Patent Number: 052395669
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1] Multi-layered mirrors A were prepared, as shown in FIG. 1, by alternately laminating a nickel-chromium alloy 2 and vanadium oxide 1 by ion beam sputtering, with predetermined thicknesses (respectively a .ANG. and b .ANG.) and with 10 layers each (number of layers being reduced in the illustration) on a silicon wafer 3. Similarly multi-layered mirrors B were prepared by alternately laminating chromium and vanadium oxide by ion beam sputtering, with predetermined thicknesses (respectively a .ANG. and b .ANG.) and with 10 layers each (number of layers being reduced in the illustration) on said wafer. Also multi-layered mirrors C were prepared by alternately laminating nickel and vanadium oxide by ion beam sputtering, with predetermined thicknesses (respectively a .ANG. and b .ANG.) and with 10 layers each on said wafer. Each of the above-mentioned multi-layered mirrors A to C was prepared with three different periodic thicknesses, 40, 50 and 60 .ANG.. The thicknesses a, b of the layers constituting the multi-layered mirrors were selected as a half of the periodic thickness thereof (a=b=d/2 (.ANG.)). For example, the layers were laminated with thicknesses of 20 .ANG. each for a periodic thickness of 40 .ANG., and of 25 .ANG. each for a periodic thickness of 50 .ANG.. The reflectivities of these multi layered mirrors A-C, measured with soft X-ray of a wavelength of 33.7 .ANG., are shown in Table 1. The angle of the incident soft X-ray to the mirror surface was selected as about 25.degree. for the periodic thickness of 40 .ANG., about 20.degree. for the periodic thickness of 50 .ANG., and about 17.degree. for the periodic thickness of 60 .ANG.. TABLE 1 ______________________________________ Multi-layered Multi-layered Multi-layered mirror A mirror B mirror C Periodic (Ni--Cr/V.sub.2 O.sub.5) (Cr/V.sub.2 O.sub.5) (Ni/V.sub.2 O.sub.5) thickness Mea- Mea- Mea- (.ANG.) Calcd. sured Calcd. sured Calcd. sured ______________________________________ 40 20.0 10.8 17.2 12.0 20.7 7.0 50 22.1 13.7 18.9 13.2 22.9 13.5 60 23.1 15.7 19.7 13.7 23.9 18.6 ______________________________________ As will be apparent from Table 1, the reflectivity is highest in the multi-layered mirror C (nickel/vanadium oxide) for the periodic thickness of 60 .ANG., but becomes higher in the multi-layered mirror A (nickel-chromium alloy/vanadium oxide) and B (chromium/vanadium oxide) as the periodic thickness becomes smaller to 40 and 50 .ANG.. Similar effects can be obtained when silicon oxide or carbon is employed, instead of vanadium oxide, as the substance showing smaller difference in refractive index from vacuum. [EXAMPLE 2] FIG. 2 is a schematic view of a soft X-ray microscope for organism observation, employing the multi-layered mirror of the present invention. A multi-layered condenser mirror 4 is formed as a part of an ellipsoid, and an X-ray source 5 and a specimen 6 are placed on the two focal points thereof. The x-ray source 5 provides soft X-ray of a wavelength of 33.7 .ANG.. Also there are provided an imaging optical system 7 consisting of a zone plate for focusing the X-ray irradiating the specimen, and a detector 8 for detecting the X-ray irradiating the specimen. In the above-explained microscope, the X-ray emitted from the X-ray source 5 is reflected by the multi-layered condenser mirror 4 and irradiates the specimen. After irradiating the specimen, the X-ray is focused onto the detector 8 by the imaging optical system 7 consisting of the zone plate. The reflectivity of the multi-layered rotary elliptical mirror, employed in the soft X-ray microscope, was measured with soft X-ray of a wavelength of 33.7 .ANG.. The multi-layered condenser mirror was prepared by laminating a nickel-chromium alloy and vanadium oxide by ion beam sputtering on an ellipsoid substrate obtained by polishing glass. The angle of the incident X-ray to the mirror surface was selected at 71.degree., at which a high reflectivity was anticipated for the multi-layered film consisting of combination of nickel-chromium alloy and vanadium oxide. The multi-layered film had 75 pairs of layers, with a periodic thickness of 54 .ANG. at the mirror center. The uniformity of the periodic thickness was maintained within 2% over the entire mirror. The dimension of the mirror was selected as 100.times.39 mm, in consideration of the numerical aperture (=0.024) of the objective zone plate. Such multi-layered condenser mirror showed a measured reflectivity of 14.3%. A multi-layered film, consisting of combination of nickel/vanadium oxide and formed under the same conditions on the substrate of said form for the purpose of comparison, only showed a reflectivity of 12%. [EXAMPLE 3] In the microscope shown in example 2, a multi-layered film consisting of chromium/vanadium oxide was employed with an angle of the incident X-ray of 65.degree. and subjected to the measurement of reflectivity as in the example 2. Said multi-layered film was formed with 200 pairs of layers with a periodic thickness of 40 .ANG. at the mirror center. The uniformity of the periodic thickness was maintained within 2% over the entire mirror. The size of the mirror was selected as 100.times.42 mm, in consideration of the numerical aperture (=0.024) of the objective zone plate. The above-mentioned multi-layered condenser mirror showed a reflectivity of 10.5% for soft X-ray with a wavelength of 33.7 .ANG.. A similar multi-layered mirror, formed with nickel/vanadium oxide for the purpose of comparison, showed a reflectivity of only 6%.