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Band Structure Lab

Computes the electronic and phonon structure of various materials in the spatial configuration of bulk , quantum wells, and wires

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Version 3.1.5 - published on 26 Sep 2014

doi:10.4231/D3XD0QZ59 cite this

This tool is closed source.

First-Time User Guide View All Supporting Documents

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    Jing Wang

    5.0 out of 5 stars

    I haven’t used nanoHUB very often since I graduated from Purdue in 2005. But today I am very glad to come back and write the following review for this bandstructure simulator.

    During my Ph.D. study at Purdue (the thesis available at https://nanohub.org/resources/1313 ), a tight-binding simulator was created to calculate the bandstructures of silicon and germanium nanowires (NWs) with arbitrary orientations. (This simulator eventually became the NW part of this Bandstructure Lab, thanks to many others’ help.) I remember that when I generated the results using my NW bandstructure simulator, I was always wondering “could one day those simulation numbers really be verified by experiments?” (We know that back in 2005, solid experimental data for NWs with very smaller diameters and various orientations were extremely limited.)

    About 7 years later, we finally found some exciting experimental data published in IEDM-2012 that well match the trends predicted in our theoretical work published in IEDM-2005! (see below).
    – Our IEDM05 papaer: J. Wang, A. Rahman, G. Klimeck, and M. Lundstrom, “Bandstructure and Orientation Effects in Ballistic Si and Ge Nanowire FETs,” IEDM Tech. Digest, p. 537, Washington D. C., Dec., 2005.
    – Experimental work by IBM (IEDM12): A. Majumdar, et al., Room-Temperature Carrier Transport in High-Performance Short-Channel Silicon Nanowire MOSFETs,” IEDM Tech. Digest, p. 179, San Francisco, Dec., 2012.

    *** Some examples of well-matched trends:
    1) Si NW PFET 110 can outperform Si NW NFET 110 when the diameter is really small. Fig. 7a in our IEDM05 paper vs. Fig. 9 in IBM’s IEDM12 paper.
    2) For Si NW PFETs, a smaller diameter leads to a higher injection velocity (higher performance). Fig. 8a in our IEDM05 paper vs. Fig. 9 in IBM’s IEDM12 paper.

    It was truly a great feeling to see an experimental support of our theretical findings, even if it came out 7 years later. But it is more important that the well-matched trends mentioned above can give us the confidence on the validity of this Bandstructure Lab. Here I would like to thank Prof. Klimeck again for introducing the sp3s*d5 tight-binding approach to our team back then, which made the whole bandstructure-related simulation possible. I also want to thank the students who has helped transform our in-house simulators (Matlab-based) into robust, web-based simulation tools available to everyone using nanoHUB. Keep up with the good work!

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    Anonymous

    5.0 out of 5 stars

    I experimented with the ‘Band Structure Lab’ in the ‘NCN supported’ category. I’m really impressed with the tool. It is very responsive compared to many other tools that I’ve tried for which you have to submit the simulation request and come back later. The data generated, and especially the plots and 3-D illustrations of the results are very informative and interactive, e.g., the mouse control of the 3-D view and the information of each data-point on the band-structure when mouse hovers over it.

    There are a couple things that came to my mind when I played with it. First, the source code is not available even to the logged-on members of the site. It would be really great if I could see the code and try to understand how the things were done inside it.

    Secondly, I can think of a number of ways in which the visualizaiton of the tool can be further improved. The band-structure diagrams that we look at as of today come from the textbook era when we did not have these interactive tools at our disposal. But now that we have that power there should be a better way to visualize and play with them. For one thing, the plot with energy in the y-axis, Gamma to L-valley on the left of the x-axis and Gamma to X-valley on the right is only a simplified form of the real band structure which is really four dimensional in nature. Even though it is difficult to visualize 4-D, we can atleast create a 3-D approximation instead of the plain old 2-D approximation. So any given plot in 3-D would have energy on it’s z-axis and k_x and k_y on it’s x and y axes.

    We can actually get away with energy axes altogether by assigning k_z to z-axis. But for that we’ll have to represent energy level with something like a ‘density of fog’. So that the low energy areas of the 3-D space have no fog and high-energy areas have a very thick fog. But I guess this kind of visualization should be used in conjunction with the 3-D approximation instead of replacing it.

    Another thing that comes to mind is the visual feedback while configuring the tool before even starting the simulation. For example, there is an illustration of a crystal lattice on the first page of the ‘Band Structure Lab’ tool (the page on which you can select the material to simulate, Si, Ge, etc). When a different material is selected there should be a change in the lattice to represent the new material. Likewise when there is a setting to adjust the length and width of some device and there is an illustration of the device on that settings page, the illustration should be updated to reflect the new length and width.

    Finally, I would emphasize that ‘Band Structure Lab’ is a really great way of exploring the band-structures of different materials and I would want spend more and more time with during the course of my research work.

    Fawad Hassan (UIUC)

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    Fawad Hassan

    5.0 out of 5 stars

    Hi I explored the tool as part of the Spring 2009 ECE 539 coursework at University of Illinois Urbana-Champaing, under Professor Umberto Ravaioli. I have put my comments on the class page wiki at the following URL:

    https://nanohub.org/groups/illinois_ece_539_advanced_theory_of_semiconductors_and_devices/ wiki/ExploringBandStructureLabbyFawadHassan

    In short, I\‘m really impressed with the tool and would want to use it further in my research work. I also suggested some further ways to visualize the results that can possibly augment the understanding of the physics involved.

    Thanks, Fawad Hassan

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    Neelanjan Bhattacharya

    5.0 out of 5 stars

    I always wondered how single crystal of a quantum wire looked like. This tool gives the unit cell and full wire structure as per the orientation. All properties depend on crystal orientation and therefore i found this tool simply excellent. I will be comparing the theoretical simulation here with my experimental data very soon. Thanks for your very good tool.

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    Anonymous

    5.0 out of 5 stars

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    Ali Khakifirooz

    5.0 out of 5 stars

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    Jing Wang

    5.0 out of 5 stars

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nanoHUB.org, a resource for nanoscience and nanotechnology, is supported by the National Science Foundation and other funding agencies. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.