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As the size of electronic devices is reducing the heat generation is increasing tremendously within the devices. Thermal management is an effective way to control the heat generation in the devices. One of the governing factors of the thermal management is thermal conductivity of the materials. Thermal conductivity varies abruptly as the material dimension shrinks and becomes concern when material dimension equals to an order of mean free path of thermal energy carriers. The state-of-art devices contains thin films and nanostructures having dimension varying from 100 µm to 10 nm, which is expected to decrease to a size of few layers of atoms in the near future. Thermal conductivity of the thin films and nanostructures measured using steady state and transient techniques. Among them, the 3- ω technique is a versatile method to find thermal conductivity of thin films, fluids, and gases quickly and efficiently. This article provides an elaborate review on the state-of-art 3- ω characterization technique and methodology, device morphology, advantages, and mathematical model for various device configurations along with its advancement for accurate thermal management in microelectronics, nanoelectronics and nanofluidics industry. Detailed description on effectiveness and limitations of various 3- ω device design is understood, and critical comments are presented. Importantly, this review will aid new graduate students and researchers in the field of thermal conductivity measurement. [ABSTRACT FROM AUTHOR]

In this paper, we have demonstrated a novel design of a liquid–solid interface triboelectric nanogenerator based on a ZnO- polyvinylidene fluoride (PVDF) flexible ferroelectric film that employs both piezoelectric and triboelectric properties to produce more electricity from water droplets. The present device gives an output voltage of ∼1.32 V and a short-circuit current of ∼0.32 μA from the conventional liquid–solid triboelectric nanogenerator (LSTENG), while an additional open-circuit voltage of ∼2.72 mV and short-circuit current of ∼20 nA is generated from the piezoelectric effect. The mechanism for generating energy in both the piezoelectric and triboelectric components is also discussed. Furthermore, we explored the effect of ions in water on the performance of the LSTENG, and the results were confirmed by Kelvin probe force microscopy measurements. The current work reveals a new LSTENG design and the benefit of employing a ferroelectric polymer as the contacting material rather than other non-piezoelectric materials for the LSTENG. [ABSTRACT FROM AUTHOR]

The temperature dependence of electrical conductivity of the Cu2ZnSnS4 (CZTS) thin films has been measured in order to identify the dominant conduction mechanism. These CZTS film have been deposited by ultrasonic assisted chemical vapor deposition method at different substrate temperatures in a single step process. All the films exhibit p-type semiconducting behaviour. In the high temperature range (> 250 K), the dominance of thermally activated band conduction is observed, whereas in the lower temperature region (250-70 K), the hopping conduction is present. Detailed analysis of the temperature dependence of conductivity of the films reveals that in the temperature range from 250-170 K, nearest neighbour hopping dominates, whereas in the lower temperature region (170-70 K), the dominant hopping conduction is Mott's 3D variable range hopping and not Efros-Shklovskii variable range hopping. The value of Mott's temperature is found to decrease for the CZTS films deposited at higher temperature, which has been attributed to enhanced density of states at the Fermi level. [ABSTRACT FROM AUTHOR]

We report on the resistive memory effects of a Ag/CoFe2O4/Pt device and a deterministic conversion between volatile and nonvolatile resistive switching (RS) memory through the tuning of current compliance (ICC). For the smaller ICC (10−4 A) the device exhibits volatile RS behavior with an atomically sized conducting filament showing the quantum conductance. For an intermediate ICC (10−2 A) nonvolatile bipolar RS behavior is observed, which could originate from the formation and rupture of filament consisting of Ag ions. The high resistance state (HRS) of the device shows a semiconducting conduction mechanism, whereas the low resistance state (LRS) was found to be Ohmic in nature. The temperature dependent resistance studies and magnetization studies indicated that the electrochemical metallization plays a dominant role in the resistive switching process for volatile and nonvolatile modes through the formation of Ag conducting filaments. For higher ICC (10−1 A) the device permanently switches to LRS. The irreversible RS memory behaviors, observed for higher ICC, could be attributed to the formation of a thick and stable conducting channel formed of oxygen vacancies and Ag ions. The compliance current controlled resistive switching modes with a large memory window make the present device a potential candidate to pave the way for future resistive switching devices. [ABSTRACT FROM AUTHOR]

We report a cobalt ferrite nanorods (CFO NRs) based magnetically tunable spur-line notch filter where vertically aligned CFO NRs has been grown on silver nanoparticles coated silicon substrate. The CFO NRs are coupled with high frequency spur-line bandstop filter in flip-chip configuration and the device showed excellent tunable microwave properties in the presence of a low bias magnetic field. The center frequency of the tunable filter is ~16.4 GHz which is shifted to ~14.9 GHz with ~8.7% tunability by applying bias magnetic field ~320 Oe. The magnetic field tuning of the center frequency is explained on the basis of the change in permeability value of the CFO NRs with bias magnetic field as the NRs are used in the partially magnetized state. For validation, permeability value is also calculated by using numerical equations. The experimental reflection of the device has been supported with a simulation using CST microwave studio software. FIG. (a) Schematic of the spur-line bandstop filter design with CFO NRs in the flip-chip geometry (b) Measured transmission characteristics of spur-line bandstop filter and (c) Shift in the center frequency with bias magnetic field. Image 1 • A novel two step approach for the fabrication of cobalt ferrite nanorods (CFO NRs) without using any template. • Demonstration of spur-line based magnetically tunable bandstop filter in the flip-chip configuration using CFO NRs. • A great tuning (~8.7%) is achieved in the presence of low bias magnetic field. [ABSTRACT FROM AUTHOR]

Among the emerging memories, resistive switching (RS) based resistive random-access memories (RRAMs) are attracting lots of attention due to their simple metal–insulator–metal structures, low power consumption, long endurance and retention characteristics, low fabrication cost, ultrafast switching, and CMOS compatibility. In recent years, several oxides, chalcogenides, polymers and their composites have been explored for RS devices. Many of these studies show a high resistance ratio of the OFF and ON states with good RS characteristics. Some of these studies also show the realization of multifunctional RS devices such as the simultaneous switching of resistance and magnetic states. In order to scale up RS-based RRAMs, a detailed understanding of the occurrence of RS is very much desirable. In this review, we provide an overview of the current understanding, recent advances and future outlook of RS-based RRAM devices along with fundamental concepts of the different types of RS, and conventional as well as novel measurement techniques which are being used to characterize RS devices. Observations of RS in different materials are presented, and RS mechanisms, such as the valence change mechanism and electrochemical metallization memory, are discussed in detail. An overview of multifunctional RS devices and the main challenges faced in scaling up RS devices is also presented. [ABSTRACT FROM AUTHOR]

Thin films of YBCO have been deposited on bare and La0.67Sr0.33MnO3 (LSMO) nanoparticle decorated single crystal SrTiO3 (STO) substrates. The effect of ferromagnetic LSMO nanoparticles, present at the substrate/film interface, on the superconducting properties of YBa2Cu3O7-δ (YBCO) thin film has been investigated by temperature dependent magnetization studies. The YBCO thin film on LSMO decorated STO substrate shows significant improvement in the critical current density and pinning force density as compared to the YBCO thin film deposited on the undecorated substrate, and this improvement is more significant at higher applied magnetic field. The presence of LSMO nanoparticles at YBCO/STO interface seems to introduce structural defects, which might be in the form of threading dislocations along the c-axis acting as correlated pinning centers leading to improved flux pinning properties of the YBCO thin film. The LSMO nanoparticles are ferromagnetic, which can also act as magnetic pinning centers and may result in the enhancement of flux pinning properties of the YBCO thin film deposited on the LSMO decorated STO substrate. [ABSTRACT FROM AUTHOR]

A ferroelectric PVDF-based flexible triboelectric nanogenerator (TENG) has been fabricated to analyze the effect of ambient temperature on the electrical outputs. The open-circuit voltage increased from 6.2 to 20 V with the increase in the ambient temperature up to 41 °C. However, beyond 41 °C, the electrical outputs start decreasing. Through tuning the ambient temperature, an ∼11-fold enhancement in the output power density of the TENG was achieved. In order to investigate the mechanism behind the temperature-tuned TENG outputs, the temperature-dependent dielectric permittivity and conductivity of the film have been studied. The dielectric permittivity and conductivity of the films are observed to increase with the temperature. The increase in the dielectric permittivity has been attributed to the PVDF segmental chains' movements, causing the enhancement in dielectric permittivity, which results in more surface charge and improvements in the TENG electrical outputs. However, a large increment in film conductivity at higher temperatures causes the leakage of surface charges, resulting in a decrement in TENG outputs. Furthermore, the temperature-dependent performance of PVDF-CdS nanocomposite-based TENG has also been investigated and found to enhance the performance from 8 to 27 V with the increase in temperature from 33 to 41 °C. The additional interfacial polarization between CdS nanoparticles and the PVDF matrix and higher ferroelectricity in nanocomposites contribute to larger TENG outputs of the PVDF/CdS nanocomposite-based TENG device. [ABSTRACT FROM AUTHOR]

In recent years, triboelectric nanogenerator (TENG) has been attracting lots of attention for harvesting electrical energy from mechanical energy, because of its simplicity in designing, cost-effectiveness, and high output power. In the present trend, the performance of TENG is improved mainly by surface modification using complex techniques. In the present work, we have demonstrated enhanced triboelectrification between polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) by incorporating ZnO nanorods into PVDF polymer. The fabricated ZnO-PVDF/PTFE based TENG showed 21% enhanced output voltage and 60% enhanced short-circuit current in comparison to PVDF/PTFE based TENG with an instantaneous output power density of ∼10.6 μW/cm2. The increase in triboelectrification comes not only from the enhancement in β-phase content, which leads to increase polarizability, but also from the enhancement in surface roughness, hydrophobicity, and a decrease in the work function of PVDF after incorporating ZnO nanorods. Image 1079 • Achieved 65.6% more instantaneous output power in nanocomposite film as compared to bare film based TENG. • Surface roughness, polarizability and hydrophobicity plays an important role in the performance of TENG. • Simple yet effective way of enhancing the triboelectric property of ferroelectric film (PVDF). • The localised ferroelectric property of PVDF was studied using PFM. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Oil to water phase conversion of superparamagnetic CoFe 2 O 4 nanoparticles. • Novel mechanochemical ligand exchange method was used. • For rapid and large scale production of water dispersible biocompatible MNPs. • Application in magnetic hyperthermia for treating the cancer cells is demonstrated. Abstract We report the hydrothermal synthesis of uniform size (∼6 nm) oleic acid capped CoFe 2 O 4 (OA-CoFe 2 O 4) nanoparticles. These OA-CoFe 2 O 4 nanoparticles were initially hydrophobic and not dispersible in water which were transformed into hydrophilic nanoparticles by modifying their surface with citric acid using a rapid mechanochemical ligand exchange process, which makes CoFe 2 O 4 nanoparticles stable colloidal solution in water. The synthesized citric acid coated CoFe 2 O 4 (CA-CoFe 2 O 4) nanoparticles show a high enough and stable zeta potential over 120 days. CA-CoFe 2 O 4 nanoparticles exhibited high biocompatibility under in vitro cell studies. The specific absorption rate (SAR) of the CA-CoFe 2 O 4 nanoparticles was measured by induction heating studies. Upon the exposure of AC external magnetic field, the viability of cancer cells was reduced considerably, suggesting efficient potentiality of these CA-CoFe 2 O 4 nanoparticles for Magnetic Hyperthermia Applications. Present mechanochemical ligand exchange method is proposed as an efficient method for large scale production of biocompatible and water dispersible magnetic oxide nanoparticles for Magnetic Hyperthermia Applications. [ABSTRACT FROM AUTHOR]

Non-volatile, multilevel bipolar Resistive Switching (RS) along with multilevel magnetization switching, in a cobalt ferrite (CFO) thin film using a simple Cu/CFO/Pt sandwich structure, has been demonstrated. Besides the low resistance state (LRS) and the high resistance state (HRS), the device exhibits two intermediate resistance states (IRSs), which are stable with time and reproducible in RS cycles. The endurance characteristics of the present RS device (>500 switching cycles) show no noticeable degradation and the ultimate resistance ratio always remains >104, which ensures reproducibility, reversibility, and controllability of the RS features of the present device. The HRS of the device shows a semiconducting conduction mechanism, whereas the LRS and both the IRSs were found to be Ohmic in nature. Simultaneous magnetization and resistive switching confirmed the multifunctional behavior of the device and suggested the presence of a valence change mechanism of resistive switching. The magnetization vs. magnetic field studies and temperature dependent resistance studies revealed that the electrochemical metallization also plays an important role during the switching process, which enhances the resistance ratio by providing an additional metallic filament of Cu atoms along with the ionic conducting filament of oxygen vacancies. The voltage controlled multilevel magnetization and resistive switching with a large memory window (resistance ratio >104) make the present device a potential candidate for paving the path for future multifunctional and multilevel memory devices with the capability of high density data storage. [ABSTRACT FROM AUTHOR]

Graphical abstract Bismuth sulfide (Bi 2 S 3) has been synthesized in the morphology of hierarchical nanostructures by facile hydrothermal method. The photocatalytic efficiency of Bi 2 S 3 nanostructures has been checked for the degradation of MB, RhB single dye solution and their binary mixture and compared with commercial TiO 2 (Degussa P25) sample under visible light illumination. The degradation rate of RhB and MB is enhanced by ∼8 times and ∼3 times in their binary solution as compared to that in single dye solution and increased by ∼14 times than that of Degussa P25 for both RhB and MB degradation in the binary solution, respectively. This remarkable improvement in the photocatalytic activity of Bi 2 S 3 is attributed to the faster separation of charge carriers at the interface due to the favourable LUMO and HOMO alignment of RhB and MB with band levels of Bi 2 S 3 in the RhB-MB-Bi 2 S 3 trio system. The photocatalytic degradation study of colourless contaminants, p-chlorophenol (CP), p-nitrophenol (NP) and their mixture (CP-NP) is also investigated. The degradation rate of NP is observed to be highest in the single solution, whereas, the degradation rate of both CP and NP is found to decrease in binary mixture solution in comparison to their individual solution. Highlights • Hierarchical nanostructures of Bi 2 S 3 have been synthesized by hydrothermal method. • Utilized Bi 2 S 3 for the photodegradation of MB, RhB and their binary solution. • Demonstrated the enhanced photocatalytic activity in RhB-MB-Bi 2 S 3 trio system. • Degradation of p-chlorophenol (CP), p-nitrophenol (NP) and CP-NP over Bi 2 S 3. • Achieved highest degradation rate of NP among all phenolic compounds. Abstract Hierarchical nanostructures of bismuth sulfide (Bi 2 S 3) have been synthesized by a facile hydrothermal method. The potentiality of Bi 2 S 3 hierarchical nanostructures for the photocatalytic degradation of Rhodamine B (RhB), Methylene blue (MB) and the mixture of RhB-MB organic dyes have been demonstrated and compared with commercial TiO 2 (Degussa P25) sample under visible light illumination. The degradation efficiency of Bi 2 S 3 and Degussa P25 is found to be higher in the single as well as in the binary dye solution for MB degradation as compared to RhB degradation. Furthermore, the degradation rate of RhB and MB is enhanced by ∼8 times and ∼3 times in their binary solution as compared to that in single dye solution. Whereas, Bi 2 S 3 has demonstrated ∼14 times higher degradation rate of both RhB and MB in their binary solution than that of Degussa P25 for RhB and MB degradation in the binary solution under visible light exposure, respectively. Interestingly, Bi 2 S 3 nanostructures has exhibited larger improvement in the degradation efficiency for RhB in its binary solution which is attributed to the faster separation of photogenerated charge carriers due to the proper alignments between the molecular orbits of dyes and band level positions of Bi 2 S 3 in RhB-MB-Bi 2 S 3 heterogenous system. The photocatalytic degradation study of colourless contaminants, p-chlorophenol (CP), p-nitrophenol (NP) and their mixture (CP-NP) is also investigated in the presence of Bi 2 S 3 nanoflowers. Among the phenolic compounds, the degradation rate of NP is observed to be highest in the single solution. However, the degradation rate of both CP and NP is found to decrease in binary mixture solution in comparison to their individual solution. A possible mechanism for the enhanced photodegradation of RhB-MB dye mixture based on the active species trapping experiment has been proposed. [ABSTRACT FROM AUTHOR]

Hierarchical nanostructures of bismuth sulfide (Bi2S3) have been synthesized in orthorhombic phase by hydrothermal method. Conducting polymer polyaniline (PANI) has been synthesized by the chemical oxidative polymerization method and further coupled with Bi2S3 in various weight percentages (1, 2, 5, and 10 wt%) of PANI/Bi2S3 nanocomposite by chemisorption method. The potentiality of these prepared nanostructures has been investigated for the photodegradation of methylene blue (MB) aqueous solutions. Among all, PANI/Bi2S3 (5 wt%) nanocomposite displayed the highest photodegradation efficiency. An ~ 9-fold augment in the photocatalytic activity of bismuth sulfide has been found after its incorporation in PANI matrix. This enhancement is ascribed to the formation of staggered heterojunction and interfacial sites between PANI and Bi2S3 that suppressed recombination of photogenerated charge carriers leading to quicker deterioration of MB. The mechanism for the photocatalytic degradation of methylene blue has been proposed. Based on our results, it is suggested that the coupling of conducting polymer with metal chalcogenides is an important approach for solving the environmental remediation challenge.Hierarchical nanostructures of Bi2S3 have been synthesized by facile hydrothermal method and coupled with conducting polymer polyaniline (PANI) via simple chemisorption method. A remarkable improvement in the photocatalytic efficiency of Bi2S3 has been observed after coupling with PANI. The enhancement in the photocatalytic efficiency of Bi2S3 after incorporating in PANI is attributed to the faster transfer of photogenerated charge carriers at the interface due to the formation of type II heterojunction between matched band edges of PANI and Bi2S3. The present study focuses on designing new nanocomposite photocatalyts for achieving enhanced visible-light-driven photocatalytic performance and improved photoresponse of narrow band gap materials. [ABSTRACT FROM AUTHOR]

The observation of voltage-flux oscillations due to the radio-frequency–superconducting quantum interference device (rf-SQUID) effect in polycrystalline bulk MgB2 superconductor is reported. This provides a direct evidence of the presence of Josephson junction-type weak-link grain boundaries in MgB2. Analysis of the SQUID modulation indicates that only a few grain boundaries are of weak-link type whereas others are strong links. Generation of even and odd harmonics are observed when the MgB2 sample is subjected to both ac and dc fields. This also indicates the presence of weak-link grain boundaries. Flux noise in the bulk rf-SQUID in MgB2 is studied and compared with the flux noise in bulk high-Tc rf-SQUID. [ABSTRACT FROM AUTHOR]

Ag-added La[sub 0.67]Ca[sub 0.33]MnO[sub 3](Ag-LCMO) polycrystalline films have been prepared on SrTiO[sub 3] substrates by the ultrasonic spray pyrolysis technique and their properties are compared with the La[sub 0.67]Ca[sub 0.33]MnO[sub 3](LCMO) films prepared under similar conditions. Addition of Ag in LCMO films improves their surface morphology and reduces their lattice constant. During the synthesis process, Ag in Ag-LCMO film melts and segregates to grain boundaries. In the Ag-LCMO film, normalized voltage noise reduces by more than one order of magnitude, and peak temperature (T[sub p]) and ferromagnetic transition temperature (T[sub c]) increase by 10 and 20 K, respectively. Improvement in surface morphology and better oxygenation of the film due to the presence of Ag leads to reduction in conduction noise of the LCMO film. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Effect of intrinsic strain on the optical band gap of single phase Cu2ZnSnS4 (CZTS) nanostructures have been studied which have been synthesized by three different methods: ultrasonic assisted vapour deposition (UACVD), microwave and solvothermal in a single step process. X-ray diffraction and Raman studies revealed the formation of single phase CZTS nanostructures. The nanostructured film deposited by UACVD exhibited crystallite size ~20nm, optical band gap of 1.4eV with intrinsic strain 5.2×10-4 whereas the nanostructures grown by solvothermal method have smaller crystal size (~7nm) with higher intrinsic strain (~52.9×10-4). With increases in the crystallite size from 7nm to 20nm, the optical band gap of CZTS nanoparticles decreases from 1.72eV to 1.4eV. The variation in the optical band gaps of the CZTS nanostructures cannot be fully accounted to the variation in the size of nanoparticles and it has been attributed to the intrinsic strain present in the CZTS nanostructures. [ABSTRACT FROM AUTHOR]

In this letter, a compact spur-line based magnetically tunable bandstop filter in the flip-chip configuration using partially magnetized ferrite thin films is reported. The spur-line bandstop filter is designed to operate at a centre frequency of ~12.75 GHz and is fabricated on a quartz substrate. Magnetic thin films of cobalt ferrite, cobalt-nickel ferrite, and nickel ferrite are used, which show tunabilities of 5.1%, 6.0%, and 7.5%, respectively, after applying the bias magnetic field ranging from 0 to 300 Oe. The difference in the tunability is attributed to the change in the permeability values of the magnetic thin films after applying the bias magnetic field. The shift in the centre frequency is confirmed by the simulations carried out using CST microwave studio software. This work demonstrates the opportunities to use the partially magnetized ferrite thin films in the presence of a low bias magnetic field for achieving higher tunability in a microwave bandstop filter. [ABSTRACT FROM AUTHOR]

Single-phase uniform-sized (~9 nm) cobalt ferrite (CFO) nanoparticles have been synthesized by hydrothermal synthesis using oleic acid as a surfactant. The as-synthesized oleic acid-coated CFO (OA-CFO) nanoparticles were well dispersible in nonpolar solvents but not dispersible in water. The OA-CFO nanoparticles have been successfully transformed to highly water-dispersible citric acid-coated CFO (CA-CFO) nanoparticles using a novel single-step ligand exchange process by mechanochemical milling, in which small chain citric acid molecules replace the original large chain oleic acid molecules available on CFO nanoparticles. The OA-CFO nanoparticle's hexane solution and CA-CFO nanoparticle's water solution remain stable even after 6 months and show no agglomeration and their dispersion stability was confirmed by zeta-potential measurements. The contact angle measurement shows that OA-CFO nanoparticles are hydrophobic whereas CA-CFO nanoparticles are superhydrophilic in nature. The potentiality of as-synthesized OA-CFO and mechanochemically transformed CA-CFO nanoparticles for the demulsification of highly stabilized water-in-oil and oil-in-water emulsions has been demonstrated. [ABSTRACT FROM AUTHOR]

A visible light active photocatalyst, Ag/TiO 2 /MWCNT was synthesized by loading of Ag nanoparticles onto TiO 2 /MWCNT nanocomposite. The photocatalytic activity of Ag/TiO 2 /MWCNT ternary nanocomposite was evaluated for the degradation of methylene blue dye under UV and visible light irradiation. Ag/TiO 2 /MWCNT ternary nanocomposite exhibits (~9 times) higher photocatalytic activity than TiO 2 /MWCNT and (~2 times) higher than Ag/TiO 2 binary nanocomposites under visible light irradiation. The enhancement in the photocatalytic activity is attributed to the synergistic effect between Ag nanoparticles and MWCNT, which enhance the charge separation efficiency by Schottky barrier formation at Ag/TiO 2 interface and role of MWCNT as an electron reservoir. Effect of different scavengers on the degradation of methylene blue dye in the presence of catalyst has been investigated to find the role of photogenerated electrons and holes. Simultaneously, the Ag/TiO 2 /MWCNT shows excellent photocatalytic stability. This work highlights the importance of Ag/TiO 2 /MWCNT ternary nanocomposite as highly efficient and stable visible-light-driven photocatalyst for the degradation of organic dyes. [ABSTRACT FROM AUTHOR]

In this report, the tuning of the optical bandgap and saturation magnetization of cobalt ferrite (CFO) thin films through low doping of zinc (Zn) has been demonstrated. The Zn doped CFO thin films with doping concentrations (0 to 10%) have been synthesized by ultrasonic assisted chemical vapour deposition technique. The optical bandgap varies from 1.48 to 1.88 eV and saturation magnetization varies from 142 to 221 emu/cc with the increase in the doping concentration and this change in the optical and magnetic properties is attributed to the change in the relative population of the Co2+ at the tetrahedral and octahedral sites. Raman study confirms the decrease in the population of Co2+ at tetrahedral sites with controlled Zn doping in CFO thin films. A quantitative analysis has been presented to explain the observed variation in the optical bandgap and saturation magnetization. [ABSTRACT FROM AUTHOR]

Presents a study that examined the periodic oscillations in radio frequency superconducting quantum interference devices (SQUID) fabricated from screen printed bismuth-strontium-calcium-copper-oxygen (BiSrCaCoO) thick films. Schematic diagram of the geometry of radio frequency SQUID; Characteristics of the SQUID at different temperatures; Background on BiSrCaCoO thick films.

Single phase cobalt ferrite (CoFe 2 O 4 , CFO) nanoparticles of a controlled size (∼6 nm) exhibiting superparamagnetic properties have been synthesized by hydrothermal technique using oleic acid (OA) as surfactant. The oleic acid coated CFO nanoparticles are stable in non-polar organic media, such as hexane but are not well dispersible in water. The surface of these nanoparticles has been further modified by citric acid using ligand exchange process, which makes CFO nanoparticles more stable colloidal solution in water. Citric acid coated CFO nanoparticles exhibits high dispersibility in water, high zeta potential, very low coercivity and moderate saturation magnetization. Biocompatibility of these CFO nanoparticles is demonstrated through cytotoxicity test in L929 cell line. [ABSTRACT FROM AUTHOR]

Single domain CoFe 2 O 4 nanoparticles with different amount of defects/strain have been synthesized by varying the growth temperature in the hydrothermal method. Nanoparticles grown at lower temperature are of larger size and exhibit more planar defects and oxygen vacancies as compared to nanoparticles grown at higher temperatures which are of smaller sizes and exhibit less planar defects and oxygen vacancies. The nanoparticles with larger amount of defects also possess a higher value of intrinsic strain as compared to nanoparticles with fewer defects. The presence of intrinsic strain in the nanoparticles is found to shift the cationic distribution at the tetrahedral and octahedral sites. The saturation magnetization ( M s ) of the nanoparticles is found to depend upon both the intrinsic strain and size of the nanoparticles. The M s increases with the decrease in the nanoparticles size from 32 nm to 20 nm, and this is correlated to the inverse of spin canting effect due to decrease in the intrinsic strain which leads to shifting of Co 2+ ions from tetrahedral to octahedral sites. However, with further decrease in the size of the nanoparticles (16 nm), the size effect dominates over the strain effect leading to decrease in M s . The coercivity is found to be higher in the nanoparticles with larger amount of defects/strain and has been attributed to strain induced strong spin canting and pinning due to defect sites. The variation of coercivity with particle size ( D ) exhibits deviation from D 3/2 dependence for the nanoparticles with larger amount of strain/defects. [ABSTRACT FROM AUTHOR]

CdS nanorods decorated with CoFe 2 O 4 (CFO) nanoparticles have been synthesized by using a facile soft chemical method. The surface of the nanorods was carefully functionalized with citrate ions to attach the CFO nanoparticles. The CFO nanoparticles decorated CdS nanorods were found to exhibit enhanced visible light driven photocatalytic activity for the degradation of methylene blue dye as compared to CdS and CFO nanostructures. The enhancement in the photocatalytic activity is attributed to the formation of heterojunction between the CdS and CFO which significantly suppresses the recombination of the photogenerated charge carriers. Also, due to the magnetic behavior of CFO this coupled nanostructure can be easily separable from the aqueous solution by applying an external magnetic field. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (RGO) coupled CdS/ZnO core/shell nanorods have been synthesized using a soft chemical route. The photocatalytic activity of CdS/ZnO/RGO nanostructure has been examined for the degradation of methylene blue dye under solar irradiation at room temperature. The CdS/ZnO/RGO nanostructure exhibits five times enhanced photocatalytic activity as compared to CdS nanostructures which is attributed to the formation of heterojunction between the CdS and ZnO and its coupling with the reduced graphene oxide which facilitates the efficient transport of photogenerated charge carriers. Also, CdS/ZnO core/shell nanostructure exhibits very good photostability due to the presence of stable ZnO as cap layer. [ABSTRACT FROM AUTHOR]

Single phase CoFe2O4 thin films are deposited on quartz substrates at 400 °C using ultrasonic assisted chemical vapor deposition, and the tuning of optical bandgap and saturation magnetization of films is demonstrated by varying the post deposition annealing temperature. The optical band gap varies from 1.58 to 1.41 eV and saturation magnetization increases from 4 to 46 emu/g as the post deposition annealing temperature is increased from 500 °C to 700 °C. The observed change in optical bandgap and the magnetic properties is attributed of the shifting of Co2+ from the octahedral to the tetrahedral site with the increase in the annealing temperature. Raman studies of the films support the redistribution of Co2+ among the octahedral and tetrahedral sites in CoFe2O4 films with the increase in the annealing temperature. [ABSTRACT FROM AUTHOR]

Ultrasonically assisted chemical vapour deposition has been used for the deposition of thin films of Cu2ZnSnS4 (CZTS) on glass substrates. The effect of substrate temperature on the structural and optical properties of thin films has been investigated. The CZTS films show a tetragonal structure with preferential orientation along the (1 1 2) plane. X-ray diffraction and Raman studies confirm the formation of a single-phase CZTS film at a deposition temperature of 325��C. These films show p-type semiconducting behaviour with a carrier concentration ∼1017�cm−3, optical absorption coefficient ∼104�cm−1 and direct optical band gap ∼1.4�eV. At higher substrate temperatures (⩾350��C), secondary phases of Cu2−xS and SnS2 also start growing along with the CZTS phase. The band gap of CZTS films increases from 1.40 to 1.50�eV as the deposition temperature increases from 325 to 400��C. The observed higher band gap for CZTS films deposited at 400��C has been attributed to the growth of the Cu2−xS and SnS2 secondary phase and a sulfur-poor CZTS phase. The activation energy of the CZTS thin film deposited at 325��C is 15�meV. [ABSTRACT FROM AUTHOR]

YBaCuO (YBCO) thin films have been deposited on bare and LaSrMnO (LSMO) modified single crystal SrTiO (STO) substrates. The effect of randomly distributed ferromagnetic LSMO nanoparticles and a complete LSMO layer, present at STO/YBCO interface, on the superconducting properties of YBCO thin films has been investigated by temperature dependent magnetization studies. The YBCO thin film on LSMO nanoparticles decorated STO substrate shows significant improvement in the critical current density and pinning force density as compared to the YBCO thin film deposited on bare STO substrate and this improvement is more significant at higher applied magnetic field. However, the LSMO/YBCO bilayer showed the improved flux pinning properties only up to a magnetic field of 1.5 T above which it deteriorates. In the case of LSMO/YBCO bilayer, the underlying LSMO layer gives rise to magnetic inhomogeneities due to domain structure, which leads to improved flux pinning properties limited to lower field. However, in the case of LSMO nanoparticles decorated substrate, the presence of LSMO nanoparticles at YBCO/STO interface seems to introduce magnetic inhomogeneities as well as structural defects, which might be acting as correlated pinning sites leading to improved flux pinning properties of the YBCO thin film over a wide range of applied magnetic field. [ABSTRACT FROM AUTHOR]

P-type polyaniline (PANI)/n-type ZnO based heterojunction is fabricated and the effect of continuous ultraviolet (UV) exposure on its current–voltage (I–V) characteristics is investigated. The I–V characteristics of PANI/ZnO showed diode-like behavior under dark condition and its ideality factor and barrier height were obtained as 1.54 and 1.35 eV, respectively. For immediate UV exposure the diode showed photo-characteristics, however, during continuous UV exposure diode characteristics started to change with exposure time. After sufficient exposure time characteristics became stable and the ideality factor and barrier height after UV exposure were obtained as 7.94 and 0.92 eV, respectively. It is proposed that the permanent physical changes in PANI film during UV exposure are responsible to change the rectifying behavior. It is found that after 10 min of continuous exposure the PANI film stabilizes and the PANI/ZnO junction shows stable characteristics. [ABSTRACT FROM AUTHOR]

Thin films of YBCO and YBCO:BaZrO (BZO) nanocomposite have been deposited using the pulsed laser deposition technique. Substantial increase in critical current density ( J) and pinning force density ( F) of the nanocomposite thin films was observed. The possible pinning mechanism in YBCO:BZO nanocomposite thin films has been explored and compared with the pinning mechanism in pure YBCO thin film by studying the variation of J with magnetic field ( B) and temperature. In the intermediate field regime (0.1-1 T), J follows B with nearly similar values of α for YBCO and YBCO:BZO nanocomposite thin films indicating similar pinning mechanism in both thin films. The variation of J with reduced temperature ( t= T/ T) has been studied for both the films and it was observed that the mechanism of pinning in both YBCO and YBCO:BZO thin films is similar ( δT pinning). The observed enhanced values of J and F of the nanocomposite thin film is attributed to the presence of BZO nanoparticles, which induces more defects due to lattice mismatch between YBCO and BZO leading to improved flux pinning properties of the nanocomposite thin film. [ABSTRACT FROM AUTHOR]

Abstract: Thin films of YBa2Cu3O7− δ (YBCO) have been deposited on undecorated and La0.67Sr0.33MnO3 (LSMO) nanoparticles decorated single crystal SrTiO3 (STO) substrate using laser ablation technique and their flux pinning characteristics have been compared using temperature dependent magnetization studies. Significant improvement in the critical current density of YBCO thin film has been observed even at higher applied magnetic field (∼7T). The improved flux pinning properties of YBCO thin films deposited on LSMO decorated STO substrate has been attributed to the presence of ferromagnetic LSMO nanoparticles at the substrate/film interface which seem to be acting as artificially generated magnetic pinning centres leading to improved flux pinning properties. [Copyright &y& Elsevier]

Abstract: ZnO nanostructures synthesized by chemical solution method were observed to exhibit a shape transition from nanoparticle to nanorod when the growth temperature was varied from 130 to 200°C. At the intermediate growth temperatures (150–170°C), nanoparticles start getting attached to form nanorods and exhibit enhanced strain and defects which seems to be due to the presence of interface between attached nanoparticles at these growth temperatures. The difference between valence band maxima and Fermi energy level at intermediate growth temperatures get increases which has been attributed to the enhancement of defects. [Copyright &y& Elsevier]

Abstract: The effect of incorporation of BaTiO3(BTO) nanoparticles on the flux pinning properties of pulsed laser deposited YBCO:BTO thin films was studied. Substantial increase in the critical current density () and the pinning force density () of the nanocomposite thin films was observed. At 77 K, and zero applied magnetic field, the value of for YBCO and YBCO:BTO (2%) thin films were 2.93 MA/cm2 and 6.43 MA/cm2, respectively. At the same temperature and an applied magnetic field of 4 T, the value of increases from 3.6×104 A/cm2 for YBCO thin film to 2.7×105 A/cm2 for YBCO:BTO (2%) nanocomposite thin film. The study of temperature and field dependence of of YBCO and YBCO:BTO thin films indicates similar type of pinning. The lattice mismatch between YBCO and BTO seems to introduce more defects resulting in the improvement of flux pinning properties. [Copyright &y& Elsevier]

Abstract: ZnO and Al-doped ZnO films have been deposited on quartz substrates by ultrasonically assisted chemical vapor deposition technique. Photoluminescence (PL) spectra of the films reveal that Al doping leads to suppression of defect related visible band. Time resolved photoluminescence studies have been carried out for the measurement of lifetime of deep level luminescence. The decay of PL intensity with time has been found to follow biexponential behavior. The relative contributions of fast decay component and slow decay component in total decay process are found to be ∼99% and ∼1% respectively. The values of and are found to decrease with Al doping in ZnO film. The decrease of both and is attributed to increase in non-radiative recombination due to reduction in grain sizes and the decrease in radiative recombination due to suppression of defects. [Copyright &y& Elsevier]

Abstract: Magnetization studies of YBCO:BaZrO3 composite superconductor have been done over a wide range of temperature and applied magnetic field using MPMS SQUID VSM and the results are compared with that of pure YBCO. The analysis of the observed results indicate that there is considerable improvement in the values of critical current density (J C ) and pinning force density (F p ) of YBCO:BaZrO3 composite samples as compared to pure YBCO sample in the entire investigated range of applied magnetic field and temperatures ranging from 4 to 77K. The variation of J C with reduced temperature t (=T/T C ) for the composite samples has been found to be similar to that of pure YBCO sample indicating similar nature of the vortex interaction with pinning centres in both pure and composite samples. The enhancement in the value of J C and F p in the composite samples as compared to pure YBCO sample has been attributed to the increased defect density in the composite samples due to the presence of BZO particles in YBCO matrix. [Copyright &y& Elsevier]

Cobalt ferrite thin film based low loss magnetically tunable bandpass filter in the flip chip configuration is fabricated. Cobalt ferrite thin film was synthesized by ultrasonic assisted chemical vapor deposition technique on the quartz substrate. This was overlaid on a resonator appropriately coupled to 50 Ω feed lines. The initial operating frequency (resonance frequency) of the bandpass filter was 13.8 GHz which was shifted to 12.82 GHz when a small magnetic field (~150 Oe) was applied showing a tunability of ~7%. A large variation in the tunability of the coupled filter is attributed to change in the permeability of the CFO thin film on the application of magnetic field. [ABSTRACT FROM AUTHOR]

Abstract: Films of polyaniline (PANI) and polyaniline–CNTs composites have been synthesized by solution casting technique. Fourier transform infrared spectroscopic studies of PANI and PANI–CNTs composite films indicated the presence of interaction between CNTs and molecular chains of PANI. Dielectric properties of PANI and composite films have been investigated in the frequency range of 8.0–12.0GHz. The real part of permittivity (ε′) and loss factor (tan δ) were found to be higher in PANI–CNTs composite films as compared to the PANI film. The increasing behavior of ε′ and tan δ has been attributed to the interaction present between CNTs and PANI molecular chains and increase of conductivity of PANI films after incorporation of CNTs. [Copyright &y& Elsevier]

Abstract: YBa2Cu3O7−δ–BaTiO3 (4wt.%) (YBCO–BTO (4%)) composite bulk polycrystalline sample has been synthesized by solid state reaction method. The structure of composite sample has been investigated by X-ray diffraction and magnetization measurements were carried out using MPMS SQUID VSM. The superconducting transition temperature of the YBCO–BTO (4%) sample was similar to that of pure YBCO. The critical current density (Jc ) for YBCO–BTO (4%) sample increases significantly as compared to pure YBCO sample. The enhancement of the critical current density in the YBCO–BTO (4%) sample has been attributed to the presence of BaTiO3 nanoparticles acting as artificial pinning centres. The introduction of BaTiO3 particles in YBCO increases pinning force density from 0.71GN/m2 to 1.41GN/m2 at 4K and 0.33MN/m2 to 0.97MN/m2 at 77K. [Copyright &y& Elsevier]

Abstract: Films of polyaniline (PANI) and PANI-nano ZnO composites have been synthesized by solution casting technique. Fourier transform infrared spectroscopic studies of PANI and PANI-nano ZnO composite films indicated the presence of interaction between nano ZnO particles and molecular chains of PANI. Dielectric properties of the PANI and composite films have been investigated in the frequency range of 8.0–12.0GHz. The real part of permittivity (ɛ′) and loss factor (tan δ) were found to decrease in PANI-nano ZnO composite films. The decreasing behavior of ɛ′and tan δ may be attributed to the interaction between nano ZnO particles and PANI molecular chains. The interaction between PANI chains and surface of ZnO nano particles restricts the motion of the dipoles and leads to the decrease of ɛ′and tan δ of the composite films. [Copyright &y& Elsevier]

Abstract: An inorganic/organic hetrojunction has been fabricated by spin coating the p-type polymer poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) on an n-type zinc oxide (ZnO) film. The ZnO film was deposited by the ultrasonically assisted chemical vapor deposition method on a patterned indium tin oxide (ITO) coated glass substrate. Gold was deposited on top of the PEDOT:PSS film by thermal evaporation. The current–voltage (–) characteristic of ZnO/PEDOT:PSS shows diode-like behavior. The – characteristic was examined in the framework of the thermionic emission model. The ideality factor and barrier height were obtained as 3.8 and 0.63 eV respectively. [Copyright &y& Elsevier]

Abstract: In this paper we report the effect of deposition temperature on the structural and optical properties of ZnO thin films prepared by rf magnetron sputtering. The films grown at lower deposition temperatures were in a state of large compressive stress, whereas the films grown at higher temperature (450°C) were almost stress free. In the absorption spectra, the ZnO excitonic and the Zn surface plasmon resonance (SPR) peaks have been observed. A redshift in the optical band gap of ZnO films has also been observed with the increase in the deposition temperature. The shift in the band gap calculated from the size effect did not match with the observed shift values and the observed shift has been attributed to the compressive stress present in the films. [Copyright &y& Elsevier]