Patent Number: 054540216
Section: summary

BACKGROUND OF THE INVENTION This invention relates to an x-ray mirror and material such as a total reflection mirror and a multilayer mirror reflective in the x-ray wavelength region. In a catoptric system wherein the wavelength of the x-ray region, 0.1 .ANG. to 200 .ANG., is employed, a total reflecting mirror, a multilayer mirror, and so on are used depending on the use and the wavelength. If radiation is incident at a small oblique angle, the mirror of the catoptric system has an increased area and on the other hand the mirror of an optical system for a focusing and an imaging mirror has a reduced aperture and thereby an increased aberration. Therefore, it is preferable that the critical angle of x-ray radiation to the mirror surface in total reflection be large. As regards reflecting material, high density substances such as Au and Pt are used because the critical angle of total reflection is in proportion to the density of the reflecting material. Au and Pt are chemically quite stable, and are thereby utilized for the reflecting surface because of the excellence of their reflecting property. In these reflecting mirrors, materials such as Au and Pt are deposited on a surface of a support substrate made of a material such as quartz glass, monocrystalline silicon, and SiC which can be polished to a very level form, by physical or chemical vapor deposition such as vacuum deposition and sputtering, or plating. X-rays have a short wavelength, which is about 1/10-1/1000 of that of visible light. So, in order to obtain highly efficient reflectance in this wavelength region, the roughness of the reflecting surface and of the interface with the reflecting material support substrate must be reduced to about 1/10-1/1000 of that for visible light. Also in a substrate, such as one made of quartz glass, polished to have a level surface, the roughness of the film surface could be increased during deposition. Particularly, substances such as Pt and Au are low in Debye temperature and thereby the mobility of atoms at room temperature is large. As a result, crystal grains grows during vacuum deposition and sputtering, which will cause the roughness of the surface to increase. Further, a film 100-1000 .ANG. thick is deposited to form a total reflecting mirror. The film thickness of one layer of a multilayer mirror is between 10 .ANG. and 100 .ANG.. If the film is formed by the above-mentioned method, the density of the film tends to be reduced by about 5-30% as compared to that of a bulk material with the above film thickness. Therefore, x-ray reflecting performance can not be sufficiently obtained. SUMMARY OF THE INVENTION An object of the present invention is to reduce the surface roughness of a Pt film formed by the above deposition method and provide a reflecting material for an x-ray mirror which has a density almost equal to that of a pure Pt film, which is superior in reflecting property and which is chemically stable. The above and other objects are achieved, according to the present invention, by providing a reflecting material constituted by a film of an alloy whose composition is expressed by the general formula Pt.sub.1-x M.sub.x, for a mirror surface of an x-ray mirror so as to reduce the surface roughness without significantly reducing the film density. However, M is one or more of the following substances; Mo, Ru, Rh, Pd, Ta, W, and Au. Preferably, x satisfies the equation; 0.005.ltoreq..times..ltoreq.0.10. If x is expressed as a percentage, then x is between 0.5% and 10% and the formula is expressed as Pt.sub.100-x M.sub.x. When M, as defined above, is added to Pt in a proportion of 0.5-10%, the crystal grain size of an alloy film according to the present invention becomes much smaller than that of a conventional pure Pt film. Further, dispersion of the crystal grain size and surface roughness both decrease. However, the film density does not decline significantly since the quantity of the additive is small. Hence, x-ray reflecting performance is improved. If M is added in a total proportion of more than 10%, surface roughness increases and film density decreases. Consequently the x-ray reflecting performance declines.