Messages

301

General Questions and Answers / Re: GNR topology

« on: January 18, 2012, 06:40 »

i am trying to produce a plot such as attached .. bandstructure for a whole device with bias .. is it possible (without doing too many things manually)? 

302

General Questions and Answers / Re: GNR topology

« on: January 18, 2012, 04:00 »

Ok this is my plan, tell me if this makes sense:

1) I make a device configuration with left and right electrodes ...
2) I script through the left and right electrodes and replace a certain number (10%, etc) of atoms there to dopant atoms
3) I create the device with the new bulk, left electrode and right electrode objects .. then continue from there ..

does this seem like a good way to dope left and right electrodes? 

otherwise i am wondering about the information here:
http://quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.deviceconfiguration.html

which talks about requiring part of the center region to match the electrodes .. is this a hard requirement, or only if you build it in a certain way ? ...

Another question also ... why can i not get a band diagram for an entire device ..?  it seems you can only do it for the central bulk region without electrodes ... is this right?

303

General Questions and Answers / Re: GNR topology

« on: January 18, 2012, 00:47 »

I need to be able to dope the source and drain electrodes in a FET topology ..

i am having a problem doing this ... when i make electrodes, it seems to copy part of the center region .. if i try to change the atoms in the electrode region in the builder tool, it automatically changes atoms in the center region ... how do i dope the electrodes?

304

General Questions and Answers / Re: GNR topology

« on: January 17, 2012, 18:57 »

thank you

305

General Questions and Answers / Re: Calculation the transport properties of graphene

« on: January 17, 2012, 10:03 »

ok thank you

306

General Questions and Answers / Re: Calculation the transport properties of graphene

« on: January 17, 2012, 07:59 »

maybe my problem is that i have no introduced any doping so i have only one type of GNR, sorry i will revisit the structure

307

General Questions and Answers / GNR topology

« on: January 17, 2012, 07:34 »

I have reviewed over 50 papers on graphene and GNR based FETs, and I believe in all these papers, AGNR ribbons are presented with alternating widths within the ribbon, ... atk creates a sort of staggered topology ... the attachment shows what i mean by "alternating" ... if you count the rings (as a simple way to see this), the wdith from left to right is 6, 5, 6, 5, 6, 5 to create the AGNR .... ATK seems to produce 6, 6, 6, 6, 6, 6, 6, where the armchair part is made by "staggerring" the rings, as opposed to alternating the widths ... does that make sense?  my question is how to make the topology so commonly used in research papers ... do I have to do it manually?  IF I make a GNR of width W, I want it to be the same as is done in published research papers

308

General Questions and Answers / Re: Calculation the transport properties of graphene

« on: January 16, 2012, 23:20 »

I see ok I just want to make sure I understand correctly. 

On the point of IV curves .. there are certainly many papers that report IV curves for what they term "perfect" GNRfet structures ... for example: http://ieeexplore.ieee.org/search/srchabstract.jsp?tp=&arnumber=5567164&openedRefinements%3D*%26filter%3DAND%28NOT%284283010803%29%29%26searchField%3DSearch+All%26queryText%3DGraphene+Nanoribbon+FETs%3A+Technology+Exploration+for+Performance+and+Reliability

Now, you say that ATK considers the ballistic regime ... I am not sure if I understand well enough, but my understand was that electrons will only move ballistically if you do not consider higher order effects in the structure, like phone scattering, nearest neighbor interactions, etc ... are you saying there is a limitation in ATK that will not allow me to produce a plot like those in the paper, or is it that I am not in full understanding here ... ?

In other words, my understanding was that ATK can calculate IV curves at the most sophisticated level, including higher order interactions and effects .. is this the case?  Is it that the way I made it, my structure is too simplistic?

309

General Questions and Answers / Re: Calculation the transport properties of graphene

« on: January 16, 2012, 22:56 »

also about "the box" ... i assume you are talking about the unit cell padding ... should i just make this arbitrarily large then?  Is there any information on this?  I am sorry i don't know what "the box" is ... I am guessing this is the region of calculation for various things, set by this unit cell padding parameter from the gui?

310

General Questions and Answers / Re: Calculation the transport properties of graphene

« on: January 16, 2012, 22:52 »

Why do you keep referring to my structure as metallic?  I created an AGNR which should be a semiconductor, and indeed I have checked and there is a significant bandgap ... also why 1d?  I make a nanoribbon, isnt that 2d?

311

General Questions and Answers / Re: null calculator

« on: January 16, 2012, 22:35 »

I think I figured this one out .. i saved multiple times and there were multiple device configurations in the file .. i used the object_id when saving and reading, and it works now. 

312

General Questions and Answers / null calculator

« on: January 16, 2012, 22:22 »

I am getting an error after reading in a file ...

File "C:\Users\patakye\Documents\EP_EDU\GradSchool\UMN\KiaResearch\QuantumSimulations\ATK\ATKSIMS\gnr_12_0_AGNR_z10.py", line 672, in doCalcs2
    calculator(electrode_voltages=(-0.1*Volt,0.1*Volt)),
TypeError: 'NoneType' object is not callable

My setup is like this ... I create the device in one function and save it as:

Code

	#----------------------------------------
	# Device Calculator
	#----------------------------------------
	calculator = DeviceHuckelCalculator(
		basis_set=basis_set,
		electrode_voltages=(-0.1*Volt,0.1*Volt),
		electrode_calculators=
			[left_electrode_calculator, right_electrode_calculator],
		)

	device_configuration.setCalculator(calculator)
	nlprint(device_configuration)
	device_configuration.update()
	nlsave(outFileName, device_configuration)

then in another function:

Code

	#read in the old configuration
	device_configuration = nlread(outFileName,DeviceConfiguration)[0]
	calculator = device_configuration.calculator()

This is where I get an error that the calculator object is null ... am i doing this incorrectly?

313

General Questions and Answers / Angstrom vs Ang

« on: January 16, 2012, 21:22 »

Maybe I am just not familiar with the unit "Ang", but when I try to modify values that are in Angstroms the program keeps giving me errors that I am not using Ang units ... How do we know when to use "Ang" and when to use "Angstrom"?   I tested 1*Ang == 1*Angstrom and it returned true, so ... are they the same or not?

314

General Questions and Answers / Re: Calculation the transport properties of graphene

« on: January 16, 2012, 20:53 »

I was unclear about the role of "the box" ... is there somewhere in the tutorials that explains this?

315

General Questions and Answers / Re: Calculation the transport properties of graphene

« on: January 16, 2012, 18:34 »

thank you