JPH0242399A - Multilayered film reflecting mirror for soft x ray - Google Patents

Abstract

PURPOSE:To realize a high reflection factor in the wavelength range of soft X rays by using a material which contains lithium as its base for a layer with a high refractive index and using nickel for a layer with a low refractive index, and combining them and constituting a multilayered film. CONSTITUTION:Materials which differ in refractive index to X rays are laminated alternately and the thickness of the respective layers is so adjusted that reflected waves in their borders increase their intensity mutually, thus obtaining the X-ray reflecting mirror with the high reflection factor. Here, nickel 2 is used for the low-refractive-index layer on a substrate 1 and the material 4 which contains lithium as its base is used for the high-refractive-index layer to form the multilayered film; and a protection film 5 is formed at the outermost part. Then when lithium 4', lithium hydride 4'', or lithium oxide 4''' is used as the material 4, the multilayered film reflecting film for an optical element which has a large reflection factor in the wavelength range of soft X rays is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multilayer film reflecting mirror for an optical element in the soft X-ray region among X-rays.

(Prior art) Conventionally, in the soft X-ray region, a combination of a multilayer reflector using nickel 2 as a low refractive index layer and beryllium 3 as a high refractive index layer on a substrate 1, as shown in FIG. It was widely known.

(Problem to be Solved by the Invention) Needless to say, beryllium vapor, dust, etc. are toxic, and when performing vacuum evaporation to reduce the thickness of the film, consideration must be given to environmental protection, including exhaust treatment, and costs. was a problem.

The present invention aims to provide a multilayer reflector that uses materials that do not require the special working environment described above and has a reflectance comparable to or higher than conventional products in terms of performance. It was done for a purpose.

(Means and actions to solve the problem) As is well known, in the soft X-ray region, the refractive index of all materials is close to 1, and it is extremely difficult to form an effective optical system. Therefore, we are trying to create a relatively efficient optical system by layering many materials with slightly different refractive indexes and skillfully controlling the phase of the tiny amount of reflected waves that occur at the boundaries.

Therefore, one of the important factors in this field is how to find a combination of materials with high efficiency, and the present invention also applies to Be/N, which is said to provide the most efficient reflection in this field.
The aim is to obtain a combination that provides an efficiency greater than the combination of i.

Each refractive index has wavelength dependence, and the reflectance of each combination was confirmed by computer simulation.
The film thickness, number of layers, etc. are determined.

The multilayer reflector provided in this application includes a combination of nickel as a low refractive index material and a lithium-based material as a high refractive index material. A diagram of reflectance when lithium is used is shown. In particular, a supplementary explanation will be provided regarding the combination of lithium oxide and nickel for biological microscope optical elements (wavelength range 2.33 to 4.4 nm).

Figure 5 shows the transmittance of each substance to X-rays of around 3 nm in the soft X-ray region, and it is clear from the figure that water and protein absorb X-rays in this region. differs by about one order of magnitude compared to the others.

Therefore, biological structures such as proteins can be seen as shading images without being hindered by water absorption. This is the optical absorption edge (2,37
This is because the absorption of X-rays by oxygen becomes smaller on the long wavelength side near 100 nm). That is, by using some kind of oxide such as water in a multilayer high refractive index layer, it is possible to form a multilayer reflective film with low absorption. After repeated simulations using atomic scattering factors for various oxides, the combination of lithium oxide and nickel was obtained.

(Example) FIG. 1 shows an example in which the present invention is applied to a plane mirror. It has the same structure as the conventional example (FIG. 6), with the substrate 1 and the nickel 2-! as a low refractive index layer. The structure is exactly the same, except that a lithium-based material 4 is used instead of beryllium 3 as a high refractive index layer, and a protective film 5 such as 8102 is formed on the outermost layer.

Figure 2.3.4 shows the reflectance for wavelength of a multilayer reflector using lithium 4', lithium hydride 4'', and lithium oxide 4'' as the high refractive index layer compared to the conventional beryllium-nickel combination. Each of these is shown in the form of a comparison with that of . The setting conditions include the incident angle of 7, including the conventional example.
0', and the number of laminated layers was 199.

In Figure 2, between lithium/nickel (solid line) and beryllium/nickel (-dot-dashed line), the former has a reflectance of 20~20% higher than the latter.
30%, the former is about 15-25% more than the latter for lithium/nickel hydride (solid line) and toberyllium/nickel (-dot-dashed line) in Figure 3, and lithium/nickel oxide and beryllium (solid line)/nickel in Figure 4. (-dotted chain line) shows the oxygen absorption edge (2.37 nm), which is the problem in biological microscopy.
It is shown that the difference is about 10% higher on the longer wavelength side.

(Effects of the Invention) As explained above, a lithium-based material is combined with nickel, a low refractive index material, as a high refractive index material for a multilayer reflector for optical elements in the soft X-ray wavelength region. Furthermore, the reflectance is much higher than the conventional combination of beryllium and nickel, and environmental problems such as toxicity during the working process are also improved, so the effects obtained are positive.

[Brief Description of the Drawings] Fig. 1 is a cross-sectional view of the multilayer film reflector of the present invention, and Figs. 2 to 4 show the reflectance of the multilayer film reflector of the present invention and the conventional reflector with respect to wavelength. Figure 2 is a diagram using lithium as a high refractive index material, Figure 3 is using lithium hydride, Figure 4 is using lithium oxide, and Figure 5 is a diagram showing the results of using each material for X-rays with a wavelength of around 3 nm. FIG. 6, which shows the absorption rate, is a sectional view of a conventional multilayer deashing mirror. 1...Pace, 2...Low refractive index material), 3
...High refractive index material (P171Jum), 4...High refractive index material (lithium-based material), 4'...
Lithium, 4''...lithium hydride, 4'''...lithium oxide. Director of the Agency of Industrial Science and Technology Yuki Iizuka L1/Old diagram - LiH/Nl ---Be/N wavelength (nm) Figure 3 LizO/N ---Ba/N wavelength (nm) Figure 3

Claims (4)

[Claims] (1) An X-ray device configured to obtain high reflectance by alternately laminating materials with different refractive indexes for X-rays and adjusting the thickness of each layer so that the reflected waves at the boundaries mutually strengthen each other. A multilayer reflective mirror for soft X-rays, characterized in that a lithium-based material is used in the high refractive index layer (light element type). (2) The multilayer reflective mirror for soft X-rays according to claim (1), wherein the material used for the high refractive index layer is lithium itself. (3) The multilayer reflective mirror for soft X-rays according to claim (1), wherein the material used for the high refractive index layer is lithium hydride. (4) The multilayer reflective mirror for soft X-rays according to claim (1), wherein the material used for the high refractive index layer is lithium oxide.