Messages

1

General Questions and Answers / Re: Effect of gate metal

« on: May 18, 2015, 13:08 »

The relation between the experimental gate potential V1, and the calculational gate potential V, is
V = V1+W1+Ef  as mentioned earlier in the post

However the units of W1 and Ef are in "electron volts(ev)" whereas the gate voltages V1 and V are in "volts".
Could you explain me this??

2

General Questions and Answers / Re: physical significance of the given transmission spectrum

« on: May 4, 2015, 05:40 »

 :-\no reply???

3

General Questions and Answers / physical significance of the given transmission spectrum

« on: April 30, 2015, 07:17 »

In the attached transmission spectrum snapshot my transmission probability is zero within the Ef and El window ,while it is finite for energies outside this window.I would like to know the physical significance of this and what could we interpret from this??

4

General Questions and Answers / Re: iv-scan for double gate

« on: April 18, 2015, 06:09 »

So if both the top and bottom gate are shorted (i.e having same gate  voltages) then the below script would hold good??

#read in the old configuration
device_configuration = nlread('/home/xyz/.vnl/abc/investigate/transistor.nc', object_id='gID000')[0]
calculator = device_configuration.calculator()
metallic_regions= device_configuration.metallicRegions()[0]

# Define gate_voltages
gate_voltage_list=numpy.linspace(0,2,10)*Volt

for gate_voltage in gate_voltage_list:
    device_configuration.setMetallicRegions(
        [metallic_regions(value = gate_voltage)] )

5

General Questions and Answers / iv-scan for double gate

« on: April 17, 2015, 11:55 »

Sir
For a double gate tansistor , how will the id-Vg  script change. Does "device_configuration.metallicRegions()" contain both the top and botton metallic region??

#read in the old configuration
device_configuration = nlread('/home/xyz/.vnl/abc/investigate/transistor.nc', object_id='gID000')[0]
calculator = device_configuration.calculator()
metallic_region0 = device_configuration.metallicRegions()[0]

# Define gate_voltages
gate_voltage_list=numpy.linspace(0,2,10)*Volt

for gate_voltage in gate_voltage_list:
    device_configuration.setMetallicRegions(
        [metallic_region0(value = gate_voltage)] )

# make a copy of the calculator and attach it to the configuration
    # restart from the previous scf state
    device_configuration.setCalculator(
    calculator(electrode_voltages=(0.0*Volt,0.2*Volt)),
    initial_state=device_configuration)
    device_configuration.update()
    nlsave("'/home/xyz/.vnl/abc/investigate/iv-transistor.nc'", device_configuration)
#Analysis
    filename= '/home/xyz/.vnl/abc/investigate/iv-transistor.nc'
    # -------------------------------------------------------------
    # transmission spectrum
    # -------------------------------------------------------------
    transmission_spectrum = TransmissionSpectrum(
    configuration=device_configuration,
    energies=numpy.linspace(-2,2,101)*eV,
    kpoints=MonkhorstPackGrid(3,3),
    energy_zero_parameter=AverageFermiLevel,
    infinitesimal=1e-06*eV,
    self_energy_calculator=KrylovSelfEnergy(),
    )
    nlsave(filename, transmission_spectrum,object_id='trans'+str(gate_voltage))
    nlprint(transmission_spectrum)
   

6

General Questions and Answers / Re: Effect of gate metal

« on: April 8, 2015, 07:04 »

thanks a lot:) indeed helpful

7

General Questions and Answers / Effect of gate metal

« on: April 6, 2015, 08:42 »

In the post
http://quantumwise.com/forum/index.php?topic=2964.msg13890#msg13890,  i understood how the  Id-VG curve shifts based upon the gate  metal in the case when both electrodes are  of same material.

But How to calculate the shift in the Id -Vg curve if both electrodes are of  different materials??

8

General Questions and Answers / Re: doping script

« on: March 4, 2015, 08:11 »

Also when i tried  doping  mos2 using

left_electrode.setExternalPotential(
      AtomicCompensationCharge([(Molybdenite, -1*doping)]))
right_electrode.setExternalPotential(
      AtomicCompensationCharge([(Molybdenite, doping)]))

NameError: name 'Molybdenite' is not defined
 what name should we use for doping entire mos2??

9

General Questions and Answers / doping script

« on: March 4, 2015, 08:00 »

1.In the p-n junction tutorial ,
the doping for n region is taken as ,doping and  for p-region it is  -1*doping. why is it opposite?

2.Secondly the length of only right electrode is considered for both p and n regions.  [  len(right_electrode_elements) ]. Has it been assumed that right and left electrodes are identicle and symetric??

3.  The doping script should come before or after
device_configuration = DeviceConfiguration(
    central_region,
    [left_electrode, right_electrode]
    )    ?
                                                                       

# -------------------------------------------------------------
# Add Doping
# -------------------------------------------------------------
doping_density = 2e+19
# Calculate the volume  and convert it to cm^-3
# Note: right and left electrodes have the same volume,
volume = right_electrode_lattice.unitCellVolume()
volume = float(volume/(0.01*Meter)**3)
# Calculate charge per atom
doping = doping_density * volume / len(right_electrode_elements)
# Add p- and n-type doping to the central region
external_potential = AtomicCompensationCharge([
        ('p_doping', -1*doping), ('n_doping',doping)
        ])
central_region.setExternalPotential(external_potential)
# Add doping to left and right electrodes
left_electrode.setExternalPotential(
      AtomicCompensationCharge([(Silicon, -1*doping)]))
right_electrode.setExternalPotential(
      AtomicCompensationCharge([(Silicon, doping)]))

10

General Questions and Answers / IndexError: list index out of range

« on: February 25, 2015, 14:46 »

Sir
I want to read the device configuration and electrostatic difference potential and device density of states from a previous .nc file .
 As soon i run the simulation  i  get error -IndexError: list index out of range.
the pseudo-code i have given below
-----------------------------------------------------------------
device_configuration = nlread("/home/tara/.vnl/tara-p2/area-scaled/elongated-iv-scan.nc", object_id="gID000")[0]

potentials=nlread("/home/tara/.vnl/tara-p2/area-scaled/elongated-iv-scan.nc",object_id="edp0.0V")[0]

ddos = nlread("/home/tara/.vnl/tara-p2/area-scaled/elongated-iv-scan.nc",object_id="ddos0.0V")[0]
-----------------------------------------------------------------

what can be the  error due to 

2. In the p-n junction tutorial , the script for contour plot was given
http://quantumwise.com/images/Tutorials/p-n_junction/ddos_edp.py

what is fname = sys.argv[1] for  ??

11

General Questions and Answers / Re: Screening length

« on: February 25, 2015, 08:29 »

In the tutorial , http://quantumwise.com/publications/tutorials/item/820-ni-silicide-si-interfaces

Does the Width of the device refer to  broadness of the device (in Y -direction)??

12

General Questions and Answers / Screening length

« on: February 25, 2015, 06:31 »

Sir

1. What would be screening length of silicon with a doping of 1e19??
I read in the tutorial  http://quantumwise.com/publications/tutorials/item/828-silicon-p-n-junction,that i need a longer device (upto 14nm) as silicon has along  screening length.So if my (all-silicon) device is 10nm long,it would give me incorrect results??

2. In the tutorial  http://quantumwise.com/publications/tutorials/item/820-ni-silicide-si-interfaces, it is mentioned that if we are using doping concentration  from 5e19 to 1e20, it would require silicon region to be 30 to 50A wide.If i am using a doping of 1e19, how much should be the  minimum  width of central silicon region??

13

General Questions and Answers / optimum K-points for convergence

« on: February 18, 2015, 19:31 »

Does optimum  K-points  for a device structure depend on the electrode bias  we apply?? I observed that for higher drain bias  ,i require higher value k points in x-diection(i have periodic boundary condition in x direction)  for slater koster  calculation convergence??

14

General Questions and Answers / Re: calculation did not converged-even-after chaning the tolerance-two-probe-job

« on: February 9, 2015, 19:34 »

For slater koster calculations, how much can we increase density mesh cut off for better convergence at higher bias??

15

General Questions and Answers / Re: transmission spectrum stuck

« on: February 1, 2015, 06:43 »

I had changed my basis set to Bassani.Si_Basis (more accurate) which took much more time (4hrs) and memory (self enegies saved ), compared to Vogl.Si_Basis basis set (30-40 min).

After approx 4hrs  it finally gave transmission spectrum results