977 research outputs found
Tailoring a two-dimensional electron gas at the LaAlO3/SrTiO3 (001) interface by epitaxial strain
Recently a metallic state was discovered at the interface between insulating
oxides, most notably LaAlO3 and SrTiO3. Properties of this two-dimensional
electron gas (2DEG) have attracted significant interest due to its potential
applications in nanoelectronics. Control over this carrier density and mobility
of the 2DEG is essential for applications of these novel systems, and may be
achieved by epitaxial strain. However, despite the rich nature of strain
effects on oxide materials properties, such as ferroelectricity, magnetism, and
superconductivity, the relationship between the strain and electrical
properties of the 2DEG at the LaAlO3/SrTiO3 heterointerface remains largely
unexplored. Here, we use different lattice constant single crystal substrates
to produce LaAlO3/SrTiO3 interfaces with controlled levels of biaxial epitaxial
strain. We have found that tensile strained SrTiO3 destroys the conducting
2DEG, while compressively strained SrTiO3 retains the 2DEG, but with a carrier
concentration reduced in comparison to the unstrained LaAlO3/SrTiO3 interface.
We have also found that the critical LaAlO3 overlayer thickness for 2DEG
formation increases with SrTiO3 compressive strain. Our first-principles
calculations suggest that a strain-induced electric polarization in the SrTiO3
layer is responsible for this behavior. It is directed away from the interface
and hence creates a negative polarization charge opposing that of the polar
LaAlO3 layer. This both increases the critical thickness of the LaAlO3 layer,
and reduces carrier concentration above the critical thickness, in agreement
with our experimental results. Our findings suggest that epitaxial strain can
be used to tailor 2DEGs properties of the LaAlO3/SrTiO3 heterointerface
Structural and Electronic Properties of the Interface between the High-k oxide LaAlO3 and Si(001)
The structural and electronic properties of the LaAlO3/Si(001) interface are
determined using state-of-the-art electronic structure calculations. The atomic
structure differs from previous proposals, but is reminiscent of La adsorption
structures on silicon. A phase diagram of the interface stability is calculated
as a function of oxygen and Al chemical potentials. We find that an
electronically saturated interface is obtained only if dopant atoms segregate
to the interface. These findings raise serious doubts whether LaAlO3 can be
used as an epitaxial gate dielectric.Comment: 4 pages, 5 figure
High-Resolution Crystal Truncation Rod Scattering: Application to Ultrathin Layers and Buried Interfaces
In crystalline materials, the presence of surfaces or interfaces gives rise to crystal truncation rods (CTRs) in their X‐ray diffraction patterns. While structural properties related to the bulk of a crystal are contained in the intensity and position of Bragg peaks in X‐ray diffraction, CTRs carry detailed information about the atomic structure at the interface. Developments in synchrotron X‐ray sources, instrumentation, and analysis procedures have made CTR measurements into extremely powerful tools to study atomic reconstructions and relaxations occurring in a wide variety of interfacial systems, with relevance to chemical and electronic functionalities. In this review, an overview of the use of CTRs in the study of atomic structure at interfaces is provided. The basic theory, measurement, and analysis of CTRs are covered and applications from the literature are highlighted. Illustrative examples include studies of complex oxide thin films and multilayers
Long-range electronic reconstruction to a -dominated Fermi surface below the LaAlO/SrTiO interface
Low dimensionality, broken symmetry and easily-modulated carrier
concentrations provoke novel electronic phase emergence at oxide interfaces.
However, the spatial extent of such reconstructions - i.e. the interfacial
"depth" - remains unclear. Examining LaAlO/SrTiO heterostructures at
previously unexplored carrier densities cm,
we observe a Shubnikov-de Haas effect for small in-plane fields, characteristic
of an anisotropic 3D Fermi surface with preferential orbital
occupancy extending over at least 100~nm perpendicular to the interface.
Quantum oscillations from the 3D Fermi surface of bulk doped SrTiO emerge
simultaneously at higher . We distinguish three areas in doped
perovskite heterostructures: narrow ( nm) 2D interfaces housing
superconductivity and/or other emergent phases, electronically isotropic
regions far ( nm) from the interface and new intermediate zones where
interfacial proximity renormalises the electronic structure relative to the
bulk.Comment: Supplementary material available at Scientific Reports websit
Formation and observation of a quasi-two-dimensional electron liquid in epitaxially stabilized SrLaTiO thin films
We report the formation and observation of an electron liquid in
SrLaTiO, the quasi-two-dimensional counterpart of SrTiO,
through reactive molecular-beam epitaxy and {\it in situ} angle-resolved
photoemission spectroscopy. The lowest lying states are found to be comprised
of Ti 3 orbitals, analogous to the LaAlO/SrTiO interface and
exhibit unusually broad features characterized by quantized energy levels and a
reduced Luttinger volume. Using model calculations, we explain these
characteristics through an interplay of disorder and electron-phonon coupling
acting co-operatively at similar energy scales, which provides a possible
mechanism for explaining the low free carrier concentrations observed at
various oxide heterostructures such as the LaAlO/SrTiO interface
Atomically flat interface between a single-terminated LaAlO3 substrate and SrTiO3 thin film is insulating
The surface termination of (100)-oriented LaAlO3 (LAO) single crystals was
examined by atomic force microscopy and optimized to produce a
single-terminated atomically flat surface by annealing. Then the atomically
flat STO film was achieved on a single-terminated LAO substrate, which is
expected to be similar to the n-type interface of two-dimensional electron gas
(2DEG), i.e., (LaO)-(TiO2). Particularly, that can serve as a mirror structure
for the typical 2DEG heterostructure to further clarify the origin of 2DEG.
This newly developed interface was determined to be highly insulating.
Additionally, this study demonstrates an approach to achieve atomically flat
film growth based on LAO substrates.Comment: 4 pages, 3 figure
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