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Benjamin Mark Lowe

Treatment of hydrogens and IS-FET modelling

I was very excited to find this software - it is wonderful for you to have made such a tool available online with such a easy-to-use interface, and I'm sure it will be very useful for education purposes and for understanding electrolyte-insulator-semiconductor systems. Thank you for also well documenting it, making the software particularly easy to use. Nonetheless, I have a few  questions I was hoping you could answer:

a) Is the hydrogen concentration modeled explicitly using the Poisson-Nernst-Plank equations in ENBIOS-1D lab? If so, I was wondering why their concentration profile can't be visualised in the simulation output.  Is the assumption that at IS-FET sensing conditions (pH 4-10), because bulk [H+] and [OH-] are between 1e-4 M and 1e-10 M, that [H+] will generally be much less than the concentration of salt, and therefore not shown?

b) Similarly, I couldn't find a detailed explanation of what the 'implict' or 'explicit' pH treatment in ENBIOS-1D lab means or how its implemented. I have read the site binding model by Yates et al. but not quite sure how this related specifically. 

c) I'm interested in modelling simple IS-FET systems and am enthusiastic to see that you suggest that an example model for IS-FET systems may come in future. In the mean time, would I be correct in saying that a simple approach to doing so with ENBIOS-1D lab at moderate ionic strength (50 mM to 500 mM) would be to simply set the 'oxide' property in the model to parameters of an oxide and stern layer. That is to say that because ENBIOS-1D only supports a single layer for the insulator, one can use the equation for two capacitors connected in series, to determine an appropriate choice of permittivity and thickness for the single layer insulator in the model. 

Thank you again for creating this tool and I will be very grateful for your response,












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    Thank you for the kind comments on the ENBIOS-1D Lab V2.0 tool.

    We have recently uploaded the version V3.0 where your suggested improvements have been implemented. In particular: 

    - the H+ and OH- concentrations are now plotted in the "results" graphs

    - a detailed description of how ENBIOS-1D Lab V3.0 behaves in the "implicit pH" and "explicit pH" has been added to the accompanying documentation

    - the user can now separately specify a compact layer and an insulator layer

    Please note that some of the default parameter choices have been changed, especially as regards the activation of site-binding charge models.

    As regards ISFETs, a dedicated tool denoted ENBIOS-2D Lab is now available to simulate simple SOI ISFET structures. The updates made to ENBIOS-1D Lab from Version 2.0 to version 3.0 are not yet available on ENBIOS-2D Lab

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