Substrate induced tuning of compressive strain and phonon modes in large area MoS 2 and WS 2 van der Waals epitaxial thin films

As one of very few room temperature multiferroic materials, bismuth ferrite (BiFeO3: BFO) has been studied extensively in recent years. The bulk form of BFO is known to have a rhombohedrally distorted quasi-cubic perovskite structure with an (a–,a–,a–) octahedral tilt pattern, exhibiting both anti-ferrodistortive displacements and a spontaneous polarization along the <111> axes. Investigating epitaxial thin films under compressive strain, several studies have reported that the polarization direction is tilted towards the [001] out-of-plane direction, while maintaining a significant in-plane component. This effect is accompanied by a significant enhancement of the spontaneous polarization and a series of phase transitions from rhombohedral (R) for small strains to R-like monoclinic (MA) to T-like monoclinic (MC) and to tetragonal (T) for larger strains [1]. Through synchrotron-based 3-dimensional reciprocal space mapping (RSM), facilitated by using X-ray area detectors (Pilatus 100K pixel detector), we have investigated the structure of ultra-thin BFO films grown on SrTiO3 (STO), LaAlO3 (LAO), and TbScO3 (TSO) substrates with thicknesses of only several unit cells. In this thickness regime, the influence of the substrate atomic structure on the properties of the ultra-thin films is very pronounced, and the films exhibit perfect heteroepitaxy up to a critical thickness when the build up of strain energy forces the films into a relaxed structure. Both on STO [2] and LAO, the ultra-thin BFO undergoes a monoclinic to tetragonal phase transition, but with very different c/a axis ratios. On TSO, a very pronounced and well-ordered stripe domainstructure evolves where the domain sizes are strongly thickness- dependent. Argonne National Laboratory's work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract DE-AC02-06CH11357.

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The Effect of Elastic Strain on the Electrical and Magnetic Properties of Epitaxial Ferromagnetic SrRuO3 Thin Films

MRS Proceedings ◽

10.1557/proc-494-269 ◽

1997 ◽

Vol 494 ◽

Cited By ~ 4

Author(s):

Q. Gan ◽

R. A. Rao ◽

J. L. Garrett ◽

Mark Lee ◽

C. B. Eom

Keyword(s):

Thin Films ◽

Magnetic Properties ◽

Elastic Strain ◽

Compressive Strain ◽

Strain Effect ◽

Epitaxial Thin Films ◽

Saturation Magnetic Moment ◽

Electrical And Magnetic Properties ◽

Lift Off ◽

Property Changes

ABSTRACTWe report the direct measurement of elastic strain effect on the electrical and magnetic properties of single domain epitaxial SrRuO3 thin films, using a lift-off technique. The as-grown films on vicinal (001) SrTiO3 substrates are subjected to elastic biaxial compressive strain within the plane and tensile strain normal to the plane. In contrast, the lift-off films prepared by chemical etching of SrTiO3 substrates, are completely strain free with bulk like lattice. Our measurements indicate that the elastic strain can significantly affect the electrical and magnetic properties of epitaxial ferromagnetic SrRuO3 thin films. For the strained films, the Curie temperature (Tc) was suppressed to 150K and the saturation magnetic moment (Ms) was decreased to 1.15μB/Ru atom as compared to a Tc of 160K and Ms of 1.45μB/Ru atom for the strain free films. These property changes are attributed to the structural distortion due to the elastic strain in the as-grown epitaxial thin films. Our results provide direct evidence of the crucial role of lattice strain in determining the properties of the perovskite epitaxial thin films.

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Application of a Desk-Side Double-Axis X-Ray Diffractometer for Very Large Area Epilayer Characterization

MRS Proceedings ◽

10.1557/proc-208-119 ◽

1990 ◽

Vol 208 ◽

Cited By ~ 2

Author(s):

Neil Loxley ◽

D. Keith Bowen ◽

Brian K. Tanner

Keyword(s):

Thin Films ◽

Lattice Mismatch ◽

Automatic Measurement ◽

Substrate Material ◽

Epitaxial Films ◽

Epitaxial Thin Films ◽

Two Dimensional ◽

Large Area ◽

X Ray ◽

Typical Data

ABSTRACTA new desk-side double-axis X-ray diffractometer capable of rapid, automatic measurement of lattice mismatch between epitaxial thin films and substrate in a two dimensional grid 150 mm square has been built. The design principles behind the five independent axis systems, specimen loading, and the fail-to-safety X-ray shutter are elucidated, and examples of typical data from substrate material and thin epitaxial films of III-V compounds are presented.

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Large area van der Waals epitaxy of II–VI CdSe thin films for flexible optoelectronics and full-color imaging

Nano Research ◽

10.1007/s12274-021-3485-x ◽

2021 ◽

Author(s):

Wenwu Pan ◽

Junliang Liu ◽

Zekai Zhang ◽

Renjie Gu ◽

Alexandra Suvorova ◽

...

Keyword(s):

Thin Films ◽

Van Der Waals ◽

Large Area ◽

Color Imaging ◽

Full Color

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TRANSPORT PHENOMENA IN La2-xBaxCuOy EPITAXIAL THIN FILMS

Modern Physics Letters B ◽

10.1142/s0217984900000859 ◽

2000 ◽

Vol 14 (17n18) ◽

pp. 639-644 ◽

Cited By ~ 1

Author(s):

G. ILONCA ◽

A. V. POP ◽

T. JURCUT ◽

C. LUNG ◽

G. STIUFIUC ◽

...

Keyword(s):

Thin Films ◽

Bond Length ◽

Spin Fluctuation ◽

Compressive Strain ◽

Resistivity Measurement ◽

Residual Resistivity ◽

Epitaxial Thin Films ◽

Superconducting Transition ◽

X Ray Diffraction ◽

Antiferromagnetic Spin

The (001) oriented thin films of La 2-x Ba xCuO4+d on SrAlO4 substrates with barium composition x = 0 to 2 were grown by DC sputtering and characterized by X-ray diffraction and resistivity measurement. The films with oxygen composition d=0 showed superconductivity for x between 0.055 and 0.30. For x = 0.15, the superconducting transition was maximized to 4.3 K. When the films had d>0, Tc reached 47 K. These values are higher than those for bulk samples. The depression of Tc around x =0.125 is smaller than that for the bulk samples. The compressive strain expands the c-axis and suppresses formation of the low-temperature tetragonal phase. Both effects result in an increase in the bond length between Cu and the apical oxygen, which is responsible for the enhancement of Tc. The samples with lower residual resistivity show a higher Tc, so we suppose that the Tc enhancement is caused by reduced antiferromagnetic spin fluctuation in the CuO2 planes due to the change in the Cu–O apical bond length.

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Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

10.26434/chemrxiv.8052218.v3 ◽

2019 ◽

Author(s):

Henrik Pedersen ◽

Björn Alling ◽

Hans Högberg ◽

Annop Ektarawong

Keyword(s):

Thin Films ◽

Thermodynamic Stability ◽

First Principles ◽

Thermal Equilibrium ◽

Density Functional ◽

Van Der Waals ◽

Chemical Vapor ◽

First Principles Calculations ◽

Functional Theory ◽

The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

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Synthesis of N-CNT/TiO2 composites thin films: surface analysis and optoelectronic properties

E3S Web of Conferences ◽

10.1051/e3sconf/202018305002 ◽

2020 ◽

Vol 183 ◽

pp. 05002 ◽

Cited By ~ 1

Author(s):

Hamza Belkhanchi ◽

Younes Ziat ◽

Maryama Hammi ◽

Charaf Laghlimi ◽

Abdelaziz Moutcine ◽

...

Keyword(s):

Thin Films ◽

Surface Analysis ◽

Sol Gel ◽

Careful Analysis ◽

Optoelectronic Properties ◽

Spectroscopic Techniques ◽

Large Area ◽

Visible Absorption ◽

Temperature Solution ◽

Good Agreement

In this study, we have investigated the surface analysis and optoelectronic properties on the synthesis of N-CNT/TiO2 composites thin films, using sol gel method for a dye synthetized solar cell (DSSC) which is found to be simple and economical route. The titanium dioxide based solar cells are an exciting photovoltaic candidate; they are promising for the realization of large area devices. That can be synthetized by room temperature solution processing, with high photoactive performance. In the present work, we stated comparable efficiencies by directing our investigation on obtaining Sol Gel thin films based on N-CNT/TiO2, by dispersing nitrogen (N) doped carbon nanotubes (N-CNTs) powders in titanium tetraisopropoxyde (TTIP). The samples were assessed in terms of optical properties, using UV—visible absorption spectroscopic techniques. After careful analysis of the results, we have concluded that the mentioned route is good and more efficient in terms of optoelectronic properties. The gap of “the neat” 0.00w% N-CNT/TiO2 is of 3eV, which is in a good agreement with similar gap of semiconductors. The incorporated “w%NCNTs” led to diminishing the Eg with increasing N-CNTs amount. These consequences are very encouraging for optoelectronic field.

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Strain effects on polycrystalline germanium thin films

Scientific Reports ◽

10.1038/s41598-021-87616-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Toshifumi Imajo ◽

Takashi Suemasu ◽

Kaoru Toko

Keyword(s):

Thin Films ◽

Solid Phase ◽

Growth Promotion ◽

Large Strain ◽

Compressive Strain ◽

Substrate Material ◽

Large Crystal ◽

Solid Phase Crystallization ◽

Strain Effects ◽

Thin Film Devices

AbstractPolycrystalline Ge thin films have attracted increasing attention because their hole mobilities exceed those of single-crystal Si wafers, while the process temperature is low. In this study, we investigate the strain effects on the crystal and electrical properties of polycrystalline Ge layers formed by solid-phase crystallization at 375 °C by modulating the substrate material. The strain of the Ge layers is in the range of approximately 0.5% (tensile) to -0.5% (compressive), which reflects both thermal expansion difference between Ge and substrate and phase transition of Ge from amorphous to crystalline. For both tensile and compressive strains, a large strain provides large crystal grains with sizes of approximately 10 μm owing to growth promotion. The potential barrier height of the grain boundary strongly depends on the strain and its direction. It is increased by tensile strain and decreased by compressive strain. These findings will be useful for the design of Ge-based thin-film devices on various materials for Internet-of-things technologies.

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Strong texture tuning along different crystalline directions in glass-supported CeO2 thin films by ultrasonic spray pyrolysis

Scientific Reports ◽

10.1038/s41598-021-81353-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Inti Zumeta-Dubé ◽

José Manuel García Rangel ◽

Jorge Roque ◽

Issis Claudette Romero-Ibarra ◽

Mario Fidel García Sánchez

Keyword(s):

Thin Films ◽

Spray Pyrolysis ◽

Spray Pyrolysis Technique ◽

Morphological Characteristics ◽

Ultrasonic Spray Pyrolysis ◽

Cost Effective ◽

Growth Direction ◽

Large Area ◽

Smart Windows ◽

Ultrasonic Spray

AbstractThe strong facet-dependent performance of glass-supported CeO2 thin films in different applications (catalysis, smart windows, etc.) has been the target of diverse fundamental and technological approaches. However, the design of accurate, cost-effective and scalable methods with the potential for large-area coverage that produce highly textured glass-supported CeO2 thin films remains a technological challenge. In the present work, it is demonstrated that under proper tuning conditions, the ultrasonic spray pyrolysis technique enables one to obtain glass-supported polycrystalline CeO2 films with noticeable texture along both the (100) and (111) directions, as well as with randomly oriented crystallites (no texture). The influence of flow rates, solution molarity, and substrate temperature on the texture and morphological characteristics, as well as optical absorption and Raman response of the deposited films, is evaluated. The obtained results are discussed on the basis of the combined dependence of the CeO2-exposed surfaces on the thermodynamic stability of the corresponding facets and the reaction kinetics, which modulate the crystallite growth direction.

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