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Synthetic perpendicular magnetic anisotropy (PMA) ferrimagnets consisting of 30-nm-thick D022-MnGa and Co2MnSi (CMS) cubic Heusler alloys with different thicknesses of 1, 3, 5, 10 and 20 nm, buffered and capped with a Cr film, are successfully grown epitaxially on MgO substrate. Two series samples with and without post annealing at 400 °C are fabricated. The (002) peak of the cubic L21 structure of CMS films on the MnGa layer is observed, even for the 3-nm-thick CMS film for both un-annealed and annealed samples. The smaller remnant magnetization and larger switching field values of CMS (1-20 nm)/MnGa (30 nm) bilayers compared with 30-nm-thick MnGa indicates antiferromagnetic (AFM) interfacial exchange coupling (Jex) between MnGa and CMS films for both un-annealed and annealed samples. The critical thickness of the CMS film for observing PMA with AFM coupling in the CMS/MnGa bilayer is less than 10 nm, which is relatively large compared to previous studies. [ABSTRACT FROM AUTHOR]

Mn3Ge has a tetragonal Heusler-like D022 crystal structure, exhibiting a large uniaxial magnetic anisotropy and small saturation magnetization due to its ferrimagnetic spin structure; thus, it is a hard ferrimagnet. In this report, epitaxial growth of a Mn3Ge film on a Rh buffer layer was investigated for comparison with that of a film on a Cr buffer layer in terms of the lattice mismatch between Mn3Ge and the buffer layer. The film grown on Rh had much better crystalline quality than that grown on Cr, which can be attributed to the small lattice mismatch. Epitaxial films of Mn3Ge on Rh show somewhat small coercivity (Hc = 12.6 kOe) and a large perpendicular magnetic anisotropy (Ku = 11.6 Merg/cm³), comparable to that of the film grown on Cr. [ABSTRACT FROM AUTHOR]

Epitaxial thin films of Y 2 MnCrO 6 (YMCO) have been fabricated on various substrates via a two-step process combining magnetron sputtering technique and ex-situ annealing method. X-ray diffraction observations revealed that film orientation and quality are dominantly governed by the lattice mismatch between film and substrate. Moreover, orientation of the films grown on SrTiO 3 can be tuned to some extent by adjusting substrate temperature and post-annealing process. The YMCO films were found to undergo a paramagnetic–ferrimagnetic transition at ~ 70 K, which is consistent with the bulk sample. Furthermore, the hysteresis loops indicate that the films may own a uniaxial anisotropy with the easy axis along the c -direction. [ABSTRACT FROM AUTHOR]

Epitaxial LiCoO 2 films are synthesized using a sol–gel method. The precursors are aqueous solutions of acetates or nitrates of Li and Co with polyvinylpyrrolidone as a thickener. The LiCoO 2 films prepared from the solutions by spin coating are epitaxially grown on sapphire (0001) substrates with c -axis orientation and in-plane alignment of LiCoO 2 [ 1 1 ¯ 0 ] ‖sapphire [100]. A two-step heat treatment of the spin-coated films consisting of preheating on a hotplate at the crystallization temperature followed by a high-temperature treatment notably promotes the c -axis orientation. In addition, the crystal orientation is controllable on different planes of the SrTiO 3 substrates; the LiCoO 2 films are grown with epitaxial relationships of LiCoO 2 (001)‖SrTiO 3 (111), LiCoO 2 (018)‖SrTiO 3 (110), and LiCoO 2 (104)‖SrTiO 3 (100). [ABSTRACT FROM AUTHOR]

Ta-doped Ga 2 O 3 (Ga 2 O 3 :Ta) epitaxial films were grown on SrTiO 3 (100) substrates via an MOCVD system. Solar-blind ultraviolet (UV) detectors with a metal-semiconductor-metal structure were fabricated based on the β -Ga 2 O 3 :Ta films, and the effects of Ta doping concentration on the photo response were investigated. The surface morphology, composition and band gap of the films were characterized. The β -Ga 2 O 3 :Ta UV detectors showed photo response characteristics under 222 nm deep UV light. As the Ta doping concentration increased, the responsivity of the detector increased significantly. For the 1.5 at.% Ta doped UV detector, the responsivity under 222 nm UV light at 8 V bias reached 8.23 A W−1, and the light-dark current ratio is close to 103. Moreover, the responsive rise time (T r1 / T r2) and decay time (T d1 / T d2) at 1 V bias were as short as 0.37 s/0.38 s and 0.41 s/0.85 s, respectively. Ta doping significantly improves the performance of β -Ga 2 O 3 ultraviolet detectors, which may be a feasible method to expand its application potential. • Solar blind UV detectors are fabricated based on Ta doped β -Ga 2 O 3 films. • The Ta doped β -Ga 2 O 3 films prepared by MOCVD have high crystalline quality. • The responsivity of the Ta doped detector to 222 nm UV light reaches 8.23 A W−1. • The detectors have a fast periodic response to continuous switching UV light. • Ta doping can effectively improve the responsivity of β -Ga 2 O 3 UV detectors. [ABSTRACT FROM AUTHOR]

The effect of preliminary low-energy (~1 keV) and low-dose (~10-10 cm) ion bombardment on the initial stages of growth of Si films on a CaF/Si surface is investigated. Ordered nanocrystal phases (thickness less than 5-6 monolayers) and homogeneous epitaxial nanofilms (thickness more than 8-10 monolayers) of silicon are shown to be formed after annealing. [ABSTRACT FROM AUTHOR]

A series of epitaxial SrTiO 3 (STO) thin films were grown on (001)-oriented LaAlO 3 (LAO) substrates by ion beam sputter deposition (IBSD) at various growth temperatures in the range of 350–800 °C. Our results have shown that the growth temperature plays an essential role in influencing the structural and morphological evolution of the STO thin films. X-ray structural analysis demonstrates that the STO thin films are grown under in-plane compressive strain due to the effect of lattice mismatch. The out-of-plane lattice constant is found to decrease with increasing growth temperature. Atomic force microscopy observation reveals that the growth mode of STO thin films transforms from a three-dimensional island mode to a two-dimensional layer-by-layer mode at a sufficiently high growth temperature of 750 °C. We believe that high-quality epitaxial STO thin films with atomically flat surface prepared by IBSD in this study would be beneficial for the fabrication of perovskite STO-based superlattices. [ABSTRACT FROM AUTHOR]

Arsenic doping by ion implantation and thermal annealing of the BaSi 2 epitaxial films grown on Si(111) substrates has been studied. Raman spectroscopy shows that a structural change can occur by annealing at 500 °C after As implantation with as high dose as 1.0 × 10 15 cm − 2 . This structural change is shown to result in the formation of an altered layer after annealing at the surface by cross-sectional scanning electron microscopy. Secondary ion mass spectroscopy reveals that the altered layer contains a significant amount of O atoms. With the altered layer present, average electron density up to 6.0 × 10 19 cm − 3 has been realized, which is revealed by the Hall measurement. On the other hand, without the altered layer, high resistance of the BaSi 2 layer prevented the electrical characterization. Current path is discussed by theoretically calculating the band alignment and resistance, and possible highest electron density without the altered layer is extracted to be less than 2 × 10 17 cm − 3 . [ABSTRACT FROM AUTHOR]

Method of synthesis of high-quality thin films of Fe chalcogenides, Fe(Te,Se) and FeSe is studied. By investigating the correlation between Tc and structural parameters, it is concluded that a compressive strain is introduced on the films on CaF2 substrate, which leads to an increase of Tc than on oxide substrates. Properties both in the normal state and in the superconducting state are measured. Results are discussed in terms of the possibility of further increasing Tc of this material. [ABSTRACT FROM AUTHOR]

InGaAs/GaAs quantum wells (QW) are grown by molecular beam epitaxy (MBE) on an artificial GaAs/Si substrate deviated by 6° from the (001) plane in the [110] direction. Optimization of growth technology of artificial GaAs/Si substrates is performed. As optimization criteria, crystalline perfection of epitaxial films and their surface morphology were chosen. Artificial substrates with different crystallographic orientations of the GaAs buffer layer with respect to the direction of the Si surface deviation were grown. The methods of high-energy electron diffraction (RHEED) and X-ray diffraction were used to study the effect of the nucleation and growth regimes of GaAs/Si layers on their crystalline perfection. The surface morphology of the epitaxial layers was studied by RHEED (in situ) and atomic force microscopy (AFM) (ex situ). It is found that the transitional layers produced using the buffer layer 250 nm GaAs/2.70 nm GaP(001)/Si have optimum crystalline perfection and surface morphology. This layer was used to grow quantum wells and bulk layers. For these structures, the photoluminescence spectra at 5 and 77 K were obtained. [ABSTRACT FROM AUTHOR]

Phosphorus doping by P implantation and thermal annealing of the BaSi2 epitaxial film grown on the Si(111) substrate has been studied. Raman spectroscopy results show that the structural damage due to P implantation can be almost removed by annealing within 30 and 1s at 500 and 700°C, respectively. The depth profile of P is investigated by secondary ion mass spectroscopy, which reveals considerably slower diffusion kinetics of P at 500°C than 700°C. The activation energy of the diffusion is roughly estimated to be 2eV from the temperature dependence. The Hall measurement of the P-doped films clarifies that the P impurity is an electron donor in BaSi2. The average electron density up to the order of 1018 cm−3 is observed. [ABSTRACT FROM AUTHOR]

Abstract: Structures, optical and magnetic properties of epitaxial Sn1−x K x O2 films were investigated experimentally. Three distinct symmetry equivalent in-plane orientations were observed between the film and substrate. The ferromagnetism enhances monotonously with doping and the largest saturation magnetization is 7.88emu/cm3 in Sn0.92K0.08O2 film. Generated K interstitials may give rise to a symmetry-lowering distortion of the surrounding lattice. The alignment of magnetic moments in Sn1−x K x O2 films is established through p–p coupling interaction between the impurity p states and host p states. The lattice distortion induced by K at both interstitial site and substitution site will disturb the arrangement of the electrons and can be remitted by post-thermal treatment. [Copyright &y& Elsevier]

Crystallinity and optical band gap of epitaxial growth ZnTe on GaAs. [Display omitted] • We report an epitaxial growth of ultrathin ZnTe film by molecular beam epitaxy. • Epitaxial ZnTe films shows small variation of c-axis lattice constants. • Band gap and in-gap states were analyzed via spectroscopic ellipsometry. Zinc telluride (ZnTe) has attracted interests for its semiconducting, optoelectronic, and electrical switching properties. However, the growth mechanism of ultrathin epitaxial films is not well established. Here we present a systematic study of the growth ultrathin ZnTe films on GaAs (0 0 1) by molecular-beam epitaxy. In situ reflection high-energy electron diffraction and synchrotron based high-resolution X-ray diffraction showed that both surface atomic ordering and single crystalline phase aligned to the substrate orientation with small variation of c -axis lattice in the ultrathin films. While the deviation of chemical compositions depended on the growth conditions, information on the variation of the band gap and in-gap states was obtained through spectroscopic ellipsometry analysis. Our study showed that single crystal ZnTe films can serve as a model system in the development of Ovonic threshold switching devices for cross-point device applications. [ABSTRACT FROM AUTHOR]

Strain accumulation and relaxation in BaSi2 epitaxial films on Si(111) substrates during thermal treatments have been studied. The 2 θ - ω X-ray diffraction analysis shows that the film-normal lattice parameters ( a) in epitaxial films are smaller than that in the bulk, indicating in-plane tensile stress is accumulated in the asgrown films. Resultant curvature of the substrate has been observed by spatially-resolved X-ray rocking curve analysis. This strain is relaxed by post-growth annealing through cracking. The conditions of cracking are revealed in terms of the film thickness and annealing temperature, from which the mechanism of strain relaxation is discussed. It is found from the tape test that the films with cracks can be exfoliated with an adhesive tape. The free-standing annealed films are subjected to the microwave-detected photoconductivity decay measurement, which reveals a long minority-carrier lifetime of 5 μs. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: LaCoO3 epitaxial films with different thicknesses (~20, 50 and 80nm) were grown on (001) SrTiO3 substrates by a simple polymer assisted deposition method. X-ray diffraction analyses including θ/2θ symmetric scan, ω-scan and in-plane φ-scan indicate that single-phase (001) oriented LaCoO3 films with a pseudotetragonal structure were grown on (001) SrTiO3 substrates successfully, with a biaxial tensile strain from +2.42% to +2.60% and tetragonal distortion from 1.47% to 1.63%. Due to the lattice relaxation effect in epitaxial thin film, the biaxial tensile strain is slightly relaxed when the thickness of the LaCoO3 film increases, resulting in an increase of the c-axis constant in contrast to a decrease of the in-plane constants of the film. It is different from LaCoO3 bulk with a nonmagnetic ground state that all the epitaxial films exhibit a ferromagnetic transition at TC ~85K. Combining with the structural and magnetic analyses, it is shown that the strain-induced ferromagnetism in LaCoO3 epitaxial films, corresponding to the higher spin states, origins from the decrease of the energy difference between eg and t 2g levels, which is caused by an increase of the unit-cell volume and suppression of the CoO6 octahedral rotations. In addition, the change of FC curve with the thickness of the film reveals that the ferromagnetism is enhanced by the thickness decrease of LaCoO3 film due to the increase of the biaxial tensile strain. [Copyright &y& Elsevier]

Abstract: Uniform, dense and continuous coatings of La0.8Sr0.2MnO3−δ (LSM) have been successfully deposited on dense/porous La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) substrates via a one-step drop-coating process using a water-based solution in order to improve the operating stability of solid oxide fuel cell cathode. The processing conditions were optimized by precise control of the composition of infiltrating solution, including chelating agents (glycine, citric acid and ethylene glycol), surfactants (polyvinyl alcohol (PVA), polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP)) and pH values (5.25, 4.29, 3.01 and 2.09). Ethanol was found to improve the wetting ability of the water-based solution significantly, but unfortunately causing precipitation. The symmetrical and full cells tests demonstrated that both performance and stability of LSCF cathode can be enhanced by surface modification with an optimized LSM film coating, leading to ∼31% reduction in cathodic polarization resistance and ∼45% improvement in power density (without observable degradation) for almost 350 h operation at 750 °C under a constant voltage of 0.7 V. [Copyright &y& Elsevier]

Phosphorus doping of BaSi2 epitaxial films by means of P implantation and rapid thermal annealing has been investigated from a structural viewpoint. Raman spectroscopy and X-ray diffraction show that the crystal structure of BaSi2 is destroyed, at least partially, by P implantation. This irradiation damage increases with increasing the P dose from 1.0×1013 to 1.0×1015 cm−2 and can be removed by rapid thermal annealing for 30s at 600–800°C, as evidenced by the variation of the full width at half-maximum of the A1-mode Raman peak. In addition to the recovery of the irradiation damage, the metastable trigonal phase of BaSi2, which is metallic and undesirable to exist in the semiconductor film, is found to form by annealing at 800°C after P implantation of 1.0×1015 cm−2. Furthermore, by annealing at 600 and 700°C, P atoms have been revealed to segregate into the surface and BaSi2/Si interface while the P segregation is suppressed at 800°C, according to the depth profile of P determined by secondary ion mass spectroscopy. Thus, we have obtained a useful guide of the P implantation dose and annealing temperature to effectively dope P atoms into the semiconducting BaSi2 film. [ABSTRACT FROM AUTHOR]

Abstract: Epitaxial films were fabricated on SrTiO3 (100) substrates using pulsed laser deposition (PLD) technique. The high quality of epitaxial growth films was confirmed by X-ray diffraction (XRD). Atomic force microscopy (AFM) images indicated the smooth surfaces and the step-flow growth of the films. In order to illuminate the electronic properties and the local structure of the epitaxial , we experimentally measured the X-ray absorption near-edge structure (XANES) spectrum at the O K-edge and compared the spectrum with the theoretical simulations by using various structure models. Our results based on XANES spectrum analysis indicated that the structure of the epitaxial film was a defective spinel with Al vacancies, which prefer to be located at the octahedral sites. [Copyright &y& Elsevier]

Abstract: The authors constructed multiferroic structures by growing La0.9Ce0.1MnO3 (LCEMO) thin films on piezoelectric 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 (PMN-PT) single-crystal substrates. Due to the efficient elastic coupling at the interface, the electric-field-induced piezoelectric strain in PMN-PT substrates is effectively transferred to LCEMO films and thus, leads to a decrease in the resistance and an increase in the magnetoresistance of the films. Particularly, it was found that the resistance-strain coefficient [] of the LCEMO film was considerably enhanced by the application of magnetic fields, demonstrating strong coupling between the lattice and the spin degrees of freedom. at 122K was enhanced by ~28.8% by a magnetic field of 1.2T. An analysis of the overall results demonstrates that the phase separation is crucial to understand strain-mediated modulation of electronic transport properties of manganite film/PMN-PT multiferroic structures. [Copyright &y& Elsevier]

Abstract: ZnO thin films are grown on Si substrates with SiC buffer layer using ion plasma high frequency magnetron sputtering. These substrates are fabricated using a technique of solid phase epitaxy. With this technique SiC layer of thickness 20–200nm had been grown on Si substrates consisting pores of sizes 0.5–5μm at SiC and Si interface. Due to mismatching in lattice constants as well as thermal expansion coefficients, elastic stresses have been developed in ZnO film. Pores at the interface of SiC and Si are acting as the elastic stress reliever of the ZnO films making them strain free epitaxial. ZnO film grown on this especially fabricated Si substrate with SiC buffer layer exhibits excellent crystalline quality as characterized using X-ray diffraction. Surface topography of the film has been characterized using Atomic Force Microscopy as well as Scanning Electron Microscopy. Chemical compositions of the films have been analyzed using Energy Dispersive X-ray Spectroscopy. Optical properties of the films are investigated using Photoluminescence Spectroscopy which also shows good optical quality. [Copyright &y& Elsevier]

Abstract: Mixed phases of rhombohedral and tetragonal ferroelectric variants have been recently observed to coexist through epitaxial constraints in bismuth ferrite films. They form stripe-like domain patterns with orientations closely parallel to the substrate edges and exhibit unusually large piezoelectric response in the stripe areas. Here a model is developed for explaining the peculiar domain orientations as well as the enhancement of piezoelectricity in the mixed phase. The former is determined by the relative magnitudes of elastic and depolarization energy, whereas the latter is ascribed to the strain-driven softening in dielectric stiffness. The predictions show the similar trend as those observed in recent experiments. [Copyright &y& Elsevier]

Abstract: The magnetic and transport properties of epitaxial La0.7Ba0.3MnO3 films on LaAlO3 substrates have been investigated and compared with those on SrTiO3 substrates. It is found that the ferromagnetic and metallic transition temperature of the highly compressive strained films on LaAlO3 substrates decreases steadily with decreasing film thickness, while it changes little in the lightly strained films on SrTiO3 substrates. The properties of the films on LaAlO3 substrates are more sensitive to a post-annealing procedure. A tendency to phase separation, which induces a difference between the insulator–metal transition temperature T MI and the Curie temperature T C, is observed for the films with a medium oxygen annealing process. We argue that the phase separation is due to both the highly compressive strain and oxygen deficiency in the films. [ABSTRACT FROM AUTHOR]

Abstract: We examined the correlation between thickness of an epitaxial VO2 phase grown on a TiO2 (001) substrate by the excimer-laser-assisted metal organic deposition (ELAMOD) process and the metal–insulator transition (MIT) property of it. The abrupt and hysteretic MIT was observed for the epitaxial films (thickness: t ≥6nm), and the epitaxial film (t ≤4nm) showed semiconductor behavior. When an amorphous VO x layer was prepared on the ultrathin epitaxial phase (t ≤4nm) by the ELAMOD, a non-hysteretic MIT was successfully observed. The non-hysteretic MIT was found to be owing to roughened interface between the epitaxial phase and the amorphous phase, where there would be a number of structural defects. [ABSTRACT FROM AUTHOR]

Abstract: Electrode–electrolyte hetero-epitaxial systems for solid oxide fuel cells (SOFCs) with two different configuration of Nd2NiO4+δ(110)//YSZ(100) and Nd2NiO4+δ(100)//YSZ(110) were successfully fabricated by pulsed laser deposition. Thin films of Nd2NiO4+δ approximately 20nm thick were grown on a commercial single crystal of YSZ. The preferred two-dimensional diffusion paths of the oxide ions were perpendicular to the substrate for both configurations and showed oxygen reduction capability different from each other. This opens up new research direction focusing on the details of anisotropic catalytic activity of SOFC cathode depending on the crystalline surface. [ABSTRACT FROM AUTHOR]

Synthesis by the hydrothermal method has various advantages, including low reaction temperature, three-dimensional substrate availability, and automatic polarization alignment during the process. In this review, powder synthesis, the fabrication of piezoelectric thin films, and their applications are introduced. A polycrystalline lead zirconate titanate (PZT) thin film was applied to a micro ultrasonic motor, and an epitaxial lead titanate (PbTiO3) thin film was estimated as a ferroelectric data storage medium. Ferroelectric and piezoelectric properties were successfully obtained for epitaxial PbTiO3 films. As lead-free piezoelectric powders, KNbO3 and NaNbO3 powders were synthesized by the hydrothermal method and sintered together to form (K,Na)NbO3 ceramics, from which reasonable piezoelectric performance was achieved. [ABSTRACT FROM AUTHOR]

Abstract: Strong phase competitions between the ferromagnetic metal and the charge-ordered-insulator have been induced in a wide temperature range of 10–256K for the shear-strained La0.67Ca0.33MnO3/NdGaO3(001) films. Based on various magnetotransport measurements, the mobility of phase boundaries was inferred to change dramatically with temperature. In the high temperature range where the phase boundaries are movable, strong relaxation in resistivity was observed, while at the frozen temperatures lower than 40K it is weakened. The resistivities tend to relax in accordance with the phase transitions driven by the temperature or magnetic field in the phase separation (PS) background. Moreover, to our surprise, while the melting fields of the insulating phase varied with film thicknesses, for a given film however, they stay unchanged when started with different phase fractions produced by the field or thermal cycling. The results show a crucial role of the inherent strain state in determining PS and phase competitions in these epitaxial thin films. [ABSTRACT FROM AUTHOR]

Abstract: Optical quality rare-earth (RE) (Nd3+, Eu3+, Gd3+ and Yb3+) doped Sr0.5Ba0.5Nb2O6 (SBN) epitaxial films of ~170nm thick have been successfully grown on MgO (100) single crystal substrates using pulsed laser deposition technique. Strong residual stress in these films has been revealed by Raman spectroscopic studies. Two kinds of in-plane orientations with respect to the MgO substrate co-exist. All the film samples show high transparency in the visible wavelength. Their band-gap energies appear to be independent of the types of dopant. Photoluminescence (PL) spectra of RE-doped SBN ceramics show a strong and broad emission band at around 600nm (2.07eV). The peak position of this emission band changes slightly with different RE-dopants. Thin film samples, however, yield a broad PL band at around 385nm (3.22eV). This UV emission shows no observable shift in the peak position for different dopants. Apart from these broad emission bands, conspicuous emission lines from Eu3+ and Nd3+ ions are also noted. The origins of these PL spectra are discussed. [ABSTRACT FROM AUTHOR]

We have introduced an improved x-ray phase-retrieval method with unprecedented speed of convergence and precision, and used it to determine with sub-Ångstrom resolution the complete atomic structure of epitaxial La2-xSrxCuO4 ultrathin films. We focus on superconducting heterostructures built from constituent materials that are not superconducting in bulk samples. Single-phase metallic or superconducting films are also studied for comparison. The results show that this phase-retrieval diffraction method enables accurate measurement of structural modifications in near-surface layers, which may be critically important for elucidation of surface-sensitive experiments. Specifically we find that, while the copper-apical-oxygen distance remains approximately constant in single-phase films, it shows a dramatic increase from the metallic-insulating interface of the bilayer towards the surface by as much as 0.45 Å. The apical-oxygen displacement is known to have a profound effect on the superconducting transition temperature. [ABSTRACT FROM AUTHOR]

Abstract: CuScO2 thin films with different Mg concentrations were grown on a-plane sapphire substrates by combining the two-step deposition and post-annealing techniques using Cu2(Sc1−x Mg x )2O y [X =0.01, 0.05, 0.10] targets. The effects of the Mg doping in the Sc-site on the structural, optical, and electrical properties of the films were investigated. A Mg-doped CuScO2[3R](0001) epitaxial film was obtained at a Mg concentration of 1at%. The slight increase in the a-axis lattice constant and the slight decrease in the c-axis lattice constant of the film were confirmed using two-dimensional X-ray reciprocal space mapping. No significant increase in optical absorption was observed in the film, and the energy gap for direct allowed transition was estimated at 3.7eV. The film showed an increase in the electrical conductivity and carrier concentration and a decrease in the Hall mobility compared with those of the non-doped epitaxial film. The decrease in the overlap of Cu 3d orbitals due to the increase in the a-axis lattice constant is one cause of the decrease in the Hall mobility of the film. The temperature dependence of the electrical transport properties of the film exhibited semiconducting characteristics, and the activation energy estimated from the temperature dependence of the carrier concentration was 0.55eV. [Copyright &y& Elsevier]

Abstract: Epitaxial thin films of CaRu1− x M x O3 (M=Ti, Mn) were fabricated on a (001)-SrTiO3 substrate by spin-coat method using organometallic solutions (metal alkoxides). Results of X-ray diffraction and transmission electron microscopy indicate that the epitaxial films were grown pseudomorphically so as to align the [00l] axis of the CaRu1− x M x O3 films perpendicular to the (001) plane of the SrTiO3 substrate. Ferromagnetism and metal–insulator transition are induced by the substitution of transition metal ions. The occurrence of ferromagnetism was explained qualitatively assuming a TiRu6 cluster model for CaRu1− x Ti x O3 film and a mixed valence model for CaRu1− x Mn x O3 film. Ferromagnetism was also observed for layered CaRuO3/CaMnO3 film and CaRuO3/CaMnO3/CaRuO3/CaMnO3 multilayer film and the magnetism was explained by an interfacial exchange interaction model with magnetic Mn3+, Mn4+, and Ru5+ ions. [Copyright &y& Elsevier]

In this work, the growth properties of Ge1-XSiX epitaxial films grown on Ge substrates were investigated. The structural perfection of the films was controlled by electron diffraction, electron microscopic and X-ray diffraction methods. It has been established that the surface structure of the sample Ge/Ge1-XSiX changes after irradiation by accelerated electrons Φ = 5⋅1016 cm-2, and generated are surface defects which play the role of traps for change carriers. [ABSTRACT FROM AUTHOR]

Abstract: The fabrication of epitaxially grown Zn-substituted LiNbO3 (Zn:LiNbO3) waveguide films and rib waveguides is reported and detailed investigations about microstructure, morphology and optical waveguide properties are provided. Zn:LiNbO3 films were grown on congruent X-cut LiNbO3 substrates by a modified liquid phase epitaxy in solid–liquid coexisting solutions. The homogeneously Zn-substituted films exhibit high crystalline perfection and extremely flat surfaces with averaged surface roughness of rms=0.2–0.3nm. At the film/substrate interface a Zn-containing transient layer has been observed, which allows the growth of elastically strained Zn:LiNbO3 film lattices. X-ray diffraction reciprocal-space measurements prove the pseudomorphic film growth. The refractive index difference between substrate and film depends on the zinc substitution content, which increase with rising growth temperatures. For films with 5.3mol% Zn (Δno ≈+5×10−3) only ordinary ray propagation was observed, while for films with 7.5mol% Zn (Δno ≈+8×10−3, Δne ≈+5×10−3) both modes, TM and TE propagate. Stress-induced refractive index changes are in the order of Δn ≈10−4. In rib waveguide microstructures singlemode propagation with nearly symmetrical field distribution has been observed. To demonstrate the potential of the proton exchange-assisted dry-etching technique interferometer microstructures were fabricated. [Copyright &y& Elsevier]

Abstract: Stress-induced surface instability and evolution of epitaxial thin films leads to formation of a variety of self-assembled surface patterns with feature sizes at micro- and nanoscales. The anisotropy in both the surface and bulk properties of the film and substrate has profound effects on the nonlinear dynamics of surface evolution and pattern formation. Experimentally it has been demonstrated that the effect of anisotropy strongly depends on the crystal orientation of the substrate surface on which the film grows epitaxially. In this paper we develop a nonlinear model for surface evolution of epitaxial thin films on generally anisotropic crystal substrates. Specifically, the effect of bulk elastic anisotropy of the substrate on epitaxial surface pattern evolution is investigated for cubic germanium (Ge) and SiGe films on silicon (Si) substrates with four different surface orientations: Si(001), Si(111), Si(110), and Si(113). Both linear analysis and nonlinear numerical simulations suggest that, with surface anisotropy neglected, ordered surface patterns form under the influence of the elastic anisotropy, and these surface patterns clearly reflect the symmetry of the underlying crystal structures of the substrate. It is concluded that consideration of anisotropic elasticity reveals a much richer dynamics of surface pattern evolution as compared to isotropic models. [Copyright &y& Elsevier]

Abstract: LiMn2O4 epitaxial thin films were synthesized on SrTiO3:Nb(111) and Al2O3(001) single crystal substrates by pulsed laser deposition (PLD) method and the electrochemical properties were discussed comparing with that of amorphous LiMn2O4 film on polycrystalline Au substrate. LiMn2O4 epitaxial film showed only a single plateau in charge–discharge curves and a single redox peak at the corresponding voltage of cyclic voltammograms. This phenomenon seems to originate from the effect of the epitaxy: the film is directly connected with the substrate by the chemical bond and this connection would suppress the phase transition of Li x Mn2O4 film during lithium (de-)intercalation. The discharge voltage of LiMn2O4 epitaxial film on SrTiO3 was lower than that of LiMn2O4 film on Al2O3. This lowered discharge voltage may be caused by the electronic interaction between LiMn2O4 film and SrTiO3:Nb n-type semiconductor substrate. We also attempted to measure the absorption spectrum change of LiMn2O4 epitaxial film on Al2O3 during the lithium (de-)intercalation. The absorption spectrum of LiMn2O4 hardly changed during charging and discharging. This suggests the d orbital of Mn does not concern the 4V region redox of LiMn2O4. [Copyright &y& Elsevier]

Abstract: The paper reports on the results of a study of the synthesis conditions effects on magnetic and transport properties of nanosized layers of high-T c diluted magnetic semiconductors (DMS), such as Ge:Mn, Si:Mn and Si:Fe, fabricated by laser-plasma deposition over a wide range of the growth temperature, T g=(20–550)°C on single-crystal GaAs or Al2O3 substrates. Ferromagnetism of the layers was detected by measurement data of the magneto-optical Kerr effect, anomalous Hall effect, negative magnetoresistance and ferromagnetic resonance (FMR) at 5–500K. The optimum growth temperature, T g, for Si:Mn/GaAs layers with T c≈400K is shown to be about 400°C. The Si:Mn/Al2O3 layers with 35% of Mn have the metal-type of conductivity with manifestation of magnetization up to room temperature. Different types of uniformly doped structures and digital alloys have been investigated. In contrast to GaSb:Mn films, Si-based ferromagnetic layers have strongly different magnetic and electric properties in case of uniformly doped structures and digital alloys. Positive results of the Fermi level variation effect on the improvement of Si- and Ge-based DMS layers have been gained on the use of additional doping with shallow acceptor Al impurity which contributes to the increase of the hole concentration and the RKKY exchange interaction of 3d-ions. The Ge:(Mn, Al)/GaAs or Ge (Mn, Al)/Si layers grown at 20°C feature surprising extraordinary angular dependence of FMR. [Copyright &y& Elsevier]

• Real time growth of Fe on Ag is monitored through RHEED. • Ion beam erosion induces morphology induced uniaxial magnetic anisotropy. • Coupled Cubic and uniaxial magnetic anisotropy leads to multi jump hysteresis loop. • Magnetic domain dynamics reveals magnetization reversal through 180° and 90° domain wall motion. Growth and magnetic characterization of Fe film on ion-sculpted Ag(0 0 1) substrate have been studied in-situ using reflection high energy electron diffraction and magneto-optical Kerr effect. Fe film is found to grow epitaxially on the Ag surface and exhibits epitaxial island formation up to ∼ 1 nm film thickness. Ion beam sculpting of the substrate surface, prior to the deposition of the Fe film, induces an uniaxial magnetic anisotropy in Fe film, which couples with the cubic four-fold anisotropy of bcc-Fe, lead to the multiple-step jump in magnetic hysteresis loops. Magnetic switching and its correlation with the domain dynamics of the film, as studied by the Kerr microscopy technique, revealed a striking difference in domain structure depending upon the direction of the applied magnetic field with respect to crystallographic direction. It is found that the magnetization reversal takes place via a "single-step jump" mechanism through sweeping of 180° domain walls, whereas the combination of coherent rotation and the sweeping of 90° domain walls is responsible for a "double step jump" magnetization reversal. [ABSTRACT FROM AUTHOR]

The transition metal oxide NiCo 2 O 4 has aroused extensive research interest due to its metallic conductivity, but the precise nature of the conductivity remains elusive. In this study, the dependence of the metallic behavior in NiCo 2 O 4 epitaxial films on temperature and film thickness are investigated for film thicknesses in the range of 7–155 nm. Our results show that a subtle lattice distortion caused by the substrate is necessary for metallic behavior in NiCo 2 O 4 films. The widest temperature window for the metallic behavior is obtained for a 31-nm thick NiCo 2 O 4 film. The NiCo 2 O 4 films thinner than 31 nm are quasi-two-dimensional, and are affected by substrate clamping. In these films, conduction is constrained by electron–electron and electron–magnon scattering. However, NiCo 2 O 4 films thicker than 31 nm are three-dimensional, exhibiting long-range structural order, with electrical transport constrained mainly by electron–phonon scattering, as well as electron–electron and electron–magnon scattering. Our study demonstrates that the metallic behavior in NiCo 2 O 4 films can be tuned using the film thickness, which is of great significance for application of NiCo 2 O 4 in development of alternative ferroelectric metal electrodes in magnetic tunnel junctions. • Metallic behavior of NiCo 2 O 4 films with different thickness was studied. • A subtle lattice distortion is necessary for metallic behavior in NiCo 2 O 4 films. • The widest temperature window for metallic behavior is 316 K. • Electron (e)–e and e–magnetron scattering dominate conduction in thinner NiCo 2 O 4 film. • The e–photon interaction becomes more apparent in the thicker NiCo 2 O 4 film. [ABSTRACT FROM AUTHOR]

The critical thickness of structural transition from a tetragonal structure to a normal bulk structure for epitaxial ultrathin films deposited on the metallic and semiconductor substrates is thermodynamically considered. It is found that equilibrium between the elastic energy of the tetrahedral structure and the film–substrate interface energy is present when a critical thickness is reached. The predictions of the critical thickness are in agreement with the experimental results of films. [ABSTRACT FROM AUTHOR]

Abstract: Ferromagnetic thin films of the ilmenite–hematite solid solution Fe2− x Ti x O3 with x=0.6 and x=0.8 have been grown on (001) sapphire substrates. X-ray diffraction analysis reveals that the films are single phase with the ilmenite crystal structure. Strong easy-plane anisotropy is observed for the two films, which are nominally n or p type with K 1=−8×106 Jm−3 for x=0.6 and −11×106 Jm−3 for x=0.8 at T=4K. The trigonal splitting of the 5T2g energy level of Fe2+ is inferred to be 0.11eV, and the zero-field splitting parameter D to be equal to 15K. [Copyright &y& Elsevier]

Tetragonal Pb(Zr, Ti)O3 films were epitaxially grown on SrRuO3-coated SrTiO3 substrates by metal organic chemical vapor deposition. Perfect polar-axis-oriented 50 nm thick tetragonal films were successfully grown on (100)SrRuO3//(100)SrTiO3 substrates. The single phase of the tetragonal symmetry region was expanded to a Zr/(Zr + Ti) ratio of around 0.6 for these films but was reduced to around 0.4 when (100)/(001)-mixture oriented 250 nm thick films were obtained. The dependence of spontaneous polarization (Ps) on the lattice parameter of c-axis to a-axis (c/a ratio) was demonstrated using perfectly polar-axis-oriented films with various Zr/(Zr + Ti) ratios. The 250 nm thick (100)/(001), (110)/(101), and (111)-oriented tetragonal films were grown on (100), (110), and (111)-oriented substrates. The domain structure was analyzed in detail, and it was found that the observed saturation polarization (Psat) value can be explained by the Ps value and the 90° domain contribution. These data clearly demonstrate the importance of epitaxial film research for actual ferroelectric random access memories applications. [ABSTRACT FROM AUTHOR]

Abstract: A CuScO2(0001) epitaxial film with an oxygen intercalation layer was formed by annealing using oxygen radicals, and the electrical and optical properties of the epitaxial film were investigated. The thickness of the layer was 60 nm from the film surface, and its electrical conductivity was analyzed by using the two-layer model. The dependence on temperature of the electrical conductivity and Seebeck coefficient revealed that the dominant conduction mechanism of the layer was a small polaron conduction above 150 K and that it changed to two-dimensional variable-range hopping conduction below 150 K. The optical average transmittance of the epitaxial film was larger than 65% in the visible/near-infrared regions, while the energy gap for direct allowed transition was estimated as 3.7 eV. [Copyright &y& Elsevier]

Abstract: The kinetics of intercalation are discussed using a pulsed laser deposition (PLD) film electrode and electrochemical impedance analysis. Films of LiNi0.8Co0.2O2, deposited on single crystal substrates, were used for the study. The films have intercalative or blocking orientations on different crystal surfaces of the substrates. Impedance spectra show that there are at least three elemental processes in intercalation. Two processes at higher frequencies suggest that they occur at the electrode surface and are influenced by the orientation of the film. The third process appearing at low frequencies below 1Hz indicates lithium motion in the bulk structure and shows the largest resistance among the three processes. This lithium conduction in a thin PLD film shows a semicircular response and is considered to be influenced more by the structure due to the nanometer-scale thickness. [Copyright &y& Elsevier]