J. H. Markna

Thickness dependent swift heavy ion irradiation effects on electronic transport of (La0.5Pr0.2)Ba0.3MnO3 thin films

Electrical resistivity and magnetoresistance measurements on (La0.5Pr0.2)Ba0.3MnO3 thin films of 50 and 200nm thicknesses, irradiated by 200MeV Ag+15 ions, have been carried out. Before irradiation, all the films exhibit insulator-metal transition at a temperature (Tp) of ∼200K. After irradiation, both resistivity and Tp remain mostly unaffected in 50nm thin film but vary largely in 200nm thin films. This disparity in irradiation effect on these films is explained to arise from the interplay of columnar defect induced (i) enhancement in resistivity with increasing thickness of the film and (ii) local release of strain at the interfaces of low thickness films, which decreases resistivity.

High field sensitivity at room temperature in p-n junction based bilayered manganite devices

The thickness dependent current-voltage (I-V) properties of the bilayered La0.6Pr0.2Sr0.2MnO3 (LPSMO)∕Nb-SrTiO3 (SNTO) p-n junction devices having two different thicknesses, grown using pulsed laser deposition (PLD) technique, have been studied. The I-V curves of these bilayered junctions show good rectifying behavior and also exhibit large positive magnetoresistance (MR) at room temperature. The p-n junction having LPSMO thickness of 200nm exhibits low saturation voltage (VC) and high positive MR as compared to junction with 100nm p-type LPSMO layer. Distinct feature such as large positive MR with respect to temperature can be understood in terms of thickness dependent modifications in the film-substrate interface.

Size-controlled electrical properties of sol–gel-grown nanostructured Gd0.95Ca0.05MnO3

In this communication, we report the results of the studies on electrical properties of cost-effective modified sol–gel-grown nanostructured Gd0.95Ca0.05MnO3 (GCMO) manganites sintered at different temperatures. Structural investigations, carried out using X-ray diffraction measurements, reveal the single-phasic nature of GCMO samples having orthorhombic unit cell structure. Frequency-dependent variation in AC conductivity (σAC) has been discussed on the basis of correlated barrier hopping (CBH) mechanism for the GCMO samples sintered at lower temperatures. Sintering temperature-induced transition from CBH mechanism to Maxwell–Wagner relaxation processes has been discussed in detail. Size-induced modifications in the impedance response of the samples have been understood, in detail, using size effects and Cole–Cole plots.Graphical Abstract

Swift-heavy-ion-irradiation-induced enhancement in electrical conductivity of chemical solution deposited La0.7Ba0.3MnO3 thin films

Epitaxial thin films of La0.7Ba0.3MnO3 manganite, deposited using chemical solution deposition technique, were irradiated by 200MeV Ag+15 ions with a maximum ion dose up to 1×1012ions∕cm2. Temperature and magnetic-field-dependent resistivity measurements on all the films (before and after irradiation) reveal a sustained decrease in resistivity with increasing ion dose. A maximum dose of 1×1012ions∕cm2 suppresses resistivity by factors of 3 and 10 at 330K [insulator-metal (I-M) transition] and at 10K, respectively. On the other hand, with increasing ion dose, the magnetoresistance enhances in the vicinity of I-M transition but decreases at low temperatures. These results, corroborated by surface morphology of films, suggest that the origin of such properties lies in the irradiation induced improved crystallinity and epitaxial orientation, enhanced connectivity between grains and conglomeration of grains, which result in better conductivity at grain boundaries.

Temperature-dependent I–V and C–V characteristics of chemically-grown Y0.95Ca0.05MnO3/Si thin films

In this communication, we report the results of the studies on temperature-dependent current—voltage (I–V) and capacitance—voltage (C–V) characteristics of chemical solution deposition-grown Y0.95Ca0.05MnO3/Si films and annealing temperature-induced modified interface dependence on device characteristics. X-ray diffraction results reveal the single phasic nature of films having polycrystalline growth on single crystalline (100) Si substrate. The magnetic nature of the films is confirmed from magnetic force microscopy studies. I–V and C–V characteristics show a strong dependence on the temperature and nature of the film—substrate interface, which has been understood on the basis of the annealing effect involved. Various models and theories have been used to understand the mechanism responsible for the transport across the film—substrate interface. A large rectifying ratio of ~1.2 × 104 has been obtained across the interface annealed at a lower temperature, which becomes almost double in the film annealed at a higher temperature. A large electroresistance of ~600% has been achieved for the interface annealed at a lower temperature. The temperature dependence of C–V behavior recorded across the interfaces of the films is discussed in detail on the basis of free and trapped charge carrier density and interface modifications.

Synthesis and Optical Characterization of CuO Nanoparticles on Solar Borosilicate Glass

In this communication we report on the optical property of CuO nanoparticles prepared by cost effective, simplistic and environment-friendly sol-gel technique on borosilicate glass by dip coating. The particle size was analyzed by Transmission Electron Microscope (TEM) which depicted particle size of CuO ~ 5 nm. To understand the optical behavior of nanosized CuO particles on borosilicate glass tube UV-visible spectrum has been taken. Effective mass model calculations determined the size of particles as 2.26 nm, which supports the TEM analysis. Samples were also analyzed by Fourier transform infrared spectrum (FT-IR) to understand the chemical bond in detail.

Nanotechnology: new hope of efficiency enhancement for solar evacuated tube collector

Purpose In the twenty-first century, the use of fossil fuels has increased drastically because the necessity of energy is increasing day by day which affects the world’s economy. The solar energy (photo-thermal energy conversion) system is the most economical and eco-friendly alternative source. To increase the use of domestic as well as commercialization purpose, the authors have reviewed this paper on the solar water heater along with its structural mechanism for energy enhancement and to create easier stair steps for climbing on the green world dream. Design/methodology/approach In this study, nanotechnology has remarkably built its own use for extending thermal efficiency by using some gradual experiments. It is a phenomenon, like nanofluid (as a working fluid for a direct solar collector), nanocoating (on the surface of a solar-evacuated tube by using the chemical vapor deposition/physical vacuum deposition/sol–gel technique) and nanorod-based solar collector tube. Findings This invention gives greater efficiency rather than the conventional systems, but also this advancement is not too much supported in a low- temperature environment also, we can consider the poor light absorption characteristics of the pure water (Bencic, et al., 2000). Originality/value The basic idea and understanding of this phenomenon to improve solar collecting performance for obtaining a high working-fluid temperature are discussed in this paper.

Analysis and design optimization of organic dye sensitized solar cell based on simulation

In the present communication, simulation of multilayers organic dye-sensitized based solar cells (DSSC) was performed because of its tremendous application in different solar energy harvesting devices and their relatively high efficiency as well as cost effectiveness.J-V and I-V curves ofmultilayer organic dye sensitized solar cell with combination of different dyes were simulated to study the performance in the vicinity of efficiency. On the basis of above parameters, optimum design and operating parameters were derived from the simulation based analysis. It had been jointly shown that a systematic variation of different dye material and its thicknessare highly useful in achieving optimum efficiency of energy harvesting devices.

Highly sensitive nanostructure SnO2 based gas sensor for environmental pollutants

A major quantity of pollutants are produced from industries and vehicles in the form of gas. New approaches are needed to solve well-known environmental pollutants like CO, CO2, NO2, SOx. Therefore detection with effective gas sensors is a vital part of pollution prevention efforts. There is a need to develop fast, rapid, cost-effective, highly sensitive, low power, and non-intrusive rugged sensors that can be easily installed. In the present study, nanostructured SnO2 used as a sensitive material in the devices and synthesized using hydrothermal process. The detailed development of the fabrication of SnO2 nanostructures gas sensor is described, which shows the remarkable change in the sensing properties with varying particle size. Additionally, we have used X-ray diffraction, scanning electron microscopy (SEM) for characterization and carefully examined the relative parameters like response magnitude (sensitivity) and selectivity of SnO2 nano structures with different particle size.

Studies on structural and electrical properties of pure and doped h-YMnO3

In the present communication, we report the results of the structural and electrical studies on pure YMnO3 (YMO) and Zr doped Y0.95Zr0.05MnO3 (YZMO) samples, synthesized using low cost sol-gel technique. To understand the structural properties, structural phases present and effect of doping on the structural behavior, X-ray diffraction (XRD) measurements were carried out for both the samples understudy. XRD results reveal the single phasic nature of both the samples having hexagonal unit cell structure. Improved crystal structure has been observed for pure YMnO3 sample while doping of Zr at Y-site degrades the structure of the sample. Improved dielectric constant and enhanced AC conductivity (σa) have been discussed on the basis of charge carrier polarization and correlated barrier hopping due to the localized state.