Monday, November 24, 2008


Process for Thin Film Coating

Before go to the process for the CNT growth on to the substrate,it is essential first to formed the thin film on to the substrate.We used quartz substrate in this process (glass,silicon wafer etc can also be used) and develop thin film on it by using RF Plasma Sputtering (others process can also be used).Its a very simple process for thin film coating on to the substrate.First placed the substrate at the desired location in the chamber,creating the vaccum and starting firing of plasma in it for certain time.Due to the ionic bombardment onto the target,material have been deposited onto the substrate.Now the sample is ready to grow the CNT/any other material on it.

CNT can be grown by using many methods:
a) Ion discharge
b) CVD
c) Laser Ablation etc

But we used CVD process at atmospheric pressure to grow CNT onto the quartz substrate:-

1):- First put the sample in the boat after cleaning the boat from acetone and insert it in the
CVD chamber

2):- Plug on the supply,Set Temp: 800 degree celcius approx and set voltage level upto 200
volts (Note: These parameters depend on the type of substrate used)

3):- Now wait till the temperature reach upto 8oo degree celcius.(Note: In our case it consume
approx 20-30 mins to reach the set temperature value.

4):- When achieve the desired temperature,get ready to pass the gases from the chamber

5):- Pass the Argon gas from the chamber which act as a inert gas for five minutes using Mass
flow controller.(Set 50 but it can be changed like can set 100 too)

6):- Now Pass the Acetylene (IUPAC name: ethyne), C2H2 from the chamber
for ten minutes using Mass flow controller..(Set 20 but this parameter can be changed too.
Note:Some other Catalyst can also be used to grow CNT like some researchers used Resin and become succeed to grow CNT on it .

7):- Now turn off the supply and the developed sample is ready to characterized it from a
Microscopy Techniques eg SEM,TEM etc (We used SEM for it and see the fine CNT structures have been developed onto the substrate.

Points to Remember:-

MWCNTs synthesized with low acetylene concentration are more regular and with a lower amount of amorphous carbon than those synthesized with a high concentration. During the synthesis of CNTs, amorphous carbon nanoparticles nucleate on the external wall of the nanotubes. At high acetylene concentration carbon nanoparticles grow, covering all CNTs’ surface, forming a compact coating. The combination of CNTs with this coating of amorphous carbon nanoparticles lead to a material with high decomposition temperature.

For more info about CVD and Acetylene,click on the given links:- for CVD for c2h2 for resin for MWCNT & SWCNT

Note: All the above given description on experimantal basis and subject to change/error---

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