Structural investigation of the three-layer system MgO/Fe/GaAs(001) by means of photoelectron spectroscopy and diffraction

Abstract

We report a combined high-resolution photoemission (XPS) and photoelectron diffraction (XPD) investigation of the three layer system MgO/Fe/GaAs(001). Each layer is investigated with regard to its structure. The two dimers model of the GaAs (4 × 2) reconstruction was confirmed by XPD patterns. We find the intermediate Fe layer in a crystalline structure. Further, the study clearly shows a well-ordered epitaxial MgO film on Fe. A careful analysis of the interface signals indicates an interdiffusion at the Fe/GaAs interface and partially shifted magnesium layers at the MgO/Fe interface.

Revealing the interfaces of the hybrid system MgO/Co/GaAs(0 0 1): a structural and chemical investigation with XPS and XPD

“…The MgO lattice sites strongly differ from their bulk structures, and lead to a new approach for theoretical calculations. The shift in every second MgO layer has been reported likewise in MgO/Fe, but in (1 0 0) instead of (0 0 1) direction [45]. Additionally, we find no indication for oxidized Co(bcc) at the MgO/Co(bcc) interface.…”

“…Compared to the pure Ga 3d signal (blue line), both new components are shifted to higher kinetic energies by roughly 0.8 eV. According to literature, the pure Ga 3d signal contains three components, referring to two surface states and one bulk state since GaAs c(8 × 2) is a Ga-rich surface reconstruction [45][46][47][48][49][50][51]. The bulk state at 236.5 eV is no longer detectable, since it is buried beneath the Co layer.…”

“…This is in clear contrast to the strongly oxidized Fe film at the MgO/Fe interface [54]. Krull et al found two separated signals in their Fe XPS spectrum, indicating a clear oxid component [45].…”

“…Vector a and b correspond to the (8×) and (×2) periodicities, respectively. More sophisticated structural information is available in the literature [45][46][47].…”

“…Additionally, the strong GaAs(0 0 1) c(8 × 2) surface reconstruction component displayed in the clean As 3d spectrum in figure 8 (bottom) has vanished. According to literature, the pure As 3d signal contains two components referring to one surface state and one bulk state [45][46][47][48][49][50][51]. The bulk state at 214.6 eV is no longer detectable like the Ga 3d bulk state.…”