29 research outputs found
Field-induced water electrolysis switches an oxide semiconductor from an insulator to a metal
Here we demonstrate that water-infiltrated nanoporous glass electrically
switches an oxide semiconductor from an insulator to metal. We fabricated the
field effect transistor structure on an oxide semiconductor, SrTiO3, using
100%-water-infiltrated nanoporous glass - amorphous 12CaO*7Al2O3 - as the gate
insulator. For positive gate voltage, electron accumulation, water electrolysis
and electrochemical reduction occur successively on the SrTiO3 surface at room
temperature, leading to the formation of a thin (~3 nm) metal layer with an
extremely high electron concentration of 10^15-10^16 cm^-2, which exhibits
exotic thermoelectric behaviour.Comment: 21 pages, 12 figure
Mapping the Spatial Distribution of Charge Carriers in LaAlO3/SrTiO3 Heterostructures
At the interface between complex insulating oxides, novel phases with
interesting properties may occur, such as the metallic state reported in the
LaAlO3/SrTiO3 system. While this state has been predicted and reported to be
confined at the interface, some works indicate a much broader spatial
extension, thereby questioning its origin. Here we provide for the first time a
direct determination of the carrier density profile of this system through
resistance profile mappings collected in cross-section LaAlO3/SrTiO3 samples
with a conducting-tip atomic force microscope (CT-AFM). We find that, depending
upon specific growth protocols, the spatial extension of the high-mobility
electron gas can be varied from hundreds of microns into SrTiO3 to a few
nanometers next to the LaAlO3/SrTiO3 interface. Our results emphasize the
potential of CT-AFM as a novel tool to characterize complex oxide interfaces
and provide us with a definitive and conclusive way to reconcile the body of
experimental data in this system.Comment: This updated version contains new experimental dat
UV radiation enhanced oxygen vacancy formation caused by the PLD plasma plume
Pulsed Laser Deposition is a commonly used non-equilibrium physical deposition technique for the growth of complex oxide thin films. A wide range of parameters is known to influence the properties of the used samples and thin films, especially the oxygen-vacancy concentration. One parameter has up to this point been neglected due to the challenges of separating its influence from the influence of the impinging species during growth: the UV-radiation of the plasma plume. We here present experiments enabled by a specially designed holder to allow a separation of these two influences. The influence of the UV-irradiation during pulsed laser deposition on the formation of oxygen-vacancies is investigated for the perovskite model material SrTiO3. The carrier concentration of UV-irradiated samples is nearly constant with depth and time. By contrast samples not exposed to the radiation of the plume show a depth dependence and a decrease in concentration over time. We reveal an increase in Ti-vacancy–oxygen-vacancy-complexes for UV irradiated samples, consistent with the different carrier concentrations. We find a UV enhanced oxygen-vacancy incorporation rate as responsible mechanism. We provide a complete picture of another influence parameter to be considered during pulsed laser depositions and unravel the mechanism behind persistent-photo-conductivity in SrTiO3