Messages

1

General Questions and Answers / Re: questions about the convergence of the IV curve of 2D monolayer MoS2

« on: April 16, 2018, 12:22 »

  Actually i have already read this convergence guide.  Thanks for your reply, i will try my best to get the result  converged......

2

General Questions and Answers / Re: Can semicondutors act as an electrode?

« on: April 16, 2018, 10:03 »

Thanks for your reply! However, I am still confused with that. As they use the intrinsic semicondutor electrode shown in the figures above, the Electrostatic Differential Potential should never be flat near the electrode when applying a bias, as there is actually no scattering point in the perfect nanoribben.
So my question is that can I use the extended semicondutor layers as an electrode to study the IV of the intrinsic semicondutor nanoribben without doping it,  for example MoS2 nanoribben? Is the explaination  of the author above correct?
   
 

3

General Questions and Answers / Can semicondutors act as an electrode?

« on: April 14, 2018, 15:00 »

Dear ATK experts:
    Nowadays, I am quite confused about whether the semicondutors can act as an electrode. In the guide "Transport calculations with ATK", it says that "In systems with semiconductor electrodes, the screening length can be quite long, and a very long central region may be required before the potential approaches the bulk value". However, in many published articles (https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.7b07921), I found that they used the intrinsic semicondutors acting as the electrode as shown in my attached figures. So, as far as i am concerned, if the system we studied does not have a interface, just an intrinsic semicondutor nanoribben, can we just using the extended semicondutors nanoribben layers as the electrode,
without doping it? Wow,  I am quite confused now. I will appreciate your suggestions.
    Best wishes!

4

General Questions and Answers / questions about the convergence of the IV curve of 2D monolayer MoS2

« on: April 12, 2018, 08:02 »

Dear Quantumwise experts：
    I meet some problem about the convergence of the IV curve of monolayer MoS2. I intent to investigate the influence of irradiation effect on the transport properties of the 2D monolayer by the IV curve change after simply deleting 1S, 1Mo, or 2S as  point defects. So the first thing is to choose a proper eletrode for the 2D MoS2 semiconductor. I have tried the doped MoS2 (using the Atomic compensation charges method), or graphene,or 1 T MoS2 as the electrode, but  the iv curves all fail to converge at a large bias  (for perfect one may above 1V and for defected one may just 0.2V). As it really takes a long time to find the convergence failure when using the DFT method, here I report the problem about the convergence using the Extended Huckel method for a rather faster result. (no appropriate basis set for MoS2 for the Slater-Koster method).
    The attached 1T_2H_EH_large_IV.py showes the structure of my study system for the perfect one. As you can see, I have used a very long electrode and a small 0.01V bias change to guarantee the convergence of the IV curve. However it still fails as shown in test1.png (a). I have calculated the Electrostatic Difference Potential curve at bias 0.79V shown in test1.png (b), and it seems the potential near the electrode is still flat. I wonder whether 0.01 V bias change is still not enough or there are problems in my systems.
   In second attached EH_doped_zerobias.py, I used the doped MoS2 as eletrodes to see whether this could help the IV curve convergence. However it remains a problem. As shown in test2.png(a), when I found the convergence problem, I lower the bias change to 0.01 V between 0.2V - 0.3V. However it is still  trapped at bias 0.26V. Then the previous claculation becomes converged after 7645 steps. However it already takes 7598 steps at 0.26V in test2.png(b), then I have canceled the latter one. It seems the shorter bias does not work in my work. Then I plot the dE\dM\dH change in test3.png(c) , it seem the convergence progress becomes sharply. So how can I determine the maximum steps during each bias change as it is impossible to predict its tendency.
   I wonder whether there are parameters-setting problems in my system or the total concept of my study is wrong? Any suggestion or comment will be appreciated.

5

General Questions and Answers / Re: How to simulate the IV curve of the monolayer MoS2?

« on: March 27, 2018, 12:47 »

  Thanks you very much！I do understand what your mean. I have already optimized the undoped MoS2 structure according the guide. Thanks for your kind advice.

6

General Questions and Answers / Re: How to simulate the IV curve of the monolayer MoS2?

« on: March 27, 2018, 12:25 »

  Thank you very much！According to your suggestion, it seems I don't have to optimize the atomic structure of the doped MoS2 as a electrode! I will try it soon.

7

General Questions and Answers / How to simulate the IV curve of the monolayer MoS2?

« on: March 26, 2018, 17:35 »

Dear QuantumWise team：
           I am a new learner of ATK. Nowadays, i want to simulate the the IV curve of the monolayer MoS2. Since the monolayer MoS2 is a semiconductor, a very long electrode may be needed. So i use the doping monolayer MoS2 as the electrode to lower the length of the valid electrode. But i have a question that the optimal structure of the doping MoS2 shoule be different from the one of undoped MoS2, so there must be a mismatch at the interface when they are contaced. I wonder which one of the optimal structures should i use?
I look forward to your help.