Nonvolatile unipolar resistive switching properties of the amorphous LaGdO3 thin films deposited by pulsed laser deposition have been studied. Reliable and repeatable switching of the resistance of LaGdO3 film was obtained between low and high resistance states with nearly constant resistance ratio ∼ 106 and non-overlapping switching voltages in the range of ∼0.6-0.75 V and 2.5-4 V respectively. The switching between low and high resistance states was attributed to the formation and rupture of conductive filaments using temperature dependent resistance measurements. The current conduction mechanisms of the LaGdO3 film in low and high resistance states were found to follow the Ohmic behavior and Poole-Frenkel emission respectively. The resistance of low and high resistance states of the film remained nearly constant for up to ∼ 104 seconds indicating good retention. The observed resistive switching characteristics of LaGdO3 thin films are promising for futuristic nonvolatile memories.

In the present work we report the synthesis of Cu2ZnSnS4 (CZTS) films by pulsed laser deposition (PLD) and the effect of sulfur annealing on structure, composition, morphological and optical characterization of CZTS thin films. Raman spectra of the films exhibited the characteristics peaks of Kesterite structure. However, annealing caused to transfer the films from amorphous state into crystalline state. Scanning electron microscope (SEM) images revealed that as-deposited film exhibited a crack free, smooth, densely packed and homogeneous surface which was changed to rigid granular appearance after annealing. Energy dispersive X-ray spectroscopy (EDS) determined the compositions of the CZTS thin films which was near stoichiometry for the annealed samples. Ultraviolet–visible (UV–Vis) spectra showed the band gap of as-deposited film was 1.60 eV which was decreased to 1.40 eV after annealing.

Many compounds have been claimed to possess powerful taenicidal activity but only a few are able to remove the tapeworms complete with scolices; accordingly better drugs are still needed. A series of 3, 5-dibromosalicylanilides, possessing a molecular framework similar to that of niclosamide (Gönnert and Schraufstätter, 1960) was tested for taenicidal activity; the most potent anticestode compound was found to be 3, 5-dibromo-2' -chlorosalicylanilide-4' -isothiocyanate (CDRI Compound 77–6). The present communication compares the efficacy of Compound 77–6 with niclosamide, N-(2' -chloro-4-nitrophenyl)-5-chlorosalicylamid (Bayer, power with 75% active ingredient) and praziquantel, 2-cyclohexylcarbonyl-1–3, 4, 6, 7, 11 b-hexahydro-2H-Pyrazino [2–1-a], isoquinoline-4-one (Droncit, E. Merck & Bayer, powder, 100% pure) (Seubert et al., 1977) in rats and mice.

Pure and Fe-doped In2O3 nanocrystalline powder was synthesized using a solution chemistry route based on the Sol-Gel process, which is a simple and inexpensive technique and produces long-time stable stock solutions. The X-ray diffraction patterns revealed the formation of nanocrystalline particle size with well-crystallized cubic bixbyte structure. The average crystal size was calculated from XRD patterns using Debye-Scherrer's equation for the (222) peak and found to be 8 nm. This observation agrees well with the particle size estimated from transmission electron microscopy (TEM). The observed Raman peaks in the doped materials are shifted towards the lower frequency up to 15 cm−1 and we did not observed any additional new Raman modes with Fe doping. This clearly indicates that Fe ions are indeed occupying interstitial/substitutional sites in the host In2O3, in agreement with XPS measurements. Magnetic properties were studied using superconducting quantum interface device magnetometer (Quantum design MPMS XL-7). Preliminary magnetic measurement results suggest the incorporation of the dopants in the diamagnetic In2O3-host structure.

Size dependence of the low frequency vibrational spectra of ZnO nanocrystals prepared using chemical method has been investigated. Optical transmission spectra of the ZnO colloid solution exhibit a shift in the onset of the absorption band edge from 332 to 350 nm due to particle growth. X-ray diffraction analysis of the prepared ZnO nanocrystals exhibit peaks corresponding to the hexagonal wurtzite structure. Two peaks with unusually very high intensity were observed in the low frequency (∼ 10- 25 cm-1) Raman spectra of these nanocrystals. The peak position of these phonon modes shifted towards lower frequencies as the size of the nanocrystals increases and assigned to the confinement of acoustic phonons in ZnO nanocrystals.

We have synthesized spinel LiMn1.99Nd0.01O4 and LiMn1.99Ce0.01O4 powder by chemical synthesis method. The synthesized powders were used to prepare cathodes for Li ion coin cells. The structural and electrochemical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry and charge-discharge studies, respectively. The cyclic voltammetry of the cathodes revealed the reversible nature of Li-ion intercalation in the cell. The charge-discharge characteristics for LiMn1.99Ce0.01O4 were obtained in 3.5 V – 4.8 V voltage range, while for LiMn1.99Nd0.01O4 the charge-discharge were carried out in 3.4 V – 4.4 V range. The initial discharge capacities of LiMn1.99Ce0.01O4 and LiMn1.99Nd0.01O4 were obtained as 134mAh/g and 149 mAh/g, respectively. The coin cells were tested for up to 25 charge-discharge cycles and after 25 cycles the discharge capacities were determined to 79.5 mAh/g and 132 mAh/g for LiMn1.99Ce0.01O4 and LiMn1.99Nd0.01O4 cathodes respectively. However, by doping with a small concentration of rare earth materials, like Ce and Nd reduces the capacity fading in pure LiMn2O4 cathodes making it suitable for Li-ion battery applications.

Thin films of Co substituted ZnO and ZnCo2O4 were deposited on c-axis (0001) oriented Al2O3 substrates using pulsed laser deposition. The XRD results showed all the films were highly (002) oriented with a less intense peak of (311) for ZnCo2O4 thin film. Micro-Raman spectra of ceramic targets showed the modes related to wurtzite ZnO and spinel ZnCo2O4 structures. In thin films of Zn1−xCoxO no modes corresponding to ZnCo2O4 were detected. The intensity of E1(LO) and multiphonon peak at 584 and 540 cm−1 respectively, increased with increase in Co substitution. The optical absorption of the films showed that the band gap decreased with increase of Co concentrations at room temperature along with the sub-bandgap absorptions due to d-d transitions of Co2+. Similar sub-bandgap d-d transition was also observed in the absorption spectra ZnCo2O4 thin films. The highest saturated magnetization (0.2μB/Co) was obtained for 5%Co substituted ZnO.

Average Li intercalation potentials were calculated for lithium-4d-transition-metal-oxides. The effect on the intercalation voltage of metal substitution was systematically studied by altering the 4d transitional metals M (M= Mo, Nb, Rh, Zr, Ru) in LiMO2 in the α-NaFeO2 structure. Lattice parameters in the layered α-NaFeO2 structure computed in the GGA approximation are in reasonable agreement with experiment. The intercalation potentials and relative formation energies of the fully lithiated LiNi1/3Mn1/3Mo1/3O2, fully delithiated Ni1/3Mn1/3Mo1/3O2 and the intermediate phases, Li1/3Ni1/3Mn1/3Mo1/3O2 and Li2/3Ni1/3Mn1/3Mo1/3O2, were computed by employing a generalized alloy theory. A minute substitution of cationic Mo in LiNiMnO2 was experimentally investigated to examine the effect of the Mo substitution on the electrochemical properties.

Lattice dynamical and electronic transition changes due to V and Co doped ZnO have been investigated using optical techniques. Vanadium and Co doped ZnO pellets were prepared using conventional ceramic processing route and thin films were fabricated by pulsed laser deposition. Raman spectra of Zn1-xVxO targets showed many additional peaks in the range of 230 to 350 cm-1 and 750 to 900 cm-1. Integrated intensities of these additional modes decreased with increase of temperature as similar to the host ZnO modes, which precludes electronic Raman scattering to be the origin. Raman peaks for stoichiometric Zn3(VO4)2 and Zn2V2O7 compounds also had additional peaks that can be attributed to the secondary phases formed in the compositions of Zn1-xVxO. Raman spectra of Zn1-xCoxO showed no additional modes besides ZnO modes, however, the intensity of the second order peak at 540 cm-1 was increased due to Co doping. Thin films of Zn1-xCoxO exhibited highly c-axis orientation deposited on (001)Al2O3 substrates. The optical absorption of the films showed that the band gap decreased with increase of Co concentrations at room temperature along with the sub bandgap absorptions due to d-d transitions of Co2+.

Lead strontium titanate (PbxSr1-xTiO3) (x=0.3–1.0) ceramic targets were prepared by the conventional powder-processing method. Thin films of these compositions were deposited on platinized silicon substrates by pulsed laser deposition technique. X-ray diffraction studies of the ceramic targets showed that the lattice structure changes from tetragonal to cubic phase with the increase of Sr content in PbTiO3. Raman spectroscopic studies of PbxSr1-xTiO3 (PST) ceramics and thin films showed that the soft mode decreases to lower frequency and finally disappear at around 60–70 at% Sr content, which confirms the tetragonal to cubic phase transition at room temperature. Dielectric constant measured for PST thin films was in the range of 900–1500 at 1 MHz, with maximum value obtained for PST30 thin film. The loss tangents at room temperature were in the range of 0.07–0.1 for PST thin films with different compositions.

Thin films of Ba1-x SrxTiO3 (BST) are being actively investigated for applications in dynamic random access memories (DRAM) because of their properties such as high dielectric constant, low leakage current, and low fatigue. Several approaches have been used to improve the properties of thin films such as doping with aliovalent dopants, graded compositions, and layered structures. We have found that interposing layers of an electronic insulator such as ZrO2 in between BST layers results in a significant reduction in the leakage current. In this paper the low temperature electrical properties of these multilayer structures are reported. The structures consist of alternate layers of Ba0.8Sr0.2TiO3 and ZrO2 deposited by a sol-gel process on platinized Si substrates. The thickness and the number of layers are varied while keeping the total thickness of the film constant. Multiple peaks in the dielectric constant vs temperature plots at all frequencies are observed in the multilayered films. The properties of the multilayer films are a complex function of the number of layers and their thicknesses. A structure with several thin layers of ZrO2 interposed between the BST layers produces smoother plots than a single layer of ZrO2 of same total thickness. This is attributed to more uniform distribution, as determined by XPS, of ZrO2 in the multilayer structure due to smaller diffusion distances.

Mn doped ZnO thin films were grown using pulsed laser deposition technique on (001) Al2O3 substrates. The x-ray diffraction data confirmed highly c-axis oriented and hexagonal structure of ZnO and Mn doped ZnO thin films. However, an unidentified secondary peak was observed at very close to ZnO (002) peak. Micro Raman spectra of ceramics as well as thin films showed disorder induced Raman bands besides standard wurtzite ZnO modes. The intensity of several LO modes of ZnO was increased with the increase of Mn concentration. Optical absorption data showed an additional absorption band towards lower than bandgap energy (3 eV) with the increase in Mn content. The incorporation of Mn in ZnO thin films reduced the value of resistivities and mobilities with an increase in carrier concentrations.

In the present work micro-Raman spectroscopy has been used to understand the lattice dynamics of cation substituted SBT ceramics and thin films. Different concentrations of Ca and V were introduced into SBT lattices. Incorporation of Ca ion at Sr-site was confirmed by decrease in the lattice parameters calculated from x-ray diffraction data. The lowest Raman modes at 27 cm-1 and 58 cm-1 showed upward shift with increasing Ca concentration and was attributed to the lower mass and lower ionic radii of Ca. The temperature dependant Raman studies revealed the increase of the phase transition temperature with increased Ca content, and was attributed to the decrease in tolerance factor. Substitution of smaller cation at Sr site in SBT compound has increased lattice mismatch between SrO and TaO2 planes inside the stable perovskite unit of SrTa2O7 which has pronounced influence on ferroelectric properties of SBT. Substitution of vanadium at Ta-site of SBT did not influence the low frequency Raman modes of SBT. However, it showed a pronounced influence on the O-Ta-O stretching modes by splitting the mode frequency at 810 cm-1. The transition temperature of SBT was reduced with increasing vanadium contents.

Ferroelectric thin films of BaZrxTi1-xO3 (BZT) were deposited on platinum (Pt) and platinized silicon (Pt/Si) substrates by sol-gel and pulse laser deposition technique respectively. The structure and preferred orientation of the films were examined by x-ray diffraction measurements. The phase formation of sol-gel derived BZT films were found to be at high temperature (1100°C) compare to the pulse laser deposited BZT films ∼ 700°C. Polycrystalline films were observed by both techniques. Ferroelectric nature of the films was confirmed by hysteresis and capacitance-voltage characteristics using platinum top electrodes. Dielectric constant as well as loss was found to decrease by increasing Zr contents. Surface morphology predicted smooth crack free surface.

In this work we present the structural, and vibrational properties of ferroelectric Pb1-xSrxTiO3 (PST). Thin films of PST were prepared by using sol-gel technique for various compositions with x values ranging from 0.0–1.0. Respective compositions were also prepared in ceramic and powder forms using sol-gel and solid-state reaction methods. X-ray diffraction was used for the structural characterization of these materials. Raman spectroscopy was utilized to study the phases and lattice vibrational modes, especially the soft mode in PST compositions. The temperature dependence of the soft mode frequency for different PST compositions revealed that the phase transition temperatures increased with increasing Pb contents in PST system. Ferroelectric properties of the films were correlated with the substitution-induced changes in the material.

During a ferroelectric phase transition or domain rearrangement, ions or molecules in a ferroelectric material move in a highly cooperative manner from their initial lattice positions into the final positions they occupy and the collective response results into a “soft” lattice vibrational mode. Moreover, the structural changes are always accompanied by at least a few other changes in the normal mode behavior of the material. In the present work, Raman spectroscopy is conveniently employed to study such vibrational modes and other related phenomena in ferroelectric materials at the sub-microscale levels. We have investigated ferroelectric thin films of various lead and barium based perovskites prepared by sol-gel technique. The effect of processing conditions, A- and B- site substitutions, and size dependence on their Raman spectra were analyzed in terms of the structure-property correlations.

Wide bandgap (∼6 eV) ZnO/MgO multilayer thin films have been fabricated using pulsed laser deposition technique from their respective targets on c-plane Al2O3 substrates. The thickness of single ZnO sublayer thickness was varied in the range of 0.75–2.5 nm with a fixed MgO sublayer thickness of 1 nm in order to achieve a total film thickness of ∼300 nm. The structural transition from hexagonal to cubic phase was observed with the decrease in the thickness of single ZnO layer from 2.5 to 0.75 nm that resulted in the increase in bandgap from 3.5 to 6.2 eV. Mg contents of the films were increased from 40 % to 60 % for hexagonal and cubic phases, respectively. The surface roughness and grain structure were not influenced much with the increase of Mg concentration. Resistivity of the films was increased six orders of magnitude with the increase in Mg incorporation. The post annealing at 750° C did not show any significant change in the crystal structure and the optical properties.

Pulsed laser deposition technique was used to fabricate Ba0.5Sr0.5TiO 3 (BST) thin-films on Pt/TiO 2/SiO2/Si substrates. The influence of thin interfacial layers of Ta2O5, TiO2, and ZrO2, on the structural and electrical properties of BST thin films was investigated. Insertion of interfacial layers does not affect the perovskite phase formation of BST thin films. Buffer layers helped to make uniform distribution of grains and resulted in a relative increase in the average grain size. The dielectric tunability of BST thin films was reduced with the presence of buffer layers. A BST thin film having a dielectric permitivity of 470 reduced to 337, 235 and 233 in the presence of Ta2O5, TiO2, and ZrO2 layers, respectively. The reduction of the relative dielectric permittivity of BST films with the insertion of interfacial layers was explained in terms of a series capacitance effect, due to the low dielectric constant of interfacial layers. The TiO2 layer did not show any appreciable change in the leakage current density. Deposition of thin Ta2O5 and ZrO2 interfacial layer on top of Pt reduced the leakage current density by an order of magnitude.

In the present work we have deposited MgO and Ba0.5Sr0.5TiO3 (BST50) thin layers in different sequences to make MgO:BST50 hetero-structured thin films. These films were characterized by X-ray diffraction and found to be highly (100) textured. The figure of merit {(C0-Cv)/(C0.tand)} of the hetero-structured films was found to be higher as compared to pure BST50 films measured at 1 MHz frequency with electric field of 25.3 kV/cm. These films were used to make eight element coupled micro-strip phase shifter and characterized in a frequency range of 13–15 GHz. The high frequency figure of merit (k factor, defined as the ratio of degree of phase shift per dB loss) measured at around 14 GHz with electric field of 333 kV/cm has been markedly improved (around 64.28 °/dB for hetero-structured film as compared to 24.65 °/dB for pure film). Improvement in dielectric properties in a wide frequency range in the MgO:BST are believed to be due to the higher densification of the hetero-structured films.

We have studied the influence of partial substitution of Ca (0%, 5%, 10% and 15%) on the structural and electrical properties of SrBi2Nb2O9 (SBN) thin films. Pulsed laser deposition technique was used to grow thin films on platinized silicon substrates. X-ray diffraction data confirmed the polycrystalline nature of the films with preferential orientation along the polarization axis. Incorporation of Ca at Sr-site of SBN reduced the lattice parameter and was attributed to the smaller ionic radii of Ca. The soft mode frequency at 29.5 cm-1 of SBN shifted towards higher wavenumber implied increasing the transition temperature upon Ca substitution. The grain sizes of SBN thin films vary from oval to rod like structures and improving the homogeneous distribution of grains with the increase in Ca contents. The ferroelectric properties of the films enhanced with maximum remanent polarization of 35.3 mC/cm2. The increase in the coercive field with incorporation of Ca at Sr-site was attributed to the higher electronegativity of Ca. The SBN thin films with the incoporation of Ca exhibited poor leakage current behavior. The reduction of dielectric permittivity with Ca concentration was attributed to the lower dielectric permittivity of CaBi2Nb2O9.