Swathi Iyer Iyer - Academia.edu (original) (raw)
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Papers by Swathi Iyer Iyer
Review of Scientific Instruments, Nov 1, 2018
X-ray masks are indispensable tools in deep X-ray lithography (XRL). To date, hardly any fabricat... more X-ray masks are indispensable tools in deep X-ray lithography (XRL). To date, hardly any fabrication technology can provide affordable and readily available masks with good structure quality. The bottleneck of adequate masks to a large extent limits the widespread use of XRL. In this article, an alternative XRL mask fabrication process is described to significantly improve availability and cost efficiency of XRL masks as key instruments in XRL processing: A 355 nm UV-laser is applied to expose SU-8 resist on an antireflective coating and a copper sacrificial substrate. The voids in this resist template are filled by a two-step electroplating process with sacrificial nickel and 3.6 µm thick gold absorbers. A second SU-8 coat embeds the absorbers, forming the 40 µm mask membrane. This configuration allows for XRL into resists of up to about 200 µm thickness at the SyLMAND beamline, Canada. The absorber structure accuracy is about 1 µm, at smallest tested lateral dimensions of 2 µm isolated features and 500 nm details. Upon release from the substrate, the membrane locally deforms by up to 1.79 µm. PMMA microstructures patterned with such a mask have smooth and vertical sidewalls. The SyLMAND chopper allows one to limit thermal deformations during exposure to the micrometer range: At a beam power of 0.42 W, typical thermal deformations are 0.5 µm-1.4 µm, depending on the layout, and position inaccuracies are about 3.3 µm.
Journal of Synchrotron Radiation, Feb 12, 2019
SyLMAND, the Synchrotron Laboratory for Micro and Nano Devices, is a recently commissioned microf... more SyLMAND, the Synchrotron Laboratory for Micro and Nano Devices, is a recently commissioned microfabrication bend magnet beamline with ancillary cleanroom facilities at the Canadian Light Source. The synchrotron radiation is applied to pattern high-aspect-ratio polymer microstructures used in the area of micro-electro-mechanical systems (MEMS). SyLMAND particularly focuses on spectral and beam power adjustability and large exposable area formats in an inert gas atmosphere; a rotating-disk intensity chopper allows for independent beam-power reduction, while continuous spectral tuning between 1-2 keV and >15 keV photon energies is achieved using a double-mirror system and lowatomic-number filters. Homogeneous exposure of samples up to six inches in diameter is performed in the experimental endstation, a vertically scanning precision stage (scanner) with tilt and rotation capabilities under 100 mbar helium. Commissioning was completed in late 2017, and SyLMAND is currently ramping up its user program, mostly in the areas of RF MEMS, micro-fluidics/ life sciences and micro-optics.
Review of Scientific Instruments, 2018
X-ray masks are indispensable tools in deep X-ray lithography (XRL). To date, hardly any fabricat... more X-ray masks are indispensable tools in deep X-ray lithography (XRL). To date, hardly any fabrication technology can provide affordable and readily available masks with good structure quality. The bottleneck of adequate masks to a large extent limits the widespread use of XRL. In this article, an alternative XRL mask fabrication process is described to significantly improve availability and cost efficiency of XRL masks as key instruments in XRL processing: A 355 nm UV-laser is applied to expose SU-8 resist on an antireflective coating and a copper sacrificial substrate. The voids in this resist template are filled by a two-step electroplating process with sacrificial nickel and 3.6 μm thick gold absorbers. A second SU-8 coat embeds the absorbers, forming the 40 μm mask membrane. This configuration allows for XRL into resists of up to about 200 μm thickness at the SyLMAND beamline, Canada. The absorber structure accuracy is about 1 μm, at smallest tested lateral dimensions of 2 μm iso...
NIST-Thin membranes of singlewall carbon nanotubes (SWCNTs) assembled from either metallic or sem... more NIST-Thin membranes of singlewall carbon nanotubes (SWCNTs) assembled from either metallic or semiconducting SWCNTs are subjected to the compressive strains imposed by a stretched elastic substrate, and the mechanical characteristics of the membranes are inferred from the topography of the wrinkling instability that emerges. By depositing comparable films on quartz, we also use optical (UV-Vis-NIR) absorption spectroscopy to compute the effective London dispersion spectra of the purified materials, and from these we compute the attractive part of the van der Waals potential between nanotubes of identical electronic type as a function of separation and relative orientation. We find significant differences in the strength and shape of the contact potential depending on electronic type, which in turn are evident in the modulus and yield strain measured from the deformation of the films.
BIE, NDSU-Strain-induced structural and electronic changes in polymer supported membranes of puri... more BIE, NDSU-Strain-induced structural and electronic changes in polymer supported membranes of purified single-wall carbon nanotubes (SWCNTs) are evaluated through the wrinkling instabilities that develop under both uniaxial and isotropic compression. Nanotubes that have been purified by length or electronic type using density-gradient ultracentrifugation are assembled as surfactant-free thin membranes on prestrained polydimethylsiloxane (PDMS) substrates, and the strain response is measured using a broad range of techniques. The small-strain behavior is inferred from kinetic changes in the wrinkling topography of the SWCNT membranes during the slow drying of pre-swelled polymer supports. The measurements suggest a remarkable degree of strain softening that strongly couples to the anisotropic sheet resistance of the films, which we in turn relate to the microscale anisotropy that develops through excluded volume interactions.
Journal of Synchrotron Radiation, 2019
SyLMAND, the Synchrotron Laboratory for Micro and Nano Devices, is a recently commissioned microf... more SyLMAND, the Synchrotron Laboratory for Micro and Nano Devices, is a recently commissioned microfabrication bend magnet beamline with ancillary cleanroom facilities at the Canadian Light Source. The synchrotron radiation is applied to pattern high-aspect-ratio polymer microstructures used in the area of micro-electro-mechanical systems (MEMS). SyLMAND particularly focuses on spectral and beam power adjustability and large exposable area formats in an inert gas atmosphere; a rotating-disk intensity chopper allows for independent beam-power reduction, while continuous spectral tuning between 1–2 keV and >15 keV photon energies is achieved using a double-mirror system and low-atomic-number filters. Homogeneous exposure of samples up to six inches in diameter is performed in the experimental endstation, a vertically scanning precision stage (scanner) with tilt and rotation capabilities under 100 mbar helium. Commissioning was completed in late 2017, and SyLMAND is currently ramping u...
Monodisperse colloidal suspensions of ligand-coated silicon nanocrystals, synthesized through a n... more Monodisperse colloidal suspensions of ligand-coated silicon nanocrystals, synthesized through a nonthermal low-pressure plasma reaction, have been prepared through density-gradient ultracentrifugation in mixed organic solvents. Density-gradient profiles of mixed chloroform and m-xylene are ...
Review of Scientific Instruments, Nov 1, 2018
X-ray masks are indispensable tools in deep X-ray lithography (XRL). To date, hardly any fabricat... more X-ray masks are indispensable tools in deep X-ray lithography (XRL). To date, hardly any fabrication technology can provide affordable and readily available masks with good structure quality. The bottleneck of adequate masks to a large extent limits the widespread use of XRL. In this article, an alternative XRL mask fabrication process is described to significantly improve availability and cost efficiency of XRL masks as key instruments in XRL processing: A 355 nm UV-laser is applied to expose SU-8 resist on an antireflective coating and a copper sacrificial substrate. The voids in this resist template are filled by a two-step electroplating process with sacrificial nickel and 3.6 µm thick gold absorbers. A second SU-8 coat embeds the absorbers, forming the 40 µm mask membrane. This configuration allows for XRL into resists of up to about 200 µm thickness at the SyLMAND beamline, Canada. The absorber structure accuracy is about 1 µm, at smallest tested lateral dimensions of 2 µm isolated features and 500 nm details. Upon release from the substrate, the membrane locally deforms by up to 1.79 µm. PMMA microstructures patterned with such a mask have smooth and vertical sidewalls. The SyLMAND chopper allows one to limit thermal deformations during exposure to the micrometer range: At a beam power of 0.42 W, typical thermal deformations are 0.5 µm-1.4 µm, depending on the layout, and position inaccuracies are about 3.3 µm.
Journal of Synchrotron Radiation, Feb 12, 2019
SyLMAND, the Synchrotron Laboratory for Micro and Nano Devices, is a recently commissioned microf... more SyLMAND, the Synchrotron Laboratory for Micro and Nano Devices, is a recently commissioned microfabrication bend magnet beamline with ancillary cleanroom facilities at the Canadian Light Source. The synchrotron radiation is applied to pattern high-aspect-ratio polymer microstructures used in the area of micro-electro-mechanical systems (MEMS). SyLMAND particularly focuses on spectral and beam power adjustability and large exposable area formats in an inert gas atmosphere; a rotating-disk intensity chopper allows for independent beam-power reduction, while continuous spectral tuning between 1-2 keV and >15 keV photon energies is achieved using a double-mirror system and lowatomic-number filters. Homogeneous exposure of samples up to six inches in diameter is performed in the experimental endstation, a vertically scanning precision stage (scanner) with tilt and rotation capabilities under 100 mbar helium. Commissioning was completed in late 2017, and SyLMAND is currently ramping up its user program, mostly in the areas of RF MEMS, micro-fluidics/ life sciences and micro-optics.
Review of Scientific Instruments, 2018
X-ray masks are indispensable tools in deep X-ray lithography (XRL). To date, hardly any fabricat... more X-ray masks are indispensable tools in deep X-ray lithography (XRL). To date, hardly any fabrication technology can provide affordable and readily available masks with good structure quality. The bottleneck of adequate masks to a large extent limits the widespread use of XRL. In this article, an alternative XRL mask fabrication process is described to significantly improve availability and cost efficiency of XRL masks as key instruments in XRL processing: A 355 nm UV-laser is applied to expose SU-8 resist on an antireflective coating and a copper sacrificial substrate. The voids in this resist template are filled by a two-step electroplating process with sacrificial nickel and 3.6 μm thick gold absorbers. A second SU-8 coat embeds the absorbers, forming the 40 μm mask membrane. This configuration allows for XRL into resists of up to about 200 μm thickness at the SyLMAND beamline, Canada. The absorber structure accuracy is about 1 μm, at smallest tested lateral dimensions of 2 μm iso...
NIST-Thin membranes of singlewall carbon nanotubes (SWCNTs) assembled from either metallic or sem... more NIST-Thin membranes of singlewall carbon nanotubes (SWCNTs) assembled from either metallic or semiconducting SWCNTs are subjected to the compressive strains imposed by a stretched elastic substrate, and the mechanical characteristics of the membranes are inferred from the topography of the wrinkling instability that emerges. By depositing comparable films on quartz, we also use optical (UV-Vis-NIR) absorption spectroscopy to compute the effective London dispersion spectra of the purified materials, and from these we compute the attractive part of the van der Waals potential between nanotubes of identical electronic type as a function of separation and relative orientation. We find significant differences in the strength and shape of the contact potential depending on electronic type, which in turn are evident in the modulus and yield strain measured from the deformation of the films.
BIE, NDSU-Strain-induced structural and electronic changes in polymer supported membranes of puri... more BIE, NDSU-Strain-induced structural and electronic changes in polymer supported membranes of purified single-wall carbon nanotubes (SWCNTs) are evaluated through the wrinkling instabilities that develop under both uniaxial and isotropic compression. Nanotubes that have been purified by length or electronic type using density-gradient ultracentrifugation are assembled as surfactant-free thin membranes on prestrained polydimethylsiloxane (PDMS) substrates, and the strain response is measured using a broad range of techniques. The small-strain behavior is inferred from kinetic changes in the wrinkling topography of the SWCNT membranes during the slow drying of pre-swelled polymer supports. The measurements suggest a remarkable degree of strain softening that strongly couples to the anisotropic sheet resistance of the films, which we in turn relate to the microscale anisotropy that develops through excluded volume interactions.
Journal of Synchrotron Radiation, 2019
SyLMAND, the Synchrotron Laboratory for Micro and Nano Devices, is a recently commissioned microf... more SyLMAND, the Synchrotron Laboratory for Micro and Nano Devices, is a recently commissioned microfabrication bend magnet beamline with ancillary cleanroom facilities at the Canadian Light Source. The synchrotron radiation is applied to pattern high-aspect-ratio polymer microstructures used in the area of micro-electro-mechanical systems (MEMS). SyLMAND particularly focuses on spectral and beam power adjustability and large exposable area formats in an inert gas atmosphere; a rotating-disk intensity chopper allows for independent beam-power reduction, while continuous spectral tuning between 1–2 keV and >15 keV photon energies is achieved using a double-mirror system and low-atomic-number filters. Homogeneous exposure of samples up to six inches in diameter is performed in the experimental endstation, a vertically scanning precision stage (scanner) with tilt and rotation capabilities under 100 mbar helium. Commissioning was completed in late 2017, and SyLMAND is currently ramping u...
Monodisperse colloidal suspensions of ligand-coated silicon nanocrystals, synthesized through a n... more Monodisperse colloidal suspensions of ligand-coated silicon nanocrystals, synthesized through a nonthermal low-pressure plasma reaction, have been prepared through density-gradient ultracentrifugation in mixed organic solvents. Density-gradient profiles of mixed chloroform and m-xylene are ...