Resonant soft x-ray reflectivity of Me/B_4C multilayers near the boron K edge

Abstract

Energy dependence of the optical constants of boron carbide in the short period Ru/B(4)C and Mo/B(4)C multilayers (MLs) are evaluated from complete reflectivity scans across the boron K edge using the energy-resolved photon-in-photon-out method. Differences between the refractive indices of the B(4)Cmaterial inside and close to the surface are obtained from the peak profile of the first order ML Bragg peak and the reflection profile near the critical angle of total external reflection close to the surface. Where a Mo/B(4)C ML with narrow barrier layers appears as a homogeneous ML at all energies, a Ru/B(4)C ML exhibits another chemical nature of boron at the surface compared to the bulk. From evaluation of the critical angle of total external reflection in the energy range between 184 and 186eV, we found an enriched concentration of metallic boron inside the Ru-rich layer at the surface, which is not visible in other energy ranges.

Spectral properties of La/B - based multilayer mirrors near the boron K absorption edge

“…To find optimal matching of optics and sources, knowledge of wavelength dependent reflectance is required. On the other hand, multilayer reflectivity spectra recorded in the vicinity of the B absorption edge hold information about the B chemical state inside the multilayer [11][12][13].…”

Element-specific structural analysis of Si/B4C using resonant X-ray reflectivity

“…On the other hand, the limited tunable probing depth at the resonance energy might be an advantage in a few problems. For example, as shown by Ksenzov et al (2010), it can be used to discriminate the information of the upper interface from that of interfaces within the multilayer. Furthermore, for very complex situations such as multi-element/compound systems where the absorption edges fall close to each other, the absorption edges of the elements/compounds would be such that at a particular energy a specific element/compound will show unique features while the optical response of the remaining components is rather flat.…”

“…The techniques based on resonant X-ray elastic scattering using both hard X-rays (Bai et al, 1995;Vaknin et al, 2003;Lé toublon et al, 2004;Kim et al, 2004;Strzalka et al, 2004;Park et al, 2006;Park & Fenter, 2007;Kemik et al, 2011) and soft X-rays (Fink et al, 2013) provide an opportunity for studying different properties and the associated parameters in condensed matter physics. Resonant soft X-ray elastic scattering has been used to study polymeric and organic materials (Wang et al, 2005;Araki et al, 2006;Mitchell et al, 2006;Mezger et al, 2011;Collins et al, 2012;Pasquali et al, 2014;Stone & Kortright, 2014;Pauli et al, 2014), to study ionic liquids (Mezger et al, 2013), for the electronic and structural analysis of hard matter (Nayak et al, 2006;Valvidares et al, 2010;Ksenzov et al, 2010;Park et al, 2013;Krumrey et al, 2011;Filatova et al, 2012;Nayak et al, 2010Nayak et al, , 2015Nayak & Lodha, 2013a,b;Macke et al, 2014) and to obtain the magnetization profile in magnetic structures (Tonnerre et al, 1995;Sacchi et al, 1998;Benckiser et al, 2011;Bertinshaw et al, 2014;Macke & Goering, 2014). However, very little effort has previously been put into using resonant soft X-ray scattering to measure the spatially resolved chemically sensitive low-Z atomic profile of low-contrast interface structures.…”

Optical Response Near the Soft X-Ray Absorption Edges and Structural Studies of Low Optical Contrast System Using Soft X-Ray Resonant Reflectivity

“…In the hard X-ray to vacuum ultraviolet region, the optical constants are generally measured using angle-dependent reflectivity measurements [64][65][66][67] (also see ref. [54,55], refraction correction in diffraction from a multilayer [68][69][70] and transmission measurements [61]. In the transmission measurements, β is measured and δ is obtained using the Kramers-Kronig relation whereas, in reflectivity measurements, both δ and β are obtained from a fitting of the Fresnel equations to the reflectivity data.…”