Effect of the surface roughness on X-ray absorption by mirrors operating at extremely small grazing angles.

This study theoretically analyzes an increase in X-ray absorption by a grazing incidence mirror due to its surface roughness. We demonstrate that the increase in absorption can be several hundred times larger than predicted by the Nevot-Croce formula. As a result, absorption enhances by several times compared to a perfectly smooth mirror despite the extremely small grazing angle of an incident X-ray beam (a fraction of the critical angle of the total external reflection) and the high quality of the reflecting surface (the roughness height was 0.

Nitridated Pd/BC multilayer mirrors for soft X-ray region: internal structure and aging effects.

Reactive sputtering with a mixture of argon and nitrogen (N partial pressure of 4%, 8%, and 15%) as the working gas is used to develop the high reflectance Pd/BC multilayers for soft X-ray region application. Compared to the pure Ar fabricated sample, the interface roughness of the nitridated multilayer is slightly increased while the compressive stress is essentially relaxed from -623 MPa (pure Ar) to -85 MPa (15% N). A maximum reflectance of 32% is measured at the wavelength of 9.

Effect of background pressure on Co/C multilayers.

Co/C multilayers with a period thickness of 3.54 nm and 30 bilayers were deposited by direct current magnetron sputtering with different background pressures. The effects of residual background gases were investigated.

Improvement of interface structure and polarization performance of Co/C multilayers by incorporation of nitrogen.

Short-period (~3.5 nm) Co/C multilayer mirrors are fabricated by the direct current magnetron sputtering technique through the addition of a small proportion of nitrogen (4-15% partial pressure) to the working gas (Ar). The addition of nitrogen has been demonstrated to significantly suppress the interdiffusion of neighboring materials due to the nitridation of carbon layers as compared with the Co/C multilayer fabricated with the use of pure Ar.

High reflectance Cr/V multilayer with B(4)C barrier layer for water window wavelength region.

To develop the high reflectance mirror for the short wavelength range of the water window region (λ=2.42-2.73  nm), Cr/V multilayers with BC barrier layers are studied.

Enhancement of soft X-ray reflectivity and interface stability in nitridated Pd/Y multilayer mirrors.

Pd/Y multilayer mirrors operating in the soft X-ray region are characterized by a high theoretical reflectance, reaching 65% at normal incidence in the 8-12 nm wavelength range. However, a severe intermixing of neighboring Pd and Y layers results in an almost total disappearance of the interfaces inside the multilayer structures fabricated by direct current magnetron sputtering and thus a dramatic reflectivity decrease. Based on grazing incidence X-ray reflectometry and X-ray photoelectron spectroscopy, we demonstrate that the stability of the interfaces in Pd/Y multilayer structures can be essentially improved by adding a small amount of nitrogen (4-8%) to the working gas (Ar).

Reflection of X-rays from a rough surface at extremely small grazing angles.

Peculiarities of X-ray diffraction from a rough surface at an extremely small grazing angle of an incident beam are theoretically studied. The interrelation of four diffraction channels (coherent reflectance, coherent transmittance, diffuse scattering in vacuum, and scattering into the matter depth) is analyzed for different limiting cases (large and small correlation length of roughness and large and extremely small grazing angle of incident radiation). Both the Debye-Waller and the Nevot-Croce factors are demonstrated to describe improperly the features of X-ray diffraction at extremely small grazing angles.