Graduate Research
PhD Thesis Projects
Novel photonic and plasmonic properties of metal-semiconductor core-shell and core-multishell nanowires
Dark-field microscopy image of a silicon nanowire
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Semiconductor nanowires are cylindrical nano-structures with diameters and lengths which range typically between 10 - 200 nm and 1 - 20 µm respectively. They are sub-wavelength structures, i.e. diameters smaller than the wavelength of light, which exhibit unique polarization and diameter dependent optical resonances. The bright color of the nanowire seen in the picture is due to an optical resonance in the visible range. Further, such nanowires can be coated with metal or semiconductors to form core-shell and core-multishell structures. Such nanowire structures consisting of both metal and semiconductor layers exhibit tunable localized surface plasmon resonance in addition to optical resonances. Exploiting both resonances, metal-semiconductor nanowires can be designed to achieve very novel photonic effects such as cloaking, negative refraction and extreme light absorption.
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Current Projects
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Plasmon resonance in Aluminum based core-multishell nanowires can be utilized to enhance visible light absorption within ultra-thin (sub-50 nm) photocatalyst layers therefore improving the efficiency of water splitting. (S. Ramadurgam, T.-G. Lin and C. Yang, Nano Letters, 14, 2014.Copyright 2014 American Chemical Society)
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Metamaterials consisting of Si-Ag-Si core-multishell nanowire arrays exhibit negative refractive index with a high figure of merit in the visible range. (S. Ramadurgam and C. Yang, Scientific Reports, 4, 2014)
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Other Collaborative Efforts
Gate tunneling devices from nanowire core-shell structures for low-power applications
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Investigators: Professor Joerg Appenzeller, Professor Chen Yang
My focus in this project was to develop a selective area deposition process for Germanium to obtain silicon-germanium core-shell nanowires with an abrupt interface for investigating band-to-band tunneling. In these unique core-multishell nanowires, top-down lithography was used to fabricate silicon nanowire cores on SOI while chemical vapor deposition was utilized to obtain the germanium and silicon shells. The additional silicon cap was deposited to prevent oxidation of the germanium shell. |
Nanowire thin film transistors for flexible displays and RFID applications
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Investigators: Professor Saeed Mohammadi, Professor David B. Janes, Professor Chen Yang
This project aims to explore the application of nanowire arrays aligned through dielectrophoresis towards flexible electronics and RFID. My focus was twofold: 1) developing processes to synthesize and tune the doping, diameter and length of silicon and silicon-germanium alloy nanowires. 2) Fabricating back- gated field effect transistors to investigate the electrical properties of single nanowires |
Undergraduate Research
Undergraduate Thesis Project
Stability of high froude number flows along an incline
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The downstream fluid-flow profile on planar inclines is typically considered to be half-poiseuille which is valid only for certain inlet Reynolds and Froude numbers. My focus was to study the linear stability of the velocity profiles of flow down an incline calculated using shallow water. (S. Ramadurgam, R. V. K. Chakravarthy, G. Tomar and R. Govindarajan, Physics of Fluids, 2012)
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Summer Internships
- Summer 2008
Mentor: Professor S. V. Raghurama Rao
Study of finite volume and meshfree methods for solving Euler equations
- Summer 2007
Mentor: Dr. Alvarinho Luis
Study of remote sensing techniques
Study of gravity anomaly and its relation to depth of the ocean floor