ABSTRACT
Using cross-sectional scanning tunneling microscopy on in situ fractured SrTiO(3), one of the most commonly used substrates for the growth of complex oxide thin films and superlattices, atomically smooth terraces have been observed on (001) surfaces. Furthermore, it was discovered that fracturing this material at room temperature results in the formation of stripe patterned domains having characteristic widths ( approximately 10 to approximately 20 nm) of alternating surface terminations that extend over a long range. Spatial characterization utilizing spectroscopy techniques revealed a strong contrast in the electronic structure of the two domains. Combining these results with topographic data, we are able to assign both TiO(2) and SrO terminations to their respective domains. The results of this experiment reveal that fracturing this material leads to reproducibly flat surfaces that can be characterized at the atomic-scale and suggest that this technique can be utilized for the study of technologically relevant complex oxide interfaces.
Subject(s)
Crystallization/methods , Nanostructures/chemistry , Nanostructures/ultrastructure , Nanotechnology/methods , Oxides/chemistry , Strontium/chemistry , Titanium/chemistry , Hardness , Macromolecular Substances/chemistry , Materials Testing , Molecular Conformation , Particle Size , Stress, Mechanical , Surface PropertiesABSTRACT
Photon absorption by carbon nanotubes creates bound electron-hole pairs called excitons, which can exist in spin-polarized triplet or spin-unpolarized singlet configurations. Triplet excitons are optically inactive owing to the weak spin-orbit coupling in nanotubes. This prevents the optical injection of electron spin into nanotubes for spintronic applications and limits the efficiency of photocurrent generation. Here, we show that it is possible to optically excite the triplet exciton by using a ferromagnetic semiconductor as a spin filter to mix the singlet and triplet excitons. The triplet contribution to the photocurrent is detected, representing the first direct evidence of the triplet exciton in carbon nanotubes.
ABSTRACT
The superconducting state can be influenced by injecting spin-polarized current in a controlled manner by properly tailoring the interfacial transmittivity between a ferromagnet (F) and a superconductor (S), resulting in a large magnetoresistance of over 1100% for a F/I/S/I/F multilayer system (I insulator). Because of the competition between ferromagnetism and superconductivity, the superconducting transition temperature (T(C)) in the spin-parallel configuration is shifted below that in the spin antiparallel configuration. The T(C) shift is attributed to ferromagnet-induced nonequilibrium spin carriers in the superconductors.
