MANOHAR CHIRUMAMILLA | Istituto Italiano di Tecnologia / Italian Institute of Technology (original) (raw)

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Papers by MANOHAR CHIRUMAMILLA

Optics Express, 2015

We experimentally investigate the near-infrared emission from simple-to-fabricate, continuous-fil... more We experimentally investigate the near-infrared emission from simple-to-fabricate, continuous-film Fabry-Perot-type resonators, consisting only of unstructured dielectric and metallic films. We show that the proposed configuration is suitable for realization of narrowband emitters, tunable in ranges from mid- to near-infrared, and demonstrate emission centered at the wavelength of 1.7 μm, which corresponds to the band gap energy of GaSb-based photodetectors. The emission is measured at 748 K and follows well the emissivity as predicted from reflection measurements and Kirchhoff's reciprocity. The considered emitter configuration is spectrally highly tunable and, consisting of only few unstructured layers, is amenable to wafer-scale fabrication at low cost by use of standard deposition procedures.

Handbook of Enhanced Spectroscopy, 2015

CLEO: 2015, 2015

ABSTRACT Nanofabrication of metallic nanostructures/nanoparticles enables the detection of analyt... more ABSTRACT Nanofabrication of metallic nanostructures/nanoparticles enables the detection of analyte molecules at ultra-low concentrations with the aid of plasmon induced hot-spots. Here we present a cost effective approach to recycle the SERS substrates for label free bio-sensing applications.

ACS Photonics, 2015

ABSTRACT The coupling of an infrared plasmon-polariton excitation of a metal nanoparticle to a vi... more ABSTRACT The coupling of an infrared plasmon-polariton excitation of a metal nanoparticle to a vibrational excitation of a similar energy enables strong vibrational signal enhancement. However, the commonly used planar substrates substantially weaken plasmonic resonances because of their polarizability and, furthermore, a great part of the enhanced near-field is inside the substrate and thus not available for an analyte. In this contribution we report on a way to reduce these undesirable influences of the substrate by fabricating gold nanowires on high pedestals and thus in reduced contact with the substrate. The influence of the height of the pedestal is an important parameter for the plasmonic near-field enhancement as we show with finite-difference time-domain simulations. Comparing the plasmonic response and the SEIRA activity of the rods prepared by standard electron beam lithography and the rods additionally treated with reactive ion etching to remove the silicon substrate at the hot-spots of the rods reveals not only the change of the plasmonic-resonance spectrum but also interesting differences of the enhanced phonon-polariton signal from the silicon dioxide layer on the silicon substrate and the about one order of magnitude stronger vibrational signal enhancement for an adsorbate monolayer.

Plasmon-Enhanced Spectroscopies for Biotechnological Applications, 2013

Nanotechnology, 2014

We report the fabrication of Au nanostar arrays by means of electron beam lithography, in which t... more We report the fabrication of Au nanostar arrays by means of electron beam lithography, in which the plasmon resonance energy can be tuned via the nanostar size from the visible into the nearinfrared region. The spectral response of the nanostar arrays was investigated by optical extinction (transmittance) experiments, and their surface enhanced Raman scattering performance has been tested at two different excitation wavelengths, 633 nm and 830 nm, using chemisorbed Cresyl violet molecules as analyte. The experimental results are supported by numerical simulations of the spatial and spectral electric field enhancement.

Singular and Chiral Nanoplasmonics, 2014

Journal of Polymer Science Part B: Polymer Physics, 2016

Top-down fabrication of electron-beam lithography (EBL)-defined metallic nanostructures is a succ... more Top-down fabrication of electron-beam lithography (EBL)-defined metallic nanostructures is a successful route to obtain extremely high electromagnetic field enhancement via plasmonic effects in well-defined regions. To this aim, various geometries have been introduced such as disks, triangles, dimers, rings, self-similar lenses, and more. In particular, metallic dimers are highly efficient for surface-enhanced Raman spectroscopy (SERS), and their decoupling from the substrate in a three-dimensional design has proven to further improve their performance. However, the large fabrication time and cost has hindered EBL-defined structures from playing a role in practical applications. Here we present three-dimensional nanostar dimer devices that can be recycled via maskless metal etching and deposition processes, due to conservation of the nanostructure pattern in the 3D geometry of the underlying Si substrate. Furthermore, our 3D-nanostar-dimer-in-ring structures (3D-NSDiRs) incorporate several advantageous aspects for SERS by enhancing the performance of plasmonic dimers via an external ring cavity, by efficient decoupling from the substrate through an elevated 3D design, and by bimetallic AuAg layers that exploit the increased performance of Ag while maintaining the biocompatibility of Au. We demonstrate SERS detection on rhodamine and adenine at extremely low density up to the limit of few molecules and analyze the field enhancement of the 3D-NSDiRs with respect to the exciting wavelength and metal composition.

Advanced materials (Deerfield Beach, Fla.), 2014

Plasmonic nanostar-dimers, decoupled from the substrate, have been fabricated by combining electr... more Plasmonic nanostar-dimers, decoupled from the substrate, have been fabricated by combining electron-beam lithography and reactive-ion etching techniques. The 3D architecture, the sharp tips of the nanostars and the sub-10 nm gap size promote the formation of giant electric-field in highly localized hot-spots. The single/few molecule detection capability of the 3D nanostar-dimers has been demonstrated by Surface-Enhanced Raman Scattering.

... Francesco Gentile1,2, Michela Perrone Donnorso1,3, Manohar Chirumamilla Chowdary1, Ermanno Mi... more ... Francesco Gentile1,2, Michela Perrone Donnorso1,3, Manohar Chirumamilla Chowdary1, Ermanno Miele1, Maria Laura Coluccio1,2, Rosanna La Rocca1, Rosaria Brescia4, Roman Krahne1, Gobind Das1, Francesco De Angelis1, Carlo Liberale1, Andrea Toma1, Luca ...

Various nanoplasmonic devices were fabricated using topdown method such as electron beam lithogra... more Various nanoplasmonic devices were fabricated using topdown method such as electron beam lithography, electroplating and focused ion beam techniques. These substrates were investigated after depositing the molecules from dye to protein, using chemisorptions techniques. Theoretical simulations were also performed on these model nanostructures in order to understand the electrical field distribution. Furthermore, the future prospects of these nanostructures were also mentioned in this report.

Microelectronic …, Jan 1, 2012

Gold cuboid nanostructures with edge size in the range of 40–65 nm and inter-particle separation ... more Gold cuboid nanostructures with edge size in the range of 40–65 nm and inter-particle separation of 20 nm were fabricated by electron beam lithography. The aim of the present work is to investigate the effect of cuboid size on surface enhanced Raman scattering intensity and, thereby, to optimize the size of nanostructures in order to maximize signal enhancement. The electric field distribution of 4 × 4 array of Au cuboid nanostructures was numerically simulated by commercial software. A monolayer of Rhodamine-6G is deposited on the device using chemisorption technique, finding an enhancement factor ∼104, which candidates the cuboid nanostructures as a promising enhanced Raman substrate.► Reproducible cuboid structures with edge size in the range from 40 to 65 nm are fabricated by EBL. ► Metallic nanostructures were shown to be highly effective SERS substrates, EF: 104. ► Cuboid structures provide a novel strategy towards bio/chemical sensing capability.

Fabrication of gold plasmonic nanostars SERS device by means of EBL.Investigation of device chara... more Fabrication of gold plasmonic nanostars SERS device by means of EBL.Investigation of device characteristics using SEM and optical absorption measurement.SERS device with maximum EF 5.90 × 104 using CV, deposited using chemisorption technique.Possible application as a biosensor.We report a reproducible plasmonic SERS device, composed of nanostars fabricated by means of electron beam lithography. Cresyl violet dye is used as a probing molecule, deposited on SERS device. Optical transmission measurements show a broad plasmonic resonance around 900 nm. SERS measurements were performed for this device using 633 nm and 830 nm excitation laser lines which are, respectively, far from and close to the plasmonic resonance band position. The estimated SERS enhancement is 1.7 × 104 and 5.9 × 104 with respect to the flat Au surface, when excited by 633 nm and 830 nm, respectively.

Optics Express, 2015

We experimentally investigate the near-infrared emission from simple-to-fabricate, continuous-fil... more We experimentally investigate the near-infrared emission from simple-to-fabricate, continuous-film Fabry-Perot-type resonators, consisting only of unstructured dielectric and metallic films. We show that the proposed configuration is suitable for realization of narrowband emitters, tunable in ranges from mid- to near-infrared, and demonstrate emission centered at the wavelength of 1.7 μm, which corresponds to the band gap energy of GaSb-based photodetectors. The emission is measured at 748 K and follows well the emissivity as predicted from reflection measurements and Kirchhoff's reciprocity. The considered emitter configuration is spectrally highly tunable and, consisting of only few unstructured layers, is amenable to wafer-scale fabrication at low cost by use of standard deposition procedures.

Handbook of Enhanced Spectroscopy, 2015

CLEO: 2015, 2015

ABSTRACT Nanofabrication of metallic nanostructures/nanoparticles enables the detection of analyt... more ABSTRACT Nanofabrication of metallic nanostructures/nanoparticles enables the detection of analyte molecules at ultra-low concentrations with the aid of plasmon induced hot-spots. Here we present a cost effective approach to recycle the SERS substrates for label free bio-sensing applications.

ACS Photonics, 2015

ABSTRACT The coupling of an infrared plasmon-polariton excitation of a metal nanoparticle to a vi... more ABSTRACT The coupling of an infrared plasmon-polariton excitation of a metal nanoparticle to a vibrational excitation of a similar energy enables strong vibrational signal enhancement. However, the commonly used planar substrates substantially weaken plasmonic resonances because of their polarizability and, furthermore, a great part of the enhanced near-field is inside the substrate and thus not available for an analyte. In this contribution we report on a way to reduce these undesirable influences of the substrate by fabricating gold nanowires on high pedestals and thus in reduced contact with the substrate. The influence of the height of the pedestal is an important parameter for the plasmonic near-field enhancement as we show with finite-difference time-domain simulations. Comparing the plasmonic response and the SEIRA activity of the rods prepared by standard electron beam lithography and the rods additionally treated with reactive ion etching to remove the silicon substrate at the hot-spots of the rods reveals not only the change of the plasmonic-resonance spectrum but also interesting differences of the enhanced phonon-polariton signal from the silicon dioxide layer on the silicon substrate and the about one order of magnitude stronger vibrational signal enhancement for an adsorbate monolayer.

Plasmon-Enhanced Spectroscopies for Biotechnological Applications, 2013

Nanotechnology, 2014

We report the fabrication of Au nanostar arrays by means of electron beam lithography, in which t... more We report the fabrication of Au nanostar arrays by means of electron beam lithography, in which the plasmon resonance energy can be tuned via the nanostar size from the visible into the nearinfrared region. The spectral response of the nanostar arrays was investigated by optical extinction (transmittance) experiments, and their surface enhanced Raman scattering performance has been tested at two different excitation wavelengths, 633 nm and 830 nm, using chemisorbed Cresyl violet molecules as analyte. The experimental results are supported by numerical simulations of the spatial and spectral electric field enhancement.

Singular and Chiral Nanoplasmonics, 2014

Journal of Polymer Science Part B: Polymer Physics, 2016

Top-down fabrication of electron-beam lithography (EBL)-defined metallic nanostructures is a succ... more Top-down fabrication of electron-beam lithography (EBL)-defined metallic nanostructures is a successful route to obtain extremely high electromagnetic field enhancement via plasmonic effects in well-defined regions. To this aim, various geometries have been introduced such as disks, triangles, dimers, rings, self-similar lenses, and more. In particular, metallic dimers are highly efficient for surface-enhanced Raman spectroscopy (SERS), and their decoupling from the substrate in a three-dimensional design has proven to further improve their performance. However, the large fabrication time and cost has hindered EBL-defined structures from playing a role in practical applications. Here we present three-dimensional nanostar dimer devices that can be recycled via maskless metal etching and deposition processes, due to conservation of the nanostructure pattern in the 3D geometry of the underlying Si substrate. Furthermore, our 3D-nanostar-dimer-in-ring structures (3D-NSDiRs) incorporate several advantageous aspects for SERS by enhancing the performance of plasmonic dimers via an external ring cavity, by efficient decoupling from the substrate through an elevated 3D design, and by bimetallic AuAg layers that exploit the increased performance of Ag while maintaining the biocompatibility of Au. We demonstrate SERS detection on rhodamine and adenine at extremely low density up to the limit of few molecules and analyze the field enhancement of the 3D-NSDiRs with respect to the exciting wavelength and metal composition.

Advanced materials (Deerfield Beach, Fla.), 2014

Plasmonic nanostar-dimers, decoupled from the substrate, have been fabricated by combining electr... more Plasmonic nanostar-dimers, decoupled from the substrate, have been fabricated by combining electron-beam lithography and reactive-ion etching techniques. The 3D architecture, the sharp tips of the nanostars and the sub-10 nm gap size promote the formation of giant electric-field in highly localized hot-spots. The single/few molecule detection capability of the 3D nanostar-dimers has been demonstrated by Surface-Enhanced Raman Scattering.

... Francesco Gentile1,2, Michela Perrone Donnorso1,3, Manohar Chirumamilla Chowdary1, Ermanno Mi... more ... Francesco Gentile1,2, Michela Perrone Donnorso1,3, Manohar Chirumamilla Chowdary1, Ermanno Miele1, Maria Laura Coluccio1,2, Rosanna La Rocca1, Rosaria Brescia4, Roman Krahne1, Gobind Das1, Francesco De Angelis1, Carlo Liberale1, Andrea Toma1, Luca ...

Various nanoplasmonic devices were fabricated using topdown method such as electron beam lithogra... more Various nanoplasmonic devices were fabricated using topdown method such as electron beam lithography, electroplating and focused ion beam techniques. These substrates were investigated after depositing the molecules from dye to protein, using chemisorptions techniques. Theoretical simulations were also performed on these model nanostructures in order to understand the electrical field distribution. Furthermore, the future prospects of these nanostructures were also mentioned in this report.

Microelectronic …, Jan 1, 2012

Gold cuboid nanostructures with edge size in the range of 40–65 nm and inter-particle separation ... more Gold cuboid nanostructures with edge size in the range of 40–65 nm and inter-particle separation of 20 nm were fabricated by electron beam lithography. The aim of the present work is to investigate the effect of cuboid size on surface enhanced Raman scattering intensity and, thereby, to optimize the size of nanostructures in order to maximize signal enhancement. The electric field distribution of 4 × 4 array of Au cuboid nanostructures was numerically simulated by commercial software. A monolayer of Rhodamine-6G is deposited on the device using chemisorption technique, finding an enhancement factor ∼104, which candidates the cuboid nanostructures as a promising enhanced Raman substrate.► Reproducible cuboid structures with edge size in the range from 40 to 65 nm are fabricated by EBL. ► Metallic nanostructures were shown to be highly effective SERS substrates, EF: 104. ► Cuboid structures provide a novel strategy towards bio/chemical sensing capability.

Fabrication of gold plasmonic nanostars SERS device by means of EBL.Investigation of device chara... more Fabrication of gold plasmonic nanostars SERS device by means of EBL.Investigation of device characteristics using SEM and optical absorption measurement.SERS device with maximum EF 5.90 × 104 using CV, deposited using chemisorption technique.Possible application as a biosensor.We report a reproducible plasmonic SERS device, composed of nanostars fabricated by means of electron beam lithography. Cresyl violet dye is used as a probing molecule, deposited on SERS device. Optical transmission measurements show a broad plasmonic resonance around 900 nm. SERS measurements were performed for this device using 633 nm and 830 nm excitation laser lines which are, respectively, far from and close to the plasmonic resonance band position. The estimated SERS enhancement is 1.7 × 104 and 5.9 × 104 with respect to the flat Au surface, when excited by 633 nm and 830 nm, respectively.