@article { ISI:000226212200001, title = {Influence of process pressure on HW-CVD deposited a-Si : H films}, journal = {Solar Energy Materials and Solar Cells}, volume = {85}, number = {3}, year = {2005}, note = {2nd International Conference on Cat-CVD (Hot-Wire CVD) Process, DENVER, CO, SEP 10-14, 2002}, month = {JAN}, pages = {301-312}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Hydrogenated amorphous silicon (a-Si:H) films were deposited using pure silane (SiH4) without hydrogen dilution by hot wire chemical vapor deposition (HW-CVD) technique. The electrical, optical, and structural properties of these films are systematically studied as a function of process pressure (P-r). The device quality a-Si:H films with a photosensitivity \> 10(5) were deposited at a deposition rate \>40 Angstrom/s at low process pressure. However, a-Si:H films deposited at higher process pressures show degradation in their electrical and structural properties. The FTIR spectroscopic analysis showed that a-Si:H films deposited at low process pressure contain hydrogen mainly in mono-hydrogen (Si-H) configuration whereas films deposited at higher process pressure have hydrogen in di-hydrogen (Si-H-2) or poly hydrogen (SiH2)(n) complexes. The hydrogen content (C-H) in the films was found to be less than 4 at.\% over the entire range of process pressure studied. This indicates that the growth of a-Si:H films is mainly from the atomic species (Si and H) evaporated from the hot filament and hydrogen gets incorporated in the film via gas-phase reactions and substrate gas interactions. The band gap, however was found similar to1.71 eV or much higher. We attribute high band gap at low hydrogen content may be due to presence of microvoids. Raman spectroscopic analysis showed increase in structural disorder and Rayleigh scattering with increase in the process pressure. (C) 2004 Elsevier B.V. All rights reserved.

}, keywords = {Electrical properties, FTIR spectroscopy, hot wire chemical vapor deposition, hydrogenated amorphous silicon, Raman spectroscopy}, issn = {0927-0248}, doi = {10.1016/j.solmat.2004.04.017}, author = {Jadkar, Sandesh R. and Sali, J. V. and Kshirsagar, S. T. and Takwale, M. G.} } @article { ISI:000240639000014, title = {Transesterification of cyclic carbonates with methanol at ambient conditions over tungstate-based solid catalysts}, journal = {Applied Catalysis A-General}, volume = {312}, year = {2006}, month = {SEP}, pages = {108-114}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Dimethyl carbonate synthesis with 80 mol\% yield is achieved through transesterification of ethylene carbonate with methanol at ambient conditions (RT and atmospheric pressure) using alkali and alkaline-earth tungstates as solid catalysts. The catalysts are efficient even at the sub-ambient temperatures. Reactions under CO2 pressure indicate that CO2 atmosphere retards the transesterification reaction completely below 100 degrees C. Experimental conditions of 150 degrees C and 3.4 MPa CO2 pressure are required to obtain maximum DMC yield of 71 mol\%. Synthesis of DMC by one-pot synthesis using epoxide, CO2 and methanol is not as effective as that by two-step method with the present catalyst system. Raman and IR spectra of methanol-interacting tungstates indicate the formation of a methoxide ion species adsorbed at the catalyst surface as one possible reaction intermediates. (C) 2006 Elsevier B.V. All rights reserved.

}, keywords = {Dimethyl carbonate, ethylene carbonate, heterogeneous catalyst, Raman spectroscopy, sodium tungstate, transesterification}, issn = {0926-860X}, doi = {10.1016/j.apcata.2006.06.034}, author = {Sankar, M. and Nair, C. Madhavan and Murty, K. V. G. K. and Manikandan, Palanichamy} } @article { ISI:000275755500010, title = {Monitoring structural defects and crystallinity of carbon nanotubes in thin films}, journal = {Pramana-Journal of Physics}, volume = {74}, number = {3}, year = {2010}, month = {MAR}, pages = {447-455}, publisher = {INDIAN ACAD SCIENCES}, address = {C V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIA}, abstract = {

We report the influence of catalyst formulation and reaction temperature on the formation of carbon nanotube (CNT) thin films by the chemical vapour deposition (CVD) method. Thin films of CNTs were grown on Fe-Mo/Al(2)O(3)-coated silicon wafer by thermal decomposition of methane at different temperatures ranging from 800 to 1000A degrees C. The electron microscopic investigations, SEM as well as HRTEM, of the as-grown CNT thin films revealed the growth of uniform multi-walled CNTs in abundance. The intensity ratio of D-band to G-band and FWHM of G-band through Raman measurements clearly indicated the dependency of structural defects and crystallinity of CNTs in thin films on the catalyst formulation and CVD growth temperature. The results suggest that thin films of multi-walled CNTs with negligible amount of defects in the nanotube structure and very high crystallinity can be obtained by thermal CVD process at 925A degrees C.

}, keywords = {Carbon nanotubes, chemical vapour deposition, Raman spectroscopy, scanning electron microscopy, Thin films}, issn = {0304-4289}, doi = {10.1007/s12043-010-0040-9}, author = {Mahajan, S. S. and Bambole, M. D. and Gokhale, S. P. and Gaikwad, A. B.} } @article { ISI:000316024500022, title = {Synthesis of low coercive BaFe12O19 hexaferrite for microwave applications in low-temperature cofired ceramic}, journal = {Journal of Electronic Materials}, volume = {42}, number = {4}, year = {2013}, month = {APR}, pages = {761-768}, publisher = {SPRINGER}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Polycrystalline M-type barium hexaferrite (BaFe12O19) samples have been synthesized by solution combustion route at different pH and calcination conditions in order to reduce the coercivity for microwave applications in low-temperature cofired ceramic (LTCC) substrates. Structural, morphological, and magnetic properties of BaFe12O19 were studied by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy, vibrating sample magnetometry (VSM), and Mossbauer spectroscopy. The formation of a single-phase hexagonal structure was confirmed by XRD. The Raman spectra reveal all characteristic peaks of BaFe12O19, illustrating the phase purity and crystal lattice symmetry of the synthesized material. Mossbauer spectra illustrate the existence of Fe3+ cations at all five crystallographic lattice sites. The microstructural features observed by FESEM disclose the growth of nanoregime particles into hexagonal platelet particles after calcination at temperatures from 800A degrees C to 1200A degrees C. The VSM results show a lower coercivity (1350 Oe to 3500 Oe) together with reasonably high saturation magnetization (55 emu/g to 60 emu/g) and a high bulk resistivity (\> 10(9) Omega-cm) at room temperature. The dependence of magnetic and electrical properties on the preparation and processing conditions is also discussed.

}, keywords = {Barium hexaferrite, coercivity, LTCC, Mossbauer spectroscopy, Raman spectroscopy}, issn = {0361-5235}, doi = {10.1007/s11664-012-2398-6}, author = {Rane, Vivek A. and Meena, Sher Singh and Gokhale, Suresh P. and Yusuf, S. M. and Phatak, Girish J. and Date, Sadgopal K.} } @article { ISI:000330201900057, title = {Temperature Dependent Phonon Shifts in Single-Layer WS2}, journal = {Acs Applied Materials \& Interfaces}, volume = {6}, number = {2}, year = {2014}, month = {JAN}, pages = {1158-1163}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Atomically thin two-dimensional tungsten disulfide (WS2) sheets have attracted much attention due to their potential for future nanoelectronic device applications. We report first experimental investigation on temperature dependent Raman spectra of single-layer WS2 prepared using micromechanical exfoliation. Our temperature dependent Raman spectroscopy results shows that the E-2g(1) and A(1g) modes of single-layer WS2 soften as temperature increases from 77 to 623 K. The calculated temperature coefficients of the frequencies of 2LA(M), E-2g(1), A(1g), and A(1g)(M) + LA(M) modes of single-layer WS2 were observed to be -0.008, -0.006, -0.006, and -0.01 cm(-1) K-1, respectively. The results were explained in terms of a double resonance process which is active in atomically thin nanosheet. This process can also be largely applicable in other emerging single-layer materials.

}, keywords = {layered materials, phonon vibrations, Raman spectroscopy, thermal effect, WS2}, issn = {1944-8244}, doi = {10.1021/am404847d}, author = {Thripuranthaka, M. and Late, Dattatray J.} } @article { ISI:000357498200004, title = {Combined experimental and theoretical study of the structural, electronic and vibrational properties of bulk and few-layer Td-WTe2}, journal = {Journal of Physics-Condensed Matter}, volume = {27}, number = {28}, year = {2015}, month = {JUL}, pages = {285401}, publisher = {IOP PUBLISHING LTD}, address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND}, abstract = {

The recent discovery of non-saturating giant positive magnetoresistance has aroused much interest in Td-WTe2. We have investigated structural, electronic and vibrational properties of bulk and few-layer Td-WTe2 experimentally and theoretically. Spin-orbit coupling is found to govern the semi-metallic character of Td-WTe2 and its structural link with the metallic 1 T form provides an understanding of its structural stability. There is a metal-to-insulator switch-over in the electrical conductivity and a change in the sign of the Seebeck coefficient around 373 K. Lattice vibrations of Td-WTe2 have been analyzed using first-principles calculations. Out of the 33 possible zone-center Raman active modes, five distinct Raman bands are observed around 112, 118, 134, 165 and 212 cm(-1) in bulk Td-WTe2. Based on symmetry analysis and calculated Raman tensors, we assign the intense bands at 165 cm(-1) and 212 cm(-1) to the A(1){\textquoteright} and A(1){\textquoteright}{\textquoteright} modes, respectively. Most of the Raman bands stiffen with decreasing thickness, and the ratio of the integrated intensities of the A(1){\textquoteright}{\textquoteright} to A(1){\textquoteright} bands decreases in the few-layer sample, while all the bands soften in both the bulk and few-layer samples with increasing temperature.

}, keywords = {Raman spectroscopy, Td-structure, tungsten ditelluride}, issn = {0953-8984}, doi = {10.1088/0953-8984/27/28/285401}, author = {Jana, Manoj K. and Singh, Anjali and Late, Dattatray J. and Rajamathi, Catherine R. and Biswas, Kanishka and Felser, Claudia and Waghmare, Umesh V. and Rao, C. N. R.} } @article { ISI:000352448800019, title = {Self-assembled vertically aligned gold nanorod super-lattices for ultra-high sensitive detection of molecules}, journal = {Nano Research}, volume = {8}, number = {3}, year = {2015}, month = {MAR}, pages = {907-919}, publisher = {TSINGHUA UNIV PRESS}, address = {TSINGHUA UNIV, RM A703, XUEYAN BLDG, BEIJING, 10084, PEOPLES R CHINA}, abstract = {

We show that self-assembled vertically aligned gold nanorod (VA-GNRs) superlattices can serve as probes or substrates for ultra-high sensitive detection of various molecules. D-glucose and 2,4,6-trinitrotoluene (TNT) have been chosen as model systems due to their very low Raman cross-sections (5.6 x 10(-30) cm(2).molecule(-1).sr(-1) for D-glucose and 4.9 x 10(-31) cm(2). molecule(-1).sr(-1) for TNT) to show that the VA-GNR superlattice assembly offers as low as yoctomole sensitivity. Our experiment on mixed samples of bovine serum albumin (BSA) and D-glucose solutions demonstrate sensitivity for the latter, and the possible extension to real samples. Self-assembled superlattices of VA-GNRs were achieved on a silicon wafer by depositing a drop of solvent containing the GNRs and subsequent solvent evaporation in ambient conditions. An additional advantage of the VA-GNR monolayers is their extremely high reproducible morphology accompanied by ultrahigh sensitivity which will be useful in many fields where a very small amount of analyte is available. Moreover the assembly can be reused a number of times after removing the already present molecules. The method of obtaining VA-GNRs is simple, inexpensive and reproducible. With the help of simulations of monolayers and multilayers it has been shown that superlattices can achieve better sensitivity than monolayer assembly of VA-GNRs.

}, keywords = {Nanostructures, Raman spectroscopy, self-assemblies, sensors, superlattices}, issn = {1998-0124}, doi = {10.1007/s12274-014-0572-2}, author = {Apte, Amey and Bhaskar, Prashant and Das, Raja and Chaturvedi, Smita and Poddar, Pankaj and Kulkarni, Sulabha} } @article { ISI:000354067400001, title = {Stable field emission from layered MoS2 nanosheets in high vacuum and observation of 1/f noise}, journal = {Nanomaterials and Nanotechnology}, volume = {5}, year = {2015}, month = {APR}, pages = {10}, publisher = {INTECH EUROPE}, address = {JANEZA TRDINE 9, RIJEKA, 51000, CROATIA}, abstract = {

Field emission and current noise of hydrothermally synthesized MoS2 nanosheets are investigated in ultra-high-vacuum and industrially suited high-vacuum conditions. The study reveals that the emission turn-on field is pressure dependent. Moreover, the MoS2 nanosheets exhibit more stable field-electron emission in high-vacuum than in ultra-high-vacuum conditions. The investigations on field-emission current fluctuations show features of 1/f-type noise in ultra-high-vacuum and high-vacuum conditions, attributed to adsorption and desorption processes. The post-field-emission results indicate the MoS2 nanosheets are a robust field emitter in high-vacuum conditions.

}, keywords = {Electron emission, layered materials, MoS2, Noise measurement, Raman spectroscopy}, issn = {1847-9804}, doi = {10.5772/60071}, author = {Kashid, Ranjit V. and Joag, Pracheetee D. and Thripuranthaka, M. and Rout, Chandra S. and Late, Dattatray J. and More, Mahendra A.} } @article { ISI:000351420300028, title = {Temperature dependent phonon shifts in few-layer black phosphorus}, journal = {ACS Applied Materials \& Interfaces}, volume = {7}, number = {10}, year = {2015}, month = {MAR}, pages = {5857-5862}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Atomically thin two-dimensional (2D) sheets of black phosphorus have attracted much attention due to their potential for future nanoelectronic and photonics device applications. Present investigations deal with the temperature dependent phonon shifts in a few-layer black phosphorus nanosheet sample prepared using micromechanical exfoliation on a 300 nm SiO2/Si substrate. The temperature dependent Raman spectroscopy experiments were carried out on a few-layer black phosphorus sample, which depicts softening of Ag-1 B-2g, and A(g)(2) modes as temperature increases from 77 to 673 K. The calculated temperature coefficients for Ag-1, B-2g, and A(g)(2) modes of the few-layer black phosphorus nanosheet sample were observed to be -0.01, -0.013, and -0.014 cm(-1) K-1, respectively. The temperature dependent softening modes of black phosphorus results were explained on the basis of a double resonance process which is more active in an atomically thin sample. This process can also be fundamentally pertinent in other promising and emerging 2D ultrathin layer and heterostructured materials.

}, keywords = {black phosphorus, layered materials, phonon vibrations, Raman spectroscopy, thermal effect}, issn = {1944-8244}, doi = {10.1021/am509056b}, author = {Late, Dattatray J.} } @article { ISI:000364355500044, title = {Temperature-dependent raman spectroscopy of titanium trisulfide (TiS3) nanoribbons and nanosheets}, journal = {ACS Applied Materials \& Interfaces}, volume = {7}, number = {43}, year = {2015}, month = {NOV}, pages = {24185-24190}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Titanium trisulfide (TiS3) has recently attracted the interest of the 2D community because it presents a direct bandgap of similar to 1.0 eV, shows remarkable photoresponse, and has a predicted carrier mobility up to 10000 cm(2) V-1 s(-1). However, a study of the vibrational properties of TiS3, relevant to understanding the electron-phonon interaction that can be the main mechanism limiting the charge carrier mobility, is still lacking. In this work, we take the first steps to study the vibrational properties of TiS3 through temperature-dependent Raman spectroscopy measurements of TiS3 nanoribbons and nanosheets. Our investigation shows that all the Raman modes linearly soften (red shift) as the temperature increases from 88 to 570 K due to anharmonic vibrations of the lattice, which also includes contributions from the lattice thermal expansion. This softening with the temperature of the TiS3 modes is more pronounced than that observed in other 2D semiconductors, such as MoS2, MoSe2, WSe2, and black phosphorus (BP). This marked temperature dependence of the Raman spectra could be exploited to determine the temperature of TiS3 nanodevices by using Raman spectroscopy as a noninvasive and local thermal probe. Interestingly, the TiS3 nanosheets show a stronger temperature dependence of the Raman modes than the nanoribbons, which we attribute to lower interlayer coupling in the nanosheets.

}, keywords = {2D semiconductors, layered materials, Raman spectroscopy, thermal effect, TiS3 nanoribbons, TiS3 nanosheets}, issn = {1944-8244}, doi = {10.1021/acsami.5b07492}, author = {Pawbake, Amit S. and Island, Joshua O. and Flores, Eduardo and Ramon Ares, Jose and Sanchez, Carlos and Ferrer, Isabel J. and Jadkar, Sandesh R. and van der Zant, Herre S. J. and Castellanos-Gomez, Andres and Late, Dattatray J.} } @article {45631, title = {Temperature-dependent phonon shifts in atomically thin MoTe2 nanosheets}, journal = {Applied Materials Today}, volume = {5}, year = {2016}, month = {DEC}, pages = {98-102}, type = {Article}, abstract = {

The present investigations deal with temperature-dependent Raman spectroscopy of bi-layer and few-layer molybdenum telluride (MoTe2) nanosheets prepared by micromechanical exfoliation method on a 300 nm SiO2/Si substrate. The temperature-dependent Raman spectroscopy was carried out using 633 nm laser excitation over the wider temperature range of 123-523 K. The temperature-dependent study illustrates the softening of A(1g), E-2g(1), and B-2g modes as temperature increases from 123 K to 523 K. The calculated temperature coefficients for A(1g), E-2g(1) and B-2g modes of the bi-layer MoTe2, nanosheet sample were found to be -0.00911 cm(-1) K-1, -0.01297 cm(-1) K-1 and -0.0159 cm(-1) K-1,respectively. For few-layer MoTe2 nanosheet sample, the temperature coefficient values were found to be -0.0113 cm(-1) K-1 (A(1g)), -0.0129 cm(-1) K-1 (E-2g(1)) and -0.0149 cm(-1) K-1 (B-2g), respectively. The present work highlights the temperature-dependent lattice vibration consequence of 2D MoTe2 nanosheet, which can be fundamentally pertinent in other promising and emerging 2D ultrathin layer and heterostructured materials to be used in future optoelectronic and nanoelectronic devices. (C) 2016 Elsevier Ltd. All rights reserved.

}, keywords = {Layered material, MoTe2, Phonon vibration, Raman spectroscopy, thermal effect}, issn = {2352-9407}, doi = {10.1016/j.apmt.2016.09.013}, author = {Late, Dattatray J.} } @conference {45710, title = {Solubility limits of ceria-zirconia-lanthana solid-solutions}, booktitle = {International Conference on Recent Trends in Engineering and Material Sciences (ICEMS)}, year = {2017}, month = {MAR}, publisher = {Elsevier Science BV, PO BOX 211, 1000 AE Amsterdam, Netherlands}, organization = {Elsevier Science BV, PO BOX 211, 1000 AE Amsterdam, Netherlands}, address = {Jaipur, India}, abstract = {

We demonstrate, the solubility limits of Ceria-Zirconia-Lanthana (CZLa) solid-solutions with the increase in heat-treatment temperature from 600 degrees C to 1300 degrees C. CZLa nano-crystalline samples were successfully synthesized by EDTA-Citrate complex method and were characterized by Raman Spectroscopy (RS) and Transmission Electron Microscopy (TEM) analysis. With an increase in temperature, it is noticed that the solubility limit is decreased in CZLa system. At 600 degrees C, a very good solubility is observed in CZLa system and is confirmed from RS analysis. At higher heat-treatment temperatures (1000 and 1300 degrees C), with an increase in La content, Zr precipitated in the CZLa system and is confirmed from RS analysis. The reason for such kind of behavior in this CZLa system is clearly explained in this work. (C) 2017 Elsevier Ltd. All rights reserved.

}, keywords = {Ceria-Zirconia Lanthana, EDTA-Citrate method, Raman spectroscopy, solubility limit, XRD}, author = {Abbas, Zenab and Surendran, Mythili and Anjana, P. A. and Jidev, P. K. and Dasari, Harshini and Naidu, Sudhakar N. and Anandhan, S. and Bhat, Udaya K. and Babu, Uday Bhaskar G. and Dasari, Hari Prasad} } @article {44488, title = {Temperature and pressure dependent Raman spectroscopy of plasma treated multilayer graphene nanosheets}, journal = {Diamond and Related Materials}, volume = {84}, year = {2018}, month = {APR }, pages = {146-156}, type = {Journal Article}, abstract = {

Understanding of the fine structure at the atomic level and properties of graphene by creating defects is important from the point of view of thermal and stress management. Here we report Raman spectroscopic studies on pristine and plasma treated multilayer graphene to explore the remarkable structure and phonon properties with temperature and pressure. Temperature dependent studies illustrate monotonic softening of G and G' bands in the temperature range 78 to 573 K. This process can be of fundamental importance in other promising and emerging nano and heterostructured materials. The pressure dependent Raman spectroscopic investigations on G-band of these samples were carried out up to 25 GPa using a diamond anvil cell. Comparatively weak and more compressible nature of the G band (E2g in-plane mode) as a function of applied pressure is found in plasma treated graphene. After pressure release, the samples recover to their original ordered structure. The present study is important for further understanding of the fine structure, properties and effect of defects in graphene, which can affect the atomic bonds, thermal expansion, specific heat, and thermal conductivity as well.

}, keywords = {graphene, high pressure, Phonon, Plasma treated graphene, Raman spectroscopy}, issn = {9259635}, doi = {10.1016/j.diamond.2018.03.021}, author = {Pawbake, Amit S. and Mishra, K. K. and Machuno, Luis G. B. and Gelamo, Rogerio V. and Ravindranathan, T. R. and Rout, Chandra Sekhar and Late, Dattatray J.} } @article {46198, title = {Temperature-dependent Raman spectroscopy and sensor applications of PtSe2 nanosheets synthesized by wet chemistry}, journal = {Beilstein Journal of Nanotechnology}, volume = {10}, year = {2019}, month = {FEB }, pages = {467-474}, type = {Article}, abstract = {

We report on a wet chemistry method used to grow PtSe2 nanosheets followed by thermal annealing. The SEM and TEM analysis confirms the formation of PtSe2 nanosheets. Furthermore, XRD, Raman, XPS and SAED patterns were used to analyze the crystal structure and to confirm the formation of the PtSe2 phase. The temperature-dependent Raman spectroscopy investigations were carried out on PtSe2 nanosheets deposited on Si substrates in the temperature range 100-506 K. The shifts in Raman active E-g and A(1g) modes as a function of temperature were monitored. The temperature coefficient for both modes was calculated and was found to match well with the reported 2D transition metal dichalcogenides. A PtSe2 nanosheet-based sensor device was tested for its applicability as a humidity sensor and photodetector. The humidity sensor based on PtSe2 nanosheets showed an excellent recovery time of approximate to 5 s, indicating the great potential of PtSe2 for future sensor devices.

}, keywords = {nanosheets, PtSe2, Raman spectroscopy, Sensor, thermal effect}, issn = {2190-4286}, doi = {10.3762/bjnano.10.46}, author = {Pawar, Mahendra S. and Late, Dattatray J.} } @article {47372, title = {Synthesis of graphene from activated carbon at liquid nitrogen temperature and its detailed structural analysis}, journal = {Applied Physics A-Materials Science \& Processing}, volume = {127}, year = {2021}, month = {MAY}, pages = {319}, type = {Article}, abstract = {

The present study deals with the synthesis of graphene using thermal quenching of pre-heated activated carbon (a-C) (1370 K for 3 h) at liquid nitrogen temperature and its detailed structural analysis using XRD, TEM, FTIR and Raman spectroscopy. The analysis of lattice parameters (L-a, L-c,L- and d) of constituent nanographitic domains using XRD shows restoration of graphene-like structure in the resultant product (a-CL). TEM image reveals porosity and partially crystallinity (from SAED) in a-C. While thin layers of graphene are observed in the TEM images of a-CL Deconvoluted Raman spectra have been used to investigate the evolution of crystalline behaviour of a-C with temperature in view of Ferrari and Robertson{\textquoteright}s three-stage model. The evolution of G peak and increase in I-D/I-G reveals restoration of crystallinity in a-CL. The development of the D peak indicates disordering of graphite but ordering of amorphous carbon. The reported method is technologically beneficial for graphene synthesis for large number of applications such as supercapacitors, H-2 storage, gas separation and purification.

}, keywords = {activated carbon, Amorphous carbon, graphene, H-2 storage applications, Raman spectroscopy, Supercapacitors}, issn = {0947-8396}, doi = {10.1007/s00339-021-04416-w}, author = {Sharma, Preeti and Sharma, Geeta and Punia, Rajesh} } @article {48672, title = {Systematic study of rare-earth ions size-dependent structural phase transition from monazite to zircon-type in rare earth chromates using Raman spectroscopy}, journal = {Journal of Raman Spectroscopy}, volume = {54}, year = {2023}, month = {JUL}, pages = {793-801}, type = {Article}, abstract = {

Rare earth chromates (RCrO4) undergo monazite to zircon-type structural phase transition due to a decreased rare-earth ion size. They also exhibit an intermediate mixed phase. However, there is no systematic study on the influence of structural distortion on their phononic behavior, which is quite sensitive to subtle environmental variations. A change in the room temperature phononic spectrum was studied in the family of RCrO4 compounds, where R was varied from La to Yb using Raman modes. With an increase in the atomic number from Nd to Yb for zircon-type phases, the external translational and rotational modes were observed to shift towards lower and higher wavenumbers, respectively. At the same time, all internal vibrational modes shifted towards higher phonon energies. A comparison between Raman modes for monazite, intermediate, and zircon-type RCrO4 phases showed a gradual shift in the internal modes towards a higher wavenumber. The confirmation of the change in Raman modes with the decreasing radius was found by comparing the rare-earth elements in DyCrO4 and LaCrO4 with non-rare-earth elements in YCrO4.

}, keywords = {monazite-type, Raman spectroscopy, rare earth chromates (RCrO4), YCrO4, zircon type}, issn = {0377-0486}, doi = {10.1002/jrs.6542}, author = {Ughade, Supriya and Poddar, Pankaj} }