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Large area single and bilayer graphene are grown on Pt/Ti/SiO2 substrates by hot filament chemical vapor deposition (HFCVD) with and without the assistance of Cu foil. The quality and number of graphene layers deposited on the substrate are assessed by Raman Spectroscopy. Atomic Force Microscopy (AFM) is used for assessing the surface topography of the graphene films grown on the Pt/Ti/SiO2 substrates. The microstructure and elemental analyses are performed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The results show that bilayer graphene growth is facilitated by a copper foil placed nearby Pt/Ti/SiO2 substrate and by a high filament temperature in the HFCVD reactor. Monolayer graphene grows only when no copper foil is placed near the Pt/Ti/SiO2 substrate at a low filament temperature. The approach paves a novel pathway towards the layer‐controlled growth of graphene on Pt/Ti/SiO2 substrates by HFCVD for frontier applications. [ABSTRACT FROM AUTHOR]

Gadolinium (Gd) and Nickel (Ni) doped bismuth ferrite (BiFeO3) nanoparticles Bi0.925Gd.075Fe0.95Ni0.05O3 (BGFNO) with spontaneous polarization (2.5 μC/cm2) were mechano‐chemically synthesized and used to achieve high capacity retention in lithium sulfur (Li−S) batteries. The BGFNO particles were coupled with single walled carbon nanotubes (SWCNT)/sulfur (S) composite cathodes as well as coated on separator. The X‐ray diffraction of BGFNO@S/SWCNT cathodes show an orthorhombic structure with particle size distribution of 20–26 nm, while Raman spectra substantiate efficient coupling of BGFNO with S/SWCNT cathodes, in agreement with SEM images, showing the interconnected network of composites. The specific discharge capacity of S60BGFNO30SWCNT10 composite cathode @ 200 mA/g together with BGFNO coated separator gains maximum capacity up to 1611 mAh/g and retains up to 1294 mAh/g after 50th cycle with improved capacity retention of 80 % showing suppression of polysulfides formation. The coated separator controls transport of carrier ions and side reactions, however modified cathodes with BGFNO particles acts as trapping center for polysulfides to enhance the electrochemical performance of the cells. The Coulombic efficiency(CE) for BGFNO/S/SWCNT composites @ 100 mA/g attained >98 % and CE @ 200 mA/g it is attained > 80 to 90 % compared to S/SWCNT composites in terms of improved cycle stability and reaction kinetics. [ABSTRACT FROM AUTHOR]

Alloy engineering are efficient methods to improve the physical properties of two‐dimensional (2D) material‐based photovoltaic application. Tin chalcogenide belonging to layered structured semiconducting family has been a significant compound due to its outstanding characteristics. Tin selenide (SnSe) is known as promising layered compound to develop 2D materials for optoelectronic devices. The current study focused onto the effect of tin sulfoselenide (SnSSe) alloy engineering on the structural, morphological, optical, and electrical characteristics. X‐ray Diffraction (XRD) confirmed that SnSSe and SnSe are exist in the orthorhombic crystal structure phase without other secondary phases, with the preferred high‐intensity peak along (111) oriented plane. Raman spectra was reported to give information about the vibrational characteristics of the compounds. The presence of Sulfur ion in SnSSe was further confirmed by Energy Dispersive X‐ray Spectroscopy (EDAX) and X‐ray Photoelectron Spectroscopy (XPS) analysis. Bandgap energy (Eg) has been analysed by Tauc's plot and the derivative of transmittance spectra. According to both sets of analyses, the bandgap of the SnSSe thin film is considerably smaller than that of the SnSe thin film. Hall measurements indicated that SnSSe exhibits the higher hole mobility. The present work's results offer useful insight into the prospective device applications of two‐dimensional alloy materials. [ABSTRACT FROM AUTHOR]

Rapidly developing electronics industry is striving for higher energy‐storage capability dielectric capacitors for pulsed power electronic devices. Both high dielectric permittivity and high dielectric breakdown strength are essential properties to meet the desired device performance. However, due to materials limitations and their preparation requirements, there are significant challenges which limit the use of current dielectrics in high‐energy storage capacitors. In addition material limitations such as, low dielectric permittivity, low breakdown strength, and high hysteresis loss decrease these materials' energy density and efficiency, restricting potential applications. Thus, a thorough understanding of the implementation, optimization and limitations of ferroelectric, relaxor‐ferroelectric, and anti‐ferroelectric thin films in high‐energy storage dielectric capacitors is an essential and important research topic for the incorporation of these materials in near future applications. [ABSTRACT FROM AUTHOR]

(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]

In the present study multiwall carbon nanotube (MWNT)/Ethyl cellulose (EC) based nanocomposite electrodes have been fabricated and tested for Li-ion batteries. The insertion of MWNTs of high surface area (140 cm2) in ethyl cellulose (EC) polymer has been implicated to obtain flexible and sufficient capacity electrodes. X-ray diffraction spectra showing enhanced crystallinity, Raman spectra showing well orientation of MWNTs in composites, scanning electron microscopy (SEM) images showing MWNTs dominance on surface of the composites, Fourier transform infrared (FT-IR) spectroscopy confirms interfacial interactions and charging-discharging profiles showing enhanced and stable charge storage capacity of composite electrodes. The electrodes of MWNT/EC nanocomposite exhibit charge capacities in between 70-240 mAh/g at charging rate (C/10). These nanocomposite electrodes can be charged up to current of 50 mA/cm2 with only 5% loss in capacity over 50 subsequent charge and discharge cycles. These composite electrodes are flexible, ultra fast and lightweight. [ABSTRACT FROM AUTHOR]

The room temperature crystal structure of potential high- k dielectric LaGdO3 has been analyzed by X-ray diffraction techniques and its structural evolution with temperature has been probed by Raman spectroscopy. Rietveld refinement of the ambient XRD data established the perfectly layered B-type monoclinic crystal structure with a = 14.43 Å, b = 3.68 Å, c = 8.99 Å, and β = 100.57° which is further validated by the 21 (14 Ag and 7 Bg) Raman-active vibrational modes with centro-symmetric space group [ABSTRACT FROM AUTHOR]

Raman spectra were obtained for graphene after irradiating the samples by pulsed laser (λ = 248 nm). Changes in the spectra were observed as the pulse laser energy density (PLED) was varied from 0.1 to 0.25 J/cm2. Changes in bilayer graphene were accompanied by the appearance of the D peak and the broadening of the G peak. Changes in multilayer graphene are more profound as the Raman spectra changes from a multilayer to bilayer and subsequently to monolayer graphene in response to a slow increase in the PLED. The threshold PLED was found to be dependent on the number of graphene layers. We also irradiate graphene with very high PLED (much above the threshold), and the Raman spectra were found to be significantly changed. The G-band became broader, and red shifted, while the intensity of the 2D-band was drastically reduced and an intense defect-related D peak appeared at about 1350 cm−1. The laser ablation of graphene, both with low- and high-energy intensity, is consistent with the reported theoretical predictions. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper reports on two new aspects of oxide perovskites: the first part is devoted to new phase transitions, especially at high temperatures; multiferroics such as BiFeO3 and Pb–Fe–W–titanate are emphasized but nonmagnetic materials such as SrSnO3 are included. The work summarized on bismuth ferrite emphasizes its metal–insulator transition near 1200 K (atmospheric pressure) and 47 GPa (room temperature); that on SrSnO3 emphasizes order–disorder phase transitions; and that on lead–iron tungstate–titanate exhibits a classic second-order ferroelectric phase transition, of which rather few are known in the literature. The second part of the paper presents a discussion of constant phase elements for oxide perovskite ceramics; this is a modern way of characterizing their dielectric relaxation, particularly near phase transition temperatures. [ABSTRACT FROM AUTHOR]

Comparative studies of the microstructure, micro-Raman spectroscopy, and dielectric properties of PbSc0.50Nb0.25Ta0.25O3 (PSNT) thin films and nanoceramics were carried out over a wide range of temperature (100–520 K) and frequency (100 Hz to 1 MHz). The microstructure of PSNT films revealed an in-plane compressive strain, whereas PSNT nanoceramics showed an average grain size of 10–15 nm although these nanoordered regions are not capable of producing relaxor behavior. We have observed a shift of 65 K in the dielectric maxima temperature in PSNT films toward the lower temperature side compared with bulk, which confirms the in-plane compressive strain in the films. We have proposed a dielectric model to calculate the shift in dielectric maxima temperature. Using our experimental data of PSNT thin films, the theoretical model predicted a shift of 62 K in the dielectric maxima temperature, which matched well with our experimental observation. The modified Curie–Wiess law showed a broad relaxation (γ∼2) and a higher disorder level (δ=90 K) for PSNT thin films compared with PSNT nanoceramics having γ∼1.60 and δ=15 K. Well-behaved hysteresis loops were observed in a broad temperature range for PSNT thin films and slim hysteresis for nanoceramics, indicating a relaxor ferroelectric and diffused ferroelectric phase transition (DFPT) nature, respectively. The temperature-dependent micro-Raman spectroscopy revealed that the ferroelectric state in PSNT nanoceramics was accompanied by the appearance of a new peak as a shoulder at ∼80 cm−1 to the lowest F2g mode ∼57 cm−1. Its half-widths and intensity reduced to zero near the phase transition temperature, whereas the A1g mode showed a doublet namely at (805 and 830 cm−1) below DFPT and an intermediate singlet frequency at 820 cm−1 above DFPT. The micro-Raman spectra for the thin film matched quite well with the nanoceramics, except that the missing second F2g mode at ∼360 cm−1 was interpreted due to a shorter coherence length in the dipole arrangement in thin films. The in-plane compressive strain, dipole arrangement, and the size of the nanoordered regions vary the dielectric response of the PSNT films compared with the nanoceramics. [ABSTRACT FROM AUTHOR]

Reports on the use of micro-Raman spectroscopy to determine the degree of mixing in each of the prepared multicomponent ceramic powder compacts. Effect of change in laser intensity and particle size distribution on degree of mixing; Production of uniform mixing; Mixing results for flocculated powders.

Multiferroic materials have driven significant research interest due to their promising technological potential. Developing new room‐temperature multiferroics and understanding their fundamental properties are important to reveal unanticipated physical phenomena and potential applications. Here, a new room temperature multiferroic nanocomposite comprised of an ordered ferrimagnetic spinel α‐LiFe5O8 (LFO) and a ferroelectric perovskite BiFeO3 (BFO) is presented. It is observed that lithium (Li)‐doping in BFO favors the formation of LFO spinel as a secondary phase during the synthesis of LixBi1−xFeO3 ceramics. Multimodal functional and chemical imaging methods are used to map the relationship between doping‐induced phase separation and local ferroic properties in both the BFO‐LFO composite ceramics and self‐assembled nanocomposite thin films. The energetics of phase separation in Li doped BFO and the formation of BFO‐LFO composites are supported by first principles calculations. These findings shed light on Li's role in the formation of a functionally important room temperature multiferroic and open a new approach in the synthesis of light element doped nanocomposites for future energy, sensing, and memory applications. [ABSTRACT FROM AUTHOR]

As the semiconductor technology approaches size limitation (according to Moore's law), significant efforts need to be focused to develop alternative gate dielectric materials that can facilitate low electrical functional thicknesses for future logic and memory nodes. Over the last few years there has been considerable interest in the application of inter‐lanthanide compounds in modern electronic devices. Researchers at University of Puerto Rico led by Professor Ram S. Katiyar have developed a novel alternative low‐loss high‐k dielectric lanthanum gadolinium oxide in their laboratory which is a significant development for nano‐electronic device applications, such as dynamic random access memories (DRAMs), resistive switching memory elements (RRAMs) and related logic electronic components (MOSFETs). Pavunny et al. (pp. 131–139) utilized X‐ray crystallography and Raman spectroscopy to characterize the crystal structure of this oxide and also discussed its high‐temperature phase transition near 900 K. This new material has a dielectric constant greater than five times that of silicon oxide which is higher than that of any of the presently used hafnium‐based high‐k dielectrics. Therefore it can have a broader impact on feature size reduction in the fabrication of CMOS logic and memory devices. [ABSTRACT FROM AUTHOR]

The room temperature crystal structure of potential high- k dielectric LaGdO3 has been analyzed by X-ray diffraction techniques and its structural evolution with temperature has been probed by Raman spectroscopy. Rietveld refinement of the ambient XRD data established the perfectly layered B-type monoclinic crystal structure with a = 14.43 Å, b = 3.68 Å, c = 8.99 Å, and β = 100.57° which is further validated by the 21 (14 Ag and 7 Bg) Raman-active vibrational modes with centro-symmetric space group [ABSTRACT FROM AUTHOR]

This paper reports on two new aspects of oxide perovskites: the first part is devoted to new phase transitions, especially at high temperatures; multiferroics such as BiFeO3 and Pb–Fe–W–titanate are emphasized but nonmagnetic materials such as SrSnO3 are included. The work summarized on bismuth ferrite emphasizes its metal–insulator transition near 1200 K (atmospheric pressure) and 47 GPa (room temperature); that on SrSnO3 emphasizes order–disorder phase transitions; and that on lead–iron tungstate–titanate exhibits a classic second-order ferroelectric phase transition, of which rather few are known in the literature. The second part of the paper presents a discussion of constant phase elements for oxide perovskite ceramics; this is a modern way of characterizing their dielectric relaxation, particularly near phase transition temperatures. [ABSTRACT FROM AUTHOR]