Zhu Jingtao

Spectral Resolution Improvement of Mo/Si Multilayers

Theoretically, the spectral resolution of a multilayer can be improved through a combination of utilizing high reflectance orders and by decreasing the thickness of the scattering layer. We fabricate Mo/Si multilayers in the first, second, third, fourth and fifth reflectance orders with Mo layer thicknesses of 3.0 nm and 2.0 nm, respectively, using direct current magnetron sputtering. The structure of the multilayers is characterized with a grazing angle x-ray diffractometer (XRD). Then the reflectivity of the multilayers is measured in a synchrotron radiation facility. The results show that the spectral resolution increases with the increasing reflectance order and with the decreasing Mo layer thickness. The highest spectral resolution is improved to 117.5 in the 5th order for dMo = 2 nm, where the reflectivity is 18%.

Measurement of the polarization for soft X-ray magnetic circular dichroism at the BSRF beamline 4B7B

Three ultra-short-period W/B_4C multilayers (1.244 nm, 1.235 nm and 1.034 nm) have been fabricated and used for polarization measurement at the 4B7B Beamline at the Beijing Synchrotron Radiation Facility (BSRF). By using the rotating analyzer ellipsometry method, the linear polarization degree of li...Three ultra-short-period W/B4C multilayers (1.244nm, 1.235nm and 1.034nm) have been fabricated and used for polarization measurement at the 4B7B Beamline of Beijing Synchrotron Radiation Facility (BSRF). By rotating analyzer ellipsometry method, the linear polarization degree of light emerging from this beamline has been measured and the circular polarization evaluated for 700eV-860eV. The first soft x-ray magnetic circular dichroism measurements are carried out at BSRF by positioning the beamline aperture out of the plane of the electron storage ring.

Hard X-ray one dimensional nano-focusing at the SSRF using a WSi2/Si multilayer Laue lens

The multilayer Laue lens (MLL) is a novel diffraction optics which can realize nanometer focusing of hard X-rays with high efficiency. In this paper, a 7.9 mu m-thick MLL with the outmost layer thickness of 15 nm is designed based on dynamical diffraction theory. The MLL is fabricated by first depositing the depth-graded multilayer using direct current (DC) magnetron sputtering technology. Then, the multilayer sample is sliced, and both cross-sections are thinned and polished to a depth of 35-41 mu m. The focusing property of the MLL is measured at the Shanghai Synchrotron Facility (SSRF). One-dimensional (1D) focusing resolutions of 205 nm and 221 nm are obtained at E=14 keV and 18 keV, respectively. It demonstrates that the fabricated MLL can focus hard X-rays into nanometer scale.

Influence of working gas pressure on the performance of W/Si multilayers

The effect of Ar pressure on the performance of W/Si multilayers is investigated. W/Si multilayers were deposited by a high vacuum DC magnetron sputtering system. The Ar pressure was changed from 1.0 to 5.0 mTorr with an interval of 1.0 mTorr during the deposition process. Electron probe microanalysis and Rutherford backscattering are performed to determine the Ar content incorporated within these multilayers. The results demonstrate that less Ar is incorporated within the sample when more Ar is used in the plasma, which could be explained by the increase of the collision probability and the decrease in the kinetic energy of Ar ions arriving at the substrate when more Ar exists. The grazing incident X-ray reflectivity (GIXR) at 0.154 nm is used to determine the structural parameters of the layers. The results show that the structures of these multilayers prepared at different Ar pressure are very similar and that the interface roughness increases quickly when the Ar pressure is higher than 3.0 mTorr. The measurements of the extreme ultraviolet (EUV) reflectivity indicate that the reflectivity decreases when Ar pressure increases. The fitting results of GIXR and EUV reflectivity curves indicate that with an increase of Ar pressure, the density and decrement of the refractive index are increased for W and decreased for Si, which is mainly due to (1) the decrease in Ar content incorporated within these multilayers which affects their performance and (2) the increase of collision probability for sputtered W and Si, the decrease of their average kinetic energy arriving at the substrate, and thus the loosing of their layers.

Design, Fabrication and Measurement of Ni/Ti Multilayer Used for Neutron Monochromator

Ni/Ti multilayers, which can be used for neutron monochromators, are designed, fabricated and measured. Firstly, their reflectivities are simulated based on the Nevot–Croce model. Reflectivities of two Ni/Ti multilayer mirrors with periods d = 10.3 nm (M1) and d = 7.8 nm (M2) are calculated. In the calculation, the reflectivity of the Ni/Ti multilayer is taken as a function of the grazing angle with different roughness factors δ = 1.0 nm and δ = 1.5 nm. Secondly, these two multilayers are fabricated by the direct current magnetron sputtering technology. Thirdly their structures are characterized by small-angle x-ray diffraction. The roughness factors are fitted to be 0.68 nm and 1.16 nm for M1 and M2, respectively. Finally their reflective performances are measured on the V14 neutron beam line at the Berlin Neutron Scattering Centre (BENSC), Germany. The experimental data show that the grazing angle of the reflected neutron intensity peak increases, but the reflected neutron intensity decreases, with the decreasing periods of the multilayers.

High Spectral Resolution Mo/Si Multilayers Working at High Order Reflection

The high reflectance orders are used to improve the spectral resolution of Mo/Si multilayers. The multilayers for the first-, second- and third-order reflectance are designed and optimized, respectively. These multilayers are fabricated by using a directed current magnetron sputtering system, and the reflectivity is measured in an extreme ultraviolet range by synchrotron radiation. The experimental results show that the spectral resolution λ/Δλ (λ = 14 nm) increases from 24.6 for the first order to 66.6 for the third order.

Design and Fabrication of Ni/Ti Multilayer for Neutron Supermirror

In the applications of neutron guides and focusing devices, by using the Ni/Ti multilayer supermirrors (SM), the neutron flux is significantly enhanced, because the critical reflective angle of supermirrors increases m times compared to the one of natural bulk Ni. We design and fabricate the Ni/Ti multilayer supermirrors by considering the effect of the interfacial imperfection, such as interface roughness and diffusion, and by using the direct current magnetron sputtering technology. The reflective performances of these supermirrors are measured on a V14 neutron beam line at the Berlin Neutron Scattering Centre (BENSC), Germany. The measurement data suggest that the critical angles of the supermirrors are 1.5 and 2.2 times that of bulk Ni, respectively.

X-ray nanometer focusing at the SSRF based on a multilayer Laue lens*

We designed and fabricated a multilayer Laue lens (MLL) as a hard X-ray focusing device. WSi2/Si multilayers were chosen owing to their excellent optical properties and relatively sharp interface. The multilayer sample was fabricated by using direct current (DC) magnetron sputtering technology and then was sliced and thinned to form an MLL. The thickness of each layer was determined by scanning electron microscopy (SEM) image analysis with marking layers. The focusing property of the MLL was measured at Beamline 15U, Shanghai Synchrotron Facility (SSRF). One-dimensional (1D) focusing resolutions of 92 nm are obtained at photon energy of 14 keV.