Synthesis and electronic properties of Ruddlesden-Popper strontium iridate epitaxial thin films stabilized by control of growth kinetics

Abstract

We report on the selective fabrication of high-quality Sr2IrO4 and SrIrO3 epitaxial thin films from a single polycrystalline Sr2IrO4 target by pulsed laser deposition. Using a combination of X-ray diffraction and photoemission spectroscopy characterizations, we discover that within a relatively narrow range of substrate temperature, the oxygen partial pressure plays a critical role in the cation stoichiometric ratio of the films, and triggers the stabilization of different Ruddlesden-Popper (RP) phases. Resonant X-ray absorption spectroscopy measurements taken at the Ir L-edge and the O K-edge demonstrate the presence of strong spin-orbit coupling, and reveal the electronic and orbital structures of both compounds. These results suggest that in addition to the conventional thermodynamics consideration, higher members of the Srn+1IrnO3n+1 series can possibly be achieved by kinetic control away from the thermodynamic limit. These findings offer a new approach to the synthesis of ultra-thin films of the RP series of iridates and can be extended to other complex oxides with layered structure.

Strange semimetal dynamics in SrIrO3

“…Thus, the value we determine here for the room temperature resistivity of our SIO film is reasonably close to that determined using conventional resistivity measurements (see Supplementary Fig. 9), and is consistent with the values of 0.5-2 mΩ cm reported in the literature 15,18,28,29 . Given, as discussed above, that the Hall measurements tends to overestimate the electron charge-carrier density, both values for the resistivity extracted from the ERS measurements are slightly underestimated, and the agreement with transport is overall very satisfactory at room temperature.…”

“…For most of the substrates, significant lattice mismatches induce large strain effects, as well as, for example, twin or grain boundaries that considerably affect the electrodynamics of the system. The Hall coefficient, the carrier density, or the resistivity have recently been reported to be strongly substrate and film thickness dependent 18 , 22 , 28 , 29 , and also indicate strong strain–relaxation effects. As both first-principles calculations 12 , 13 and ARPES 15 , 16 investigations have shown that the hole and electron pockets crossing the Fermi level occupy distinct regions of the reciprocal space, the way towards momentum-selective studies of the charge dynamics 30 – 32 in SIO via electronic Raman scattering (ERS) is paved.…”

Interfacial charge-transfer Mott state in iridate–nickelate superlattices

“…All superlattices were deposited on a (001) SrTiO 3 substrate. Sintered Sr 2 IrO 4 and LaNiO 3 targets were alternately ablated by a KrF excimer laser (λ = 248 nm, fluence ∼2 J·cm −2 ) at 2 Hz and 10 Hz, respectively (38,51). A substrate temperature of 650 • C and an oxygen partial pressure of 50 mTorr were maintained during deposition.…”

Highly Efficient Adsorption of Sr2+ and Co2+ Ions by Ambient Prepared Alkali Activated Metakaolin

“…However, the adsorption kinetics observed in the present work and the experimental data all fitted the PSO model, regardless of the initial concentration, implying that no obvious desorption occurred. The PSO model is based on the assumption that the rate-limiting-step is chemisorption, involving a sharing or exchange of electron between the adsorbent and adsorbate [ 25 , 26 , 27 , 28 ]. In addition, the rate constant was dependent on the initial concentration, which was another characteristic of the chemical exchange reaction [ 22 ].…”