446 research outputs found
Metallicity of the SrTiO3 surface induced by room temperature evaporation of alumina
It is shown that a metallic state can be induced on the surface of SrTiO3
crystals by the electron beam evaporation of oxygen deficient alumina or
insulating granular aluminium. No special preparation nor heating of the SrTiO3
surface is needed. Final metallic or insulating states can be obtained
depending on the oxygen pressure during the evaporation process.
Photoconductivity and electrical field effect are also demonstrated.Comment: 8 pages, 3 figure
Local probing of coupled interfaces between two-dimensional electron and hole gases in oxide heterostructures by variable-temperature scanning tunneling spectroscopy
The electronic structure of an epitaxial oxide heterostructure containing two spatially separated two-dimensional conducting sheets, one electronlike (2DEG) and the other holelike (2DHG), has been investigated using variable temperature scanning tunneling spectroscopy. Heterostructures of LaAlO3/SrTiO3 bilayers on (001)-oriented SrTiO3 (STO) substrates provide the unique possibility to study the coupling between subnanometer spaced conducting interfaces. The band gap increases dramatically at low temperatures due to a blocking of the transition from the conduction band of the STO substrate to the top of the valence band of the STO capping layer. This prevents the replenishment of the depleted electrons in the capping layer from the underlying 2DEG and enables charging of the 2DHG by applying a negative sample bias voltage within the band gap region. At low temperatures the 2DHG can be probed separately with the proposed experimental geometry, although the 2DEG is located less than 1 nm belo
Understanding the nature of electronic effective mass in double-doped SrTiO
We present an approach to tune the effective mass in an oxide semiconductor
by a double doping mechanism. We demonstrate this in a model oxide system
SrLaTiO, where we can tune the effective mass ranging
from 6--20 as a function of filling or carrier concentration and
the scattering mechanism, which are dependent on the chosen lanthanum and
oxygen vacancy concentrations. The effective mass values were calculated from
the Boltzmann transport equation using the measured transport properties of
thin films of SrLaTiO. Our method, which shows that
the effective mass decreases with carrier concentration, provides a means for
understanding the nature of transport processes in oxides, which typically have
large effective mass and low electron mobility, contrary to the tradional high
mobility semiconductors.Comment: 5 pages with 4 figure
Critical thickness and orbital ordering in ultrathin La0.7Sr0.3MnO3 films
Detailed analysis of transport, magnetism and x-ray absorption spectroscopy
measurements on ultrathin La0.7Sr0.3MnO3 films with thicknesses from 3 to 70
unit cells resulted in the identification of a lower critical thickness for a
non-metallic, non-ferromagnetic layer at the interface with the SrTiO3 (001)
substrate of only 3 unit cells (~12 Angstrom). Furthermore, linear dichroism
measurements demonstrate the presence of a preferred (x2-y2) in-plane orbital
ordering for all layer thicknesses without any orbital reconstruction at the
interface. A crucial requirement for the accurate study of these ultrathin
films is a controlled growth process, offering the coexistence of
layer-by-layer growth and bulk-like magnetic/transport properties.Comment: 22 pages, 6 figures, accepted for publication in Physical Review
Parallel electron-hole bilayer conductivity from electronic interface reconstruction
The perovskite SrTiO-LaAlO structure has advanced to a model system
to investigate the rich electronic phenomena arising at polar interfaces. Using
first principles calculations and transport measurements we demonstrate that an
additional SrTiO capping layer prevents structural and chemical
reconstruction at the LaAlO surface and triggers the electronic
reconstruction at a significantly lower LaAlO film thickness than for the
uncapped systems. Combined theoretical and experimental evidence (from
magnetotransport and ultraviolet photoelectron spectroscopy) suggests two
spatially separated sheets with electron and hole carriers, that are as close
as 1 nm.Comment: Phys. Rev. Lett., in pres
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