Epitaxial growth and magnetic properties of a new group‐IV ferromagnetic semiconductor: Ge 1– x Fe x

Abstract

Epitaxial growth and magnetic properties of group-IV ferromagnetic semiconductor Ge1–xFex thin films were investigated by employing in-situ reflection high-energy electron diffraction (RHEED), transmission electron microscopy (TEM), and magnetic circular dichroism (MCD). When Ge1–xFex films were grown at substrate temperatures (TS) of 100–200 °C, their RHEED pattern showed streaks with a 2×2 reconstruction pattern, indicating two-dimensional growth mode with atomically flat surface morphology. Single-phase crystallographic structure without Fe-Ge intermetallic compounds was observed in the films by TEM. MCD measurements revealed that s,p-d exchange interactions induced by the incorporation of Fe atoms that occupied the substitutional sites of the host Ge matrix cause single-phase ferromagnetic ordering in the Ge1–xFex films. Above TS = 300 °C, the growth mode was changed from two-dimensional growth mode to three-dimensional growth mode. It was found from MCD observations that when Ge1–xFex films are grown at TS = 300–400 °C, phase separation occurs and the films contain ferromagnetic precipitates. A ferromagnetic semiconductor phase was obtained for TS ranging from 100 °C to 200 °C, and higher Curie temperature was obtained for TS = 200 °C. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)