Observation of strontium segregation in LaAlO3/SrTiO3 and NdGaO3/SrTiO3 oxide heterostructures by X-ray photoemission spectroscopy

Treske, Uwe; Heming, Nadine; Knupfer, M.; Büchner, B.; Koitzsch, A.; Gennaro, Emiliano Di; Uccio, U. Scotti di; Granozio, F. Miletto; Krause, Stefan

doi:10.1063/1.4861797

Cited by 13 publications

(12 citation statements)

References 38 publications

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“…The grey component is thus attributed to Ti atoms in a TiO 2 environment, and labelled Ti-TiO 2 in the following. Similarly, the chemical shift between the blue and pink components in the Sr3d core levels of samples A, B and E is 1.24 eV, in the same range as that reported for the chemical shift between Sr in a SrO environment and Sr in a STO environment (in the 1-1.2eV range 21,22,23 ). This component, labelled Sr-SrO in the following, is thus attributed to Sr atoms in a SrO environment.…”

Section: Figure 1 : Stem Images Of Samples C D E and Hsupporting

confidence: 81%

Epitaxy of SrTiO₃ on Silicon: The Knitting Machine Strategy

et al. 2016

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Functional oxides of the perovskite family present a variety of physical properties (ferroelectricity, ferromagnetism, superconductivity, high Pockels coefficients, …) that make them very attractive for applications in the micro-optoelectronic field. 1 These materials are classically used as thin layers grown on oxide substrates, mainly SrTiO 3 (STO). Important perspectives for the integration of new functionalities on silicon and other semiconductor platforms, and therefore for the fabrication of innovative devices combining the physical properties of functional oxides and semiconductors, are offered by the advances in epitaxy of ABO 3 perovskites on semiconductors using molecular beam epitaxy (MBE). From the material science point of view, STO/Si can be considered as a prototypical system to understand the impact of structural and chemical heterogeneity on crystal growth. Controlling the chemical reactions between the growing layer and the substrate is one of the main challenges related to the epitaxial growth of perovskite oxides on semiconductor and particularly STO on Si, as the interface between these materials has been predicted as thermodynamically instable. 2 This is to a certain extent made possible by using a Sr-based treatment of the Si surface, as evidenced since the very first studies of this system 3,4 , and popularized by McKee et al. 5 Such procedure or its

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Section: Figure 1 : Stem Images Of Samples C D E and Hsupporting

confidence: 81%

Epitaxy of SrTiO₃ on Silicon: The Knitting Machine Strategy

et al. 2016

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“…The clear defect candidate for this is a strontium vacancy V 00 Sr . As reported in the literature [18,20,21,32,80], these are readily induced at oxide interfaces during growth and annealing procedures [24], such as indicated, e.g., by observation of SrO segregation during growth of LAO (and NGO) [34]. The Schottky equilibrium is active during the PLD growth process [21,54,80], so that the variation of the p dep affects the strontium vacancy concentration present at the NGO/STO interface.…”

Section: ••mentioning

confidence: 78%

“…Sharing a similar ionic structure with LAO (A 3þ B 3þ O 3 ), NGO generally causes a similar interface reconstruction as LAO when grown on f100g STO [32][33][34]. However, NGO possesses Nd 3þ ions carrying a magnetic moment that is not present in LAO.…”

Section: Introductionmentioning

confidence: 99%

Defect Control of Conventional and Anomalous Electron Transport at Complex Oxide Interfaces

et al. 2016

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Using low-temperature electrical measurements, the interrelation between electron transport, magnetic properties, and ionic defect structure in complex oxide interface systems is investigated, focusing on NdGaO 3 =SrTiO 3 (100) interfaces. Field-dependent Hall characteristics (2-300 K) are obtained for samples grown at various growth pressures. In addition to multiple electron transport, interfacial magnetism is tracked exploiting the anomalous Hall effect (AHE). These two properties both contribute to a nonlinearity in the field dependence of the Hall resistance, with multiple carrier conduction evident below 30 K and AHE at temperatures ≲10 K. Considering these two sources of nonlinearity, we suggest a phenomenological model capturing the complex field dependence of the Hall characteristics in the low-temperature regime. Our model allows the extraction of the conventional transport parameters and a qualitative analysis of the magnetization. The electron mobility is found to decrease systematically with increasing growth pressure. This suggests dominant electron scattering by acceptor-type strontium vacancies incorporated during growth. The AHE scales with growth pressure. The most pronounced AHE is found at increased growth pressure and, thus, in the most defective, low-mobility samples, indicating a correlation between transport, magnetism, and cation defect concentration.

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“…A recent experiment revealed that, in the well-known (TiO 2 ) 0 /(LaO) 1+ LAO/STO HS system, the Sr atoms can even diffuse from the interface to the surface, forming SrO surface layer. [28] As discussed later, after structural relaxation, strong polarization may occur in the CZO/STO HS models. The periodic boundary condition in the supercell approach determines that there might exist an electric-field interaction between the surface of the STO substrate and the surface of the CZO film, though the strength strongly depends on the vacuum thickness.…”

Section: Structural Modeling and Computational Detailsmentioning

confidence: 91%

Creating Two-Dimensional Electron Gas in Nonpolar/Nonpolar Oxide Interface via Polarization Discontinuity: First-Principles Analysis of CaZrO₃/SrTiO₃ Heterostructure

Nazir

Cheng

Yang

2015

ACS Appl. Mater. Interfaces

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We studied strain-induced polarization and resulting conductivity in the nonpolar/nonpolar CaZrO3/SrTiO3 (CZO/STO) heterostructure (HS) system by means of first-principles electronic structure calculations. By modeling four types of CZO/STO HS-based slab systems, i.e., TiO2/CaO and SrO/ZrO2 interface models with CaO and ZrO2 surface terminations in each model separately, we found that the lattice-mismatch-induced compressive strain leads to a strong polarization in the CZO film, and as the CZO film thickness increases, there exist an insulator-to-metal transition. The polarization direction and critical thickness of the CZO film for forming interfacial metallic states depend on the surface termination of CZO film in both types of interface models. In the TiO2/CaO and SrO/ZrO2 interface models with CaO surface termination, the strong polarization drives the charge transfer from the CZO film to the first few TiO2 layers in the STO substrate, leading to the formation of Two-Dimensional Electron Gas (2DEG) at the interface. In the HS models with ZrO2 surface termination, two polarization domains with opposite directions were formed in the CZO film, which results in the charge transfer from the middle CZO layer to the interface and surface, respectively, leading to the co-existence of the 2DEG on the interface and the Two-Dimensional Hole Gas (2DHG) at the middle CZO layer. These findings open a new avenue to achieve 2DEG (2DHG) in perovskite-based HS systems via polarization discontinuity.

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Observation of strontium segregation in LaAlO3/SrTiO3 and NdGaO3/SrTiO3 oxide heterostructures by X-ray photoemission spectroscopy

Cited by 13 publications

References 38 publications

Epitaxy of SrTiO₃ on Silicon: The Knitting Machine Strategy

Epitaxy of SrTiO₃ on Silicon: The Knitting Machine Strategy

Defect Control of Conventional and Anomalous Electron Transport at Complex Oxide Interfaces

Creating Two-Dimensional Electron Gas in Nonpolar/Nonpolar Oxide Interface via Polarization Discontinuity: First-Principles Analysis of CaZrO₃/SrTiO₃ Heterostructure

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Observation of strontium segregation in LaAlO3/SrTiO3 and NdGaO3/SrTiO3 oxide heterostructures by X-ray photoemission spectroscopy

Cited by 13 publications

References 38 publications

Epitaxy of SrTiO3 on Silicon: The Knitting Machine Strategy

Epitaxy of SrTiO3 on Silicon: The Knitting Machine Strategy

Defect Control of Conventional and Anomalous Electron Transport at Complex Oxide Interfaces

Creating Two-Dimensional Electron Gas in Nonpolar/Nonpolar Oxide Interface via Polarization Discontinuity: First-Principles Analysis of CaZrO3/SrTiO3 Heterostructure

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Product

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Epitaxy of SrTiO₃ on Silicon: The Knitting Machine Strategy

Epitaxy of SrTiO₃ on Silicon: The Knitting Machine Strategy

Creating Two-Dimensional Electron Gas in Nonpolar/Nonpolar Oxide Interface via Polarization Discontinuity: First-Principles Analysis of CaZrO₃/SrTiO₃ Heterostructure