The present study is focused on the influence of vacuum thermal treatment on surface/interface electronic properties of Si/Ge multilayer structures (MLS) characterized using X-ray photoelectron spectroscopy (XPS) technique. Desired [Si(5 nm)/Ge(5 nm)](x10) MLS were prepared using electron beam evaporation technique under ultra high vacuum (UHV) conditions. The core-level XPS spectra of as-deposited as well as multilayer samples annealed at different temperatures such as 100 degrees C, 150 degrees C and 200 degrees C for 1 h show substantial reduction in Ge 2p peak integrated intensity, whereas peak intensity of Si 2p remains almost constant. The complete interdiffusion took place after annealing the sample at 200 degrees C for 5 h as confirmed from depth pro. ling of annealed MLS. The asymmetric behaviour in intensity patterns of Si and Ge with annealing was attributed to faster interdiffusion of Si into Ge layer. However, another set of experiments on these MLS annealed at 500 degrees C suggests that interdiffusion can also be studied by annealing the system at higher temperature for relatively shorter time duration. (C) 2009 Elsevier B.V. All rights reserved.