Structure and depth profile composition analysis of Cr/(B4C)/V/(B4C) multilayer for water window application

Abstract Ultrathin B 4 C barrier layers have been recently used to reduce the interface widths of soft X-ray Cr/V multilayers and improve the reflectance at the water window region. To further study the chemical changes in the multilayer induced by the barrier layers, Cr/V multilayers (period equals to 4 nm) with and without B 4 C barrier layers were characterized by grazing incidence X-ray reflectometry (GIXR) and X-ray photoelectron spectroscopy (XPS). The GIXR results show that the B 4 C barrier layers significantly reduce the interface widths of the 4 nm-period Cr/V multilayer as already observed for the short-period multilayer. The XPS depth profile confirms an enhanced elemental contrast between Cr and V in the multilayer with B 4 C, as compared to the one with no barriers. According to the fitting results of the photoelectron peaks, the compound formation of VB 2 , extra VC and B 4 C were found in the structure with barrier layers. These compounds help suppress the interdiffusion between Cr and V and contribute to the small interface widths of the multilayer.