Influence of oxygen reduction on the structural and electronic properties of electron-doped Sr1−xLaxCuO2 thin films

Abstract

Single phase, c-axis oriented, e-doped, Sr 1-x La x CuO 2 thin films were epitaxially grown on KTaO 3 and DyScO 3 substrates by reactive rf sputtering. As-grown films being insulating due to oxygen excess, oxygen reduction is necessary to observe superconductivity. Two different procedures were employed to reach superconductivity.On one hand an in-situ reduction process was conducted on a series of films deposited on both types of substrates. On the other hand, an ex-situ reduction procedure was performed sequentially on a single film deposited on DyScO 3 . The study of the influence of oxygen reduction on the structural and electronic properties of the thin films is presented and discussed.

Properties of the electron-doped infinite-layer superconductor Sr1−xLaxCuO2Tomaschko1, Leca2, Selistrovski3 et al. 2012Phys. Rev. B182100View full textAdd to dashboardCite

“…12 (b). In accordance with literature 27,48 we found that the c-axis decreases and the a-axis increases monotonically during reduction. Furthermore, we found that the unit cell volume V increases as well (cf.…”

“…As excess oxygen forms O 2− ions on interstitial sites, it traps free charge carriers from the CuO 2 planes, which increases the resistivity and suppresses superconductivity. Therefore, ρ 300K decreases and T c increases with the removal of excess oxygen, as reported before 27,48 . We further observed the reduction process by analyzing the evolution of the lattice constants with proceeding t a , as displayed in Fig.…”

“…Therefore, as for T ′ -compounds 25 , a vacuum annealing step was introduced to remove excess oxygen and to induce superconductivity. Mean-while, this reduction step is commonly used for synthesis of superconducting IL films grown by numerous techniques, such as sputtering 26,27 , pulsed laser deposition (PLD) 20,21 and MBE 22,23 . However, too strong reduction generates oxygen vacancies in the CuO 2 planes and destroys superconductivity 22,27,28 .…”

“…Mean-while, this reduction step is commonly used for synthesis of superconducting IL films grown by numerous techniques, such as sputtering 26,27 , pulsed laser deposition (PLD) 20,21 and MBE 22,23 . However, too strong reduction generates oxygen vacancies in the CuO 2 planes and destroys superconductivity 22,27,28 . A secondary phase can be formed if the oxygen vacancies arrange in an ordered structure, referred to in literature as the "long c-axis" phase or "infinite-layer-related" (IL-r) phase 20,26,[29][30][31] .…”

Spin and charge excitations in artificial hole- and electron-doped infinite layer cuprate superconductors

“…IL cuprates are particularly interesting because of their crystallographic structure: the simplest among layered cuprates. On the other hand, the IL compounds are metastable and single crystal can be stabilized only in thin film form [23][24][25][26][27][28] .…”