Optical constants in the EUV soft x-ray (5÷152 nm) spectral range of B 4 C thin films deposited by different deposition techniques

Abstract

B₄C optical coating represents, together with Ir, Pt, SiC, one of best choice for high reflectance in the extreme ultraviolet region (EUV 160-30 nm). This material is also used in multilayer for soft X-ray applications, such as Si/B₄C or W/B₄C, or as interlayer in Mo/Si multilayer to avoid interdiffusion also because of its high thermal stability. Our work concerns on B₄C thin films deposited on Si [100] substrates by means of three different deposition techniques: RF plasma magnetron sputtering, e-beam evaporation, pulsed laser ablation (PLD). We performed reflectance vs incidence angle measurements from 5 nm to 152 nm on different samples deriving the optical constants with a least-square fitting method. Complete films characterization have been carried out with compositional (XPS), structural (XRD) and morphological (AFM, SEM) analyses.