Multilayer gratings for X-UV optics

Multilayer gratings are thin film structures possessing periodicities both in the normal and lateral directions. They combine the properties of surfac e gratings and planar multilayers thus providing a high throughput and high spectral resolution on higher diffraction orders. The unique diffraction p roperties are utilized in the X-ray and ultraviolet optics where no lenses or mirrors comparable with those for visible light are available. Multilaye r gratings act as constant resolution dispersion elements in a broad spectr al range. A fan of grating diffractions in real space is represented by a s et of points on equidistant truncation rods in the reciprocal space. The ki nematical theory of X-ray scattering explains well the positions of the gra ting truncation rods while the dynamical theory is inevitable to calculate the intensities along the truncation rods (grating efficiency). The propert ies of multilayer gratings are exemplified on two differently prepared lame llar gratings with the nominal normal and lateral periods of 8 nm and 800 n m, respectively. The fabrication steps are described in detail. The specula r and non-specular X-ray reflectivities at wavelength 0.15418 nm were measu red on one of the samples. The dynamical theory of X-ray scattering with a matrix modal eigenvalue approach was applied to extract the real structural parameters such as the surface and interface roughnesses, individual layer thicknesses, and the lamella width to the grating period ratio. The X-ray reflectometry is completed by microscopy observations which provide complem entary and direct information on the local surface profile.