Epitaxial optimization of atomically smooth Sr3Al2O6 for freestanding perovskite films by molecular beam epitaxy

Sun, Haoying; Zhang, C.C.; Song, Jianhui; Gu, Jianfei; Zhang, T.W.; Zang, Yipeng; Li, Y.F.; Gu, Zheng‐Bin; Wang, P.; Nie, Yuefeng

doi:10.1016/j.tsf.2020.137815

Cited by 25 publications

(40 citation statements)

References 38 publications

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“…Reported texture analysis for physical deposited SAO films, molecular beam epitaxy (MBE), show rocking curve FWHM values slightly smaller, that is, FWHM = 0.015° (FWHM= 0.013° for STO). [20] Cross-sectional Z-contrast high angle annular dark field (HAADF) using scanning transmission electron microscopy (STEM), Figure 3d,e, further confirms the epitaxial growth of SAO film on the STO (001) substrate. The HAADF-STEM images show high crystal quality and sharp interface.…”

Section: (3 Of 7)mentioning

confidence: 60%

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Facile Chemical Route to Prepare Water Soluble Epitaxial Sr₃Al₂O₆ Sacrificial Layers for Free‐Standing Oxides

Sallés

Cano

Guzmán

et al. 2021

Adv Materials Inter

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crystal substrates when epitaxial growth is pursued. These requirements dramatically limit their applicability excluding the possibility to prepare many artificial multilayered architectures to investigate emergent phenomena that arise in thin films and at their interfaces, [2] as well as the fabrication of flexible devices and monolithic integration into silicon. [3-5] Many efforts have been devoted to develop procedures to detach the functional oxide film from the growth substrate in order to be able to freely manipulate it. They include mechanical exfoliation, [6] dry etching, [7,8] and wet-chemical etching. [9,10] Among the chemical etching procedures, the use of a sacrificial layer, which is incorporated between the substrate and the functional oxide, appears as a fast and relatively low-cost process. For this approach to be successful, the sacrificial layer should transfer the epitaxy from the substrate to the desired oxide, stand the deposition process of the functional oxide and be selectively removed by a chemical treatment, which allows to retrieve the original single-crystal substrate. (La,Sr)MnO 3 has been proved effective to be selectively etched by an acid blend allowing the transfer of single epitaxial Pb(Zr,Ti)O 3 layers [11] and more complex architectures such as SrRuO 3 /Pb(Zr,Ti)O 3 /SrRuO 3. [12] Recently, the use of water-soluble Sr 3 Al 2 O 6 (SAO) sacrificial layer enlarged the family of free-standing epitaxial perovskite oxide layers (SrTiO 3 , BiFeO 3 , BaTiO 3) [13-15] and multilayers (SrTiO 3 /(La,Sr) MnO 3) [16] that can be manipulated opening a whole new world of opportunities. [5,10,17] The deposition techniques to prepare such structures is also a key factor to be considered not only for film quality but also for process scalability. While high vacuum deposition techniques such as molecular beam epitaxy and pulsed laser deposition are well established techniques to produce high quality films, [1,18-20] alternate procedures that can deliver low-cost production such as solution processing and atomic layer deposition are gaining interest. [21,22] Chemical solution deposition (CSD) is considered a mature technique for the preparation of oxide films. The synthesis of ternary and quaternary oxides is not a trivial task but the pioneering work done in ferroelectric lead zirconate titanate inspired many researchers to extend it to other compositions and broaden the application fields. [23,24] Nonetheless, there is still a myriad of compositions to be explored, including SAO, The growth of epitaxial complex oxides has been essentially limited to specific substrates that can induce epitaxial growth and stand high temperature thermal treatments. These restrictions hinder the opportunity to manipulate and integrate such materials into new artificial heterostructures including the use of polymeric and silicon substrates and study emergent phenomena for novel applications. To tackle this bottleneck, herein, a facile chemical route to prepare water-soluble epitaxial Sr 3 Al 2 O 6 thin films to be ...

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Section: (3 Of 7)mentioning

confidence: 60%

“…Note that MBE and pulsed laser deposition films of thickness ranging from 8 unit cells to 20 nm show a step-and-terrace surface morphology (with rms <0.7 nm), replicating the STO surface. [15,16,20] Importantly, SAO exposure to ambient moisture can severely degrade the surface morphology.…”

Section: (3 Of 7)mentioning

confidence: 99%

Facile Chemical Route to Prepare Water Soluble Epitaxial Sr₃Al₂O₆ Sacrificial Layers for Free‐Standing Oxides

Sallés

Cano

Guzmán

et al. 2021

Adv Materials Inter

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“…Therefore, the growth condition of the SAO sacrificial buffer layers should be optimized to show clear fourfold reconstructed electron diffraction pattern that illustrates four intensity oscillation periods in the growth of one u.c. SAO as seen in Figure 1b (left) and descripted elsewhere . After the growth of PTO layer, reflection high‐energy electron diffraction (RHEED) patterns still remain visible (Figure 1b, right), which indicates high quality of the films.…”

mentioning

confidence: 86%

Giant Uniaxial Strain Ferroelectric Domain Tuning in Freestanding PbTiO₃ Films

Han

Fang

Zhao

et al. 2020

Adv Materials Inter

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regenerated much attention to the search for phases that do not exist in the parent bulk materials. [1] Structures such as vortex pairs, super-tetragonal phase, and polar skyrmions have been experimentally reported. [2][3][4][5][6][7][8] In essence, the formation of ferroelectric domain structures strongly relies on the balance between electrostatic and elastic energies which is sensitively affected by film thickness, substrate mismatch strain, depolarization field, cooling rate, etc. [9][10][11][12][13] Previous works have both experimentally and theoretically studied the size and strain effects in ferroelectric thin films; however, continuously manipulating the strain or tuning the dimensionality without the influence of strain is rarely achieved due to the substrate clamping. [14][15][16][17][18][19] In order to stabilize and manipulate domain structures in ferroelectrics which usually depend on precise control of strain and thickness, as well as to understand the intrinsic evolution of ferroelectricity and domain structures, it is essential to investigate freestanding films that are free of substrate constraints and allow in situ and continuous strain engineering.In principle, several ways are feasible to prepare freestanding films, including the mechanical polishing to micrometer scales, [20][21][22] etching rigid substrates, [23] and "grow-transfer" multi-step methods (first growing films on rigid substrates, and then transferring to other substrates). [24][25][26][27] These techniques are highly selective or difficult to generalize to a wide range of perovskite oxides. Recently, Lu et al. [28] reported a new way to synthesize high-quality freestanding perovskite oxides using water-soluble Sr 3 Al 2 O 6 (SAO) as a sacrificial buffer layer, allowing the synthesis of high-crystalline-quality freestanding films, [29,30] even down to the monolayer limit. [31] Herein, we synthesize freestanding PbTiO 3 (PTO) films with thicknesses from 60 to 4 unit cells (u.c.), showing single-crystalline c-axis oriented domain. The tetragonality and ferroelectricity are suppressed with the decreasing of film thickness, and at the same time, by applying uniaxial tensile strain up to 6.4% along a-axis, we flip the long axis (c-axis) into [100] direction and observe the switchable behavior of these a domains. Our work demonstrates that giant uniaxial strain can be achieved continuously in the freestanding films, paving the way for the usage of high electromechanical conversion efficiency actuators, such as Dimensionality and epitaxial strain have been recently utilized to engineer the interplay between the electrostatic and elastic energies to stabilize exotic ferroelectric domain structures and topological textures in epitaxial heterostructures and superlattices. As the strain state is fixed to the substrate lattice, the strain tunability is discrete and limited, which puts a hard constraint on the exploration and engineering of emergent ferroelectric properties in these thin films and heterostructures. Here, by using water-solub...

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“…As mentioned above, the precise deposition time of each source is not available using the shuttered mode. In the codeposition, although the oscillations are observed, the overall intensity shows little dependence on the variation of the Nd:Ni flux ratio, which is commonly employed in the growth of other systems [40,41]. Hence, another specific way is demanded to conduct the calibration.…”

Section: Effect Of Cation Stoichiometry On Ndnio 3 Filmsmentioning

confidence: 99%

Impact of Cation Stoichiometry on the Crystalline Structure and Superconductivity in Nickelates

Sun

Yang

et al. 2021

Front. Phys.

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The recent discovery of superconductivity in infinite-layer nickelate films has aroused great interest since it provides a new platform to explore the mechanism of high-temperature superconductivity. However, superconductivity only appears in the thin film form and synthesizing superconducting nickelate films is extremely challenging, limiting the in-depth studies on this compound. Here, we explore the critical parameters in the growth of high-quality nickelate films using molecular beam epitaxy. We found that stoichiometry is crucial in optimizing the crystalline structure and realizing superconductivity in nickelate films. In precursor NdNiO3 films, optimal stoichiometry of cations yields the most compact lattice while off-stoichiometry of cations causes obvious lattice expansion, influencing the subsequent topotactic reduction and the emergence of superconductivity in infinite-layer nickelates. Surprisingly, in-situ reflection high energy electron diffraction indicates that some impurity phases always appear once Sr ions are doped into NdNiO3 although the X-ray diffraction data are of high quality. While these impurity phases do not seem to suppress the superconductivity, their impacts on the electronic and magnetic structure deserve further studies. Our work demonstrates and highlights the significance of cation stoichiometry in the superconducting nickelate family.

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Epitaxial optimization of atomically smooth Sr3Al2O6 for freestanding perovskite films by molecular beam epitaxy

Cited by 25 publications

References 38 publications

Facile Chemical Route to Prepare Water Soluble Epitaxial Sr₃Al₂O₆ Sacrificial Layers for Free‐Standing Oxides

Facile Chemical Route to Prepare Water Soluble Epitaxial Sr₃Al₂O₆ Sacrificial Layers for Free‐Standing Oxides

Giant Uniaxial Strain Ferroelectric Domain Tuning in Freestanding PbTiO₃ Films

Impact of Cation Stoichiometry on the Crystalline Structure and Superconductivity in Nickelates

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Epitaxial optimization of atomically smooth Sr3Al2O6 for freestanding perovskite films by molecular beam epitaxy

Cited by 25 publications

References 38 publications

Facile Chemical Route to Prepare Water Soluble Epitaxial Sr3Al2O6 Sacrificial Layers for Free‐Standing Oxides

Facile Chemical Route to Prepare Water Soluble Epitaxial Sr3Al2O6 Sacrificial Layers for Free‐Standing Oxides

Giant Uniaxial Strain Ferroelectric Domain Tuning in Freestanding PbTiO3 Films

Impact of Cation Stoichiometry on the Crystalline Structure and Superconductivity in Nickelates

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Facile Chemical Route to Prepare Water Soluble Epitaxial Sr₃Al₂O₆ Sacrificial Layers for Free‐Standing Oxides

Facile Chemical Route to Prepare Water Soluble Epitaxial Sr₃Al₂O₆ Sacrificial Layers for Free‐Standing Oxides

Giant Uniaxial Strain Ferroelectric Domain Tuning in Freestanding PbTiO₃ Films