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The interplay of bulk and boundary scattering is explored in a regime where quantum size effects modify mesoscopic transport in a degenerate Fermi liquid film of He on a rough surface. We discuss mass transport and the momentum relaxation time of the film in a torsional oscillator geometry within the framework of a quasiclassical theory that includes the experimentally determined power spectrum of the rough surface. The theory explains the anomalous temperature dependence of the relaxation rate observed experimentally. We model further studies on He confined in nanofluidic sample chambers with lithographically defined surface roughness. The improved understanding of surface roughness scattering can be extended to the analogous system of electrons in metals and suggests routes to improve the conductivity of thin metallic films. [ABSTRACT FROM AUTHOR]

Transmission spectra (400–1500 nm) of thermally evaporated amorphous [(As2Se3)90Ge10]95M5 thin films have been analyzed to study the effect of impurities (M = Cd and Pb) on their optical properties. The refractive index increases with addition of metal impurities. The dispersion of refractive index has been studied using Wemple–DiDomenico single oscillator model. The optical gap has been estimated using Tauc’s extrapolation and was found to decrease with the addition of metal impurities from 1.46 to 1.36 eV (Cd) and 1.41 eV (Pb) with an uncertainty of ±0.01 eV. The change in optical properties with metal impurities has been explained on the basis of density, polarizability and bond energy of the system. [ABSTRACT FROM AUTHOR]

Polycrystalline Pb1− x Sr x (Fe0.012Ti0.988)O3 (0.2≤ x≤0.4) (PSFT) thin films have been grown on fused quartz substrates by metallo-organic decomposition technique. The grown films were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), source meter and UV–Vis–NIR spectrophotometer to determine the structural, microstructural, dc resistivity and optical properties. The XRD pattern confirmed that the PSFT films has distorted tetragonal single phase, which close to cubic at higher Sr concentration. AFM analysis revealed that the grains size reduces with increasing Sr concentration and their average values lies in the range of 26–9 nm. The higher values of dc resistivity of PSFT nano grains indicate that the transmission of light occurs within these grains up to short wavelength. The refractive index and the extinction coefficient were determined from the optical transmission spectrum in the wavelength range of 200–1100 nm and compared with that theoretically calculated, when fitted to a single oscillator model. The values of optical band gap were determined from Tauc’s extrapolation fitting and suggests that the transformation of electrons during transmission of light through local states within Fermi gap. [ABSTRACT FROM AUTHOR]

The effect of deposition parameters, i.e. type of substrate (microscope glass, quartz and mica) and thickness (500 nm, 800 nm and 1100 nm), on the optical properties of Ge10Se90-xTex (x = 0, 10, 20, 30, 40, 50) thin films was investigated. Thin films were deposited by the vacuum evaporation technique at a base pressure 10-4 Pa. Optical transmission measurements were used to determine the refractive index (n) and optical energy gap [image omitted]. Transmission spectra were obtained in the spectral range 400-1500 nm. With an increase of film thickness, the optical energy gap was found to increase, whereas no significant change was observed for the refractive index within experimental error. For different substrates used in deposition of the thin films, the refractive index follows the order nmica > nmicroscope glass > nquartz. The optical energy gap of films deposited on mica substrate is the smallest, whereas for microscope glass and quartz substrates it remains nearly the same. [ABSTRACT FROM AUTHOR]

Abstract: Incorporation of impurities into the semiconductors by high energy heavy ions is a non-equilibrium process, which can result in intriguing near surface or subsurface property changes depending upon the energy of the ion. Present work deals with the optical study of Ni ion irradiated Ge20Se80−xBix thin films samples. The thin film samples were deposited by the flash evaporation method at 10−5Torr and were characterized by XRD, XRF, EPMA and DSC. Irradiation was done on samples with a Ni ion beam of 75MeV energy. The optical spectra of the films were recorded and the optical band gap study was done both as a function of dose (5×1012 to 1014 ions/cm2) as well as composition of the samples. The optical band gap was found to decrease with increasing Bi content as well as with increasing dose. [Copyright &y& Elsevier]

The simple binary compound, MgB[sub 2], has created enormous excitement, due to its remarkably high T[sub c] (39 K), its exotic electronic and phononic structure, as well as its potential technological application. However, contrary to the initial expectation, worldwide efforts to enhance the T[sub c] of this material by means of chemical doping and applying hydrostatic pressure have failed. Investigations of other diborides or related materials have also resulted in finding of lower T[sub c]'s. In this letter we report a slight, but significant enhancement of T[sub c] in MgB[sub 2] films grown on boron crystals, which may stem from tensile-type strain. This finding opens up a new possibility for further optimizing T[sub c] in MgB[sub 2] and perhaps in related materials. © 2001 American Institute of Physics. [DOI: [10.1063/1.1427157]. [ABSTRACT FROM AUTHOR]

In this paper we show that experimentally realizable apparently piezoelectric thin-film superlattices can be created from nonpiezoelectric materials provided an odd-order (e.g., trilayer) stacking sequence is used. The size-dependent mechanism of flexoelectricity, which couples gradients of strain to polarization, allows such a possibility. We present closed-form analytical expressions for the response of various thin-film and superlattice configurations. We also clarify some of the subtleties that arise in considering interface boundary conditions in the theory of flexoelectricity as well as the relationship of flexoelectricity to the frequently used polarization gradient terms used in modeling ferroelectrics. We find that for certain (optimum) material combinations and length scales, thin-film superlattices yielding apparent piezoelectricity close to 75% of ferroelectric barium titanate may be achievable. [ABSTRACT FROM AUTHOR]

The room temperature electronic transport properties of 1 μm thick Bi0.4Sb1.6Te3 (BST) films correlate with overall microstructural quality. Films with homogeneous composition are deposited onto fused silica substrates, capped with SiN to prevent both oxidation and Te loss, and postannealed to temperatures ranging from 200 to 450 °C. BST grain sizes and (00l) orientations improve dramatically with annealing to 375 °C, with smaller increases to 450 °C. Tiny few-nanometer-sized voids in the as-deposited film grain boundaries coalesce into larger void sizes up to 300 nm with annealing to 350 °C; the smallest voids continue coalescing with annealing to 450 °C. These voids are decorated with few-nanometer-sized Sb clusters that increase in number with increasing annealing temperatures, reducing the Sb content of the remaining BST film matrix. Resistivity decreases linearly with increasing temperature over the entire range studied, consistent with improving crystalline quality. The Seebeck coefficient also improves with crystalline quality to 350 °C, above which void coalescence and reduced Sb content from the BST matrix correlate with a decrease in the Seebeck coefficient. Nevertheless, a plateau exists for an optimal power factor between 350 and 450 °C, implying thermal stability to higher temperatures than previously reported. [ABSTRACT FROM AUTHOR]

• Nano-deposits at different deposition temperatures have hexagonal wurtzite structures with (1 0 1) plane. • Deposits prepared at 723 K have higher crystallinity with few dislocations' density. • Films deposited at 723 K demonstrate enhanced electrical properties. • Photoluminescence studies indicate near-white light emission across all thin films. • The total nonlinear susceptibility decreases as the deposition temperature rises. This study reports the influence of deposition temperature (573 K-773 K) on the microstructural, linear and nonlinear optical properties of zinc oxide nano thin films synthesized using the chemical spray pyrolysis method. Synthesized films are polycrystalline, exhibiting a dominant (1 0 1) orientation, for which the crystallite size is found to increase with deposition temperature up to 723 K followed by a decrease. Concurrently, the deposit prepared at 723 K showed improved electrical properties, i.e. higher charge carrier concentration and mobility. Optical studies reveal increased transmittance in the visible region and a gradual increase of optical bandgap with deposition temperature. The photoluminescence studies show a near-white light emission for all thin films, however, the density of defect states was comparatively higher for thin films deposited at lower temperatures. A saturable absorption behaviour was observed due to the presence of defects. The thin films show a negative refractive index with self-defocusing phenomena. The total nonlinear susceptibility is found to decrease with increasing deposition temperature, and the solution-processed functional thin films thus have potential implications for nonlinear optical applications such as nonlinear optical switching, optical memory management, and saturable absorbers. [ABSTRACT FROM AUTHOR]

Abstract: The effect of hydrogen absorption on the electrical resistance and activation energy of thin film was investigated. The samples were prepared by oblique deposition at different angles (, and ) simultaneously at a pressure of Torr at room temperature and thickness of thin film were measured using quartz crystal thickness monitor. It was found that the resistance and activation energy of thin films increases with the angle of deposition. The activation energy of films is found to be higher than films for the same deposition angle and also increases with angle of deposition. The activation energy of hydrogenated samples in lower temperature range is found to increase with hydrogen charging cycle but in higher temperature range activation energy of hydrogenated samples is found to decrease due to discharge of hydrogen. [Copyright &y& Elsevier]

Amorphous Fe73.9Nb3.1Cu0.9Si13.2B8.9 thin films have been produced by ion beam sputtering with two different beam energies (500 and 1000 eV). Magnetic measurements indicate that the samples display a uniaxial magnetic anisotropy, especially for samples prepared with the lower beam energy. Magnetization relaxation has been measured on both films with an alternating gradient force magnetometer and magneto-optical Kerr effect. Magnetization relaxation occurs on time scales of tens of seconds and can be described with a single stretched exponential function. Relaxation intensity turns out to be higher when measured along the easy magnetization axis. [ABSTRACT FROM AUTHOR]

Phenyl C 61 butyric acid methyl ester (PCBM) is a fullerene derivative and most commonly used in organic photovoltaic devices both as electron acceptor and transporting material due to high electron mobility. PCBM is easy to spin caste on some substrate as it is soluble in chlorobenzene. In this study, the spin coated thin films of PCBM (on two different substrate, glass and double sided silicon) were irradiated using 90 MeV Ni 7+ swift heavy ion beam at low fluences ranging from 1 × 10 9 to 1 × 10 11 ions/cm 2 to study the effect of ion beam irradiation. The pristine and irradiated PCBM thin films were characterized by UV–visible absorption spectroscopy and fourier transform infrared spectroscopy (FTIR) to investigate the optical properties before and after irradiation. These thin films were further analyzed using atomic force microscopy (AFM) to investigate the morphological modifications which are induced by energetic ions. The variation in optical band gap after irradiation was measured using Tauc’s relation from UV–visible absorption spectra. A considerable change was observed with increasing fluence in optical band gap of irradiated thin films of PCBM with respect to the pristine film. The decrease in FTIR band intensity of C 60 cage reveals the polymerization reaction due to high energy ion impact. The roughness is also found to be dependent on incident fluences. This study throws light for the application of PCBM in organic solar cells in form of ion irradiation induced nanowires of PCBM for efficient charge carrier transportation in active layer. [ABSTRACT FROM AUTHOR]