QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: huangshenjie on July 25, 2012, 13:35

Title: an error in the calculation of IV curve
Post by: huangshenjie on July 25, 2012, 13:35

Dear all,
I made a MTJ by ATK, but the I-Vcurve shows that when the bias is increasing, firstly, the current also increases, but then the current quickly declines to zero.

I don't know how to explain it, since I think that the current should always increases with the increase of the bias.

Waiting for your answer.

Title: Re: an error in the calculation of IV curve
Post by: mads.engelund on July 30, 2012, 11:47

I am not sure if your MTJ should have this feature, but it is possible for the current to go down when the bias is increased.
http://en.wikipedia.org/wiki/Negative_differential_conductivity (http://en.wikipedia.org/wiki/Negative_differential_conductivity)
Check if others have observed this feature, if they have not, return.

Title: Re: an error in the calculation of IV curve
Post by: Anders Blom on July 30, 2012, 12:36

I don't think if one can say anything about your results. The graph looks like it has 5-6 points only, and the current is exactly zero for the higher bias. However, that can also be caused by bad convergence, esp. if you are using older versions of ATK that could happen (the whole calculation converged to zero electron density). You need smaller steps in bias to really get a proper smooth curve.