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Numerical Simulation of Nanostructure GrowthNanoscale structures, such as nanowires and carbon nanotubes (CNTs), are often grown in gaseous or plasma environments. Successful growth of these structures is defined by achieving a specified crystallinity or chirality, size or diameter, alignment, etc., which in turn depend on gas mixture ratios. pressure, flow rate, substrate temperature, and other operating conditions. To date, there has not been a rigorous growth model that addresses the specific concerns of crystalline nanowire growth, while demonstrating the correct trends of the processing conditions on growth rates. Most crystal growth models are based on the Burton, Cabrera, and Frank (BCF) method, where adatoms are incorporated into a growing crystal at surface steps or spirals. When the supersaturation of the vapor is high, islands nucleate to form steps, and these steps subsequently spread (grow). The overall bulk growth rate is determined by solving for the evolving motion of the steps. Our approach is to use a phase field model to simulate the growth of finite sized nanowire crystals, linking the free energy equation with the diffusion equation of the adatoms. The phase field method solves for an order parameter that defines the evolving steps in a concentration field. This eliminates the need for explicit front tracking/location, or complicated shadowing routines, both of which can be computationally expensive, particularly in higher dimensions. We will present results demonstrating the effect of process conditions, such as substrate temperature, vapor supersaturation, etc. on the evolving morphologies and overall growth rates of the nanostructures.
Document ID
20040086920
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Hwang, Helen H.
Bose, Deepak
Govindan, T. R.
Meyyappan, M.
Date Acquired
August 21, 2013
Publication Date
January 1, 2004
Subject Category
Solid-State Physics
Meeting Information
Meeting: AVS 51st International Symposium
Location: Anaheim, CA
Country: United States
Start Date: November 14, 2004
End Date: November 19, 2004
Sponsors: American Vacuum Society
Funding Number(s)
OTHER: 21-302-05-42
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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