Study on the Structure and Reflectivity of Yb/Al Multilayers Prepared by Different Base Pressure

In order to study the effect of base pressure on the microstructure and optical properties of Yb/ Al multilayers,a series of SiC/(Yb/Al)(3) period multilayers with the same structure were prepared by DC magnetron sputtering under base pressure conditions of 4 x 10(-5) Pa, 8 x 10(-5) Pa, 1 x 10(-4) Pa, 2 x 10(-4) Pa and 4 x 10(-4) Pa,respectively. The surface and internal structures of Yb/Al multilayers were characterized by X- ray grazing incident reflection, atomic force microscopy and wide- angle X-ray diffraction. The results show that the average interface width of Yb/Al multilayers decreases from 2.15 nm to 1.82 nm with the raise of base pressure from 4 x 10(-4) Pa to 4 x 10(-5) Pa;the surface roughness decreases from 1.87 nm to 1.43 nm. Yb, Yb2O3 and Al polycrystalline grains are formed in the film,and the grain size increases slightly. The stress of SiC/(Yb/Al)(3) period multilayer is tensile,and the stress increases from 85 MPa to 142 MPa with the base pressure raising from 4 x 10(-4) Pa to 4 x 10(-5) Pa. The reflectivity of the sample prepared under 4 x 10(-5) Pa base pressure was measured. When the wavelength is 73.6 nm and the incident angle is 5 degrees,the reflectivity of the sample is 31.3%.