Atom-rearrangement in Ge layer grown on Si substrate during anneal observed in real time by coaxial impact collision ion scattering spectroscopy

Abstract

The atom-rearrangement in thin Ge layers grown on Si(001) substrates during post-growth anneal has been studied using coaxial impact collision ion scattering spectroscopy (CAICISS). CAICISS measurements were carried out in real time during the anneal. A Ge layer was grown at 130°C by molecular beam epitaxy, and after growth the sample temperature was raised to 600°C at a rate of 1°C/s. The intensity of the back-scattered ion beam with incidence along the [01 1 ] direction was measured during the anneal. A gradual decrease in the scattering intensity was observed while the temperature was raised from 300 to 520°C. The decrease in the scattering intensity observed here can be understood in terms of a reduction in the number of interstitial atoms due to atom-rearrangement along the [01 1 ] direction. Plan-view transmission electron microscope (TEM) images showed clear moiré fringes for the sample after anneal, while such moiré fringes were not observed for an as-grown sample. The result of a TEM observation also shows atom-rearrangement in the Ge layer due to the anneal, which is in good agreement with the results of CAICISS measurements.