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(Ba0.955Ca0.045)(Zr0.17Ti0.83)O3 [BCZT] epitaxial were grown on La0.67Sr0.33MnO3 (LSMO)‐coated (100)‐oriented MgO single crystal substrates by the pulsed laser deposition (PLD) technique. Herein, we report crystal structure, ferroelectric, piezoresponse force microscopy (PFM), and energy storage properties near the morphotropic phase boundary (MPB) composition of [Ba0.850Ca0.15Zr0.1Ti0.90O3] solid solution. Epitaxial growth of the films was confirmed using X‐ray diffraction (XRD) spectra. Room‐temperature Raman spectroscopy confirms perovskite phase of BCZT films. Room‐temperature polarization‐electric field (P‐E) loops confirm the ferroelectric nature of BCZT films. Ferroelectric hysteresis loops demonstrate high saturation polarization (Pmax ~ 97.96 μC/cm2) and remanant polarization (Pr ~ 70.1 μC/cm2) at an applied maximum electric field ~2.77 MV/cm. The optimized BCZT epitaxial thin films have shown moderate dielectric properties at different measured frequencies (10‐100 kHz). Nanoscale piezoresponse force microscopy (PFM) images demonstrate switchable ferroelectric polarization of these thin films above ±9 V of dc voltage applied. Energy storage properties measured from ferroelectric loops revealed a high discharge curve energy density ~27.5 J/cm3 at a maximum electric field of 2.77 MV/cm. Epitaxial‐grown BCZT films are suitable candidate materials for capacitor applications. [ABSTRACT FROM AUTHOR]

The search for a room temperature single phase multiferroic material displaying strong magnetoelectric coupling and low leakage current for practical device applications has been underway and a long-standing challenge. In continuation to our investigations for achieving robust ME coupling and enhanced electrical insulation at room temperature, we report magnetic, electrical insulation, and magneto-dielectric properties of Nd and Mn co-doped BiFeO3 (Bi0.95Nd0.05)(Fe0.97Mn0.03)O3 (BNFM) polycrystalline electro-ceramics. Magnetic studies have been carried out in two different temperature regions, i.e., 15–300K and 300–800K. The doping of Nd and Mn in the BiFeO3 (BFO) lattice slightly reduces the Néel temperature (TN) with broad weak ferromagnetic (FM) to paramagnetic (PM) phase transition by increasing ferromagnetic domain fractions. A small amount of magnetic frustration is also found in the low temperature regions, below 300K at fields of 100 and 200Oe, and below 200K at higher field cooled and zero field cooled; this may be due weak long range ordering and small magnitude of magnetic moments. High temperature magnetic results imply the existence of a weak ferromagnetic phase with a FM to PM phase transition around 630K (±5K) and significant suppression of the spin frustration and canting properties of BFO. The Nd and Mn co-doping also substantially improved the electrical insulating properties of BFO. The leakage current analysis suggests that the Simmons’ mechanism is probably a dominant conduction mechanism in BNFM at room temperature. The observation of dielectric anomaly around the TN and significant variation of dielectric parameters with different static magnetic field in BNFM implies the existence of strong magnetodielectric coupling. The enhanced magnetic and electrical insulation properties with strong magnetodielectric coupling at room temperature elucidate the possible potential candidates for multifunctional and spintronics device applications. [ABSTRACT FROM AUTHOR]

Vanadium sesquioxide V2O3, a transition metal oxide, is an important metal transition insulator due to its potential applications in novel electronic and memory devices. V2O3 thin films of thickness around 230 nm were grown on Si/SiO2/Ti/Pt substrates at deposition temperature of 723 K in a controlled Ar:O2 atmosphere of 35:2.5 sccm employing Direct Current (DC) magnetron sputtering. X-ray diffraction studies confirmed single phase of the material stabilized in corundum rhombohedral R 3 ¯ C phase. X-ray photoelectron spectroscopic results revealed chemical oxidation states are of V3+ and O2− and have nearly stochiometric elemental compositions in the films. Magnetization studies down to 10 K predicts a canted antiferromagnetic transition around 55 K. Out of 7 expected Raman active modes (2A1g + 5Eg), two A1g Raman active modes at 242 and 500 cm−1 were observed at ambient R 3 ¯ C phase. Temperature dependent Raman spectroscopic studies carried out from 80 to 300 K identified a monoclinic to rhombohedral phase transition at ~143 K. [ABSTRACT FROM AUTHOR]

Solid acid composite electrolytes (1−x)CsH2PO4(CDP)/xSiO2 (0 ≤ x ≤ 0.35) were prepared and observed the structural, thermal, and transport properties by XRD, EDX, FESEM, FTIR, DSC, TGA, DTA, and conductivity measurements. The crystallite size was obtained between the range of 36 and 64 nm. We have investigated the superprotonic phase transition at 230 °C in CDP, at which the conductivity increased up to four orders of magnitude. The initial dehydration event in CDP occurred at 250 °C. The performance of CDP was increased due to the addition of SiO2 in the form of conductivity and stability. Thermal characterization showed that by introducing the additives, dehydration behavior shifted to the lower in DSC and DTA at the higher temperature. The lowest weight loss was found in 65CDP/35SiO2. The stable protonic conductivity was observed with time for CDP, 95CDP/05SiO2, and 85CDP/15SiO2 in a hermetically closed chamber. The electrodes were prepared by vapor deposition of silver. [ABSTRACT FROM AUTHOR]

With the rapid development of new device miniaturization technology, there is invigorated interest in magnetic nanostructures for potential application in novel multifunctional devices. In continuation to our search for a suitable magnetic material having Curie temperature (Tc) well above room temperature for multifunctional applications, we have studied the dielectric, optical, magnetic, and resistance switching characteristics of Ni0.65Zn0.35Fe2O4 (NZFO) thin films. The observation of only (004) reflection in the X-ray diffraction patterns confirms the c-axis orientation and high quality growth of NZFO thin films. The presence of mixed valences of Fe2+/Fe3+ cations is probed by X-ray photon spectroscopy, which supports the cationic ordering-mediated large dielectric response. Our investigations reveal NZFO to be an indirect band gap material (~1.8eV) with a direct gap at ~2.55eV. These nanostructures exhibit high saturation magnetization and a low coercive field with a ferrimagnetic-paramagnetic phase transition of ~713K. Magnetic force microscopy studies revealed the stripe-like domain structure of the investigated thin films. In addition, these thin films exhibit reliable and repeatable unipolar resistive switching characteristics. The observed high dielectric permittivity with low loss tangent, large magnetization with soft magnetic behavior, striped magnetic domain structure and reliable resistance switching in NZFO thin films above room temperature suggest potential application in memory, spintronics, and multifunctional devices. [ABSTRACT FROM AUTHOR]

A detailed study of the effect of off-center donor ion (Sc3+) substitution on structural, microstructural, optical, dielectric, electrical, and ferroelectric properties of morphotropic composition of lead zirconate titanate electroceramics with the stoichiometric formula Pb0.85Sc0.10Zr0.53Ti0.47O3 (PSZT) and synthesized using a high energy solid-state reaction technique was carried out. Powder x-ray diffractometry was used to identify the stabilized tetragonal phase (space group P4mm) with considerably reduced tetragonal strain, c=a=1.005. An analysis of the thermal dependence of the Raman results indicated a smooth displacive (ferroelectric-paraelectric) phase transition as revealed by the observed disappearance of the soft modes A1 (1TO) and A1 (2TO) above 460K. The dielectric response of Pt/PSZT/Pt metal-ferroelectric-metal capacitors was probed over a wide range of thermal excursions (85-600K) and ac signal frequencies (10²-106 Hz). Thermally activated dynamic and static conduction processes indicate hopping conduction mechanism (Eact ≤0.015 eV) and the formation of small polarons caused by the electron and/or hole-lattice (phonon) interaction (Eact ≥0.1 eV) at low (100-300K) and high temperatures (300-600 K), respectively. The reduction in remnant polarization obtained is in good agreement with the largely reduced tetragonal strain observed in this sample, (Pr ∝√c/a-1). DC conduction is dominated by Poole-Frenkel mechanism that assumes a Coulombic attraction between detrapped electrons and positively charged stationary defect species in the polycrystalline matrix. [ABSTRACT FROM AUTHOR]

Thermal stability of quasi particles, i.e., exciton and trion, and a strong particle-particle interaction significantly tune the optical properties of atomically thin two dimensional (2D) metal dichalcogenides. The present work addresses the effect of inherent defects upon optical properties of chemical vapor deposition grown 1 L-WS2 and proposes the use of chemical transfer doping as a reversible and simple method for identification of the type of excess charge in the system. Photoluminescence (PL) studies in pristine 1 L-WS2 show that an additional band at ∼0.06 eV below trion (X±) PL band was evolved (at low temperature) which was associated to the bound exciton with charged/neutral defect. Using 7,7,8,8-Tetracyanoquinodimethane and 2,2-bis1,3-dithiolylidene as p and n-type dopants, respectively, we determined that the inherent defects/metal vacancies, which could be due to the presence of Tungsten metal deficiency, contributed in p-type nature of the pristine 1 L-WS2. Doping of 2D transition metal dichalcogenides materials with organic molecule via the surface charge transfer method is not only a way to provide a handy way to tailor the electronic and optical properties but also can be used as a tool to determine the nature of defects in the material. [ABSTRACT FROM AUTHOR]

Solid acid composite electrolytes CsH2PO4(CDP)/NaH2PO4(SDP)⋅2H2O were prepared and observed the structural, thermal and transport properties by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray analysis, differential scanning calorimetry, fourier transform infrared spectroscopy, and conductivity measurement. We have investigated superprotonic phase transition at 235°C in CDP, at which the conductivity increased up to 2 to 3 orders of magnitude. The initial dehydration event in CDP occurs at 250°C. The performance of CDP was increased due to the addition of SDP⋅2H2O in the form of stability. Thermal characterization showed that introducing the additivities, dehydration behavior shifted to the lower at the higher temperature. The conductivity is increased above the temperature of 170°C which was found of the composite electrolytes 70CDP/30SDP⋅2H2O, 60CDP/40SDP⋅2H2O. The electrodes were prepared by a vacuum coating unit of silver. [ABSTRACT FROM AUTHOR]

Graphitic carbon nanospheres (GCNSs) were prepared by a unique acidic treatment of multi-walled nanotubes. Spherical morphology with a narrow size distribution was confirmed by transmission electron microscopy studies. The room temperature Raman spectra showed a clear signature of D- and G-peaks at around 1350 and 1591 cm-1, respectively. Temperature dependent Raman scattering measurements were performed to understand the phonon dynamics and first order temperature coefficients related to the D- and G-peaks. The temperature dependent Raman spectra in a range of 83-473K were analysed, where the D-peak was observed to show a red-shift with increasing temperature. The relative intensity ratio of D- to G-peaks also showed a significant rise with increasing temperature. Such a temperature dependent behaviour can be attributed to lengthening of the C-C bond due to thermal expansion in material. The estimated value of the thermal conductivity of GCNSs ~0.97W m-1 K-1 was calculated using Raman spectroscopy. In addition, the effect of pulsed laser treatment on the GCNSs was demonstrated by analyzing the Raman spectra of post irradiated samples. [ABSTRACT FROM AUTHOR]

We studied the resistive memory switching in pulsed laser deposited amorphous LaHoO3 (a-LHO) thin films for non-volatile resistive random access memory applications. Nonpolar resistive switching (RS) was achieved in Pt/a-LHO/Pt memory cells with all four possible RS modes (i.e., positive unipolar, positive bipolar, negative unipolar, and negative bipolar) having high RON/ROFF ratios (in the range of ~104-105) and non-overlapping switching voltages (set voltage, VON~±63.6-4.2V and reset voltage, VOFF~±1.3-1.6V) with a small variation of about 65-8%. Temperature dependent current-voltage (I-V) characteristics indicated the metallic conduction in low resistance states (LRS). We believe that the formation (set) and rupture (reset) of mixed conducting filaments formed out of oxygen vacancies and metallic Ho atoms could be responsible for the change in the resistance states of the memory cell. Detailed analysis of I-V characteristics further corroborated the formation of conductive nanofilaments based on metal-like (Ohmic) conduction in LRS. Simmons-Schottky emission was found to be the dominant charge transport mechanism in the high resistance state. [ABSTRACT FROM AUTHOR]