Low-energy ion scattering spectrometry (LEISS) and x-ray photoelectron spectroscopy (XPS) have been employed to quantifyin situthe near-surface composition of strainedSi1−xGexepitaxial thin films grown on Si(100) substrates usingGeH4andSi2H6as sources. The use of LEISS reveals the Ge concentration in essentially the first monolayer, whereas XPS is sensitive to several monolayers. We find that the extent of Ge surface segregation implied by each technique follows the trend:LEISS-Ge&percent;≫XPS-Ge&percent;≫bulk-Ge&percent;.A two-site model (involving surface and bulk states) cannot account for both the XPS and LEISS results, rather a model invoking Ge enrichment in the subsurface layers is required to explain the data. ©1998 American Institute of Physics.