presented by:
Snigdha Rai
M.Sc. Physics (Spec. in Electronics)

---

[attachment=8662]
Experimental & Theoretical Characterization of CNTs
Objectives
THERE IS A PLENTY OF ROOM AT THE BOTTOM” - Richard Feynman

• Synthesizing CNTs using Arc Plasma Method.
• Experimental Characterization using SEM.
• Theoretical Characterization by observing IV characteristics of CNT using virtual nanolab.
• Numerical modeling of CNTFET.
How actually a nanotube is made ???
Classification of CNTs
Single walled CNT Diameter between 1 to 20 nm and length lies between 100 nm to few microns.
Multiwalled CNT consisting of nested coaxial array of single walled nanotubes separated from one another by 0.34 nm.
Experimental approach to CNTs
Applied Methodology
 “Arc Plasma Method”
 Schematic of Arc Plasma Method
Set up Description
• Stainless steel cylindrical chamber
• 2 ports, one is used for observing the events and another is used for doing the initial adjustments.
• 2 flanges on the top and bottom of the surface (for the electrodes)
• Movable cathode and anode holder.
• Cooling adjustments are done using pipe
Experimental Setup
Plasma “fourth state of matter
 Distinct phase of matter
 Collection of charged particles that respond strongly and collectively to electromagnetic fields
 Also called as ionized gas.
Plasma ..a good thought..
• High temperature process: ceramic nanoparticles can be synthesized.
• Plasma promotes high rates of chemical reaction.
• Yields high purity products.
• High vacuum condition not needed.
• Low synthesis time scales as compared to chemical methods.
Experimental Characterization using SEM
Sample for SEM
Results from analysis
• Theoretical Characterization
I-V Characteristics of CNT
• Virtual nanolab is used for Characterization.
• Simulations run on it by selecting the carbon nanotube and placing it between two gold electrodes with gold-cnt distance between 2.002 Å to 2.027 Å.
• IV characteristics are observed by changing the (n,m) values of the chiral vector
Scaling Obstacles
• Diffusion areas will no longer be separated by a low doped channel region.
• Equivalent gate oxide thickness will fall below the tunneling limit.
• Lithography costs will increase exponentially.
Mathematical Model of CNTFET
• Consider Vds and ψS
• Compute the total charge on the nanotubes for a given Vds and ψS
Conclusion
From Experimental Characterization:
 The length of CNTs are lying in the range of 2-5 micrometers (most of them in the range of 3-4 µm).
 The diameter of CNTs are lying in the range of 10-70 nanometers (most of them in the range of 30-50 nm).
From Theoretical Characterization:
 Conductance for metallic NTs is much larger in comparison to the semiconducting and the semimetallic NTs.
 Characteristics symmetric on both the sides and almost a linear relationship is obtained in metallic NTs.