Control of the growth and domain structure of epitaxial SrRuO3 thin films by vicinal (001) SrTiO3 substrates

Gan, Q.; Rao, R. A.; Eom, C. B.

doi:10.1063/1.118792

Cited by 122 publications

(82 citation statements)

References 10 publications

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“…At the scan of SrRuO 3 ͑221͒ reflection, measured for 100 nm thick film, four peaks separated by 90°from each other were observed. This result, as shown before in PLD experiments, 27 indicates the coexistence of two orthorhombic SrRuO 3 domains with ͓110͔ axis normal to the substrate and two in-plane epitaxial arrangements of SrRuO 3 ͓001͔ ʈ SrTiO 3 ͓010͔ and SrRuO 3 ͓001͔ ʈ SrTiO 3 ͓100͔.…”

Section: Resultssupporting

confidence: 65%

“…The best films, with a room temperature resistivity of about 150-300 ⍀ cm, root mean square ͑rms͒ roughness about 0.1 nm, and rocking curves with full width at half maximum ͑FWHM͒ lower than 0.1°, have been produced at temperatures of 640-800°C and oxygen pressures of 0.1-0.4 mbar. 11,26 Several other procedures, such as 90°o ff-axis sputtering 27 in temperature and pressure ranges of 300-680°C and 0.03-0.1 mbar, respectively, techniques requiring extremely low oxygen pressures ͑10 −6 -10 −3 mbar͒ such as magnetron sputtering, 28 ion beam sputtering, 12 or molecular beam epitaxy, 29 but also high pressure sputtering, 30 metal organic chemical vapor deposition, 31 or spin coating, 32 have been successfully applied. Most of them give results comparable to PLD.…”

Section: Introductionmentioning

confidence: 99%

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Surface layer of SrRuO3 epitaxial thin films under oxidizing and reducing conditions

Młynarczyk

Szot

Petraru

et al. 2007

Journal of Applied Physics

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Imperfect stoichiometry and heterogeneity of a surface layer of SrRuO3 epitaxial thin films, grown on SrTiO3 substrates, are presented with the help of various methods. Rutherford backscattering spectroscopy, x-ray photoemission spectroscopy (XPS), and time of flight secondary ion mass spectrometry are used to obtain information about the stoichiometry and uniformity of the SrRuO3 structure. The temperature of chemical decomposition is first determined for polycrystalline samples under different conditions using thermogravimetry analysis. Then the determined values are used for thin film annealings in high and low oxygen pressure ambients, namely, air, vacuum, and hydrogen. The surface deterioration of the thin film together with changes in its electronic structure is investigated. O1s and Sr3d core lines measured by XPS for as-made samples obviously consist of multiple components indicating different chemical surroundings of atoms. Thanks to different incident beam angle measurements it is possible to distinguish between interior and surface components. Valence band spectra of the interior of the film are consistent with theoretical calculations. After annealing, the ratio of the different components changes drastically. Stoichiometry near the surface changes, mostly due to ruthenium loss (RuOX) or a segregation process. The width and position of the Ru3p line for as-made samples suggest a mixed oxidation state from metallic to fully oxidized. Long annealing in hydrogen or vacuum ambient leads to a complete reduction of ruthenium to the metallic state. Local conductivity atomic force microscopy scans reveal the presence of nonconductive adsorbates incorporated in the surface region of the film. Charge transport in these measurements shows a tunneling character. Scanning tunneling microscopy scans show some loose and mobile adsorbates on the surface, likely containing hydroxyls. These results suggest that an adequate description of a SrRuO3 thin film should take into account imperfections and high reactivity of its surface region.

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Section: Resultssupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Surface layer of SrRuO3 epitaxial thin films under oxidizing and reducing conditions

Młynarczyk

Szot

Petraru

et al. 2007

Journal of Applied Physics

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“…If the step edges run only along SrTiO 3 [100] or [010] directions then a single domain SrRuO 3 layer is formed. On the other hand, if the step edges run along direction rotated by some angle from [100] or [010] directions, SrRuO 3 will attach to steps with its longer unit cell axis parallel to the steps resulting in twinned structure, due to the serrated nature of the step edge, as was already observed by Gan et al 9 SrRuO 3 layers on substrates with low miscut angles exhibit twinned structures due to large length of the substrate terraces as compared to the diffusion length of SrRuO 3, which results in island growth. In this regime SrRuO 3 tetragonal unit cell tends to align randomly along [100] and [010] directions of the SrTiO 3 substrate.…”

mentioning

confidence: 60%

Strain-induced single-domain growth of epitaxial SrRuO3 layers on SrTiO3: A high-temperature x-ray diffraction study

Vailionis

Siemons

Koster

2007

Applied Physics Letters

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Temperature dependent structural phase transitions of SrRuO 3 thin films epitaxially grown on SrTiO 3 (001) single crystal substrates have been studied using high-resolution x-ray diffraction. In contrast to bulk SrRuO 3 , coherently strained epitaxial layers do not display cubic symmetry up to ~730 o C and remain tetragonal. Such behavior is believed to be induced by compressive strain between the SrRuO 3 layer and SrTiO 3 substrate due to lattice mismatch. The perovskite SrRuO 3 (SRO) thin films have attracted considerable interest due to their low room temperature resistivity and small lattice mismatch with a range of functional oxide materials. [1][2][3] In order for SrRuO 3 to grow coherently on a single crystal substrate, matching of layer in-plane lattice parameter to that of a substrate is required. The mismatch between in-plane lattice parameters of a film and the substrate introduces strain which affects the structural and electrical properties of the SrRuO 3 layer.For bulk SrRuO 3 , x-ray and neutron diffraction studies show that at room temperature the SrRuO 3 structure possesses an orthorhombic Pbnm symmetry with a = 5.5670 Å, b = 5.5304 Å, and c = 7.8446 Å, similar to other ABO 3 perovskite compounds, and is isostructural with GdFeO 3 . 4 The orthorhombic phase can be obtained by rotation of BO 3 (RuO 3 ) octahedra counterclockwise about the [010] cubic and [001] cubic directions and clockwise rotation about the [100] cubic direction of an ABO 3 cubic perovskite. At around 550 o C, the orthorhombic structure transforms into a tetragonal one with the space group I4/mcm. 5 In the tetragonal unit cell, RuO 3 octahedra are rotated only about the [001] cubic ABO 3 direction. At even higher temperatures of about 680 o C, tetragonal SrRuO 3 transforms into a cubic structure with a standard perovskite space group Pm3m where no rotations of RuO 3 octahedra are observed. 5 As reported by Maria et al.,6 thin SRO films grown on SrTiO 3 (001) (STO) substrates undergo an orthorhombic to tetragonal (O-T) structural phase transition at a somewhat lower temperature of ~350 o C. They also measured a tetragonal to cubic (T-C) phase transition temperature of ~600 o C, but this was obtained from a bulk SrRuO 3 sample. The suggested transitions imply that SrRuO 3 exhibits cubic symmetry during film synthesis, which is typically in the range of 600-700 o C. 6 Since the T-C transition was observed on a powder SrRuO 3 sample, which does not represent conditions of commensurate strained layer growth, it is still unclear what crystal symmetry strained epitaxial SrRuO 3 layer possesses during growth under constrained geometries imposed by the substrate.

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“…1 The strong magnetocrystalline anisotropy in single-domain thin films 2,3 as well as crystals makes SrRuO 3 especially suitable for use in magnetic tunnel junctions, provided that single-domain heterostructures are achievable. 4,5 Furthermore, ferromagnetic SrRuO 3 has been used as a model system to study the initial growth, with special attention to surface termination and growth mode. 6 Because their application is mostly in mirror-symmetric trilayer junction configurations, growth control of the individual layers, as well as the atomic stacking sequence at the interfaces, is required.…”

mentioning

confidence: 99%

Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth

Rijnders

Blank

Choi

et al. 2004

Applied Physics Letters

170

188

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During the initial growth of the ferromagnetic oxide SrRuO 3 on TiO 2 -terminated SrTiO 3 , we observe a self-organized conversion of the terminating atomic layer from RuO 2 to SrO. This conversion induces an abrupt change in growth mode from layer by layer to growth by step advancement, indicating a large enhancement of the surface diffusivity. This growth mode enables the growth of single-crystalline and single-domain thin films. Both conversion and the resulting growth mode enable the control of the interface properties in heteroepitaxial multilayer structures on an atomic level.

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Control of the growth and domain structure of epitaxial SrRuO3 thin films by vicinal (001) SrTiO3 substrates

Cited by 122 publications

References 10 publications

Surface layer of SrRuO3 epitaxial thin films under oxidizing and reducing conditions

Surface layer of SrRuO3 epitaxial thin films under oxidizing and reducing conditions

Strain-induced single-domain growth of epitaxial SrRuO3 layers on SrTiO3: A high-temperature x-ray diffraction study

Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth

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