Zinc Oxide –from Dilute Magnetic Doping to Spin Transport (phys. Status Solidi B 9/2014)

Conventional electronics relies on the controlled transport and storage of electrical charge in semiconductors. Spintronics exploits the spin degree of freedom as well, providing fascinating perspectives for novel device concepts with improved functionality and performance. One of the interesting materials for spintronics is the wide bandgap, II–VI semiconductor ZnO because early reports on dilute magnetic doping and its small spin-orbit coupling imply a large spin coherence length. Opel et al. (pp. 1700–1709) investigate ZnO thin films, grown epitaxially on (0001)-oriented Al2O3 substrates via laser molecular beam epitaxy. The front cover schematically shows three important aspects of the experiments. First, the lattice mismatch between ZnO and Al2O3 is reduced by rotating the ZnO lattice by 30°. Second, dilute magnetic doping with cobalt results in phase segregation and the formation of nanometer-sized metallic clusters, as indicated via the bright red contrast of the energy-filtered TEM image (background). Third, the sketched device allows for studying spin transport properties. A spin-polarized current from a magnetic Co electrode is injected into ZnO, and the spin polarization is determined optically via the polarization of refl ected photons. The source files for the front cover image were prepared by Matthias Althammer.