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A novel -SCO was formed from the BM-SCO parent material by Cu-substitution. Although the oxygen content was lowered, the electric conductivity improved by 2–3 orders of magnitude, and the OER performances were greatly improved.

The half-metallic manganite oxide La

Integrating characteristics of materials through constructing artificial superlattices (SLs) has raised extensive attention in multifunctional materials. Here, we report the synthesis of BiFeO3/BiMnO3 SLs with considerable ferroelectric polarizations and tunable magnetic moments. The polarization of BiFeO3/BiMnO3 SLs presents a decent value of 12 μC/cm2, even as the dimensionality of BiFeO3 layers per period is reduced to about five-unit cells when keeping the BiMnO3 layers same. Moreover, it is found that the tunable magnetic moments of SLs are linked intimately to the dimensionality of BiFeO3 layers. Our simulations demonstrate that the superexchange interaction of Fe-O-Mn tends to be antiferromagnetic (AFM) with a lower magnetic domain formation energy rather than ferromagnetic (FM). Therefore, as the dimensionality of BiFeO3 per period is reduced, the AFM superexchange interaction between BiFeO3 and BiMnO3 in the SLs becomes weak, promoting a robust magnetization. This interlayer modulation effect in SLs presents an alluring way to accurately control the multiple order parameters in a multiferroic oxide system.

Introducing large oxygen deficiencies while retaining low resistivity is important for enhancing the overall thermoelectric properties in 3d transition-metal oxides. In this study, a new synthesis route to reconstruct the insulating brownmillerite SrCoO2.5 is adapted. Through a step-by-step nano-blocks modification, a series of highly-conductive layered structures is evolved, which are [Sr2O2H2]0.5CoO2, [Sr2O2]0.4CoO2, and [Sr2CoO3]0.57CoO2, while still retaining considerable Seebeck coefficient (˜100 µV K-1). Coexistence of low resistivity and high oxygen deficiency is realized in the latter two polymorphs by forming a majority of sintered oxygen vacancies in the rock-salt layer and a minority of normal oxygen vacancies in the CoO2 layer. A room-temperature in-plane power factor of 3.6 mW K-2 m-1, power output density of 4.5 W m-2 at a temperature difference of 28 K, and an out-of-plane thermal conductivity of 0.33 W K-1 m-1 are obtained in the [Sr2O2]0.4CoO2 thin film that exhibits the highest oxygen deficiency (d = 2.95), which is on par with Bi2Te3, the benchmark. It is pointed out that proper distribution of oxygen vacancy is essential in tailoring the physical and chemical properties of transition-metal oxides. The sintered/normal oxygen vacancy layer model provides guidance to the exploration of materials with both low electric resistivity and thermal conductivity.

Materials with reduced dimensions have been shown to host a wide variety of exotic properties and novel quantum states that often defy textbook wisdom. Polarization switching and metallic screening are well-known examples of mutually exclusive properties that cannot coexist in bulk solids. Here we report the fabrication of (SrRuO3)1/(BaTiO3)10 superlattices that exhibits reversible polarization switching in an atomically thin metallic layer. A multipronged investigation combining structural analyses, electrical measurements, and first-principles electronic structure calculations unravels the coexistence of two-dimensional (2D) metallicity in the SrRuO3 layer accompanied by the breaking of inversion symmetry, supporting electric polarization along the out-of-plane direction. Such a 2D ferroelectric-like metal paves a novel way to engineer a quantum multistate with unusual coexisting properties, such as ferroelectrics and metals, manipulated by external fields.

Multiferroic materials with multifunctional characteristics play a critical role in the field of microelectronics. In a perovskite oxide, ferroelectric polarization and ferromagnetism usually cannot coexist in a single-phase material at the same time. In this work, we design a superlattice structure composed of alternating BiFeO3 and BiMnO3 layers and illustrate how tuning the supercell size of epitaxial BiFeO3/BiMnO3 superlattices facilitates ferroelectric polarization while maintaining relatively strong ferromagnetism. A comprehensive investigation reveals that the enhanced ferroelectric polarization of BiMnO3 layers originates from the induction effect induced by a strong polarization field generated by the adjacent ferroelectric BiFeO3 layers. For the magnetic behavior, we consider the existence of interfacial antiferromagnetic superexchange interaction of Fe-O-Mn between BiFeO3 and BiMnO3 layers in our superlattices. This modulation effect of artificial superlattices provides a platform to accurately control the multiple order parameters in a multiferroic oxide system.

Negative and near-zero Poisson's ratio materials are mechanical metamaterials that host an improved strain energy absorption property with respect to conventional materials. By using first-principles calculations, we report the negative and near-zero Poisson's ratios in van der Waals (vdW) heterostructures, such as graphene/hexagonal molybdenum disulfide (G/MoS2) and graphene/hexagonal boron nitride (G/h-BN), sharing distinct crystal structures from all other known negative and near-zero Poisson's ratio materials. However, the Poisson's ratios of the interfacial layer in bilayer MoS2 and h-BN are positive and near-zero along the out-of-plane direction, respectively, which are quite different from the Poisson's ratios of G/MoS2 and G/h-BN heterostructures. Therefore, these behaviors are unique to vdW heterostructures. We attribute these negative Poisson's ratio behaviors to the special interaction of pz orbitals between the interfacial layers. Furthermore, we observed among them high-order elastic constants in the out-of-plane direction, which exhibit nonlinear stress–strain responses. These results are significant for the preparation of G/h-BN and G/MoS2 heterostructures. The combinations of tunable negative/near-zero Poisson's ratios with the excellent electrical/optical properties of G/MoS2 and G/h-BN heterostructures will pave the way to a wide range of applications in novel auxetic molecular sieves and electrodes.

Freestanding perovskite thin films display many unprecedented properties and exhibit the potential to be easily integrated on other non-oxide substrates or layers. In this work, we demonstrated a pathway to synthesis freestanding perovskite oxide thin films by using brownmillerite SrCoO2.5 as a sacrificial layer. Four representative freestanding perovskite oxide films, e.g., ferromagnetic SrRuO3, La0.7Sr0.3MnO3, dielectric SrTiO3, and ferroelectric Pb(Zr0.2Ti0.8)O3, were produced by etching SrCoO2.5 in Fe(NO3)3 weak acidic solution at room temperature. A 80 nm SrRuO3, which served as an H+ conduction channel, was deposited as a bottom layer of SrCoO2.5 to trigger a quick dissolution for the exfoliation of SrTiO3 and Pb(Zr0.2Ti0.8)O3 poor H+ conductor. Their crystal structure and physical properties were well retained in transferred films. Our work demonstrated the wide applicability of SrCoO2.5 as a sacrificial layer on the synthesis of freestanding perovskite oxide thin films.

Protonated 3d transition-metal oxides often display low electronic conduction, which hampers their application in electric, magnetic, thermoelectric, and catalytic fields. Electronic conduction can be enhanced by co-inserting oxygen acceptors simultaneously. However, the currently used redox approaches hinder protons and oxygen ions co-insertion due to the selective switching issues. Here, a thermal hydration strategy for systematically exploring the synthesis of conductive protonated oxides from 3d transition-metal oxides is introduced. This strategy is illustrated by synthesizing a novel layered-oxide SrCoO3H from the brownmillerite SrCoO2.5. Compared to the insulating SrCoO2.5, SrCoO3H exhibits an unprecedented high electronic conductivity above room temperature, water uptake at 250 °C, and a thermoelectric power factor of up to 1.2 mW K-2 m-1 at 300 K. These findings open up opportunities for creating high-conductive protonated layered oxides by protons and oxygen ions co-doping. CC acknowledges support from the Spanish Ministry of Science, Innovation, and Universities under the “Ramón y Cajal” fellowship RYC2018-024947-I.

Multiferroic materials with flexibility are expected to make great contributions to flexible electronic applications, such as sensors, memories, and wearable devices. In this work, super‐flexible freestanding BiMnO3 membranes with simultaneous ferroelectricity and ferromagnetism are synthesized using water‐soluble Sr3Al2O6 as the sacrificial buffer layer. The super‐flexibility of BiMnO3 membranes is demonstrated by undergoing an ≈180° folding during an in situ bending test, which is consistent with the results of first‐principles calculations. The piezoelectric signal under a bending radius of ≈500 µm confirms the stable existence of electric polarization in freestanding BiMnO3 membranes. Moreover, the stable ferromagnetism of freestanding BiMnO3 membranes is demonstrated after 100 times bending cycles with a bending radius of ≈2 mm. 5.1% uniaxial tensile strain is achieved in freestanding BiMnO3 membranes, and the piezoresponse force microscopy (PFM) phase retention behaviors confirm that the ferroelectricity of membranes can survive stably up to the strain of 1.7%. These super‐flexible membranes with stable ferroelectricity and ferromagnetism pave ways to the realizations of multifunctional flexible electronics., As flexible device have become vital in the forefront of technology, the maintenance of multifunctional performances under high flexion is highly desired. Here, the synthesis of super‐flexible freestanding BiMnO3 membranes with stable ferroelectricity and ferromagnetism simultaneously by pulsed laser deposition using recently promising water‐soluble Sr3Al2O6 as the sacrificial layer is reported.

Integrating characteristics of materials through constructing artificial superlattices (SLs) has raised extensive attention in multifunctional materials. Here, we report the synthesis of BiFeO

Protonated 3d transition-metal oxides often display low electronic conduction, which hampers their application in electric, magnetic, thermoelectric, and catalytic fields. Electronic conduction can be enhanced by co-inserting oxygen acceptors simultaneously. However, the currently used redox approaches hinder protons and oxygen ions co-insertion due to the selective switching issues. Here, a thermal hydration strategy for systematically exploring the synthesis of conductive protonated oxides from 3d transition-metal oxides is introduced. This strategy is illustrated by synthesizing a novel layered-oxide SrCoO

Cobalt oxides with multiple local Co-O coordination environments such as octahedral, tetrahedral, and tetragonal networks display versatile electronic and magnetic properties which have attracted great interest in many fields. Understanding the ground-state properties and determining the fundamental band gap remain challenges in cobalt-based compounds and thin films, which have been investigated here using synchrotron-based Co ${L}_{23}$-edge x-ray absorption measurements followed by configuration interaction cluster calculations. We focus on the detailed Co ${L}_{23}$-edge absorption spectral variations in different octahedral crystal fields as well as in the less investigated tetrahedral and tetragonal systems, taking into account Co ions with different valence states. From a quantitative comparison between the simulated spectrum and an accurately measured absorption spectrum of a specified compound, the crystal field value can be extracted from the Co ${L}_{23}$-edge absorption spectrum, which is complementary to the results obtained in optical measurements and other calculations. Furthermore, Co ${L}_{23}$-edge x-ray linear dichroism shows the same spectral evolutions as a result of either local ${\mathrm{CoO}}_{6}$ cluster with tetragonal symmetry or the magnetic exchange field, whereas both coexist in most antiferromagnetic cobalt oxide thin films. Detailed temperature and polarization-dependent Co ${L}_{23}$-edge absorption measurements have been proposed to distinguish both contributions, which show different spectral variations due to the specified modifications of the ground and final states at different temperatures. Our results offer theoretical guidance for understanding the multiplet structure of Co ${L}_{23}$-edge absorption spectrum, obtaining the precise crystal field value for cobalt oxides with versatile coordinations, and explaining the underlying mechanism of x-ray linear dichroism, as well as understanding the fundamental physical properties and their potential applicability of cobalt oxides and their thin films.

Oxygen nonstoichiometry plays a critical role in determining the physical and chemical functionalities of oxide materials. For widespread applications involving oxygen transport and exchange with t...

Recently, spin spiral type multiferroic materials are widely investigated for their unusual properties and potential applications in memory technology, sensors, and field-effect transistors. It is of interest to investigate surface magnetism in iron vanadate (FeV2O4) due to varying physical properties. Here, the temperature-dependent magnetic domain evolution has been systematically investigated by using cryogenic magnetic force microscopy (MFM). We find irregular and asymmetrical magnetic domain coarsening and shrinking as a function of temperature and also different domain evolution between field cooled and zero field cooled MFM. These findings provide an improved understanding of physical properties related to domain structures.

The self-assembly of nickel from nanoparticles to nanowires and foils can be achieved by controlling the concentrations of sodium citrate during the electroless deposition process. The metal nickel possesses tunable coercivity: nanoparticles (75 Oe), nanochains (100 Oe), nanowires (290 Oe), nanowire nonwoven fabrics (280 Oe), and foils (130 Oe), which is related to their morphologies and sizes. This feasible approach shows an effective strategy to fabricate the magnetic material assembly.

Large data storage at reduced dimension is of a great deal of interest in spintronic devices in which magnetic oxide films lead for realizing the modulation of perpendicular magnetic anisotropy (PMA). Herein, we report the modulation of PMA in oxide heterostructures composed of one manganite layer sandwiched between two cobaltite layers, i.e., LaCoO3− δ/La0.7Sr0.3MnO3/LaCoO3− δ via oxygen vacancies. The PMA is originated by the orbital reconstruction and ferromagnetic exchange interaction at the interface between the CoO6 and MnO6 octahedra layers. The modulation ratio up to a significant value ∼200% of PMA can be realized through the phase transition of LaCoO3− δ layers between perovskite and brownmillerite via deprivation or replenishment of oxygen sites. The antiferromagnetic superexchange interaction at the interface between the oxygen-deficient CoO4 tetrahedra layer and the adjacent MnO6 octahedral layer with lattice distortion may suppress the magnetization and PMA. This work ensures promising outcomes in situ modulation of PMA in oxide films such as ferroelectric polarization or ionic liquid gating via the transport of oxygen vacancies.

Multiferroic materials with multifunctional characteristics play a critical role in the field of microelectronics. In a perovskite oxide, ferroelectric polarization and ferromagnetism usually cannot coexist in a single-phase material at the same time. In this work, we design a superlattice structure composed of alternating BiFeO

The strain effect on charge transfer in correlated oxide La0.8Sr0.2MnO3/NdNiO3 (LSMO/NNO) heterostructures is investigated. This is achieved by carefully tailoring the strain on the two layers using various substrates. In contrast to bare LSMO films, the strain dependence of the enhanced magnetic moment of the LSMO/NNO bilayers strongly suggests that the charge transfer can be controlled via strain engineering in complex oxide heterostructures. Furthermore, our study also reveals that the coercive field, exchange bias, and conductivity are dramatically affected by the strain-modulated charge transfer in LSMO/NNO heterostructures. Our work thus points out a new path to control electronic states in oxide heterostructures to advance the use of interfaces in oxide-based electronics.

Magnetic materials with large magnetic anisotropy are essential for workaday applications such as permanent magnets and magnetic data storage. There is widespread interest in finding efficient ways of controlling magnetic anisotropy, among which strain control has proven to be a very powerful technique. Here, we demonstrate the strain-mediated magnetic anisotropy in SrCoO3−δ thin film, a perovskite oxide that is metallic and adopts a cubic structure at δ ≤ 0.25. We find that the easy-magnetization axis in SrCoO3−δ can be rotated by 90° upon application of moderate epitaxial strains ranging from −1.2 to +1.8%. The magnetic anisotropy in compressive SrCoO3−δ thin films is huge, as shown by magnetic hysteresis loops rendering an anisotropy energy density of ∼106 erg/cm3. The local variance in magnetic force microscopy upon temperature and magnetic field reveals that the evolution of magnetic domains in the SCO thin film is strongly dependent on magnetic anisotropy.

ZnTe epitaxial layers with different crystalline quality were grown by molecular beam epitaxy. ZnTe:O was achieved by oxygen incorporation in ZnTe films using ion implantation. The proper concentrations of O ions attributed to the formation of the intermediate band which was approximately 1.88 eV above the valence band maximum. Pulsed laser melting was then carried out on the samples. ZnTe with high crystalline quality and appropriate concentrations of oxygen ions led to the improvements of absorption efficiency of the intermediate band. The results suggest that factors such as the crystalline quality and the dose of O concentration are important to achieve better ZnTe:O intermediate-band photovoltaic materials. The way we utilize to fabricate ZnTe:O intermediate band solar cell materials is applicable, and the position and intensity of O states could be well controlled.

In this study, we report the effect of doping in morphotropic BiFeO3 (BFO) thin films on mechanical properties, revealing variations in the elasticity across the competing phases and their boundaries. Spectroscopic force–distance (F–D) curves and force mapping images by AFM are used to characterize the structure and elastic properties of three BFO thin-film candidates (pure-BFO, Ca-doped BFO, La-doped BFO). We show that softening behavior is observed in isovalent La-doped BFO, whereas hardening is seen in aliovalent Ca-doped BFO. Furthermore, quantitative F–D measurements are extended to show threshold strengths for phase transitions, revealing their dependence on doping in the system. First-principles simulation methods are also employed to understand the observed mechanical properties in pure and doped BFO thin films and to provide microscopic insight on them. These results provide key insight into doping as an effective control parameter to tune nanomechanical properties and suggest an alternative fram...

Oxide materials facilitating high-ion mobility and fast-ion transport are highly sought after for applications requiring intensive redox cycling. Some of these materials, in addition, may exhibit interesting multifunctional properties originating from electron correlation such as magnetism and metal–insulator transitions. SrCoO3-δ (SCO) is one such compound, which recently has attracted a lot of interest due to its ability of taking on and releasing oxygen fluently. Here we investigate thoroughly the dynamics of oxygen vacancies and redox cycles in SCO under broad epitaxial strain conditions (−1.2% ≤ η ≤ +3.9%). We show that the capacity of this material to act as an “oxygen sponge” depends strongly on the strain conditions, with moderate strains of ca. +2% providing the optimal conditions for reversible redox cycling. First-principles simulation methods are employed to understand the experimental trends observed for SCO reduction in vacuum, and to provide microscopic insight into the formation of oxygen ...

Exchange bias lies in the core of cutting-edge technologies, for instance, high-density data storage, spin valves, and high-frequency magnetic devices. As the devices with flexibility have become vital in the forefront of technology, the maintenance of exchange bias under high flexion is highly desired. This paper reports the strong exchange bias in flexible freestanding La0.7Sr0.3MnO3/BiFeO3 membranes with decent mechanical durability. The La0.7Sr0.3MnO3 layer is biased strongly by the BiFeO3 layer even in the freestanding state. At the same time, the strain is demonstrated to affect the strength of the exchange bias of the La0.7Sr0.3MnO3/BiFeO3 bilayer. Furthermore, the saturation magnetization and exchange bias field of the freestanding La0.7Sr0.3MnO3/BiFeO3 membranes are preserved well after 1000 bending cycles. Our work on freestanding membranes paves the way for manufacturing advanced flexible spintronic devices.

Recently, layered materials have been extensively studied and attracted unprecedented attention. Layered oxides with superior properties have potential applications for nanoscale devices. Here, we report variable supercells in layered bismuth manganite controlled by oxygen pressure and reveal the strong piezoelectric responses from the layered supercells with tunable physical properties, including an approximately three-times difference in the magnetization range and 10% difference in the optical transmittance. The tunability of the sublattice from Bi3O3 to Bi2O2 in supercells is realized by a precise oxygen pressure control of 10 mTorr and 100 mTorr, respectively. The results presented here show a tantalizing opportunity to discover emerging multifunctional oxides for future nanoelectronics.

Magnetic materials with large magnetic anisotropy are essential for workaday applications such as permanent magnets and magnetic data storage. There is widespread interest in finding efficient ways of controlling magnetic anisotropy, among which strain control has proven to be a very powerful technique. Here, we demonstrate the strain-mediated magnetic anisotropy in SrCoO

The CdTe/Sb2Te3 interface was prepared by co-evaporation on an ultra-thin glass substrate and studied “in-situ” by photoelectron spectroscopy using a tunable synchrotron radiation photon source. The results indicated that the as-deposited antimony telluride was a mixture of Sb–Te phase and Sb2Te3 structure. The band diagram showed a conduction band offset (ΔECB) of 0.65 eV at the interface. A thin layer of Sb2Te3 came into being on the surface of CdTe with a subsequent 300 °C anneal. The sputter depth profile suggested that the annealed interface was actually constituted by the “substrate CdTe/interface Sb+Cd donors/inner Sb–Te mixture/surface Sb2Te3” structure. The band diagram gave ΔECB=1.35 eV for the annealed interface. It was found that there was a thin barrier of 0.2 eV induced by Sb+Cd donors for the hole transportation at the interface. To create a thin p+ layer between CdTe and the back electrode, a 50 A thick Sb2Te3 layer was used for the back contact to CdTe thin film solar cells. J–V characteristic showed that this thin p+ back contact greatly enhanced the cell performance.

Magnonic devices that utilize electric control of spin waves mediated by complex spin textures are an emerging direction in spintronics research. Room-temperature multiferroic materials, such as bismuth ferrite (BiFeO3), would be ideal candidates for this purpose. To realize magnonic devices, a robust long-range spin cycloid with well-known direction is desired, since it is a prerequisite for the magnetoelectric coupling. Despite extensive investigation, the stabilization of a large-scale uniform spin cycloid in nanoscale (100 nm) thin BiFeO3 films has not been accomplished. Here, we demonstrate cycloidal spin order in 100 nm BiFeO3 thin films through the careful choice of crystallographic orientation, and control of the electrostatic and strain boundary conditions. Neutron diffraction, in conjunction with X-ray diffraction, reveals an incommensurate spin cycloid with a unique [11] propagation direction. While this direction is different from bulk BiFeO3, the cycloid length and Néel temperature remain equivalent to bulk at room temperature., Whilst possessing potential for electrically-controlled magnonic applications, the spin cycloid of bulk BiFeO3 is lost in technologically-relevant thin films. Here, the authors demonstrate the stabilization of a long-range spin cycloid in BiFeO3 thin films through careful choice of electrostatic and strain conditions during thin film growth.

Sb2Te3thin films with thickness of 70, 100, 300, and 600nm were co-evaporated by vacuum evaporation. These films were annealed by 423K, 473K, 523K and 573K, respectively, in the protection of N2ambient. After that, the film structures were investigated by XRD. Composition of the films was surveyed XRF and XPS. Stoichiometric Sb2Te3thin films were prepared. Then the Sb2Te3thin films were applied to CdTe thin film solar cells as back contact layer. The influence of Sb2Te3thin films thickness on the performances of CdS/CdTe thin film solar cells were surveyed by light I-V characteristics and an efficiency of 12.27%, Voc=808.2mV, Jsc=25.1mA/cm2, FF= 0.6051 was obtained.

Cd1−xZnxS thin films at low Zn content were prepared both by chemical bath deposition (CBD) and vacuum co-evaporation. The X-ray fluorescence (XRF) and X-ray photoelectron spectroscopy (XPS) analysis were performed to determine the composition of the films, while the structural properties were investigated by X-ray diffraction (XRD). As a probable window layer, the optical band gaps of Cd1−xZnxS thin films prepared by the dry and wet process were calculated. Finally, the surface morphologies of the thin films were survey by scanning electron microscopy (SEM) and atomic force microscopy (AFM).

Deposition ofSb2Te3thin films on soda-lime glass substrates by coevaporation of Sb and Te is described in this paper.Sb2Te3thin films were characterized by x-ray diffraction (XRD), x-ray fluorescence (XRF), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), electrical conductivity measurements, and Hall measurements. The abnormal electrical transport behavior occurred fromin situelectrical conductivity measurements. The results indicate that as-grownSb2Te3thin films are amorphous and undergo an amorphous-crystalline transition after annealing, and the posttreatment can effectively promote the formation of Sb-Te bond and prevent oxidation of thin film surface.

It has been well established that both in bulk at ambient pressure and for films under modest strains, cubic SrCoO$_{3-\delta}$ ($\delta < 0.2$) is a ferromagnetic metal. Recent theoretical work, however, indicates that a magnetic phase transition to an antiferromagnetic structure could occur under large strain accompanied by a metal-insulator transition. We have observed a strain-induced ferromagnetic to antiferromagnetic phase transition in SrCoO$_{3-\delta}$ films grown on DyScO$_3$ substrates, which provide a large tensile epitaxial strain, as compared to ferromagnetic films under lower tensile strain on SrTiO$_3$ substrates. Magnetometry results demonstrate the existence of antiferromagnetic spin correlations and neutron diffraction experiments provide a direct evidence for a G-type antiferromagnetic structure with Ne\'el temperatures between $T_N \sim 135\,\pm\,10\,K$ and $\sim 325\,\pm\,10\,K$ depending on the oxygen content of the samples. Therefore, our data experimentally confirm the predicted strain-induced magnetic phase transition to an antiferromagnetic state for SrCoO$_{3-\delta}$ thin films under large epitaxial strain., Comment: 6 pages, 4 figures

We investigate the mechanical properties of BiFeO3 (BFO) thin films grown on SrTiO3 (001) substrates that were manually bent using a specially designed uniaxial bending stage. X-ray measurements under variable uniaxial strain show that excessive strains up to ∼2% could be applied along the [100] direction with little cross talk between [100] and [010] directions. X-ray reciprocal space maps were acquired to investigate the evolution of -a and c-axis lattice constants under variable strain and Poisson's ratio of BFO thin films vzx was determined to be 0.30 ± 0.01.

CdS polycrystalline thin films were fabricated by magnetron sputtering and the influence of substrates, sputtering powers, pressures, and substrate temperatures on the structure of thin films is investigated. The films deposited on substrates of glass, quartz, SnO 2 : F and p-type single silicon are hexagonal phase and they grow preferentially along (002) planes. As the radio-frequency power and substrate temperature increase, the preferential growth is improved, while it is decreased with the increases of pressure especially over 0.2 Pa. In addition, annealing in air or N 2 or with CdCl 2 can increase the grain size greatly and promote preferential growing.

High quality epitaxial SrCoO x (oxygen deficient SrCoO 3 ) thin films were grown on (110) DyScO3 substrates by pulsed laser deposition.The disappearance of half order peaks in X-ray diffraction as well as the XAS at the O K-edge indicates an oxygen content of x ≈ 2.8 in the thin films. Magnetization measurements reveal that the specific substrate strain suppresses the ferromagnetism found in the corresponding bulk material and the emergence of an antiferromagnetic-type spin correlation as predicted by theoretical calculations. Our work demonstrates that the magnetism can be tuned by in-plane strain in SrCoO x thin films.

Sb2Te3 thin films were prepared by vacuum co-evaporation and the crystallinity of the films was greatly improved after annealing at 573 K in N2 ambient. Then they were deposited on the CdTe thick films. Band diagrams of the as-deposited and annealed CdTe/Sb2Te3 interfaces were constructed. Consequently, Sb2Te3 was used as a back contact layer for CdTe thin film solar cells and the cell performance was investigated. It was found that the Sb impurities accumulated in the CdTe grain boundaries diffuse deeply in the CdTe layer, and more photogenerated electrons and holes are separated by the segregated SbCd + donors into the GBs. What is more, the doping concentration in the vicinity of the CdTe/CdS heterojunction increases for the formation of substitutional SbTe - acceptors under the Cd-rich conditions. For the introduction of the p-type Sb2Te3 layers as the back contact to the CdTe thin film solar cells, the performance of CdTe thin film solar cells has been greatly improved and an efficiency of 13.1% (FF=62.3%, Jsc=25.8 mA/cm2, Voc= 815.8 mV) obtained.