Formation of amorphous layers by solid-state reaction from thin Ir films on Si(100)

The initial stages of thin Ir film/Si(100) reaction are studied by means of grazing incidence X-ray reflection and transmission electron microscopy. W e observe amorphous layers between the Ir film and the Si(100) substrate al ready to be present after deposition at high vacuum and at ultra-high vacuu m conditions. At room temperature an amorphous interlayer forms with an thi ckness of about 2 nm. Deposition at 400 degrees C results in an 8-nm-thick amorphous layer in which crystallites are present. The formation of the amo rphous phase can be explained by calculating the reduction of free energy w hen an amorphous mixture of Ir and Si atoms is formed. To investigate inter mixing of Si and Ir atoms, we use impurities as markers and conclude that d uring room-temperature-deposition Ir atoms move into the Si(100) substrate. During annealing of room-temperature-deposited samples at 500 degrees C, S i outdiffusion is predominant.