Metallic states appearing at interfaces between dissimilar insulating oxides exhibit intriguing phenomena such as superconductivity and magnetism. Despite tremendous progress in understanding their origins, very little is known about how to control the conduction pathways and the distribution of charge carriers. Using optical spectroscopic measurements and density-functional theory (DFT) simulations, we examine the effect of SrTiO3 (STO) spacer layer thickness on the optical transparency and carrier distribution in La δ-doped STO superlattices. We experimentally observe that these metallic superlattices remain highly transparent to visible light; a direct consequence of the appropriately large gap between the O 2p and Ti 3d states. In superlattices with relatively thin STO layers, we predict that three-dimensional conduction would occur due to appreciable overlap of quantum mechanical wavefunctions between neighboring δ-doped layers. These results highlight the potential for using oxide heterostructures in optoelectronic devices by providing a unique route for creating novel transparent conducting oxides.
|State||Published - Aug 11 2014|
Bibliographical noteFunding Information:
The authors thank Y. Lee and L. Balicas for experimental assistance, P. D. C. King for helpful discussions and N. Sivadas for technical assistance. This work was supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division (V.R.C., W.S.C., S.S.A.S., S.O., H.N.L.), and the Office of Science Early Career Research Program (V.R.C.). S.L. was supported by the Korea Institute of Science and Technology (KIST) through Grant No. 2E24001. This research used resources of the National Energy Research Scientific Computing Center, supported by the Office of Science, U.S. Department of Energy under Contract No. DEAC02-05CH11231.
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