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High reflectance Cr/C multilayer at 250eV for soft X-ray polarimetry

DOI: 10.1016/j.tsf.2015.06.005 DOI Help

Authors: Mingwu Wen (Tongji University) , Li Jiang (Tongji University) , Zhong Zhang (Tongji University) , Qiushi Huang (Tongji University) , Zhanshan Wang (Tongji University) , Rui She (Tsinghua University) , Hua Feng (Tsinghua University) , Hongchang Wang (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Thin Solid Films

State: Published (Approved)
Published: June 2015
Diamond Proposal Number(s): 5028

Abstract: X-ray reflection near 45° via multilayer mirrors can be used for astronomical polarization measurements. A Cr/C multilayer mirror (designed for X-ray polarimetry at 250 eV), with a period thickness of 3.86 nm and a bi-layer number of 100, was fabricated using direct current magnetron sputtering. Grazing incidence X-ray reflectometry at 8 keV and transmission electron microscopy were used to investigate the multilayer structure. Different models were introduced to fit the hard X-ray reflectivity curve, which indicates that the layer thickness of two materials slightly drifts from the bottom to the top of the stack. Both the chromium and carbon layers are amorphous with asymmetric interfaces, while the Cr-on-C interface is slightly wider. Based on the good quality of the multilayer structure, a high reflectivity of 21.8% for the s-polarized light was obtained at 250 eV at a grazing incidence angle of 40.7°. The fabricated Cr/C multilayer mirror exhibits high reflectivity and polarization levels in the energy region of 240 eV–260 eV.

Journal Keywords: Soft X-Ray; Polarization; Chromium; Carbon; Cr/C Multilayer; Direct Current Magnetron Sputtering; Transmission Electron Microscopy

Subject Areas: Physics, Technique Development

Instruments: I06-Nanoscience