@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: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.} } @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.} }