Photoemission study of the gadolinium/GaAs(100) interface with synchrotron radiation

Soft-X-ray photoemission spectroscopy was used to characterize the Gd/GaAs(100)-interface formation at room temperature. At low Gd coverage (< 1 Angstrom), the interface is near-abrupt, because no evidence of reaction is observed. With increasing Gd coverage, photoemission signals from chemically reacted product at the interface are observed, causing some intermixing between the overlayer and the substrate. For As atoms, they remain near the interface and have little diffusion. Ga atoms, however, are not kept near the interface, and they can diffuse into the Gd overlayer and segregate onto the surface instead. From the observed variations with metal coverage of binding energies and relative intensities of photoemission signals from the reacted layer, a profile of the interface structure is proposed, and some parameters (decaying length, segregation density and solution density, etc.) have been obtained. The results show that the deposition of Gd onto the GaAs(100) surface induces limited substrate disruption except for some diffusion and segregation of Ga atoms into the metal overlayer. This paper demonstrates that the disruption and epitaxial growth are not mutually exclusive in the Gd/GaAs(100) system.