Nanosession: Ionics ‐ Lattice Disorder and Grain Boundaries

Unravelling the Origin of Ultra‐Low Conductivity in SrTiO3 Thin Films: Sr Vacancies and Ti on A‐Sites Cause Fermi Level Pinning

“…Comparing the near surface signal of the film with the signal of the pure bulk sample reveals several differences. In the thin film, the predominant point defect is the Sr vacancy (lifetime: 281ps [ 58 ] ), which is in agreement with the chemical analysis (see Section 2.2) as well as the RSM data (see Section 2.3). In undoped single crystals the predominant cation vacancies seem to be titanium vacancies (lifetime: 189ps [ 58 ] ), see ref.…”

“…In the thin film, the predominant point defect is the Sr vacancy (lifetime: 281ps [ 58 ] ), which is in agreement with the chemical analysis (see Section 2.2) as well as the RSM data (see Section 2.3). In undoped single crystals the predominant cation vacancies seem to be titanium vacancies (lifetime: 189ps [ 58 ] ), see ref. [80] for a more detailed discussion of single crystals.…”

“…[ 70 ] Variation of the deposition parameters were often linked to the resulting thin film stoichiometry. [ 29,58 ] A proper adjustment of these parameters may thus lead to stoichiometric films and thereby prevent the effects we describe here. In our specific case, some moderate changes of laser fluence and pulse frequency were performed, but turned out to be not sufficient to achieve fully stoichiometric films, while growth from targets with Sr excess yielded stoichiometric films.…”

“…[ 51 ] SrTiO 3 thin films as well as other perovskite‐type thin films are known to show a behavior different to their single or poly‐crystalline counterparts. [ 5,19,37,52,53 ] Structural differences (interfaces, strain, stress), [ 54–56 ] dominating space charge zones, [ 5,57 ] or nonstoichiometry accommodation [ 19,29,58,59 ] in thin films have been discussed in literature and may explain deviating behavior. Even pseudo‐intrinsic electronic conductivity was previously reported for Fe‐doped SrTiO 3 thin films, meaning that a mid‐gap Fermi level pinning leads to extremely low electron and hole concentrations in differently doped samples.…”

Quantitative Determination of Native Point‐Defect Concentrations at the ppm Level in Un‐Doped BaSnO3 Thin Films

“…[ 60 ] Furthermore, if the growth kinetics would determine the defect concentrations, one would expect much higher vacancy concentrations on both cation sublattices. [ 28,62,63 ] The assumption of equilibrium values has consequences for the possibilities of lowering the concentration of BaO‐Schottky pairs. If chemical equilibrium has been attained, increasing the Ba/Sn ratio during growth will diminish the concentration of v Ba but increase the concentrations of v Sn and Ba Sn .…”