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The structural, microstructural and electronic band gap properties of bilayer Bi/As2Se3 thin films prepared on glass substrate have been discussed in detail. The thin films prepared by thermal evaporation technique under high vacuum were characterized by X-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FESEM) and UV–visible–NIR spectrophotometer. The bilayer films with small Bi thickness showed amorphous nature, while large Bi thickness film led to the development of sharp XRD peaks corresponding to Bi and Bi2Se3 phase. The band gap of the studied film decreased with increasing Bi layer thickness which is explained on the basis of high concentration of localized defect states in the band gap region. The FESEM images showed the smooth and homogeneous surface for all the films. The Raman spectra showed the different structural units like AsSe3 pyramidal unit and Se8 rings that change with the Bi layer thickness. The present study reveals the interface diffusion of Bi into As2Se3 layer and interaction of Bi with Se due to exposure of the films to UV radiation.

The effect of Ni doping in BiFe1−xNixO3 (BFNO) multiferroics are studied by X-ray diffraction (XRD), Fourier transmission infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), hysteresis loop (M–H), temperature dependent magnetization (FC-ZFC) measurements and electron spin resonance (ESR) techniques. The XRD and FTIR studies indicate that the BFNO compounds remain in rhombohedral (R3c) phase without appearance of any structural transformation due to Ni doping. The XPS studies show the oxidation states of Fe ions as 3+, whereas Bi is found to be in a mixed valence state of 2+ and 3+ in BFNO. The Ni ion doping enhances the saturation magnetization from 0.179 emu/g (x = 0.025) to 2.38 emu/g (x = 0.20), which is higher than the reported values found in literature. The FC-ZFC magnetization studies suggest the presence of a magnetic phase transition from a weak ferromagnetic to a spin glass state at low temperature. The ESR studies confirm the ferromagnetic state of BFNO samples.

Ni1−xZnxO/Ni nanocomposite samples synthesized by wet chemical method were characterized by X-ray powder diffraction, Fourier Transform Infrared (FTIR) spectrometer, UV–Vis spectrometer and Nine Tesla Physical Property Measurement System (PPMS)-based vibrating sample magnetometer (VSM). XRD spectra contained peaks due to NiO and Ni. Rietveld refinement of XRD data indicated the change in lattice parameter is more than twice in NiO than in Ni suggests that Zn goes more favorably into NiO than in Ni. The band gap of NiO in Ni1−xZnxO/Ni samples increased from 3.58 to 3.81 eV with increasing x from 0 to 0.07 and thereafter the band gap slightly decreases. NiO/Ni nanocomposites show strong room temperature ferromagnetism. The ferromagnetic interaction further enhanced with 1% of Zn doping into NiO in NiO/Ni nanocomposite. Beyond this doping concentration, the magnetic interaction does not show any systematic variation. The observation of room temperature ferromagnetism in nanocomposite samples is explained by combining the effect of bound magnetic polaron and the magnetization of system with the distribution of magnetic ions as meagerly dispersed in large clusters. Our study indicated that Ni0.99Zn0.01O/Ni nanocomposite sample could be useful for magnetic recording device application.

With progressing miniaturization of modern electronic devices, interconnects become increasingly smaller. Additionally, as electronic devices move away from rigid substrates toward flexible ones, understanding their mechanical and structural stability is becoming crucial. In this work, a thorough mechanical characterization of copper thin films deposited on flexible substrates was performed with two techniques, namely well-established synchrotron X-ray diffraction (sXRD) and the rather new usage of reflectance anisotropy spectroscopy (RAS) for mechanical characterization of thin films. The comparison of these two techniques shows that RAS can be reliably used for the accurate and prompt yield stress measurements. The acquisition time of RAS is much faster than that of sXRD: 1 second per data point compared to several seconds per data point for sXRD experiments. Moreover, the signal-to-noise ratio of the RAS data is much higher than that of the sXRD. Our results show that yield stress of Cu films increases with the decrease in the film thickness, going from 352 MPa for a 500 nm films to 793 MPa for a 50 nm thick film. Microstructure analyses of the films by electron microscopy allowed correlation of the mechanical behavior of the films to their grain morphologies. We have shown that RAS can supplement sXRD measurements due to a faster acquisition rate which allowed us to analyze the creep behavior of our copper thin film at different strain rates.

BiFeO3 (BFO) thin films of thickness about 800 nm deposited on Si (100) substrates by sol–gel spin coating method were irradiated by 200 MeV Ag ions. Modification of structure and surface morphology of the films under irradiation was studied using glancing incidence X-ray diffraction (GIXRD) and atomic force microscope (AFM). Fluence dependence of GIXRD peak intensity indicated formation of 10 nm diameter cylindrical amorphous columns in crystalline BFO due to 200 MeV Ag ion irradiation. AFM analysis indicated that the pristine film consists of agglomerated grains with diffuse grain boundary. Irradiation led to reduced agglomeration of the grains with the formation of sharper grain boundaries. The rms roughness (σ rms) estimated from AFM analysis increased from 6·2 in pristine film to 12·7 nm when the film irradiated at a fluence of 1 × 1011 ions cm − 2 . Further irradiation led to decrease of σ rms which finally saturated at a value of 7–8 nm at high ion fluences. The power spectral density analysis indicated that the evolution of surface morphology of the pristine film is governed by the combined effect of evaporation condensation and volume diffusion processes. Swift heavy ion irradiation seems to increase the dominance of volume diffusion in controlling surface morphology of the film at high ion fluences.

Photo-absorption properties of Co implantation in rutile TiO2(110) have been investigated. Nearly five times enhancement in absorbance of visible light and 1.7 times increase in UV light have been observed. Formation of crystalline CoTiO3 and Ti1−x Co x O2 phases at high and low fluences, respectively, demonstrates a crucial role in increasing the photo-absorbance, especially in the visible regime. Ti-rich nanostructures and Ti3+ vacancies that develop after ion implantation also reveal significant contribution in these observations. These Co implanted rutile TiO2 surfaces will be useful for visible light photo-catalysis.

NiO thin films grown on Si(100) substrates by electron beam evaporation, were sintered at 500 °C and 700 °C. The films were irradiated with 120 MeV Au9+ ions. Irradiation had different effects depending upon the initial microstructure of the films. Irradiation of the films at a fluence of 3 × 1011 ions cm−2 leads to grain growth for the films sintered at 500 °C and grain fragmentation for the films sintered at 700 °C. At still higher fluences of irradiation, grain size in 500 °C sintered film decreased, but the same improved in 700 °C sintered film. Associated with the grain size, texturing of the films was also shown to undergo significant modifications under irradiation.

We report preparation of phase pure BiFeO3 thin films on glass, ITO and Si(100) substrates through chemical route using spin coating technique. Sol-gel process was adopted to prepare the films using bismuth nitrate and iron nitrate as precursors. X-Ray diffraction and Raman spectroscopy studies revealed amorphous nature of the as deposited films. Rhombohedral crystalline phase of BiFeO3 evolved on annealing the films at 500°C, but with Bi2Fe4O9 and Bi24Fe2O39 as impurity phases. Increasing the annealing temperature to 550°C caused a drastic reduction of the impurity phases and at 600°C, the films were phase-pure BiFeO3. Micro Raman spectra showed features consistent with the reported characteristic peaks of BiFeO3 crystalline phase for films annealed at 500 and 550°C. Crystallite size obtained from X-ray diffraction line width analysis are within 30 to 40 nm. Atomic force microscopy (AFM) however showed grain size of ∼192 nm, indicating polycrystalline nature of the grains.

Ferroelectrics and high temperature superconductors are two promising materials for future electronic devices. Both being perovskite ceramic structures with similar crystal chemistry a set of samples were prepared from the composite of (1−x)YBa2Cu307−δ −(x)BaTiO3 (YBCO/BT). These samples were investigated with temperature dependent resistance, FTIR, X-ray diffraction and SEM-EDX analysis. It has been found that the critical exponent in the Tc0 (R = 0) region is in agreement with the percolation theory. A long-range superconducting order results from thermally assisted percolation process through weak-links between the grains. The connectivity in the coherent transition region can be explained by a power law.

Mott-Hubbard anti-ferromagnetic insulator, NiO shows p-type semiconducting behaviour due to vacancy at Ni2+ site in its bunsenite structure. We report the modification of structural and magnetic order in NiO on Fe doping. NiO samples at different Fe concentrations in the range 0 to 5 at.% have been prepared by chemical co-precipitation and post thermal decomposition method. Both structural and magnetic characterization reveal that with increasing Fe doping concentration, NiO evolves as a magnetically inhomogeneous state out of the parent homogeneous antiferromagnetic state. In addition, structural inhomogeneity was also observed with Fe precipitating to γ-Fe2O3 phase, the signature of which could be clearly seen for Fe content beyond 2 at.%. At lower Fe content however, some amount of Fe occupies lattice and interstitial sites in the NiO matrix and drive the latter to acquire ferromagnetic ordering, which was evident from a clear hysteresis loop at 300 K.

Ferromagentic semiconductors have been actively pursued because of their potential as spin polarized carrier sources and easy integration into semiconductor technology. One such material, ZnO has been shown to be a potential Diluted Magnetic Semiconductor (DMS). The appearance of ferromagnetism, however, is found to be sensitive to the processing conditions. We report synthesis of ZnO nanoparticles of size ∼20 nm by a simple co-precipitation technique using metal nitrates and NaOH as precipitant. The particles are self-organised and reveal single crystalline behaviour in electron diffraction pattern. Incorporation of Co in ZnO matrix leads not only to the reduction in crystallite size but also to the modification of the structure. At 5% Co, the particles are highly textured. The particles also aggregate and the aggregated mass have nearly rectangular shape as seen through TEM. Increasing Co to 10%, results into further reduction of particle size and the particles self organize in a line, which looks like nanofibers. This alignment of particles increases by increasing the Co content further. This type of growth of nanofibers above Co ≥ 10% is well correlated with the anisotropic peak broadening observed in the XRD spectra. In addition, Co substitute Zn site up to 20% without showing any extra phase in XRD spectra as compared to 7 to 10% in case of bulk. Transport and magnetic studies indicate that conductivity increases with increasing Co content, but carrier mediated ferromagnetism is absent down to 10 K.

Manganese doped zinc sulfide nanoparticles are fabricated on polyvinyl alcohol dielectric matrix. They are bombarded with energetic chlorine ions (100 MeV). The size of the crystallites is found to increase with ion fluence due to melting led grain growth under ion irradiation. The increased size as a result of grain growth has been observed both in the optical absorption spectra in terms of redshift and in electron microscopic images. The photoluminescence (PL) study was carried out by band to band excitation (λex = 220 nm) upon ZnS : Mn, which results into two emission peaks corresponding to surface states and Mn+2 emission, respectively. The ion fluence for irradiation experiment so chosen were 1 × 1011, 5 × 1011, 5 × 1012 and 1013 Cl/cm2.

Temperature-dependent electrical resistivity in a set of YBa2Cu3O7−x/Ag composites, all prepared under an identical sintering schedule, is analyzed to extract granularity information. The weak-link resistivity ρwl across the grain boundaries and the percolation factor α arising due to current frustration caused by misalignment of anisotropic grains and sample defects such as voids and cracks are estimated from the residual resistivity ρ0 and the temperature coefficient of resistivity dρ/dT. Variation of these parameters with Ag vol.% quantifying the extent of granularity indicates that granularity in the composites decreases and their electrical characteristics tend to be identical to that of Ag-free YBa2Cu3O7−x single crystals and epitaxial thin films as Ag vol.% approaches a value where onset of current percolation occurs through Ag channels. The increased α and decreased ρwl observed at higher Ag vol.% explains the larger grains in the composites with narrow size distribution.

A series of samples of YBa2Cu3-xAgxO7-y with 0≤x≤0.12 composition was studied to probe into the Ag substitution effect on oxygen stoichiometry, lattice parameters, and superconducting properties. With the samples prepared at a relatively lower sintering temperature, Ag could be doped in the grains rather than precipitate at grain boundaries. Thus, unlike in the case of YBCO + Ag composites or in doped systems annealed at high temperatures where Ag occupies mostly the grain boundary, the present system showed a drastic change inT c, oxygen stoichiometry, and lattice parameters with Ag concentration, indicating the substitution of Ag at the Cu(l) sites in the grains. The stable 2-fold oxygen coordination of Ag substituting Cu(l)’s explains the observed variation of oxygen deficiency with Ag. A crystallochemical analysis has been made to reveal the crucial role of Ag-substitution-induced coordination incompatibility and charge state instability on carrier concentration andT c.

Using a genetic approach, Chinese hamster ovary (CHO) cells sensitive (aphS) and resistant (aphR) to aphidicolin were grown in the presence or absence of various DNA polymerase inhibitors, and the newly synthesized DNA isolated from [32P]dNMP-labelled, detergent-permeabilized cells, was characterized after fractionation by gel electrophoresis. The particular aphRmutant CHO cell line used was one selected for resistance to aphidicolin and found to possess an altered DNA polymerase of the a-family. The synthesis of a 24 kb replication intermediate was inhibited in wild-type CHO cells grown in the presence of aphidicolin, whereas the synthesis of this replication intermediate was not inhibited by this drug in the mutant CHO cells or in the aphidicolin-resistant somatic cell hybrid progeny constructed by fusion of wild-type and mutant cell lines. Arabinofuranosylcytosine (ara-C), like aphidicolin, inhibited the synthesis of this 24 kb DNA replication intermediate in the wild-type CHO cells but not in the aphR mutant cells. However, carbonyldiphosphonate (COMDP) inhibited the synthesis of the 24 kb replication intermediate in both wild-type and mutant cells. N2-(p-n-Butylphenyl)-2′ deoxyguanisine-5′-triphosphate (BuPdGTP) was found to inhibit the formation of Okazaki fragments equally well in the wild-type and mutant cell lines and thus led to inhibition of synthesis of DNA intermediates in both cases. It appears that aphidicolin and ara-C both affect a common target on the DNA polymerase, which is different from that affected by COMDP in vivo. These data also show that aphidicolin, ara-C and COMDP affect the elongation activity of DNA polymerase but not the initiation activity of the enzyme during DNA replication. This is the first report of such differentiation of the DNA polymerase activities during nuclear DNA replication in mammalian cells. The method of analysis described here for replication intermediates can be used to examine the inhibitory activities of other chemicals on DNA synthesis.

Various defects arising from lattice mismatch and coordination incompatibility at the cation sites are known to lend the cuprates a metastable state at temperatures and pressures where they exhibit superconductivity. The present paper considers the metastability induced by coordination incompatibility at Cu(1) sites in oxygen-deficient 123 type systems and looks for their possible effects on charge and spin degrees of freedom. Depending upon the concentration of oxygen vacancies, the resulting unstable charge state at the Cu(1) sites is shown to either temporally fluctuate or spatially equilibrate, providing a mechanism for the 90 K and the 60 K plateaus, with a peak in the former observed in the YBa[sub 2]Cu[sub 3]O[sub 7[minus]y] samples prepared under thermodynamic equilibrium conditions. 35 refs., 5 figs.