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Studying size effects on the modification of thin film physical properties requires the preparation of films with desired microstructures and stress states. For the model system of epitaxial niobium thin films on sapphire [ 11 2 ¯ 0 , miscut < 0.1°] substrates surface topographies and stress states were systematically studied depending on the films' thickness (5 nm – 100 nm) and the deposition temperature (470 °C to 870 °C). Initial stresses, domain structures and textures of the films were characterized using X-ray diffraction techniques. The films' surface topographies were measured by scanning tunneling microscopy and atomic force microscopy, and classified into three different regimes: smooth (2D), rough (3D) and pitted (or 'meander-like'). Determination of the regimes' transition temperatures enables the tuning of the films microstructures and related stress states for each film thickness. • Topography of epitaxial Nb films depends on film thickness and deposition temperature. • Film surface splits up in 2D and 3D morphologies. • Tayloring of film topography and stress state is possible. • Proper sputter conditions for smooth films with thickness varying from 5 nm to 100 nm are deduced. [ABSTRACT FROM AUTHOR]

Abstract Bismuth ruthenate (Bi 2 Ru 2 O 7) thin films were deposited on (111) yttria-stabilized zirconia (YSZ) single crystals and (111)YSZ//(111)Si substrates by chemical vapor deposition using Bi(CH 3) 2 [2-(CH 3) 2 NCH 2 C 6 H 4 ] and Ru(C 7 H 11)(C 7 H 9) as source materials and oxygen as a reactant gas. The film composition and X-ray diffraction ω -2 θ scan profiles for thin films deposited using various source flow rate ratios revealed the existence of a process window to obtain stoichiometric Bi 2 Ru 2 O 7. Within the process window, the kind of substrates did not strongly affect the deposition rates of Bi and Ru or the Bi/Ru ratio of the deposited films. It was also confirmed that the Bi 2 Ru 2 O 7 thin films grew epitaxially on both substrates within the process window. In particular, epitaxial Bi 2 Ru 2 O 7 thin films grew on the Si substrate with a YSZ buffer layer. Scanning electron microscopy revealed the formation of continuous dense Bi 2 Ru 2 O 7 films without any cracks or voids, and a relatively smooth interface between Bi 2 Ru 2 O 7 and the YSZ buffer layer on Si. The resistivity of the Bi 2 Ru 2 O 7 films was almost constant (~550 and ~950 μΩcm for the films deposited on (111)YSZ single-crystal substrates and (111)YSZ//(111)Si substrates, respectively), even when the ratio of Bi and Ru source gas flow rates was changed in the process window. In addition, the resistivity of Bi 2 Ru 2 O 7 films prepared on both kinds of substrates was almost independent of temperature from 10 to 300 K. Highlights • Bi 2 Ru 2 O 7 thin films were deposited by chemical vapor deposition process. • The process window for epitaxial pyrochlore Bi 2 Ru 2 O 7 film growth was confirmed. • The resistivity of the Bi 2 Ru 2 O 7 films was close to that of a single crystal Bi 2 Ru 2 O 7. [ABSTRACT FROM AUTHOR]

Epitaxial magnesium ferrite thin films have been grown by molecular beam epitaxy (MBE) on MgO(100). Growth conditions such as substrate temperature and growth rates were optimized. By using different characterization techniques, structural, electrical and optical properties of the films were studied as a function of Mg content. In particular, we highlight the importance of the growth rate on the actual Mg/Fe ratio in the film. [ABSTRACT FROM AUTHOR]

Fabrication of highly oriented Y doped BaZrO 3 (Ba(Zr,Y)O 3 :BZY) films on YBa 2 Cu 3 O x (YBCO) sacrificial buffer layers was investigated. To clarify requirements of orientation control, BZY films were fabricated on various substrates using pulsed laser deposition (PLD). Cube-on-cube orientation relationship was obtained in BZY films on SrTiO 3 , LaAlO 3 , and MgO(100) regardless of PLD conditions, but orientation of BZY was strongly dependent on PLD conditions on yttria stabilized zirconia(YSZ) and CeO 2 (100), showing that perovskite structure or almost the same lattice parameter as BZY is needed to obtain cube-on-cube orientated BZY films. Cube-on-cube orientated BZY films were fabricated on YBCO, whose structure was perovskite, under wide ranging PLD conditions, showing that YBCO sufficiently controls crystalline orientation of BZY films. In addition, highly oriented BZY films were obtained on YBCO/YSZ/Si(100), demonstrating epitaxial BZY films on Si. Since good selective etching ability is also needed in sacrificial buffers, YBCO/BZY films were etched using H 3 PO 4 . H 3 PO 4 etching removed the YBCO sacrificial buffers without damaging BZY with etching rate of ~ 30 nm/s. The present results show that YBCO sacrificial buffer layers are promising for fabrication of the μSOFCs with highly oriented BZY. [ABSTRACT FROM AUTHOR]

Electrical properties of ferroelectric capacitors based on PbZr 0.52 Ti 0.48 O 3 thin films grown by pulsed laser deposition on silicon substrate with SrTiO 3 buffer layer grown by molecular beam epitaxy were studied. A SrRuO 3 layer was deposited as bottom electrode also by pulse laser deposition and Pt, Ir, Ru, SrRuO 3 were used as top contacts. Electrical characterization comprised hysteresis and capacitance–voltage measurements in the temperature range from 150 K to 400 K. It was found that the macroscopic electrical properties are affected by the electrode interface, by the choice of the top electrode. However, even for metals with very different work functions (e.g. Pt and SrRuO 3 ) the properties of the top and bottom electrode interfaces remain fairly symmetric suggesting a strong influence from the bound polarization charges located near the interface. [ABSTRACT FROM AUTHOR]

Ilmenite–hematite solid solution (Fe 2– x Ti x O 3 ) is one of the candidates for high-temperature magnetic semiconductors. Well-crystallized and epitaxially formed Fe 2– x Ti x O 3 films on α-Al 2 O 3 (112¯0) single-crystalline substrates were tried to fabricate by using reactive sputtering technique. The detailed structural properties of (112¯0)-oriented epitaxial Fe 1.4 Ti 0.6 O 3 films were analyzed by using transmission electron microscope (TEM). The films showed large magnetization and typical semiconductive conduction at room temperature. However their anisotropic properties were rather small than expected, though the films had good crystallinity with preferred orientation. The TEM observations clearly revealed that the (112¯0)-oriented Fe 1.4 Ti 0.6 O 3 films on α-Al 2 O 3 (112¯0) were partly composed of the (0001)-oriented grains. Formation of the (0001)-oriented grains could reduce the anisotropic properties of the (112¯0)-oriented films. [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]

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]

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]

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: 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: 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: 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]

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: Hall and conductivity measurements have been performed on epitaxial and polycrystalline CuGaSe2 films. Temperature dependencies of charge carrier concentration and mobility are analyzed in terms of band transport model and standard scattering mechanisms, and are fitted simultaneously. Defect concentrations are lower than previously reported. Dominant scattering mechanisms in the single crystalline films are nonpolar optical phonon and acoustical phonon scattering, and charged defect scattering. Room temperature mobility in polycrystalline films is considerably lower than in epitaxial films. This can not only be attributed to scattering at extended defects. [Copyright &y& Elsevier]

Preparation of the single crystal-like thin films of zinc oxide (ZnO), which is expected to be a next generation semiconductor, is usually studied using sapphire substrates because there is no other appropriate oxide substrate that has the same hexagonal crystal structure as ZnO. Here we study the fabrication of ZnO films on the (111) plane of cubic crystals such as (LaAlO3)0.3(Sr0.5Ta0.5O3)0.7 (LSAT) which have the same C6 symmetry as ZnO, since film preparation on substrates is involved in developing opto-electronic devices. By using pulsed laser ablation deposition, high quality ZnO(0001) epitaxial films were fabricated on the cubic(111) substrate plane as well as the sapphire(0001) plane. These have a band gap of ∼3.25 eV and high electric-resistivity of over 0.40 Ω-cm, and show a high optical transmittance of over 85% in the near ultraviolet and visible region. Those are fundamental characteristics for the starting matrix in developing wide band gap semiconductors by hole and electron doping. [Copyright &y& Elsevier]

Abstract: Single-crystalline Ti1−x Nb x O2 (x =0.2) films of 40 nm thickness were deposited on SrTiO3 (100) substrates by the pulsed laser deposition (PLD) technique. X-ray diffraction measurement confirmed epitaxial growth of anatase (001) film. The resistivity of Ti1−x Nb x O2 films with x ≥0.03 is 2–3×10−4 Ω cm at room temperature. The carrier density of Ti1−x Nb x O2, which is almost proportional to the Nb concentration, can be controlled in a range of 1×1019 to 2×1021 cm−3. Optical measurements revealed that internal transmittance in the visible and near-infrared region for films with x =0.03 was more than 97%. These results demonstrate that the presently developed anatase Ti1−x Nb x O2 is one of the promising candidates for the practical TCOs. [Copyright &y& Elsevier]