Ghafoor, N.; Birch, J.; Aquila, A.; Gullikson, E.; Schäfers, F.: Impact of B4C on structure and optical performance of Cr/Sc multilayer X-ray mirrors. Optics Express 25 (2017), p. 18274-18287
10.1364/OE.25.018274
Open Access Version
Abstract:
The influence of B 4 C incorporation during magnetron sputter deposition of Cr/Sc multilayers intended f or soft X -ray reflective optics is investigated. Chemical analysis suggests formation of metal: boride and carbide bonds which stabilize an amorphous layer structure, resulting in smoother interfaces and an increased reflectivity. A near -normal incidence r eflectivity of 11.7%, corresponding to a 67% increase, is achieved at λ = 3.11 nm upon adding 23 at.% (B + C). The advantage is significant for the multilayer periods larger than 1.8 nm, where amorphization results in smaller interface widths, for example, giving 36% reflectance and 99.89% degree of polarization near Brewster angle for a multilayer polarizer. The modulated ion -energy -assistance during the growth is considered vital to avoid intermixing during the interface formation even when B + C are adde d.