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Title:Energy relaxation and thermal rectification in carbon devices
Author(s):Ramasubramanian, Balaji
Advisor(s):Pop, Eric
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):carbon nanotubes
energy relaxation
power dissipation
graphene nanoribbons
thermal rectification
thermal diode
tunnel transistors
Zener tunneling
band-to-band tunneling
electron-phonon interaction
acoustic phonons
boundary scattering
acoustic simulation
Abstract:Power dissipation is a major challenge in modern electronics, from battery-limited portable devices to cooling in massive data centers. The most often cited technological roadblock of nanoscale electronics is the \textquotedblleft{}power problem\textquotedblright{} i.e. power densities and device temperatures reaching levels that will prevent their reliable operation. A majority of the power is dissipated during individual transistor switching, but a great deal of power is also dissipated through thermionic leakage. Therefore, a deeper understanding of power dissipation and energy efficiency at the individual device level could have a global impact, affecting all future electronics. In general, power in electronic devices is dissipated in the form of heat and is slowly lost to the environment. Given that all integrated circuits have a gate oxide (SiO$_2$) and several layers of inter-level-dielectric, the bulk of the heat is likely to be retained in the device because SiO$_2$ has a much lower thermal conductivity (1.4 W/m-K) than silicon (150 W/m-K). This leads to self-heating, mobility degradation and unreliable performance over time. This work examines the physics of energy relaxation in nanoscale transistors based on new popular materials like carbon nanotubes and graphene nanoribbons. The results hold significance for the design of future low power nanoscale devices and show that tunnel devices based on carbon nanotubes with a band gap less than 0.44 eV dissipate less than one sixtieth the power dissipated in traditional thermionic transistors. In addition, this thesis explores ways of efficient cooling of electronic devices by controlling heat flow and shows that thermal rectification in patterned graphene structures is possible.
Issue Date:2010-05-18
Rights Information:Copyright 2010 Balaji Ramasubramanian
Date Available in IDEALS:2010-05-18
Date Deposited:May 2010

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