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The ground-breaking properties of biaxially textured thin films have attracted increasing attention to the characterization and growth theory of their crystal morphologies. In particular, multi-faceted columnar structures developed during oblique angle deposition (OAD) show abnormal tilt angles that have not been previously captured by existing models. Current theories for the formation of biaxially aligned columnar structures overlook the fact that the surface diffusion on individual facets can be finite. In this work, a continuum model incorporating finite adatom mobility, flux-dependent sticking coefficient, and material-specific surface energies is employed to study the growth of a well-known MgO-OAD system. Experimentally observed morphologies are reproduced by simulating the shadowing growth of an array of preferentially oriented single crystals. We show that the abnormal tilting is elusive considering only the effects of faceting and shadowing. A proposed sticking coefficient in our model, determined by the component of adatom momentum parallel to the surface, is responsible for the development of abnormal tilting. The role of faceting is demonstrated by its effect on the resulting columnar morphologies. Using the proposed model, the characteristic morphology and tilting behavior of a CaF 2 -OAD system are also obtained, which agree with experiments. [ABSTRACT FROM AUTHOR]

Angle-resolved photoemission spectroscopy (ARPES) measurements have established the phenomenon of kink in band dispersion of high-Tc cuprate superconductors. However, systematic studies of the kink in electron-doped cuprates are still lacking experimentally. We performed in situ ARPES measurements on La2−xCexCuO4±δ (LCCO) thin films over a wide electron doping (n) range from 0.05 to 0.23. While the nodal kink is nearly invisible, an antinodal kink around 45 meV, surviving above 200 K, is observed for n ~ 0.05–0.19, whose position is roughly independent of doping. The fact that the antinodal kink observed at high temperatures and in the highly overdoped region favors the phonon mechanism with contributions from the Cu–O bond-stretching mode and the out-of-plane oxygen buckling mode. [ABSTRACT FROM AUTHOR]

Anatase TiO2 nanorods with a well-defined ⟨ 110 ⟩ texture have been studied using a model-based characterization technique based on a previous modeling framework. Intricate secondary side facet characteristics of tilt angles of 26.5 ° have been indexed, and a ⟨ 112 ⟩ growth direction of the well-aligned facets is identified. These results have not been accessed experimentally but crucial in understanding the nature of the most abundant facets and their structural properties. We find agreement between our results and indirect experimental measurements. Highly exposed {116} facets are found to be responsible for excellent electrochemical surface properties in nanostructured anatase TiO2 thin films. [ABSTRACT FROM AUTHOR]

The finite size effect power law in Cu-doped Ni thin film were investigated by probing the Curie temperature (Tc)-dependence on the NixCu1-x thin film thickness. It is found that both magnetization and Tc decreases proportional to the Cu content. Tc is directly proportional to the number of pairwise spin-spin interactions in a manifold cluster of spins according to the mean field approximation. The experiment results confirm the spin bag model built in ultrathin magnetic films previous, in which each spin interacts equally strongly with neighbors over some finite interaction length N0. Furthermore, upon varying the composition of the Ni-Cu alloys, the range of spin-spin interactions N0 decreases with increasing concentration of the Cu. Since there is little change of the band structure and conduct electron properties in NixCu1-x alloy films, this phenomenon was attributed to the decreasing of the propagation distance of conduct electrons due to the scattering by the Cu impurities. The present results indicate the ferromagnetic order in 3d metal probably delivered by the itinerant electrons. [ABSTRACT FROM AUTHOR]

Two thin epitaxial GaAs films on Ge substrates were characterized by photoluminescence (PL), contactless electroreflectance (CER), and piezoreflectance (PzR) techniques. The GaAs films containing antiphase domains (APDs) and those APD free were grown at 650 °C by metal organic vapor phase epitaxy. The PL intensity of the APD-containing film is four orders of magnitude lower than that of the APD-free sample. The reduction in intensity is due to the electrically active Ga–Ga and As–As bonds at the boundaries between the different APDs. The electric fields deduced from Franz–Keldysh oscillations of the CER spectra were used to determine the net carrier concentration of the GaAs films. In addition, the conduction to light-hole band transitions and the conduction to heavy-hole band transitions that originated from strain induced valence band splitting in GaAs thin films were observed and identified through a comparison of the relative intensities of light- and heavy-hole related features in the PzR and CER spectra. The results demonstrate that PL, CER, and PzR are useful nondestructive tools to characterize thin epitaxial GaAs films on Ge substrates. [ABSTRACT FROM AUTHOR]

A stiff thin film on a heated compliant substrate may buckle when the system is cooled due to the thermal expansion mismatch between the film and substrate. Highly ordered and disordered herringbone patterns (wavy structures) then emerge as the system continues to cool. We have established an analytic approach to study one-dimensional, checkerboard, and ordered herringbone buckling patterns. The analytical approach gives the buckle wave length and amplitude in terms of the thin film and substrate elastic properties, thin film thickness, and the thermal strain. It is shown that the herringbone mode has the lowest energy, which explains why this mode is frequently observed in experiments. These classes of materials might be interesting as a route to high performance electronics with full, two-dimensional stretchability. [ABSTRACT FROM AUTHOR]

In this study we investigate the possibility of nucleating nanocrystalline cubic boron nitride (c-BN) thin films directly onto suitable substrates without the soft turbostratic BN (t-BN) interlayer that is usually observed. This would open a path to the epitaxial growth of c-BN films which is essential particularly for practicable applications in electronic devices. Appropriate substrates are required to exhibit a lattice that matches the c-BN crystallite structure, survives the ion bombardment imperative for c-BN film formation, and is not disturbed by the development of a heterogeneous interface layer. In accordance with these criteria, monocrystalline AlN is selected and employed as a potential substrate for direct c-BN film growth using mass selected ion beam deposition. A detailed examination of the BN/AlN interface microstructure by cross-sectional high-resolution transmission electron microscopy reveals that the AlN crystallinity is indeed retained, with no amorphous layer next to the BN film as commonly observed on Si substrates. Nanocrystalline BN grains with the cubic, and, more frequently, with the wurtzitic structure are found in direct contact with certain regions of the rugged AlN substrate, covering about one-third of its entire surface with no mediating t-BN or other interface layer. The c-BN and w-BN growth areas are textured and exhibit definite preferential orientation relationships with the faceted AlN substrate surface. The consequences of these findings for the understanding of the role of the t-BN interlayer in c-BN film nucleation are discussed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

MnBi is a promising ferromagnetic material for applications at elevated temperatures due to its high Curie temperature, sizable magnetocrystalline anisotropy, and increasing coercivity with temperature. However, fabrication of MnBi thin films with ferromagnetic low-temperature phase (LTP) is conventionally difficult due to the peritectic Mn-Bi reaction and Mn oxidization. In this work, in situ Ar+-ion beam bombardment was introduced to modify the microstructure and magnetic properties of (Mn/Bi)n superlattice. Structural characterization revealed formation of MnBi LTP in the as-deposited ion-beam-bombarded samples. Vacuum annealing further promoted growth of MnBi LTP grains with c-axis orientation, leading to remarkably improved perpendicular magnetic anisotropy. Ion-beam bombardment resulted in a 200% increase in the saturation magnetization of the annealed MnBi thin film. This advancement is attributed to the enhanced interdiffusion and reaction of Mn and Bi in the ion-beam-bombarded thin films. A stability test after 150 days in air revealed a remarkable reduction in ferromagnetism due to MnBi decomposition. This work provides an effective approach for fabrication of high-quality MnBi thin films. [ABSTRACT FROM AUTHOR]

Provides information on a study concerning the growth and characterization of bismuth-lead-strontium-calcium-copper-oxygen thin films on single crystal magnesium oxide substrates by magnetron sputtering with a single target. Comparison of the post-annealing conditions of thin films; Application of sintering method in thin films.

Highly anisotropic face-centered-tetragonal (fct) CoPt and fct FePt nanoparticles have been prepared and embedded in a C or BN matrix by cosputtering from pure Co[sub 50]Pt[sub 50], BN, and Fe[sub 50]Pt[sub 50], C solid targets using a tandem deposition mode. The as-made films show a disordered face-centered-cubic structure which is magnetically soft and have low coercivity (<20 Oe). Magnetic hardening occurs after heat treatment at elevated temperatures, which leads to increase in coercivity to values up to 15 kOe at room temperature. The hardening is due to the formation of nanoparticles with the highly anisotropic fct with anisotropy K>10[sup 7] erg/cm[sup 3]. Transmission electron microscope studies showed FePt particles embedded in C matrix with a size increasing from below 3 nm in the as-made state to about 8 nm in the optimum annealed state. These results are very promising and make these materials potential candidates for high-density magnetic recording. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Searching strain sensitive materials for electronic skin is of crucial significance because of the restrictions of current materials such as poor electrical conductivity, large energy consumption, complex manufacturing process, and high cost. Here, we report a flexible strain sensor based on the Zr55Cu30Ni5Al10 metallic glass thin film which we name metallic glass skin. The metallic glass skin, synthesized by ion beam deposition, exhibits piezoresistance effects with a gauge factor of around 2.86, a large detectable strain range (~1% or 180° bending angle), and good conductivity. Compared to other e-skin materials, the temperature coefficient of resistance of the metallic glass skin is extremely low (9.04 x 10-6K-1), which is essential for the reduction in thermal drift. In addition, the metallic glass skin exhibits distinct antibacterial behavior desired for medical applications, also excellent reproducibility and repeatability (over 1000 times), nearly perfect linearity, low manufacturing cost, and negligible energy consumption, all of which are required for electronic skin for practical applications. [ABSTRACT FROM AUTHOR]

Presents a study that examined magnetic properties of ion-beam sputter-deposited iron-nickel-boron-silicon films. Experimental procedure; Results and discussion; Conclusion.

Obtaining high-quality thin films of 5d transition metal oxides is essential to explore the exotic semimetallic and topological phases predicted to arise from the combination of strong electron correlations and spin-orbit coupling. Here, we show that the transport properties of SrIrO3 thin films, grown by pulsed laser deposition, can be optimized by considering the effect of laser-induced modification of the SrIrO3 target surface. We further demonstrate that bare SrIrO3 thin films are subject to degradation in air and are highly sensitive to lithographic processing. A crystalline SrTiO3 cap layer deposited in-situ is effective in preserving the film quality, allowing us to measure metallic transport behavior in films with thicknesses down to 4 unit cells. In addition, the SrTiO3 encapsulation enables the fabrication of devices such as Hall bars without altering the film properties, allowing precise (magneto)transport measurements on micro- and nanoscale devices. [ABSTRACT FROM AUTHOR]

In this study, hydrogenated amorphous silicon (a-Si:H) single junction and amorphous/microcrystalline silicon tandem (a-Si:H/µc-Si:H) solar cells with different back-reflectors (BRs) are systematically investigated. A novel white polyvinyl butyral (PVB) foil was used as BR. In addition, the specular aluminum (Al) films and rough Al films were deposited on back float glasses as BRs as well, which were integrated onto the front glass covered with solar cells by laminating with a transparent PVB encapsulation foil. It is found that both types of solar cells (a-Si:H and a-Si:H/µc-Si:H) with white PVB foil BRs show a higher short circuit current density ( Jsc) compared to the cells with a specular Al BR. It is mainly due to a high light scattering of white PVB foils. Moreover, the cell with a rough Al film BR shows a low Jsc close to that of cell without any BRs. The great light losses inside the solar cell may be mainly caused by the plasmonic absorption on the rough Al film surface. An a-Si:H solar cell of 8.3% and an a-Si:H/µc-Si:H tandem solar cell of 10.1% were obtained, in which the white PVB foils were used as BRs. [ABSTRACT FROM AUTHOR]

The degradation behaviors of hydrogenated amorphous/microcrystalline silicon (a-Si:H/µc-Si:H) tandem solar cells are systematically investigated. It is found that the degradation of the tandem solar cells takes place not only under the light soaking but also after dark storage. The degradation in the efficiency of tandem solar cells is mainly due to a reduction of fill factor (FF) in our study. Different from light-induced degradation (LID) behaviors for the tandem solar cells, the degradation behaviors under dark storage, i.e., the dark degradation could be mainly caused by the cracks or voids formed in the bottom µc-Si:H cell. These defects could lead to an oxidization of internal silicon surfaces by the oxygen atoms. The stabilities of the top a-Si:H cells and the ZnO:B electrodes are also investigated. Furthermore, adjusting the crystallinity of intrinsic µc-Si:H material and inserting an intermediate light reflective (ILR) layer between the top cell and bottom cell can improve the performances of the novel structure tandem solar cells. A gain of 0.7% in efficiency is achieved, and meanwhile no dark degradation is observed for the novel tandem solar cells. [ABSTRACT FROM AUTHOR]

Abstract: Crystalline silicon carbide alloys have a very high potential to be used as transparent conductive window layers in thin-film solar cells provided they can be prepared in thin-film form and at compatible deposition temperatures. Using Hot-Wire Chemical Vapor Deposition (HWCVD) technique, silicon carbide in microcrystalline form (μc-SiC:H) has been prepared at low substrate temperature. Monomethylsilane and hydrogen are used as the precursor gases. The material is highly conductive, unintentionally n-type in nature, and possess wide optical gap. These properties have been utilized by employing the μc-SiC:H layer as the window layer in n-side illuminated single junction microcrystalline silicon (μc-Si:H) solar cells. Some typical issues related to this device research and development are described here. In particular the nucleation of the intrinsic μc-Si:H absorber layer on the n-type μc-SiC:H layer needs attention. With proper device design high short-circuit current densities of 29.6mA/cm2 and quantum efficiencies up to 90% are obtained resulting in a maximum conversion efficiency of 9.6% within a 2-μm-thick μc-Si:H solar cell. [Copyright &y& Elsevier]