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25 results on '"Singh, Sajan"'

7. Fabrication of high-κ dielectric metal oxide films on topographically patterned substrates: polymer brush mediated depositions

Author

Yadav, Pravind, Gatensby, Riley, Prochukhan, Nadezda, Padmanabhan, Sibu C., Davó-Quiñonero, Arantxa, Darragh, Philip, Senthamaraikannan, Ramsankar, Murphy, Brid, Snelgrove, Matthew, McFeely, Caitlin, Singh, Sajan, Conway, Jim, O'Connor, Robert, McGlynn, Enda, Lundy, Ross, and Morris, Michael A.

Subjects
ultrathin films, high-κ dielectric, polymer brush, conformal deposition, ion infiltration, Chemistry, Semiconductors, Electronic circuits, Nanotechnology, Materials, Spectrum analysis
Abstract

Fabrication of ultrathin films of dielectric (with particular reference to materials with high dielectric constants) materials has significance in many advanced technological applications including hard protective coatings, sensors, and next generation logic devices. Current state-of-the-art in microelectronics for fabricating these thin films is a combination of atomic layer deposition and photolithography. As feature size decreases and aspect ratios increase, conformality of the films becomes paramount. Here, we show a polymer brush template assisted deposition of highly conformal, ultrathin (sub 5 nm) high-κ dielectric metal oxide films (hafnium oxide and zirconium oxide) on topographically patterned silicon nitride substrates. This technique, using hydroxyl terminated poly-4-vinyl pyridine (P4VP-OH) as the polymer brush, allows for conformal deposition with uniform thickness along the trenches and sidewalls of the substrate. Metal salts are infiltrated into the grafted monolayer polymer brush films via solution deposition. Tailoring specific polymer interfacial chemistries for ion infiltration combined with subsequent oxygen plasma treatment enabled the fabrication of high-quality sub 5 nm metal oxide films.

Published
2022

8. Fabrication of High-κ Dielectric Metal Oxide Films on Topographically Patterned Substrates: Polymer Brush-Mediated Depositions

Author

Yadav, Pravind, primary, Gatensby, Riley, additional, Prochukhan, Nadezda, additional, C. Padmanabhan, Sibu, additional, Davó-Quiñonero, Arantxa, additional, Darragh, Philip, additional, Senthamaraikannan, Ramsankar, additional, Murphy, Bríd, additional, Snelgrove, Matthew, additional, McFeely, Caitlin, additional, Singh, Sajan, additional, Conway, Jim, additional, O’Connor, Robert, additional, McGlynn, Enda, additional, Lundy, Ross, additional, and Morris, Michael A., additional

Published
2022
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23. Simultaneous Type-I/Type-II Emission from CdSe/CdS/ZnSe Nano-Heterostructures

Author

Soni, Udit, Pal, Anuushka, Singh, Sajan, Mittal, Mona, Yadav, Sushma, Elangovan, Ravikrishnan, and Sapra, Sameer

Abstract

Core/intermediate/shell (C/I/S) structures with Type-I emission are well-known and are gaining immense importance due to their superior luminescence properties. Here, we report a unique C/I/S structure composed of CdSe/CdS/ZnSe that exhibits both Type-I and Type-II phenomena. The structures have been well characterized using a combination of optical and structural techniques. The photoluminescence (PL) and photoluminescence excitation (PLE) data indicate the formation of a combined Type-I and Type-II structure in one material, results supported by simple theoretical calculations. Single particle fluorescence reveals colocalization of both the emissions. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results confirm the structure of these particles. The time-resolved fluorescence studies show the possibility of tuning the lifetime of these materials by changing the Type-I/Type-II thickness ratios. It is possible to form these two separate excitons in the same system separated by a CdS intermediate layer that acts both as a barrier and an active member of the Type-II system allowing the generation and recombination of two excitons, in violation of Kasha’s rule.

Published
2014
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24. A Numerical Study of High Temperature and High Velocity Gaseous Hydrogen Flow in a Cooling Channel of a NTR Core

Author

Singh, Sajan B

Subjects
Nuclear, Rocket, Temperature, Velocity, Model, Heat Transfer, Combustion, Mechanical Engineering
Abstract

Two mathematical models (a one and a three-dimensional) were adopted to study, numerically, the thermal hydrodynamic behavior of flow inside a single cooling channel of a Nuclear Thermal Rocket (NTR) engine. The first model assumes the flow in the cooling channel to be one-dimensional, unsteady, compressible, turbulent, and subsonic. The working fluid (GH2) is assumed to be compressible. The governing equations of the 1-D model are discretized using a second order accurate finite difference scheme. Also, a commercial CFD code is used to study the same problem. Numerical experiments, using both codes, simulated the flow and heat transfer in a cooling channel of the reactor. The steady state predictions of both models were compared to the existing experimental results and it is concluded that both models successfully predict the steady state fluid temperature distribution in the NTR cooling channel.

Published
2013

25. Hollow Au@TiO 2 porous electrospun nanofibers for catalytic applications.

Author

Kumar L, Singh S, Horechyy A, Formanek P, Hübner R, Albrecht V, Weißpflog J, Schwarz S, Puneet P, and Nandan B

Abstract

Catalytically active porous and hollow titania nanofibers encapsulating gold nanoparticles were fabricated using a combination of sol-gel chemistry and coaxial electrospinning technique. We report the fabrication of catalytically active porous and hollow titania nanofibers encapsulating gold nanoparticles (AuNPs) using a combination of sol-gel chemistry and coaxial electrospinning technique. The coaxial electrospinning involved the use of a mixture of poly(vinyl pyrrolidone) (PVP) and titania sol as the shell forming component, whereas a mixture of poly(4-vinyl pyridine) (P4VP) and pre-synthesized AuNPs constituted the core forming component. The core-shell nanofibers were calcined stepwise up to 600 °C which resulted in decomposition and removal of the organic constituents of the nanofibers. This led to the formation of porous and hollow titania nanofibers, where the catalytic AuNPs were embedded in the inner wall of the titania shell. The catalytic activity of the prepared Au@TiO 2 porous nanofibers was investigated using a model reaction of catalytic reduction of 4-nitrophenol and Congo red dye in the presence of NaBH 4 . The Au@TiO 2 porous and hollow nanofibers exhibited excellent catalytic activity and recyclability, and the morphology of the nanofibers remained intact after repeated usage. The presented approach could be a promising route for immobilizing various nanosized catalysts in hollow titania supports for the design of stable catalytic systems where the added photocatalytic activity of titania could further be of significance., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Published
2020
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