ABSTRACT
Bcc metals and MgO are used in technological research for building magnetic tunnel junctions (MTJs), because they yield a high tunnel magnetoresistance. Thin insulating barriers are of great importance in realizing MTJs. Combined with electrons spin-injected into GaAs, tunneled electrons can be detected and manipulated. We report on a synchrotron radiation based x-ray photoelectron spectroscopy and x-ray photoelectron diffraction study on the system MgO/Co(bcc)/GaAs(0 0 1) for ultra-low Co and MgO coverages ([Formula: see text], [Formula: see text]). As a result, we obtain a Co3Ga alloy at the Co/GaAs interface in the rare D03 structure. This structure is only 6.07 Å thick, and serves as a template for the metastable Co(bcc) structure. Co(bcc) itself grows heavily distorted in the (0 0 1) direction for the first two unit cells, due to the D03 template. The MgO/Co interface reveals a weak bonding between MgO and Co(bcc) without Co oxidation, since no compound formation was observed. Additionally, MgO grows in an amorphous phase for a thickness of [Formula: see text]. At [Formula: see text], it crystallizes in a compressed unit cell where every second layer is shifted toward the (0 0 1) direction compared to the bulk halite structure.
ABSTRACT
The atomic structure is one key property for any material. Despite great efforts during the last few years unveiling the internal structure of silicon nano-ribbons, analysis of the interfacial structure and bonding was neglected. We report on a comprehensive photoelectron spectroscopy and photoelectron diffraction study that reveals the weak interaction of silicon nano-ribbons with the underlying silver substrate identifying the specific locations of the individual silicon, as well as silver atoms. Furthermore, we provide unique experimental evidence that clarifies the origin of the two distinct chemically shifted components in the silicon photoelectron spectra.
ABSTRACT
Magnetotactic bacteria are of great interdisciplinary interest, since a vast field of applications from magnetic recording media to medical nanorobots is conceivable. A key feature for a further understanding is the detailed knowledge about the magnetosome chain within the bacteria. We report on two preparation procedures suitable for UHV experiments in reflective geometry. Further, we present the results of scanning electron microscopy, as well as the first photoemission electron microscopy experiments, both accessing the magnetosomes within intact magnetotactic bacteria and compare these to scanning electron microscopy data from the literature. From the images, we can clearly identify individual magnetosomes within their chains.
