[DFTB-Plus-User] CNT Gate Settings

[Gabriele Penazzi]

Hi George,

there's two things I am not sure I get, before trying to comment.
Is your CNT semiconducting or you have some kind of virtual doping? I am 
not sure I understand if you get what you expect for the Ids/Vg curve 
because I am not sure what to expect. I see it behaves kind of an n-like 
depletion, is it expected?

Second, the Vgs get very large, in general the larger the potential the 
bigger the system will need to be. When you set a transport set up with 
Green's function you generally assume that you reach a bulk-like 
potential and charge distribution at the electrode region. If you have 
large bias/gate voltages you easily need a fairly large system or a 
buffer with good screening properties. Are you checking if the 
electrostatics looks physically sound during your calculations?

There's some an old work on CNT-FET (doi  10.1109/TNANO.2006.886782),  
maybe you know it already but it can help you to see some published 
results.

Gabriele

On 12/10/2015 11:49 PM, George D Kubas wrote:
>
> I have ran a 7 unit cell long 8,0 CNT which has resulted in an okay 
> drain current versus gate voltage curve. I am currently running 
> transport calculations on an 8,0 CNT that is 13 unit cells long, but 
> there seems to be spikes in different sections of the drain current 
> vs. gate voltage curve. I thought that maybe the gate dimensions I am 
> using for the longer tube are poor, so I have been making curves for 
> different gate lengths in the transport direction . I still am seeing 
> spikes in the current at some gate voltages. So does anyone have any 
> advice on gate dimensions or even about another setting that I may 
> have incorrectly used in the device file? I have attached the device 
> file, the IV curve for the 7 unit cell long tube as a reference, and 
> the IV curves for two different gate lengths in the transport 
> direction for the 13 unit cell long tube. Thank you for your time and 
> help.
>
>
> George D. Kubas
> Materials Science PhD. Candidate
> Youngstown State University
> gdkubas at student.ysu.edu
> (330) 261-2967
>
>
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-- 
Dr. Gabriele Penazzi
BCCMS - University of Bremen

http://www.bccms.uni-bremen.de/
http://sites.google.com/site/gabrielepenazzi/

phone: +49 (0) 421 218 9328
fax: +49 (0) 421 218 4764

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