Fe thin films grown on single-crystal and virtual Ge(001) substrates

Abstract

Thin Fe films have been epitaxially grown at room temperature on standard single-crystal Ge(001) substrates and virtual Ge∕Si(001) substrates. Their structural, magnetic, and electronic properties have been investigated in situ by spin-polarized inverse photoemission, x-ray photoemission spectroscopy, x-ray photoelectron diffraction, low-energy electron diffraction, and magneto-optical Kerr effect. In both cases Fe grows in a layer-by-layer fashion with very low Ge incorporation in the film (less than 3%) and the bcc local structure becomes evident for coverage larger than 5 ML. The onset of ferromagnetism appears definitively at 3 ML, while the coercive field and the spin polarization of unoccupied Fe states increase with thickness up to 30 ML. The overall behavior is very similar in the case of standard and virtual substrates, so the latter can be employed for growing high-quality Fe∕Ge interfaces.