Status of small d-spacing x-ray multilayers development at Osmic

Abstract

ABSTACTThe deposition and X-ray performance of multilayer structures with d-spacings ranging from 1 .2nm to 3 .5nm has been presented. Different pairs of materials such as W (Mo, Ni, Cr, and La)/B4C, Ni (Cr, Co, V)/C have been considered. Xray reflectivity ofthe multilayers has been measured in the photon energy range from O. l8keV to -400keV. W/B4C structures with d-4.25nm showed reflectivity greater than 30% at Cu-K a (E8keV). Performance of a W/B4C structure with dl.5nm has been compared with TIAP crystal performance in analysis of SKa (l.74keV), AlKa (1 .5keV), Mg-Ka (1 .25keV) and Na-Ka (1 .O4keV) radiation. Results showed that small d-spacing multilayers can be considered for TIAP crystal replacement in Wavelength Dispersive X-Ray Fluorescence (WDXRF) spectrometers.The absolute reflectivity of near normal incidence structures at OKa (293eV), CKa ('277eV) and BKa (1 83eV) radiation lines has been measured to be 1.5%, 14% and 43% respectively with spectral resolution ofup to O.6%.

Cr/B4C multilayer mirrors: Study of interfaces and X-ray reflectance

“…In the spectral range between the Si L 2,3 -edge and the B K-edge (100 eV < E < 180 eV), B 4 C is often used as the "spacer" material in multilayer coatings. Proposed combinations include Mo/B 4 C, 5,6 La/B 4 C, [5][6][7][8] Ru/B 4 C, 9 and Pd/B 4 C. 10 At higher energies (typically E > 500 eV), short-period multilayer mirrors are required, and B 4 C is often used as a substitute to C because it provides smoother layer interfaces and higher reflectance values. [11][12][13] Common multilayer material pairs for this spectral domain are W/B 4 C, 2,3,11,14 Ni/B 4 C, or Mo/B 4 C, 7,15 but other combinations have been reported as well, for example, Fe/B 4 C and Rh/B 4 C. 11 B 4 C has also been used in the EUV domain (E < 100 eV), as for instance in Si/ B 4 C, 16 Si/Mo/B 4 C, 17 or Al/Mo/B 4 C 18 multilayers.…”

Fabrication and characterization of Sb/B4C multilayer mirrors for soft X-rays

“…The interface roughness which might include some intermixing was found to be of 0.32-0.4 nm rms. The obtained value of the roughness is somewhat higher as compared to W/B 4 C and Mo/B 4 C multilayers, but it is close to the roughness measured for Cr/B 4 C, Co/C, Ni/C multilayers [15] and [16]. Thus, Sb/B 4 C multilayers fabricated with dc-magnetron sputtering have fairly smooth interfaces with roughness as low as the one for X-ray multilayers made of other materials.…”

“…5. Reflectivity of multilayer mirrors typically reduces slightly as the period decreases down to a threshold value of 2.5-6 nm (depending on the multilayer materials) and then drops steeply [15] and [20]. For the Sb/B 4 C multilayers, this sharp reflectivity fall occurs at the period less than 4 nm.…”

A proposal for a collecting mirror assembly for large divergence x-ray sources

“…This relationship indicates that the wavelength of x ray becomes shorter, either the grazing incident angle becomes smaller or the periodic length becomes shorter. Due to the technical limitations of the fabrication process, multilayers with a periodic length less than about 1 nm cannot be fabricated, so large incident angles above a few degrees cannot be obtained in the hard x-ray region [19]. Thus, the optical path in the x-ray region is limited to small changes of angle.…”