r _e denotes the classic electron radius, which is 2.818 × 10 ^-15 m. Z is the atomic number of the atoms of matter.

Equation (7) applies to λ _ν «λ _K-edge and approximately for all wavelengths λ apart from the absorption _edges . b _ν is monotonically dependent on Z. There are resonances depending on λ _ν .

b _n denotes the coherent scattering length of the neutron-nuclear interaction. b _n is highly isotope-dependent. In addition, there are also resonances depending on λ _n .

In ferromagnets, b _{n has} to be replaced by (b _n + p _n ). The scattering length p _n describes the magnetic interaction. Because of the adjustment of the magnetic moment of the neutron with respect to the magnetic moment of the shell electrons of matter, positive and negative values result.

The atomic density of matter N is calculated as follows:

Herein, N _A denotes the Avogadro constant (N _A = 6.0225 × 10²³ mol ^-1 ). ρ is the density of matter. A _r is the relative atomic mass of the atoms of matter.

The following applies to the wavelength of the X-ray photons λ _ν :

E _ν denotes the photon energy.

The de Broglie wavelength of the neutrons λ _n results from:

Herein, E _{n is} the neutron energy.

In the majority of cases, the refractive index for matter is n _n <1 and n _n <1. External total reflection thus occurs when the angle of incidence R of the X-ray photons or neutrons is smaller than the critical angle R _c :

R _c = (11)

Typical values of R _c are 0.5 °.

For angles of incidence 0 <R <R _c , the penetration depth L _{n , n} for X-rays and neutron beams decreases to a few nm. The minimum value L _min is:

The low penetration depth results in surface selectivity. This also allows analysis methods with X-ray or neutro Carry out ultra-selective surface radiation, although this Methods usually not the analysis of the sample surface, but serve the inside of the sample. With total reflection X-ray gene fluorescence analysis (TRFA, TXRF) and the total reflect xions neutron activation analysis (TNAA) is grazing with the incident X-ray photons or neutrons selectively the upper area stimulated. The atoms excited on the surface can emitting x-rays (fluorescent radiation) or return from gamma radiation to a stable state. Out the energy of the radiation (X-ray or gamma radiation) the sample atoms identify themselves chemically. this makes possible a multi-element analysis. The intensity of the radiation is a Measure of the number of sample atoms. TRFA and TNAA thus represent surface-selective analysis methods for determining the elec ment composition of surfaces and thin layers.

Already from the publication Y. Yoneda and T. Horiuchi, Rev. Sci. Instr. 42 (1971) 1069; P. Wobranschek and H. Aiginger, Anal. Chem. 47 (1975) 852 and DE-OS 26 32 001, US-PS 43 58 854 devices for total reflection X-ray fluorescence analysis (TRFA) are known. X-ray sources (X-ray tubes) provide polychromatic X-rays. The X-ray absorption in the sample shows strong dependencies on the X-ray energy. The absorption coefficient and thus the excitation of a certain fluorescence radiation drops sharply above the corresponding absorption edge to higher energies. Nevertheless, in order to ensure selective excitation of the surface atoms (total reflection), the angle of incidence of the excitation radiation must be selected so that total reflection is ensured for the excitation spectrum. Because of the dependency on λ in equation 5, the shortest wavelength in the excitation spectrum that comes before this determines the critical angle R _c , even if these short-wave components of the spectrum only make a small contribution to the measurement signal. If one deviates from this principle, the measurement signal of the analyte on the surface would overlap with the measurement signal of a similar element from the inside of the sample. This would falsify the result, since the absolute number of atoms, even of an element with a low concentration inside the sample, is generally much higher than that of an analyte on the surface. Known measuring arrangements had the disadvantage of either having to choose an extremely small angle of incidence or of having to accept excitation of the sample volume in addition to the surface excitation. In the further developments, attempts were therefore made to cut off the excitation spectrum below a lower, practically chosen limit wavelength. Such cutting off short-wave radiation was achieved by total reflection on polished quartz glass plates (DE-PS 27 36 960, US-PS 44 26 717 and DE-PS 29 11 596).

Ultimately, for the detection limit of the analysis method the intensity of the background and measurement signal is decisive. There, ins especially when stimulating x-ray photons, the stimulating Radiation is only partially absorbed and fluorescence radiation provides, but is largely scattered and thus contributing to the subsurface must improve the aftermath the excitation spectrum can be selected so that in the Fluorescence spectrum of the analytes sought no scattered radiation of the excitation spectrum occurs. On the other hand, the suggestion  spectrum fall as far as possible on the absorption edge of the analytes, to get an intense measurement signal. More recently has been tries to achieve this goal through monochromatic excitation achieve, with single crystals or multi as monochromators layer were used (A. Bohg and M. Briska, DE-OS 27 27 505 and U.S. Patent 4,169,228; M. Brunel, Acta Cryst. A42 (1986) 304; R. S. Becker, J.A. Glovchenko and J.R. Patel, Phys. Rev. Lett. 50 (1983) 153; A. Iida and Y. Gohshi, Jpn. J. Appl. Phys. 23 (1984) 1543; A. Iida, K. Sakurai, A. Yoshinaga and Y. Gohshi, Nucl. Instr. Meth. Phys. Res. A246 (1986) 736; C. T. Yap, R. E. Ayala and P. Wobrauschek, X-Ray Spectrometry, 17 (1988) 171; P. Wobrauschek and P. Kregsamer, Spectrochimica Acta 44B (1989) 453). According to literature (K. Taniguchi, S. Sumita, A. Saski, K. Nishihagi and N. Fujino, Abstracts 39th Annual Denver Conference on Applications of X-Ray Analysis, Steamboat Springs CO, 30.07.-03.08.1990, p. 39; M. Schuster, Abstracts 39th Annual Denver Conference on Applications of X-Ray Analysis, Steamboat Springs CO, 30.07.-03.08.1990, p. 40) Detection limits compared to the spectrometers with a Excitation spectrum that only towards the short-wave side is cut off, improve up to a factor of 10.

DE 90 05 414 U, for example, describes a device the preamble of claim 1 known.

The object of the present invention is now a device of the type specified at the outset, which in particular for series analysis of selected elements, e.g. B. such  which are particularly critical for a manufacturing process, below Based on optimal analysis conditions.

In solving this problem, the known mono chromatic suggestions the problem that although the elements with Absorption edges or resonances in the area of the monochromati excitation wavelength can be excited very well and thus can be detected sensitively (e.g. (Y), Sr, Br, As at Suggestions with Mo-Kα; (Co), Fe, Mn, Cr,. . . with suggestion with Cu-Kα; (Zn), Cu, Ni, Co, Fe,. . . with excitation with W-Lβ), however the elements with absorption edges lying away only are difficult to detect (e.g. P, S, Cl, Ca and Pd, Cd, In, Sn,. . . Ba when excited with Mo-Kα, Cu-Kα or W-Lβ).

The previously given task is gem. of the present invention achieved by a special structure of the monochromator arranged in the analysis device, which can direct a closely collimated beam of two, but also several, discrete wavelengths onto the sample. Four solutions according to the invention are given for this:
The first solution acc. Claim 1 is that the monochromator has layer structures with normal periodicity (super lattice, incoherent multilayer and alloys with a modulated composition (composition modulated alloys)) on a crystal substrate. Layer structures are suitable for this purpose, which were applied to a crystalline substrate by vapor deposition, sputtering, liquid phase epitaxy (LPE), organometallic gas phase epitaxy (MOVPE), molecular beam epitaxy (MBE), atomic layer epitaxy (ALE). The single-crystalline substrate must be required to have a smooth, polished surface that runs parallel to the network planes with the desired d _S value. In addition, a thickness is required which limits the curvature of the substrate to less than 0.002 ° even in the case of tensions between the substrate and the layer structure. It is essential here that layer sequences with the periodicity length d _{M are} applied to a substrate with the crystal periodicity length d _S , N ( FIGS. 2a, 2b). This allows Bragg reflection to be achieved simultaneously for two wavelengths. The short wavelength is reflected at the crystal network planes, the long wavelength at the interfaces of the layer structure. For example, if the sample surface is to be excited simultaneously with Mo-K _α and Mo-L _{α, β} , this can be achieved with a W / Si layer sequence on an Si (111) substrate if the following conditions are met:

Since d _S of Si (111) is 0.314 nm, the multilayer must have a periodicity d _M of 4.785 nm. Of course, the monochromator can also be tuned in such a way that in addition to combinations of characteristic lines of the anode material, combinations of a characteristic line and a band from the brake radiation spectrum also bring about the excitation.

By choosing the layer thickness ratio d _M1 : d _M2 , higher diffraction orders of the layer structure can be eliminated if they should interfere with the excitation spectrum. If you choose d _M1 : d _M2 = 1: 1, the 2nd, 4th, 6th,. . . Diffraction order and thus the wavelengths

deleted in the excitation spectrum. d _M1 : d _M2 = 1: 2 deletes the 3rd, 6th, 9th,. . . Diffraction order and thus the wavelengths

in the excitation spectrum, etc.

The proportion of Mo-L _{α, β} and proportion of Mo-K _α radiation can be controlled within wide limits by the number of shift periods N (JH Underwood and TW Barbee Jr., Topical Con. On Low Energy X-Ray Diagnostics, Monterey CA, June 8-10, 1981, in AIP Conf. Proc. 75 (1981) 170; BL Henke, P. Lee, TJ Tanaka, RL Shimabukuro, and BK Fujikawa, Atomic Data Nucl. Data Tables 27 (1982) 1 ). Based on the above example with d _M1 : d _M2 = 1: 1, in the range N = 0. . . 50 the reflectivity of the multilayer for the Mo-L _{α, β} radiation varies between 0 and 35%, the reflectivity of the Mo-K _α radiation remaining almost unchanged at approximately 90%. When the number of layers N is increased to 1000, the reflectivity of Mo-L _{α, β increases} slightly, while that of Mo-K _α decreases to 2%.

Si (111), Ge (111), GaAs (111), LiF (100) and graphite are particularly suitable as substrate crystals. The substrate crystals should have a high reflectivity, do not emit any disruptive fluorescent radiation and should be chemically stable. The materials for which the layer pairs of the multilayers should have a large difference in the refractive index and should not emit disruptive fluorescent radiation. Mo / B ₄ C, Mo / C or Mo / Si layer sequences are suitable for examining contaminated Si sample surfaces when excited with Mo-K _α and Mo-L _{α, β} ; W / B ₄ C, W / C and W / Si layer structures when excited with WK _α , WL _β and WL _α .

Preferred embodiments of this first solution are in the Subclaims referenced to claim 1.

It is advantageous if the periodicity length of the substrate d _S and the layer structure d _M are coordinated with one another in such a way that two monochromatic spectral components can be simultaneously directed onto the sample in order to be able to excite heavy and light elements optimally. The choice d _S / d _M = λ K radiation / λ / L radiation is particularly suitable. Under certain circumstances, however, it can also be advantageous to combine parts of the brake radiation spectrum with characteristic radiation. The intensity ratio of the two monochromatic spectral components to one another can be controlled by the choice of the number of layers N.

A second solution to the problem specified at the outset results from claim 6. Here, the monochromator is constructed from layer structures with normal and lateral periodicity (superlattice) on a crystal substrate. Analogous to the previously discussed solution, in which layer structures with normal periodicity were specified on a crystal substrate, the lateral periodicity of the layer structure can also be used together with the periodicity of the crystal substrate in order to apply various “mono-chromatic” portions of the excitation spectrum to the sample to steer. The advantage of such a periodicity compared to the previously discussed solution acc. Claim 1 and the subordinate claims relating back to this consist in the fact that even with a layer structure which consists of highly absorbent materials (for the long-wave X-ray radiation), many periods lying laterally on the surface contribute to the interference. This provides intense sharp reflexes. Examples of the embodiments of layer structures with normal and lateral periodicity are shown in FIG. 3. AlAs / GaAs and GaAS / GaAs _1-x Sb _x layer structures are known from the literature (cf. DA Neumann, H. Zabel and H. Morkoc, J. Appl. Phys. 64 (1988) 3024; T. Fukui, H. Saito and Y. Tokura, Jpn. J. Appl. Phys. 27 (1988) L1320; T. Fukui and H. Saito, Appl. Phys. Lett. 50 (1987) 824; T. Fukui and H. Saito, J. Vac. Sci. Technol. B6 (1988) 1373; JM Gaines, PM Petroff, H. Kroemer, RJ Simes, RS Geels and JH English, J. Vac. Sci. Technol. 6 (1988) 1378), which are used for Achieving certain electronic properties with MOVPE and MBE were made.

The solution acc. Claim 6 is preferred in subclaim 7.

A third solution to the problem stated at the outset results from claim 8. According to this solution, the monochromator consists of an intercalate. These are layer structures consisting of a graphite lattice into which atoms, preferably alkali metals (e.g. Li, Na, K, Rb, Cs) or whole molecules (e.g. FeCl ₃ , AsF ₆ ) (see MS Dresselhaus and G. Dresselhaus, Advances in Physics 30 (1981) 139; H. Zabel, Structure and Dynamics of Graphite Intercalation Compounds in Proc. Int. Conf. On Neutron Scattering, 19.-23 August 1985, Santa Fe; H. Zabel, WA Kamitakahara and RM Nicklow, Phys. Rev. B26 (1982) 5919). This can be done in different stages (see FIG. 4). In step 1, a graphite layer alternates with an intercalate layer. In step 2, an intercalate layer follows each after 2 graphite layers, etc. (cf. FIG. 4). For the use of the intercalates as a monochromator in X-ray fluorescence analysis (TRFA) or neutron activation analysis (TNAA), the same applies as for the first solution.

The solution according to claim 8 is according to subclaim 9 be preferably designed.

Further configurations of the previously specified solutions result derive from subclaims 10 to 13.

Further details and advantages of the present invention the on the basis of the embodiments shown in the figures explained in more detail. It shows

Fig. 1 is a schematic diagram of a first embodiment of the device according to the invention,

Fig. 2a shows the schematic overall structure of the monochromator according to a preferred embodiment of the constricting vorlie invention,

FIG. 2b shows the schematic structure of the layer structure of the monochromator gem. the embodiment shown in FIG. 2a,

Fig. 3 shows a schematic overall configuration of monochro mators according to another embodiment of the prior invention lie

Fig. 4 shows a schematic construction of the monochromator according to a third embodiment of the present the invention,

Fig. 5 is a schematic representation of the device according to the Invention in accordance with another imple mentation of the invention,

Fig. 6 is a schematic representation of the device according to a further embodiment of the prior invention, and

Fig. 7 is a diagram showing the function of the course of the intensity of the Si-K _α fluorescence radiation as a function of the angle of incidence 0.

In Fig. 1, the device for irradiating samples under grazing incidence with monochromatic X-rays for the X-ray fluorescence analysis is shown in a schematic representation. The radiation source designated 1 is an X-ray tube. The sample to be examined, for example a silicon wafer to be examined, is designated by 4 . The sensor 6 , for example a semiconductor detector for X-ray spectrometry, is arranged above the sample, to which a stray radiation shield 5 is connected upstream. In the beam path of the beam 10 , which can be an X-ray beam, an aperture 9 , a monochromator 8 and an aperture 7 are connected downstream of the radiation source 1 . The angle Φ is the diffraction angle on the monochromator unit, while the angle Φ shown in FIG. 1 denotes the angle of incidence of the radiation on the sample.

From Fig. 2a, the overall schematic structure of the monochroma gate according to a first solution of the present invention is Darge, which consists of a layer structure on a crystal substrate. In this figure, 1 ' denotes one layer and 2' the other layer of the pair of layers. The entire layer structure is denoted by 3 ' and the crystal substrate by 4' . d _M shows the periodicity length of the layer structure and d _S denotes the periodicity length of the crystal substrate. With d _{M1, 2} , the thickness of the layer 1 ' or 2' is designated. N shows the number of pairs of layers. The depth coordinate is designated with z.

In Fig. 2b the schematic structure of the layer structure 3 'of the monochromator is gem. shown in Fig. 2a in more detail. An incoherent multilayer is indicated with 5 ' . 6 ′ shows an alloy with a modulated composition. Finally, 7 ' relates to a superlattice (epitaxial layer sequences). These three layer structures shown next to one another thus represent alternative embodiments for the layer structure of the monochromator according to the invention.

Fig. 3 shows the schematic overall structure of a monochromator according to a second solution of the present invention. Here the layer structure with lateral periodicity is shown on a crystal substrate. In the exemplary embodiment shown here, the layer structure consists of sequentially grown AlAs and GaAs. d _{M ∥} , ⟂ denotes the lateral or normal periodicity length of the layer structure. The periodicity length of the crystal substrate is again indicated by d _S. The direction [100] denotes the orientation of the crystal substrate. Misalignment of the surface of the crystal substrate is required for the growth of lateral periodic structures.

Fig. 4 shows the schematic structure of the monochromator according to a further solution of the present invention. Intercalates based on graphite of levels 1, 2 and 3 are shown here. The periodicity length of the intercalate is denoted by d. This quantity corresponds to the periodicity length d _M in the description of the monochromator type according to the first solution of the present invention. d _c indicates the periodicity length of the undisturbed graphite layers. In the case of higher-level intercalates, this quantity corresponds to the periodicity length d _S in the description of the monochromator type according to the first solution of the invention.

Fig. 5 shows a preferred embodiment for an analysis device according to the present invention. Here, compared to the embodiment form of FIG. 1, the same device parts are provided with the same reference numerals, so that in this respect reference can be made to the explanation there. In this device the Mono monochromator in the middle between the anode focus 11 of the X-ray tube and the point of incidence defined 3 of the radiation on the sample so positio that the Monochromatoroberfläche line parallel to the connection 2 between the anode focus 11 and Probenauftreffpunkt 3 is aligned and the distance t of the Monochromatoroberfläche from this connecting line 2 is adjustable.

According to the further embodiment according to FIG. 6, in which in turn the same device parts and geometries are provided with the same reference numerals or characters, the tube and the monochromator are each arranged in such a way that when the distance t increases, that is to say at larger diffraction angles Φ the tap winch angle from the anode surface Ω is also increased.

With reference to FIG. 7, a method for determining the incidence angle can be explained. The intensity of the Si-K _α fluorescence radiation of the silicon substrate as a function of the angle of incidence Φ is shown here. The turning point of the measurement curve is set equal to the total reflection limit angle winkel _c , as it results from the theory. This enables the zero angle of incidence to be determined, so that the angle of incidence of the beam on the sample can be adjusted.

Claims (13)

1. Device for total reflection X-ray fluorescence analysis (TRFA), in which the smooth flat surface of a sample or thin layer on a sample is excited by the incident X-ray radiation and the emitted X-ray fluorine essence radiation is spectrally detected, essentially consisting of a radiation source, a monochromator from layer structures with normal periodicity on a substrate, an anti-scattering aperture and a sensor, characterized in that the layer structure with a large jump in the refractive index of incoherent multilayers is applied to a crystal substrate with high reflectivity, the periodicity length of the substrate d _S and the layer structure d _M are coordinated with one another in such a way that two mono-chromatic spectral components can be directed onto the sample simultaneously in order to be able to excite heavy and light elements optimally, one of the spectral components being reflected off the crystal substrate rd, and the number of layers of the multi layer is selected so that the radiation reflected from the substrate and the radiation reflected from the multilayer are in a predetermined ratio. 2. Device for total reflection X-ray fluorescence analysis (TRFA) according to claim 1, characterized in that the layer structure of the monochromator ( 8 ) made of W / B4C, W / C, W / Si, Mo / B ₄ C, Mo / C or Mo / Si and the crystal substrate with high reflectivity and mechanical and chemical stability consist of Si, Ge, GaAs, LiF or graphite. 3. Device for total reflection X-ray fluorescence analysis (TRFA) according to claim 1, characterized in that the Layer structure made of a super lattice or an alloy with a modulated composition. 4. Measuring device for total reflection X-ray fluorescence analysis (TRFA) according to claim 3, characterized in that the super lattice made of Si / Ge, (AL, Ga, In) (N, P, As) / GaAs or (Al, Ga, In) (N, P, As) / InP. 5. Device for total reflection X-ray fluorescence analysis (TRFA) according to claim 3, characterized in that the alloy with a modulated composition of Nb / Ta or Cu / Ni consist. 6. Device for total reflection X-ray fluorescence analysis (TRFA) where the smooth flat surface of a sample or  Thin film on a sample by the incident x-ray radiation is excited and the emitted x-ray fluorine Essence radiation is recorded spectrally, essentially the best starting from a radiation source, a monochromator Layer structures with a normal periodicity on one Substrate, an anti-scatter diaphragm and a sensor, characterized, that the substrate is a crystal substrate and that the Layer structures additionally have lateral periodicity sen. 7. The device for total reflection X-ray fluorescence analysis (TRFA) according to claim 6, characterized in that the monochromator ( 8 ) from a super lattice, which is composed for example of AlAs / GaAs, GaAs / GaAs _1-x Sb _x , with nor painter and lateral periodicity on a crystal substrate which is formed, for example, from GaAs, the periodicity length of the substrate d _{S being selected in} accordance with a desired higher energy energy range and the normal and lateral periodicity _{length of} the layer structure d _{M ∥} , ⟂ being coordinated with one another in accordance with a desired low energy energy range are that two monochromatic spectral components can be directed to the sample simultaneously in order to optimally excite heavier and lighter elements. 8. Device for total reflection X-ray fluorescence analysis (TRFA) where the smooth flat surface of a sample or Thin film on a sample by the incident x-ray radiation is excited and the emitted x-ray fluorine essence radiation is detected, consisting essentially of  a radiation source, a monochromator made of layer structure structures with normal periodicity, an anti-scatter aperture and a sensor, characterized, that the monochromator consists of an intercalate, i.e. H. one Layer structure, which consists of a graphite grid, in the one between each or more carbon planes Layer of atoms or molecules is embedded. 9. A device for total reflection X-ray fluorescence analysis (TRFA) according to claim 8, characterized in that in the inter kalat with at least two successive Gra phitschichten the distances between the undisturbed graphite layers d _C and the atomic or molecular layers d are coordinated so that simultaneously two monochromatic spectral components can be directed onto the sample in order to optimally excite heavier and lighter elements. 10. A device for total reflection X-ray fluorescence analysis (TRFA) according to one of the preceding claims, characterized in that the monochromator ( 8 ) in the middle between the anode focus of the X-ray tube ( 1 ) and the point of incidence ( 3 ) of the beam ( 10 ) is positioned on the sample ( 4 ) so that the monochromator surface is aligned parallel to the connecting line ( 2 ) between the anode focus ( 11 ) and the specimen impact point ( 3 ) and the distance (t) of the monochro mator surface from this connecting line ( 2 ) is adjustable ( Fig. 6). 11. A device for total reflection X-ray fluorescence analysis (TRFA) according to claim 10, characterized in that the tube ( 1 ) and the monochromator ( 8 ) are arranged in such a way that when the distance (t) is increased, ie at larger ren diffraction angles Φ Tap angle from the anode surface Ω is also increased ( Fig. 7). 12. A device for total reflection X-ray fluorescence analysis (TRFA) according to claim 10 or 11, characterized in that different monochromators ( 8 ) with different distances (t) in the beam path ( 10 ) can be moved. 13. Device for total reflection X-ray fluorescence analysis (TRFA) according to one of the preceding claims, characterized in that the space between the sample ( 4 ) and the semiconductor detector ( 6 ) can be evacuated or flooded with nitrogen, helium or hydrogen.