Using an indigenously built DC magnetron sputtering system short period (~ 42Å ) Co/Ti multilayer and Co/Ti multilayer with ~ 4Å Cu buffer layer at both interfaces with 20 bilayers in each case have been prepared for use as reflecting optics in the water window soft X-ray regime of 23–44 Å. The samples have been subsequently characterized by specular and diffused grazing incidence X-ray reflectivity (GIXR) measurements as well as cross-sectional transmission electron microscopy (TEM) to carry out detail investigations on the interfaces. Analysis of GIXR data and TEM measurements clearly reveal that interface roughness is the major contributor to the interface imperfections in these short period multilayers and interface roughness in the multilayer are significantly reduced after the introduction of Cu barrier layers.