- Saha Institute of Nuclear Physics
Sector-1, Block-AF
Bidhannagar
Kolkata - 700064
INDIA - +91-33-23375345(46,47,48) Ext 4214
Tapas Chini
Saha Institute of Nuclear Physics, Surface Physics, Faculty Member
- Professor, Saha Institute of Nuclear Physicsedit
We performed cathodoluminescence (CL) spectroscopy and imaging in a scanning electron microscope (SEM) to investigate localized surface plasmon (LSP) assisted optical effects arising in the substrate supported single tilted gold... more
We performed cathodoluminescence (CL) spectroscopy and imaging in a scanning electron microscope (SEM) to investigate localized surface plasmon (LSP) assisted optical effects arising in the substrate supported single tilted gold octahedron of side edge length 170 nm. The site specific e-beam excitation reveals a single resonant peak around 580 nm. Stronger photon emission is observed in the visible region from those corners and tip of the octahedron which are situated far from the substrate. The experimental results corroborate well with the finitedifference time-domain (FDTD) numerical simulation. Using extensive FDTD simulation we also show that the observed radiative mode is higher order mode other than the dipolar mode and also discuss their dependency on the Si Substrate. Our findings provide a better understanding of the plasmon induced luminescence from the octahedron nanoparticle at single particle level that might have far reaching consequences in various novel applications...
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This paper reports on a simple and cost-effective process of developing a stable surface-enhanced Raman scattering (SERS) substrate based on silver (Ag) nanoparticles deposited on silicon (Si) surface. Durability is an important issue for... more
This paper reports on a simple and cost-effective process of developing a stable surface-enhanced Raman scattering (SERS) substrate based on silver (Ag) nanoparticles deposited on silicon (Si) surface. Durability is an important issue for preparing SERS active substrate as silver nanostructures are prone to rapid surface oxidation when exposed to ambient conditions, which may result in the loss of the enhancement capabilities in a short period of time. Here, we employ the galvanic displacement method to produce Ag nanoparticles on Si(100) substrate prepatterned with arrays of micropyramids by chemical etching, and subsequently, separate pieces of such substrates were annealed in oxygen and nitrogen environments at 550 °C. Interestingly, while nitrogen-annealed Si substrates were featured by spherical-shaped Ag particles, the oxygen annealed Si substrates were dominated by the formation of triangular shape particles attached with the spherical one. Remarkably, the oxygen-annealed substrate thus produced shows very high SERS enhancement compared to the either unannealed or nitrogen annealed substrate. The hitherto unobserved coexistence of triangular morphology with the spherical one and the gap between the two (source of efficient hot-spots) are the origin of enhanced SERS activity for the oxygen-annealed Ag particle-covered Si substrate as probed by the combined finite-difference time domain (FDTD) simulation and cathodoluminesensce (CL) experiment. As the substrate has already been annealed in an oxygen environment, further probability of oxidation is reduced in the present synthesis protocol that paves the way for making a novel long-lived thermally stable SERS substrate.
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Nanoscale surface structures emerging from medium energy (50–60 keV) sputtering of p‐type GaAs (100) and semi‐insulating GaAs (111) substrates have been investigated. For normally incident 50 keV of fluence on GaAs (100) and GaAs (111)... more
Nanoscale surface structures emerging from medium energy (50–60 keV) sputtering of p‐type GaAs (100) and semi‐insulating GaAs (111) substrates have been investigated. For normally incident 50 keV of fluence on GaAs (100) and GaAs (111) features in the form of nanoscale pits∕ holes without short range ordering are observed with densities and respectively along with irregularly shaped patches of islands. For GaAs (111) on increasing the influence to the pit density increases marginally to For 60° off‐normal incidence of 60 ...
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Employing cathodoluminescence (CL) spectroscopy and imaging in a field emission gun (FEG) scanning electron microscope (SEM), we study localized surface plasmon (LSP) modes on individual tilted gold nanodecahedron sitting on a silicon... more
Employing cathodoluminescence (CL) spectroscopy and imaging in a field emission gun (FEG) scanning electron microscope (SEM), we study localized surface plasmon (LSP) modes on individual tilted gold nanodecahedron sitting on a silicon substrate. We experimentally resolve three distinct LSP modes in the far-field radiation acquired via CL. The experimental spectra and intensity maps of plasmon modes are in excellent agreement with the spectra and 2D-CL image obtained from finite difference time domain (FDTD) simulations. Detail analysis reveals the signature of a quadrupolar surface plasmon mode in addition to the two dipolar modes along azimuthal and polar direction of the decahedron. The experimental method and the theoretical formalism presented here provide useful insight into the plasmonic behavior of complex shaped metal nanoparticle supported by a high index substrate.
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ABSTRACT Cathodoluminescence (CL) spectroscopy and imaging in a high resolution scanning electron microscope (SEM) is used to probe and directly map the localized surface plasmon resonance (LSPR) modes of a penta-twinned gold nanorod... more
ABSTRACT Cathodoluminescence (CL) spectroscopy and imaging in a high resolution scanning electron microscope (SEM) is used to probe and directly map the localized surface plasmon resonance (LSPR) modes of a penta-twinned gold nanorod deposited on a silicon substrate. Finite-difference time-domain simulation of CL enables us to gain insight into the origin of the plasmon modes. Our experimental results and simulations demonstrate that the substrate plays a very crucial role in the observed plasmonic property of gold nanorod. We have shown that, in the visible domain of the spectrum, the plasmon mode gets split into two distinct peaks due to substrate induced hybridization of in-plane and out-of-plane modes. With increasing the refractive index of the substrate, the intensity of these hybridized modes increases. We provide a detailed analysis on the origin and coupling of various plasmon modes mediated by the substrate.
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We report the measurement on the angular distribution of material sputtered from Ge target bombarded with normally incident Ar+ and Ne+ ions at room temperature. The energy of the ions was varied from 0.6 keV to 4.0 keV. Sputter deposited... more
We report the measurement on the angular distribution of material sputtered from Ge target bombarded with normally incident Ar+ and Ne+ ions at room temperature. The energy of the ions was varied from 0.6 keV to 4.0 keV. Sputter deposited material was collected on Al foils and subsequently analyzed by an electron probe micro analyzer (EPMA) to obtain the angular
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ABSTRACT We report here, the first experimental realization on the selective excitation of two closely lying tips from the same spherical core of a multitipped gold nanoparticle with flower-like morphology. This gives strong multipeaked... more
ABSTRACT We report here, the first experimental realization on the selective excitation of two closely lying tips from the same spherical core of a multitipped gold nanoparticle with flower-like morphology. This gives strong multipeaked resonance in the near-infrared region of the far-field emission spectra showing a clear signature of tip to tip coupling. The cathodoluminescence (CL) technique in a scanning electron microscope (SEM) combined with finite-difference timedomain (FDTD) simulation has helped us to identify the coupled plasmon modes to be originated from the interaction between two closely spaced tips with a narrow angular separation. Our analysis further estimates a range of angular separation between the tips that triggers the onset of the intertip coupling.
Dentritic silver nanostructures prepared by a galvanic displacement reaction on germanium substrates show a new type of heteroepitaxy where significantly large lattice mismatch is accommodated by the formation of low-energy asymmetric... more
Dentritic silver nanostructures prepared by a galvanic displacement reaction on germanium substrates show a new type of heteroepitaxy where significantly large lattice mismatch is accommodated by the formation of low-energy asymmetric tilt boundaries.
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The spatial and spectral characteristics due to localized surface plasmon resonance of individual gold nanorod (NR) have been studied using cathodoluminescence (CL) in a high resolution scanning electron microscope (SEM). Simultaneous... more
The spatial and spectral characteristics due to localized surface plasmon resonance of individual gold nanorod (NR) have been studied using cathodoluminescence (CL) in a high resolution scanning electron microscope (SEM). Simultaneous determination of morphology and luminescence with spatial resolution down to a few nanometers, from the same area of interest enables us to map different plasmonic modes supported by Au NR.
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The angular dependence of the physical sputtering yield of germanium bombarded by Ar ions has been studied at 23 keV and 30 keV. The sputtering yield increases with increasing incident angle and reaches a maximum around 70° to 75°.... more
The angular dependence of the physical sputtering yield of germanium bombarded by Ar ions has been studied at 23 keV and 30 keV. The sputtering yield increases with increasing incident angle and reaches a maximum around 70° to 75°. Results are compared with other experimental data and are discussed in the light of predictions of the existing theoretical and semiempirical
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... The detailed results will be presented in a forthcoming paper. Acknowledgements The support of the Ministry of Education, Science and Culture, Japan for the research studentship to TK Chini is gratefully acknowledged. ... [ll] X. Hou,... more
... The detailed results will be presented in a forthcoming paper. Acknowledgements The support of the Ministry of Education, Science and Culture, Japan for the research studentship to TK Chini is gratefully acknowledged. ... [ll] X. Hou, M. Yu and X. Wang, Chin. Phys. Lett. ...
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ABSTRACT In this study, morphologies of as-deposited and rapid thermal annealed films of silver nanoclusters are studied using scanning electron microscope (SEM) and atomic force microscope (AFM). Size-selected silver nanoclusters,... more
ABSTRACT In this study, morphologies of as-deposited and rapid thermal annealed films of silver nanoclusters are studied using scanning electron microscope (SEM) and atomic force microscope (AFM). Size-selected silver nanoclusters, containing 5000 atoms in a cluster, produced by the gas condensation method are deposited on Si substrate for a period of 8 min. In order to get an idea about the melting of clusters, the film is treated by rapid thermal annealing at 200 and 400 degrees C. The remarkable changes of morphology due to annealing signify a lowering of melting temperature of silver in the form of nanoscale particles. (C) 2009 Elsevier B.V. All rights reserved.
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... Rev. Lett. 72 (1994), p. 3040. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (228). 2. TK Chini, SR Bhattacharyya, D. Ghose and D. Basu Jpn. J. Appl. Phys. 30 (1991), p. 2895. Full Text via CrossRef | View Record... more
... Rev. Lett. 72 (1994), p. 3040. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (228). 2. TK Chini, SR Bhattacharyya, D. Ghose and D. Basu Jpn. J. Appl. Phys. 30 (1991), p. 2895. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (5). ...
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ABSTRACT The redistribution of Ni in InP is studied by annealing samples of InP implanted with 0.9 MeV Ni at 60o angle of ion incidence with respect to target surface normal as a function of dose (8.5×1012−4.5×1015 cm−2). Ni profiles are... more
ABSTRACT The redistribution of Ni in InP is studied by annealing samples of InP implanted with 0.9 MeV Ni at 60o angle of ion incidence with respect to target surface normal as a function of dose (8.5×1012−4.5×1015 cm−2). Ni profiles are measured by secondary ion mass spectrometry (SIMS) and implantation induced damage by Rutherford backscattering spectrometry in channeling (RBS/C) condition. The highest dose sample is characterised by remarkable Ni accumulation near the surface (at ∼ ) that has not been observed earlier along with two other distinct accumulation zones at R np+ and after annealing at 650 °C for 30 min. Here, R np is the normal component of the projected range for oblique angle bombardment.
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We have reported low temperature growth (300°C) of ZnO nanorod flower structures by depositing zinc acetate vapor on Ge (100) substrate in the form of a jet using chemical vapor condensation technique. The flowers were comprised of... more
We have reported low temperature growth (300°C) of ZnO nanorod flower structures by depositing zinc acetate vapor on Ge (100) substrate in the form of a jet using chemical vapor condensation technique. The flowers were comprised of hierarchical arrangement of highly crystalline ZnO nanorods oriented isotropically around a common nucleus. The temperature window for stability of these structures was found
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ABSTRACT The results of TiC crystals and cobalt matrix microstructure studies by means of transmission electron microscope are presented. TiC crystals were obtained by the HTS method using cobalt as a high-temperature solvent. The... more
ABSTRACT The results of TiC crystals and cobalt matrix microstructure studies by means of transmission electron microscope are presented. TiC crystals were obtained by the HTS method using cobalt as a high-temperature solvent. The morphology of the obtained crystals was studied by physical metallurgy methods. X-ray phase analysis of the obtained samples was also performed. It was found that TiC crystals are the primary crystals during solidification of the Co-Ti-C melt. No dislocation loops were revealed in the boundary region: TiC — martensitic cobalt matrix.