Hi Juan, hi all!
I have recently started to look into ways of simulating electronic properties of semiconductor structures I am dealing with in my research (I have very little experience in this regard, was so far primarily using optically pumped, “non-electric” samples) and I came across DEVSIM.
First of all - thanks for the opportunity to use the software! It looks very promising and I am eager to try it!
I have a question regarding the 1D capacitor example:
The result for the 1D capacitor example is a charge of ~3.45x10^(-13) from the simulation. The manual gives as a unit F/(cm²). I was wondering about this unit. I tried to estimate the result (as expected) from a simple plate capacitor:
Q = C*U
Q = epsiolon_r * epsilon_0 * A / d * U
Q/A = epsiolon_r * epsilon_0 / d * U
epsilon_r being the relative permittivity (3.9 for SiO2 in the example)
epsilon_0 being the vacuum permittivity (~8.85x10^(-12) As/(V*m) or 8.85x10^(-14) As/(Vcm) as used in the example)
A being the area of the capacitor plates
U being the Bias voltage (1 V in the example)
d being the distance between the plates (1 m if I understand the mesh creation according to the manual correctly, meaning 100 cm)
Using the above values I get a result of
Q/A = 3.45x10^(-11) As/(Vm²) = 3.45*10^(-11) F/m² = 3.45x10^(-15) F/cm²
I would also get this value if I set the position to 100 (cm) and leave the vacuum permittivity at 8.85x10^(-14) As/(Vcm).
Did I overlook something, or is the answer given in the manual incorrect, and should rather be 3.45x10^(-11) F/m² = 3.45x10^(-15) F/cm²?
Or am I making a mistake, because the distance simulated is not 1 m, but actually 1 cm?
I would also be interested what the “spacing” as a parameter in the add_1d_mesh_line() command is?
Does it mean a 0.1(unit?) extension of the contact? Or is it a parameter for the mesh?
And if it is an extension of the contact, and both contacts are extended by 0.1 in the same (positive) direction, is the distance then not 0.9, if one contact is at position 0.0 and the other at 1.0, and would we then not expect other charge values?
Thank you very much for your help! And please excuse the long post, if I simply overlooked something or made a mistake elsewhere.