Effect of various deposition conditions on the electrical properties of LAO/STO hetero interfaces

Abstract

We have examined the effects of partial oxygen pressure and laser energy density on the electrical transport properties of thin LAO films grown on (100) TiO 2-terminated SrTiO 3 substrates. Films were grown by pulsed laser deposition monitored by in-situ reflection highenergy electron diffraction (RHEED). Layer-by-layer growth, as indicated by clear RHEED oscillations, can be obtained in a wide range of oxygen partial pressures from 10-6 to 5x10-2 mbar. Transmission electron microscopy (TEM) analysis shows that the interface is coherent and atomically sharp for all deposition conditions. The STO substrate is oxygen self reduced at an oxygen pressure of 10-6 mbar and the electrical properties of the interface are dominated by the presence of oxygen vacancies. By increasing the oxygen pressure above 10-4 mbar, the substrate itself is insulating but the interface still shows metallic conductivity. However, the interface becomes insulating at an oxygen pressure of 5x10-2 mbar. We also found that the interface exhibits insulator-to-metal transition by changing the laser fluence during the deposition of the film. The interface prepared at 5x10-2 mbar shows metallic conductivity at high fluence, above 3.5 J/cm 2 .

Cationic Disorder and Phase Segregation inLaAlO3/SrTiO3Heterointerfaces Evidenced by Medium-Energy Ion Spectroscopy

“…Another important feature of the LAO/STO interface is the dependence of its electrical properties on oxygen pressure during deposition of the LAO film. An increase of the oxygen pressure results in decreased conductivity and even insulating behavior [7,8]. These observations are difficult to explain altogether assuming electronic or ionic models separately.…”

Optoelectronic Functionality of BiFeO3–SrTiO3 Interface

“…As it was previously reported, STO is a wide band gap semiconductor with a band gap of about 3.2 eV and is n‐doped by the pristine oxygen vacancies. [ 21 ] The oxygen vacancy in STO introduces defect levels at 0.28–0.7 eV under the conduction band, which can be easily photoionized. [ 10 ] Moreover, previous studies showed that the STO surface (within a few nm) accumulates oxygen vacancies that induce shallow defect levels within the band gap.…”

Ultrathin Perovskites: From Bulk Structures to New Interface Concepts

“…Consequently, a polar discontinuity arises at the interface. Depending on the substrate termination, this system can be either insulating or conductive, where the charge carrier density and mobility depends on the LaAlO 3 thickness and the growth conditions [15][16][17][18][19]. Although a large number of complementary method have been applied to investigate the system, the reason for its unusual behavior is still under debate.…”