Quasi-medium energy ion scattering spectroscopy study of Ge δ-layer on Si(001)

We have investigated a Ge δ-layer on Si(001) formed by solid phase epitaxy (SPE) using recently developed quasi-medium energy ion scattering spectroscopy (Q-MEIS). We found that SPE of a top Si buffer layer results in a diffusion of Ge atoms from the δ-doped layer around the interface. This result is in contrast with the molecular beam epitaxy (MBE) case where Ge atoms are segregated to the grown surface. The incident angle dependence of Si and Ge intensities shows that the diffused Ge atoms occupy the Si lattice sites, indicating the GeSi alloying near the interface region. Our results demonstrates that Q-MEIS is suitable for in-situ observation of buried layers during thin film growth processes.