QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: naomi on June 6, 2017, 17:17

Title: MoS2 bandstructure
Post by: naomi on June 6, 2017, 17:17

Hey Dear,

It would be great if someone can help me to understand MoS2 bandstructure and the rest of 2D materials theory.
You are wondering what I am looking for? Well, we know Monolayer MoS2 is n-type So, how I got right bandgap value but p-type. ? if I am right n-type or p-type structure means  Ef located near conduction or valence band, but My graph shows Ef located in the middle.  why?
 
I used 1.1.1 to get MoS2 bandstructre. LDA-PZ
If you need extra information please let me know.


Thanks in advanced.

Title: Re: MoS2 bandstructure
Post by: Jess Wellendorff on June 7, 2017, 08:14

In ATK, the Fermi level of an intrinsic semiconductor is nearly always positioned in the middle of the gap. There is no real physical insight to be gained from that fact. If you explicitly doped the semiconductor, you would see the Fermi level move up/down.

Title: Re: MoS2 bandstructure
Post by: naomi on June 7, 2017, 12:42

Dear Jess,

Thanks for your reply.
I have another question.  Pristine MoS2 is n-type, am I right? So If yes,  why I got p-type? :-(
 
If you look precisely into attached file you will see I have right bandgap but confused with n-type , p-type.

Title: Re: MoS2 bandstructure
Post by: Petr Khomyakov on June 7, 2017, 13:57

I would guess that pristine MoS2 is an intrinsic semiconductor. It might be unintentionally doped in experiment, but you are doing simulations, so that we will need to dope it with electrons manually to have it n-type doped. Otherwise, it is assumed to be intrinsic by default.