Local surface conduction of the (001)-orientated SrTiO3:Nb crystal with a terrace-structured morphology has been studied by means of conductive atomic force microscope analysis. We found that the surface conductance is inhomogeneous on the atomic scale; it is high near step edges and low on terrace plateaus. The surface conductance fluctuation is susceptible to post annealing, first enhancing and then weakening while repeatedly annealed at 700 °C in vacuum. Considering the fact that the oxygen content is most sensitive to vacuum annealing for the temperatures adopted here, the inhomogeneous conductance implies the difference of oxygen vacancy content at step edges and terrace plateaus. The present work clearly demonstrated the influence of surface microstructure on physical properties, and could be helpful for the understanding of the atomic scale non-uniformity of the ultrathin films fabricated on step-featured SrTiO3 surface.
The spin coherence time (T2*) in ZnO single crystals at 8.5 K decreases significantly from ∼11.2 ns to ∼2.3 ns after annealing at 500 °C, as indicated by time-resolved Kerr-rotation pump-probe magneto-optical spectroscopy. The annealing-induced spin coherence degradation in ZnO arises neither from crystallinity degradation during the annealing process, as confirmed by x-ray rocking curves; nor from reflection variations of the probe laser beam induced by surface roughness changes during the annealing process, as confirmed by atomic force microscopy. Temperature-dependent Hall-effect studies indicate that decreased mobility and increased shallow-donor concentration in the annealing-induced surface conducting layer on top of the bulk ZnO are most likely to be the reasons for the spin coherence degradation in ZnO during the annealing process.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.