UHV-CVD GE SI(100) HETEROEPITAXY MONITORED BY IN-SITU ELLIPSOMETRY/

A low cost ellipsometer based on the four detector photopolarimeter wa s utilized for in situ monitoring of Ge film deposition on Si, The bes t fit of the Psi-Delta trajectory, correlated with XPS analysis, allow ed to evidence the sensitivity in the sub-monolayer range of this tech nique. The comparison with results given by complementary analysis tec hniques showed that the early stage of growth is well monitored by thi s diagnostics. On the contrary, poor agreement is achieved for thick f ilms, when the microstructure dimensions are no longer negligible with respect to the wavelength and the optical properties of the film cann ot be properly described by the effective medium approximation.