doping in graphene

[harsha]

sir
Glad to use AtK tool trail version, I want to build graphene pn junction of 30 nm size.

 Project is :

                      15 nm i need to dope with P+ atoms

                      15 nm i need to dope with n+ atoms

 Problem is :

                      1.  Graphene is purely conductive and Carbon atoms in the sheet did not have any free electrons to get paired with dopant atoms.

                      2. I want to know is doping mean replacing of single carbon atom with dopant atom?Huh??

                      3. If it is so in what concentration i need to replace carbon atoms with dopant atoms?Huh?

 
         Please help me with the above questions. It will be so helpful to me.

[Anders Blom]

Please don't cross post, and don't reuse old subjects, but create a new topic for a new question.

You question is more of the nature "how do I solve my task" than "how do I use the software for a particular thing", which is the primary type of questions that can be answered by someone without deep insight into your particular task.

Yes, doping typically means replacing an atom by another one, as in bulk semiconductors, although you can make doped electrodes as described in this thread by charging the electrodes, in which case no explicit dopants are included, but it's rather a way to shift the Fermi level in the same way doping will.

[harsha]

thank you for your replay sir, sorry for cross posting.
 

[harsha]

 
    how doping can be done in electrodes through graphene sheet using ATK 12.8.1?

[Anders Blom]

Either replace atoms explicitly, or modify the script to add a "charge" keyword to the electrode calculator, as described in the other posts you read.

[harsha]

Thanking you sir,
  i want to build heavely doped pn junction by using of ATK12.8.1, then how much charge i suppose to give in p type & n type ?

[Anders Blom]

You could study the band structure of the electrode as a function of the charge, and see at what point you get the Fermi level inside the conduction/valence band. But in general the amount of charge is the number of electrons/unit cell of the electrode, so you can just compute the volume of the electrode cell and compute the necessary charge for the doping concentration you want.

[harsha]

How to separate the electrode? and How to find out the band structure? please send me any tutorial is there....

[Anders Blom]

Each electrode is defined explicitly in the Python script so you can just copy out the part defining it. It may be easier to test the effect of the charge on the corresponding smallest bulk cell, like a simple fcc Si crystal (if your electrode is Si), and then just renormalize the charge to the larger volume of the electrode.