Stefania Benedetti

Electrical, optical, and electronic properties of Al:ZnO films in a wide doping range

The combination of photoemission spectroscopies, infrared and UV-VIS absorption, and electric measurements has allowed to clarify the mechanisms governing the conductivity and the electronic properties of Al-doped ZnO (AZO) films in a wide doping range. The contribution of defect-related in-gap states to conduction has been excluded in optimally doped films (around 4 at. %). The appearance of gap states at high doping, the disappearance of occupied DOS at Fermi level, and the bands evolution complete the picture of electronic structure in AZO when doped above 4 at. %. In this situation, compensating defects deplete the conduction band and increase the electronic bandgap of the material. Electrical measurements and figure of merit determination confirm the high quality of the films obtained by magnetron sputtering, and thus allow to extend their properties to AZO films in general.

Depth-dependent magnetization reversal and spin structure of Fe/NiO exchange-coupled epitaxial bilayers

We investigate the depth-dependent magnetization reversal and spin structure of Fe/NiO epitaxial bilayers before and after field cooling. Using nuclear resonant scattering of synchrotron radiation we selectively probe the spin structure of the interfacial layers in contact with NiO. We provide a direct evidence that magnetization reversal involves a rotation in the film plane perpendicular to the applied field, except for the interfacial Fe layers. Moreover, we show that the spin structure of the ferromagnetic layer is not modified by field cooling and that the exchange bias in the Fe layer is independent of the distance from the antiferromagnetic phase.

Initial Stages of Cobalt Film Growth on MgO(001) Surface

The initial stages of cobalt film growth on a MgO(001) surface was studied by methods of sample surface structure imaging by reflected electrons, low-energy electron diffraction, and Auger electron spectroscopy. The measurements were performed at room temperature for cobalt layer thicknesses up to 40 Å. It is established that cobalt film growth proceeds according to the island mechanism. In the interval of cobalt film thicknesses below ∼ 10 Å, the dominating surface phase has the form of cobalt islands with an fcc structure; at greater layer thicknesses, the surface film consists predominantly of cobalt grains with an hcp structure.