Special Session 2:
Modeling and Analysis of Carbon Nanotubes (CNT)
for VLSI Interconnection and Application in Solar Cell Design.
ORGANIZERS
Masud H. Chowdhury, University of Illinois at Chicago, USA
SYNOPSIS
Carbon nanotubes (CNTs) have been among the most interesting and intriguing areas of research for more than a decade. Many applications of CNTs have recently been reported. Its applications, for instance, range from carbon based magnetic data storage, carbon nanotube gecko adhesives, improved lasers for telecommunications, possible interconnects for VLSI circuits and systems, carbon nanowires, CNTFETs and many more. Recently it has been found that Carbon based Solar cells is also an area that needs to be deeply explored and researched. There is an urgent short-term and long-term need to address the increasing bandwidth and power constraints of on-chip copper interconnect with technology scaling. One of the radical alternatives is the Carbon Nanotubes (CNT) based interconnect. Considering the potentials of CNT a detail analysis and modeling of its parasitic components need to be performed. This investigation will enable initiating long term research project to develop methodologies to use CNT in interconnect applications, and optimize its performance. The investigation has another distinct goal of exploring the feasibility and challenges of using CNT in solar cells. Successful completion of this project will lead to comprehensive research initiatives merging two different fields of technology - nanoelectronics and alternative energy technology.
CNTs are found in two forms - Single Wall Carbon Nanotube (SWCNT) and Multi Wall Carbon Nanotube (MWCNT). Each of these tubes can either be semi-conducting or metallic by nature depending on their structural properties. It is theoretically deducted that if a combination of SWCNT and MWCNT is used as a bundle a higher number of tubes will participate in conduction, and provides higher current density. It is noted that on increasing the percentage of metallic nanotubes within the bundle improves the conduction. The conductance of a single CNT is highly dependent on the length of the nanotube. It is necessary to verify for what ranges of length of CNT bundles this boost in performance can be observed. The conductance of CNT bundle is also dependent on the conducting channels per shell, the number of shells, and the contact properties. Observations from a number of works indicate that CNTs could be used as global, intermediate, and local interconnects. The conduction capacity of CNTs will depend on their effective resistance, capacitance and inductance. Electrostatic and electromagnetic behaviors will also have an impact. Other factors come into play when the length of the bundle is greater than the mean free path ( ). Mixed CNT bundles will also experience capacitive and inductive crosstalk among CNTs within the bundle and other bundles in the interconnect system. Therefore, possible orientations, structural properties, and arrangements of CNTs in the bundles need to be explored to avoid loss in performance.
CNTs also seem to be highly promising for photovoltaic solar cells due to their properties like high current density, high conductivity, large strength and elasticity (with Young’s modulus for SWCNTs as 1 Tera Pascal), and thermal conductivity. Typically, a Photovoltaic Cell is a large cell that converts solar energy to electricity by photovoltaic effect. Until now, solar cells that convert sunlight to electric power have been dominated by solid state junction devices, often made of silicon wafers. With the progress of nanotechnology, this is now being challenged by the development of a new generation of solar cells based on thin film materials, nanocrystalline materials and conducting polymeric films. These offer the prospects of cheaper materials, higher efficiency and flexible features.
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