generally, MWCNTs behave as semiconductor at room temperature..
in my case at room temperature, its i-v is perfect ohmic,
but when we record i-v with temperatures.. i found that its resistance is decrease...curve is not like exponentially decay... its like that..
Dear colleague Shivani Dhall
Have a nice time and good day.
You said "MWCNTs behave as semiconductor at room temperature."
The decreasing of resistance with temperature in a linear plot is one of the most important characteristics of semiconductors. So your material has a semiconductor behavior not only at room temperature but also above room temperature.
I wish that help you and be useful.
Yours
A. El-Denglawey
Dear Eldenglawey
i am very grateful to you for this kind reply.
i am totally agree with u. i have attched one of result. plz go through it and suggest me possible mechanism..
It is very common features of semiconductor materials. But decreasing resistance with temperature as compared to room temperature is due to internal effect . At room temperature surface electronic effect make it ohmic in nature. But high temperature might be internal properties of MWCNTs to contribute to dominate the carrier transport issue. That's why it is varying due to different temperatures
I think your MWCNT material is a thermoresistive composite with the negative coefficient of temperature. But it not be a semiconductor in the classical sense. The final decision may be proved after common analysis of both electric and optical data.
To unambiguously establish conductivity mechanism one must perform additional measurements, for example, the gap width and its temperature dependence.
I think you have to use the good old Drude conductivity model for further explanation of the temperature behavior of the MWCNT. The key sign of semiconductor is exponential dependence of resistance decay but we can see the other dependences. And we have to use the 4-probe method only to prevent the contact effects.
Your testing temperature (220 C) is low to see the result. All interesting things may be visible after 1200 C only. And indicate the method for measuring of resistance.
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