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Transparent conducting oxides: a δ-doped superlattice approach.

Cooper VR, Seo SS, Lee S, Kim JS, Choi WS, Okamoto S, Lee HN - Sci Rep (2014)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.

ABSTRACT
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.

No MeSH data available.


Fractional occupations of dxz/yz orbitals versus dxy as a function of the relative c-axis coordinate for (a) [L1/S2] and (b) [L1/S6]. (c) The magnitude of the Ti displacements, /ΔzTi/, away from the La δ-doped layer. Coordinates are relative to the LaO plane and dashed lines indicate the position of the LaO planes in each system.
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f5: Fractional occupations of dxz/yz orbitals versus dxy as a function of the relative c-axis coordinate for (a) [L1/S2] and (b) [L1/S6]. (c) The magnitude of the Ti displacements, /ΔzTi/, away from the La δ-doped layer. Coordinates are relative to the LaO plane and dashed lines indicate the position of the LaO planes in each system.

Mentions: To better understand the effects of delocalization due to enhanced wavefunction overlap, we compute the fractional occupation, f, of the dxz/yz vs. dxy orbitals: where ni (i = xz, yz or xy) is the number of electrons in the dxz, dyz or dxy orbital, respectively. As depicted in Figure 5, it is clear that the reduction in STO thickness results in a substantial increase in the relative fraction of dxz/yz orbitals at the heterostructure interface. Assuming that these states remain mostly delocalized, this would suggest higher mobility at these interfaces. Similar effects are likely the cause of the anomalous enhancement in mobilities in the previously studied δ-doped oxide superlattices18. Interestingly, we find that the number of dxy electrons, nxy, at the interface remains constant in the [L1/S2] and [L1/S6] superlattices (See Supplementary Information Figure S2), and the large change in fractional occupation at the interface is a consequence of an increase in dxz and dyz populations.


Transparent conducting oxides: a δ-doped superlattice approach.

Cooper VR, Seo SS, Lee S, Kim JS, Choi WS, Okamoto S, Lee HN - Sci Rep (2014)

Fractional occupations of dxz/yz orbitals versus dxy as a function of the relative c-axis coordinate for (a) [L1/S2] and (b) [L1/S6]. (c) The magnitude of the Ti displacements, /ΔzTi/, away from the La δ-doped layer. Coordinates are relative to the LaO plane and dashed lines indicate the position of the LaO planes in each system.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4127498&req=5

f5: Fractional occupations of dxz/yz orbitals versus dxy as a function of the relative c-axis coordinate for (a) [L1/S2] and (b) [L1/S6]. (c) The magnitude of the Ti displacements, /ΔzTi/, away from the La δ-doped layer. Coordinates are relative to the LaO plane and dashed lines indicate the position of the LaO planes in each system.
Mentions: To better understand the effects of delocalization due to enhanced wavefunction overlap, we compute the fractional occupation, f, of the dxz/yz vs. dxy orbitals: where ni (i = xz, yz or xy) is the number of electrons in the dxz, dyz or dxy orbital, respectively. As depicted in Figure 5, it is clear that the reduction in STO thickness results in a substantial increase in the relative fraction of dxz/yz orbitals at the heterostructure interface. Assuming that these states remain mostly delocalized, this would suggest higher mobility at these interfaces. Similar effects are likely the cause of the anomalous enhancement in mobilities in the previously studied δ-doped oxide superlattices18. Interestingly, we find that the number of dxy electrons, nxy, at the interface remains constant in the [L1/S2] and [L1/S6] superlattices (See Supplementary Information Figure S2), and the large change in fractional occupation at the interface is a consequence of an increase in dxz and dyz populations.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.

ABSTRACT
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.

No MeSH data available.