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Abstract: We present an efficient detection of liquefied petroleum gas (LPG) using zinc oxide (ZnO) thin films irradiated with swift heavy ions (SHI) of 120MeV Au9+ ions. The nanostructured ZnO thin films on ITO glass substrates were synthesized using a simple, low cost, and efficient successive ionic layer adsorption and reaction (SILAR) technique. The as-synthesized thin films were annealed at 250°C (pristine) in vacuum atmosphere (10−2 Torr) for 1h and these films were further irradiated using SHI of 120MeV Au9+ ions with different fluence 3×1012 and 5×1012 ions/cm2, respectively. SHI induced modification in structural, morphological, optical and electrical properties of ZnO thin films were studied. We observed significant enhancement in LPG gas sensing properties in the ZnO thin films on irradiation with fluence 5×1012 ions/cm2, especially showing maximum sensitivity to LPG at (200°C) with LPG concentration of 200ppm. In addition, irradiated ZnO thin film sensors displayed fast response and recovery time. The observed improvement in gas sensing properties is mainly attributed to the formation of cabbage leaf-like porous ZnO nanostructures throughout the film surface after irradiation. These results along with a simple fabrication process demonstrate that the ZnO thin films irradiated using 120MeV Au9+ ions with fluence 5×1012 ions/cm2 is promising for developing low cost and high performance LPG sensors. [Copyright &y& Elsevier]

Abstract: Herein, we report engineering of nanostructured p-CuIn3Se5/n-CdS heterojunction thin film on a glass substrate, which is prepared at room temperature using simple wet chemical approach involving ion exchange reactions between CdS and Cu+, In3+ and Se2− ions in alkaline medium. The uniform deposition of heterojunction thin films is achieved by optimizing the pH, temperature and molarity of the reactant bath. The as-deposited thin-films were annealed at 200°C in air for 1h and further characterized for structural, optical and electrical properties using UV–Vis spectrophotometer, X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), Hall effect for type of conductivity, and I–V measurement to investigate the charge conduction phenomenon. The characteristic (112) and (110) planes in XRD and the electron diffraction pattern could confirm the formation of CuIn3Se5. The chemical composition and the band gap energy E g =1.4eV of the nanostructured p-CuIn3Se5/n-CdS heterojunction thin-films were confirmed using XPS and the absorbance spectra, respectively. Based on the data and energy band gap calculations of CuIn3Se5 and CdS thin films, the probable band alignment between the nanostructured p-CuIn3Se5/n-CdS heterojunction is proposed. [Copyright &y& Elsevier]

Abstract: Zinc oxide (ZnO) thin-films were grown on glass substrates by using simple wet chemical approach and then the films were annealed at 450°C in air atmosphere for 2h. The scanning electron microscopy images could confirm the uniform deposition and formation of cabbage leaf-like ZnO nanostructures. The optical band gap was found to be 3.14eV for annealed films. The sensor showed higher sensitivity towards liquid petroleum gas (LPG) at optimized temperature of 200°C. The response and recovery times with 200ppm of LPG were found to be ∼6 and ∼ 8s, respectively. [Copyright &y& Elsevier]

Slow time-dependent fluctuations, or noise, in the electrical resistance of dc magnetron sputtered thin films of nickel-titanium shape memory alloys have been measured. Even in equilibrium, the noise was several orders of magnitude larger than that in simple diffusive metallic films and was found to be nonmonotonic around the martensitic transformation regime. The results are discussed in terms of the dynamics of structural defects, which also lay the foundation to a new noise-based characterization scheme of martensite transformation. [ABSTRACT FROM AUTHOR]

Studies the dc transport properties and the low-frequency conductivity noise in films of charge-ordered rare earth manganate Nd[sub 0.5]Ca[sub 0.5]MnO[sub 3] grown on silicon substrate. Revelation of the existence of a threshold field in the charge-ordered regime.

Atomically-abrupt interfaces in transition metal oxide (TMO) heterostructures could host a variety of exotic condensed matter phases that may not be found in the bulk materials at equilibrium. A critical step in the development of such atomically-sharp interfaces is the deposition of atomically-smooth TMO thin films. Optimized deposition conditions exist for the growth of perovskite oxides. However, the deposition of rutile oxides, such as VO 2 , with atomic-layer precision has been challenging. In this work, we used pulsed laser deposition to grow atomically-smooth VO 2 thin films on rutile TiO 2 (101) substrates. We show that an optimal substrate preparation procedure followed by the deposition of VO 2 films at a temperature conducive for step-flow growth mode is essential for achieving atomically-smooth VO 2 films. The films deposited at optimal substrate temperatures show a step and terrace structure of the underlying TiO 2 substrate. At lower deposition temperatures, there is a transition to a mixed growth mode comprised of island growth and layer-by-layer growth modes. VO 2 films deposited at optimal substrate temperatures undergo a sharp metal to insulator transition, similar to that observed in bulk VO 2 , but at a transition temperature of ∼ 325 K with ∼ 10 3 times increase in resistance. [ABSTRACT FROM AUTHOR]

Abstract: We employ a fluctuation-based technique to investigate the athermal component associated with martensite phase transition, which is a prototype of temperature-driven structural transformation. Statistically, when the phase transition is purely athermal, we find that the temporal sequence of avalanches under constant drive is insensitive to the drive rate. We have used fluctuations in electrical resistivity or “noise” in nickel titanium shape memory alloys in three different forms: a thin film exhibiting well-defined transition temperatures, a highly disordered film, and a bulk wire of rectangular cross-section. Noise is studied in the realm of dynamic transition, viz., while the temperature is being ramped, which probes into the kinetics of the transformation at real time scales, and could probably stand out as a promising tool for material testing in various other systems, including nanoscale devices. [Copyright &y& Elsevier]

We report the observation of linear magneto-resistance (LMR) with a very low cross-over magnetic field (Bc) at room temperature in bismuth(110) thin films fabricated using thermal evaporation. The magneto-resistance at different temperatures (T) indicate that Bc has a strong T-dependence, and displays a remarkably small magnitude of 180 mT at T = 300 K. The parameter Φ, defined as the MR% (B = 1 T)/ Bc is 248, is considerably higher at room temperature compared to values previously reported in literature. The observed LMR is likely due to the recombination of carriers in compensated systems near charge neutrality. Our measurements demonstrate that the LMR can be observed at a very low field and high T, which can be utilized in a variety of applications. [ABSTRACT FROM AUTHOR]

We report a detailed investigation of resistance noise in single layer graphene films on Si/SiO2 substrates obtained by chemical vapor deposition (CVD) on copper foils. We find that noise in these systems to be rather large, and when expressed in the form of phenomenological Hooge equation, it corresponds to Hooge parameter as large as 0.1-0.5. We also find the variation in the noise magnitude with the gate voltage (or carrier density) and temperature to be surprisingly weak, which is also unlike the behavior of noise in other forms of graphene, in particular those from exfoliation. [ABSTRACT FROM AUTHOR]

We report a detailed study on low-frequency 1/f -noise in large-area molecular-beam epitaxy grown thin (~10 nm) films of topological insulators as a function of temperature, gate voltage, and magnetic field. When the Fermi energy is within the bulk valence band, the temperature dependence reveals a clear signature of generation-recombination noise in the defect states in the bulk band gap. However, when the Fermi energy is tuned to the bulk band gap, the gate voltage dependence of noise shows that the resistance fluctuations in surface transport are caused by correlated mobility-number density fluctuations due to the activated defect states present in the bulk of the topological insulator crystal with a density of Dit =3:2× 1017 cm-2 eV-1. In the presence of the magnetic field, noise in these materials follows a parabolic dependence, which is qualitatively similar to mobility and charge-density fluctuation noise in non-degenerately doped trivial semiconductors. Our studies reveal that even in thin films of (Bi,Sb)2Te3 with thickness as low as 10 nm, the internal bulk defects are the dominant source of noise. [ABSTRACT FROM AUTHOR]

We probe the presence of long-range correlations in phase fluctuations by analyzing the higher-order spectrum of resistance fluctuations in ultrathin NbN superconducting films. The non-Gaussian component of resistance fluctuations is found to be sensitive to film thickness close to the transition, which allows us to distinguish between mean field and Berezinskii-Kosterlitz-Thouless (BKT) type superconducting transitions. The extent of non-Gaussianity was found to be bounded by the BKT and mean field transition temperatures and depends strongly on the roughness and structural inhomogeneity of the superconducting films. Our experiment outlines a novel fluctuation-based kinetic probe in detecting the nature of superconductivity in disordered low-dimensional materials. [ABSTRACT FROM AUTHOR]

Abstract: CdS quantum dots thin-films have been deposited onto the glass substrate at room temperature using modified chemical bath deposition technique. The prepared thin films were further annealed in air atmosphere at 150, 250 and 350°C for 1h and subsequently characterized by scanning electron microscopy, ultraviolet–visible spectroscopy, electrical resistivity and I–V system. The modifications observed in morphology and opto-electrical properties of the thin films are presented. [Copyright &y& Elsevier]

Abstract: The copper chalcogenide (CuX, X=S, Se) thin films have been irradiated with 100MeV gold swift heavy ions (SHI) at 1011 and 1012 ions/cm2 fluences. The irradiation effects were probed by characterizing physical properties such as XRD, AFM, optical band gap and electrical resistivity of copper chalcogenide thin films. The increase in irradiation fluence increases the particle size, electrical conductivity and PL intensity of the materials, and the optical band edges were red shifted. The results are explained by quantifying electronic energy loss of ions in both the materials. [Copyright &y& Elsevier]