R. Aggarwal

Raja Ramanna Centre for Advanced Technology

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Alka Ingale

Raja Ramanna Centre for Advanced Technology

Alka Ingale

Raja Ramanna Centre for Advanced Technology

Vandna K. Gupta

Chalmers University of Technology

V. K. Dixit

Raja Ramanna Centre for Advanced Technology

Suparna Pal

University of Kalyani

Vasant Sathe

UGC DAE Consortium for Scientific Research

C. Mukherjee

Raja Ramanna Centre for Advanced Technology

R. S. Ajimsha

Raja Ramanna Centre for Advanced Technology

Abhinav Mahapatra

Homi Bhabha National Institute

Arnab Bhattacharya

Tata Institute of Fundamental Research

Cooperative Institutions

Raja Ramanna Centre for Advanced Technology

Homi Bhabha National Institute

Devi Ahilya Vishwavidyalaya

UGC DAE Consortium for Scientific Research

Bhabha Atomic Research Centre

Tata Institute of Fundamental Research

Indian Institute of Technology Bombay

Indian Institute of Technology Indore

Indian Institute of Science Bangalore

Indian Institute of Technology Madras

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Identification and control of crystalline nuclei facets imparting to the breaking of symmetry selection rules of optical phonon modes in GaP/Si (001)

Surfaces and Interfaces (2023)

R. Aggarwal V. K. Dixit Alka Ingale R. Roychowdhury Geetanjali Vashisht

Identification

10.1016/j.surfin.2023.103720

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Citations (1)

Novel Use of Selectivity of Resonance Raman Spectroscopy to Study Polytypism and Mixed to Pure Phase Conversion in Individual InAs NWs on Laser Irradiation

SSRN Electronic Journal (2021)

Vandna K. Gupta Alka Ingale R. Aggarwal

Conversion of Wurtzite to Zincblende phase of InAs NWs at high simulated temperature (>1300 K) is investigated using resonance Raman spectroscopy with specially designed two step heating-cooling experiment. For smaller nanowires (diameter < 700 nm), the certainty of determining the polytypism using polarized Raman spectroscopy, reduces significantly. Low signal to noise ratio for smaller diameter NWs is improved by employing the wavelength dependent unpolarized and polarized Raman spectroscopy to examine the sensitivity of resonance Raman spectroscopy as an alternate for probing polytypism. Innovative use of resonance Raman spectroscopy to probe phase purity of the III-V individual nanostructures, where, conventional methods may not be applicable is realized in this work. This work paves the way for online monitoring of the conversion of mixed phase to phase pure III-V nanowires using laser irradiation for their fast electronic device applications. Further, this kind of surface modification study provides basis for the futuristic crystal structure engineering, which can facilitate the controlled tailoring of material properties in order to enhance their functionality.

Resonance Raman spectroscopy

10.2139/ssrn.3973577

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Determination of Ethanol Content in Gasoline Fuel Using Raman Spectroscopy

Applied Spectroscopy Practica (2025)

Beena Jain R. Aggarwal Deb Kumar Rath Rajesh Kumar V. B. Tiwari

The ability to detect the ethanol rapidly and sensitively in ethanol–gasoline blends has become important in recent times, both for engine performance and for fuel economy. In order to achieve this, a deterministic methodology based on Raman spectroscopy is employed for quantitative estimation of ethanol in commercial ethanol–gasoline blends of fuel. The different concentrations of anhydrous ethanol were mixed with pure gasoline to calibrate the Raman spectroscopy measurement setup. The variation in the ratio of the heights of Raman peaks at wavenumbers ∼885 and 1005 cm –1 is found to be linear with the fractional volumes of ethanol and gasoline in the blends. Using this methodology, the volume percentage of ethanol in commercial gasoline is determined to be ∼10%. This methodology can also be adopted for detection of other additives/adulterants in commercial gasoline.

Ethanol content

10.1177/27551857251316505

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Intersubband Plasmon - Phonon Coupling in GaAsP∕AlGaAs Single Quantum Well: A Raman Spectroscopy Study

AIP conference proceedings (2011)

R. Aggarwal Alka Ingale Suparna Pal S. M. Oak Alka B. Garg

A Raman scattering study of GaAs1−yPy (y = 0.14)/AlxGa1−xAs (x = 0.7) single quantum wells has shown two mode behavior for both barrier and quantum well alloys. In this report we present investigation of origin of an additional mode ∼284 cm−1. From wavelength and intensity dependent Raman measurements, it was concluded that the mode is intersubband plasmom‐phonon coupled mode due to photoexcited carriers. The coupled mode frequency dependence on free carrier density as predicted by theory is qualitatively in agreement with observed coupled mode frequencies in intensity dependent Raman measurements.

10.1063/1.3606247

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Spatially resolved Raman spectroscopy study of uniform and tapered InAs micro‐nano wires: correlation of strain and polytypism

Journal of Raman Spectroscopy (2017)

Vandna K. Gupta Alka Ingale Suparna Pal R. Aggarwal Vasant Sathe

The asymmetric peak ~212–218 cm −1 occurring in InAs micro‐nanowires (MNWs: diameter: 2 μm – 400 nm) is investigated using spatially resolved Raman spectroscopy of uniform, bent and long tapered MNWs grown on a Si (001) substrate. It is attributed to superposition of E 2h phonon (wurtzite: WZ) and TO phonon (zinc blende: ZB) of InAs. Polarized and wavelength‐dependent spatially resolved Raman spectroscopy establishes the presence of WZ and ZB phases in these MNWs. However, formation of WZ phase for larger diameter InAs MNWs is not commensurate with existing growth mapping studies. Further, study of these MNWs suggests that the fraction of WZ to ZB content in a MNW depends not only on the diameter but also seems to be governed by local growth seeding/conditions. This in turn leads to either tapered or uniform MNW growth under the same (external) growth conditions. The variation of these wavenumbers that of bulk value is correlated to the residual stress present in ZB and WZ phases due to the presence of the other (WZ/ZB) phase. Consistently, temperature‐dependent Raman data show that there is a measurable contribution of stress to dω/dT, a positive for ZB and negative for WZ phonons, due to differences in their thermal expansions. Further, effective thermal expansion coefficient of WZ InAs in the presence of ZB phase is calculated to vary in the range 10–19 × 10 −6 /K from base to tip of a MNW at ~80 K, which is not possible to determine otherwise. Copyright © 2017 John Wiley & Sons, Ltd.

Wurtzite crystal structure

10.1002/jrs.5138

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Insight into co-operative growth of nearly monodispersive CdS nanocrystals embedded in polyvinyl pyrrolidone

Journal of Materials Science (2015)

Ekta Rani R. Aggarwal Alka Ingale Komal Bapna C. Mukherjee

Energy-dispersive X-ray spectroscopy

Chemical bath deposition

10.1007/s10853-015-9481-3

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Textile-Integrated Mos2-Pdms Single Electrode Triboelectric Nanogenerator for Vibrational Energy Harvesting and Biomechanical Motion Sensing

Abhinav Mahapatra R. S. Ajimsha Deepak Deepak R. Aggarwal Susanta Sinha Roy

With the increasing demand for portable electronics, the durable and flexible textile-based single electrode triboelectric nanogenerators (TENGs) have received a significant amount of attention. In this work, we have proposed a flexible textile based single electrode TENG (STENG) composed of MoS2-PDMS composite film. The effect of concentration (0-10 wt%) of MoS2 in PDMS on the output of performance of the as fabricated devices was systematically studied. STENG with 6 wt% concentration of MoS2 exhibits the best output performance with open-circuit output voltage, short-circuit output current density and maximum instantaneous output power density is ~ 320 V, ~ 30 µA/cm2 and ~ 3.2 mW/cm2, respectively. The enhancement in the output characteristics of STENG can be explained by the formation of network of nanocapacitors, where the layers of MoS2 behaves as electrodes and the insulating PDMS behaves as nanodielectric. The powering capability of the as fabricated STENG was tested by charging of commercial capacitors and directly flashing of 100 commercially available LEDs without any external charge storage component. The textile based MoS2-PDMS composite is not only used as STENG, but also as a human motion sensor capable of detecting diverse human actions including wrist bending, arm bending, and leg bending. As a result of its flexible structure, scalable manufacturing process, and ability to sense human motions, the developed MoS2-PDMS composite STENG have promising applications in self-powered wearable electronics and human-machine interaction.

Nanogenerator

Vibrational energy

Textile

10.2139/ssrn.4481002

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Investigation of relative content of zinc-blende and wurtzite phases in GaP/Ge(111) using Raman spectroscopy

AIP conference proceedings (2019)

R. Aggarwal Alka Ingale V. K. Dixit

GaP/Ge(111) heterostructure with high residual strain is investigated for identification of allotrope, zincblende (ZB) and wurtzite (WZ) phase distribution in the grown GaP layer. Spatially resolved Raman spectroscopy across the cross-sectional surface of GaP/Ge(111) heteostructure show continuous blue shift in optical phonon frequencies from near interface to surface of GaP/Ge. Polarized Raman spectroscopy from cross-sectional surface, at near and away from interface positions, establishes that WZ phase is dominant at GaP-Ge interface. Further, higher strained regions of GaP/Ge heterostructure show larger content of wurtzite phase in GaP film. This work paves the way for probing the spatial dependent existence of allotropes and their relative content in micro/nanostructured thin films using Raman spectroscopy.

Wurtzite crystal structure

Wide-bandgap semiconductor

10.1063/1.5113161

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Template based room temperature growth of high density CdS nanowires from aqueous electrolyte using high frequency alternating current

Journal of Materials Science Materials in Electronics (2017)

R. Aggarwal P. Ram Sankar Anil Kumar Sahu Alka Ingale A. K. Sinha

Alternating current

10.1007/s10854-017-7931-1

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Understanding the effect of nanowire orientation on time evolution of Raman spectra from laser irradiated InAs nanowire surface

Nanotechnology (2018)

Vandna K. Gupta Alka Ingale Arnab Bhattacharya M. R. Gokhale R. Aggarwal

We investigate differences observed in the time evolution of Raman spectra for differently oriented (in plane) InAs nanowires (NWs), using polarized Raman spectroscopy. Specially designed polarized Raman spectroscopy experiments elucidate that laser irradiation leads to the formation of an oriented crystalline oxide film on the InAs NW surface. Both the formation of oriented crystalline oxides and Raman selection rules leading to the presence/absence of oxide peaks in the unpolarized Raman spectra are uncommon occurrences and can lead to incorrect interpretations of the oxidation process, if not looked into carefully. Further, the specially designed heating and cooling experiments for a mixed phase (wurtzite + zinc blende) InAs NW revealed the formation of specific allotropes of elemental As, i.e. gray-As (rhombohedral) and black-As (orthorhombic: metastable) at low (700-950 K) and high simulated temperatures (1000-1300 K) on the InAs NW surface, respectively. Both have high electrical conductivity due to a layered structure and control over the growth of only a few layers using laser irradiation envisages properties similar to graphene. This kind of surface of InAs NWs has the potential for novel device applications, where a semiconductor-insulator-metal heterostructure is required.

Wurtzite crystal structure

Orthorhombic crystal system

10.1088/1361-6528/aad672

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Citations (2)