Spectroscopic properties of oxygen vacancies inLaAlO3

Abstract

Oxygen vacancies in LaAlO 3 (LAO) play an important role in the formation of the 2-dimensional electron gas observed at the LaAlO 3 /SrTiO 3 interface and affect the performance of MOSFETs using LAO as a gate dielectric. However, their spectroscopic properties are still poorly understood, which hampers their experimental identification. Here we predict the absorption spectra and ESR parameters of oxygen vacancies in LAO using periodic and embedded cluster methods and Density Functional Theory (DFT). The structure, charge distribution, and spectroscopic properties of the neutral (V 0 O) and charged (V + O and V 2+ O) oxygen vacancies in cubic and rhombohedral LaAlO 3 are investigated. The highest intensity optical transitions (calculated using time dependent DFT (TDDFT)), from the oxygen vacancy states to the conduction band states have onsets at 3.5 and 4.2 eV for V 0 O and 3.6 eV for V + O in rhombohedral LAO and 3.3 and 4.0 eV for V 0 O and 3.4 eV for V + O in cubic LAO, respectively. Also reported are the isotropic g-value (2.004026) and hyperfine coupling constants of V + O which are compared to the experimental data obtained using electron spin resonance (ESR) spectroscopy, and accurately predict both the position and the width (3 mT) of its ESR signature. These results may further facilitate the experimental identification of oxygen vacancies in LAO and help to establish their role at the LAO/STO interfaces and in nanodevices using LAO.

Oxygen Diode Formed in Nickelate Heterostructures by Chemical Potential Mismatch

“…V O formation energies of BTO, [55,56] LAO, [57,58] and STO [59][60][61][62][63][64] are much greater than that of LNO. Therefore, one would expect that the V O would form preferentially in the underlying LNO layer rather than in the capping layers.…”

Room-Temperature Giant Charge-to-Spin Conversion at the SrTiO3–LaAlO3 Oxide Interface

“…[31][32][33] It is known that the defects, such as the oxygen vacancies (VO), can be present in the LAO layer during film growth and form localized states (LS) in the LAO band gap. [34][35][36][37] Hence, the IET process via these LS [31][32][33][38][39][40] via LS is the main mechanism of the spin transmission through the LAO layer, the SOT efficiency is expected to exhibit a very strong temperature dependence as indicated by the Glazman-Matveev (GM) theory, 31,33,38,41 , which describes the IET with a power law dependence on temperature.…”

“…The second possible mechanism is the inelastic tunneling (IET) process, which can be predominant when the tunneling barrier becomes thicker. − It is known that the defects, such as the oxygen vacancies (V O ), can be present in the LAO layer during film growth and form localized states (LS) in the LAO band gap. − Hence, the IET process via these LS − ,− might account for the spin transmission in our devices. The schematic of the IET process is depicted in the inset of Figure a, where the spin-polarized electrons (denoted by the blue dots) in the 2DEG layer inelastically tunnel into the CFB layer via the LS (the oxygen vacancies V O are denoted by the short red lines) in the LAO band gap with the assistance of phonon or electrical field.…”

The Role of Rare Earth Lanthanum Oxide in Polymeric Matrix Brake Composites to Replace Copper

“…Compared with La 2 O 3 , LaAlO 3 shows hexagonal crystals as well [39], which is similar to layered structures with lower melting points and lower hardness, and is more conducive to the formation of continuous and compacted friction films. LaAlO 3 can be used in functional ceramics with high quality [40].…”