Role of C and B₄C barrier layers in controlling diffusion propagation across the interface of Cr/Sc multilayers

Abstract

Optical performances of low bilayer thickness metallic multilayers (ML) can be improved significantly by limiting the intermixing of consecutive layers at the interfaces. Barrier layers are supposed to exhibit decisive...

Impact of B4C buffer layer on interface diffusion in Cr/Sc multilayers: combined study by x-ray reflectivity, scattering and fluorescence

“…According to the growth model proposed by Forgerini and Marchiori [35], wetting (de-wetting) of a material with a lower (higher) ( ) g being more likely to take place when deposited on a material with higher (lower) . ( ) g Thus, Sc will wet the underlying Cr surface as Sc is having lower surface energy than Cr resulting in a 2-dimensional or layer-by-layer growth [21]. On the other hand, Cr will follow island-type growth on Sc and would generate larger interface width.…”

“…It has resulted in drastic improvement in the performance of the multilayers with material combinations like Mo/Si [17], Sc/Si [18], Cr/Ti [19], Cr/V [20] etc. Materials having lower surface energy such as C that helps in wetting of the interface [19] whereas B 4 C which is known to reduce interlayer mobility of metal atoms, are generally chosen as barrier layers as these results in two-dimensional growth of the multilayers with abrupt interfaces and reduced interface roughness [21,22]. In case of Cr/Sc multilayer system also, there are a number of reports with B 4 C [22,23], however, the above works mostly have reported the improvement in reflectivities and thermal stability obtained in Cr/Sc multilayer system upon inclusion of B 4 C [24,25] and have not really estimated the elemental diffusion at the interfaces of Cr/Sc multilayers and the extent to which B 4 C helps to reduce it.…”