Messages

1

General Questions and Answers / Re: Problem on study gate effect onto MoS2 monolayer

« on: June 30, 2014, 21:41 »

It would seem you are studying intrinsic MoS2 without doping. The article considers PMOS and NMOS.

Thanks for your reply.
Yeah, you're right. But, as shown in the attached 'py' script, we also take the doping into consideration by setting up the charge state of electrode (charge=+/-0.01182). Such doping can ensure the  doping density ~10^20 /cm^3. (refer to the paper "We consider highly doped (10^20 /cm^3) n++ and p++ regions as the source/drain for the n-MOSFET and the p-MOSFET, respectively").

In the paper, they also mention they place MoS2 on the SiO2/Si substrate. Does this matter a lot? If it is, how to set it up in ATK?

2

General Questions and Answers / Re: Problem on study gate effect onto MoS2 monolayer

« on: June 28, 2014, 16:28 »

Please, any idea!

3

General Questions and Answers / Problem on study gate effect onto MoS2 monolayer

« on: June 27, 2014, 20:51 »

 I am new to ATK. I am trying to reproduce the results from the paper: IEEE TRANSACTIONS ON ELECTRON DEVICES, 2013, 60, 2782. However, I cannot get the similar results.

The 'py' scripts I used are attached. First, I used 'mos2-hfo2-lad.py' to do device calculation and then calculate transmission spectrum with 'iv-anal.py'. With this procedure, I obtained IV curve with gate voltage fixed at 0V and  0.35 V (refer to the attached figure, please). The 0.35 V gate voltage supposes to greatly enhance the current. However, for my results, It seems the applied gate voltage has no effect on the current. Could you help check the script and device I build if there is something wrong?

I also tried the device with thinner (~10 angstrom) dielectric materials so that the gate can be placed closer to MoS2 monolayer. However, the gate voltage still gives little effect.

 I will appreciate if somebody can help.

4

General Questions and Answers / Re: Different values of start_mixing_after_step gave out distinctive results

« on: October 4, 2013, 17:29 »

Thanks for reply.

Yeah, the system we are studing is the perfect nanoribbon and need to now the transmission properties ((I-V) curve). We already tried to change other possible parameters (i.e. mixing parameter, self_energy_calculator_real, initial_density_type, preconditioner, temperature) to solve the converge problem. But it is still not converging. The start_mixing_after_step=8 indeed help the calculation converge much faster for the bias situation. However, as you said it obviously gave out wrong results. Is this parameter similar to 'NELMDL' in vasp? It is supposed to give the right results or it just not fit for some cases?

5

General Questions and Answers / Different values of start_mixing_after_step gave out distinctive results

« on: October 3, 2013, 18:41 »

When calculating the transmission spectrum of nanoribbon, I  obtained very different results with start_mixing_after_step = 0 (ref. 0.png) and =8 (ref. 8.png).
The bandstructure shows it is metallic. So start_mixing_after_step =0 probably gave the reasonable results. However, the calculation is not converged for the bias higher than 0.3 V. That's why I tried to use start_mixing_after_step =8, which indeed make the calculation converge fast.

Any idea what's going on here?