Fabrication and Investigation of W/Mg2Si Multilayer X-Ray Mirrors for the 0.9-2.5 nm and 25–35 nm Wavelength Ranges

This study investigates the fabrication and properties of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{W}/\mathbf{Mg_{2}}\mathbf{Si}$</tex> multilayer X-ray mirrors (MXMs) using DC magnetron sputtering. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{W}/\mathbf{Mg_{2}}\mathbf{Si}$</tex> MXMs with a period of about 3 nm were grown and characterised by X-ray reflectivity (XRR) and electron microscopy. The interlayer boundaries exhibited a roughness of ~0.3 nm, suitable for mirrors with such fine periods. During fabrication, interlayer interactions resulted in formation of a mixed zone at the Mg2Si-on-W interface within the tungsten layer. The composition of this mixed zone varied with layer thickness. Experimental XRR patterns showed mixed zone densities of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{16.1}\mathbf{g}/\mathbf{cm^{3}}$</tex> for a period of 3.1 nm and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{3.2}\mathbf{g}/\mathbf{cm^{3}}$</tex> for a period of 14.2 nm. Reflectivity measurements at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Mg}-\mathbf{K}\boldsymbol{\alpha}$</tex> (9.89 nm) showed that the unoptimised <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{W}/\mathbf{Mg_{2}}$</tex> Si MXM performed comparably to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{W}/\mathbf{B}_{4}\mathbf{C}$</tex> MXMs, with a 5% advantage at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Na}-\mathbf{K}\boldsymbol{\alpha}$</tex> (1.191 nm). These results highlight the potential of short period <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{W}/\mathbf{Mg2}$</tex> Si MXMs in X-ray spectral analysis for the detection of elements such as Mg, Na, F and O.