I want to determine the figure of merit (FOM) for the transparent conducting film (TCFs). According to the journal by Ellmer et al. (http://www.nature.com/nphoton/journal/v6/n12/abs/nphoton.2012.282.html), there are a few FOM equations for TCFs that can be used such as equation by Haacke et al.
For TCFs on the substrate, the following equation is used:
T= (16nsub2)/〖(1+nsub)〗^4 1/〖[1+Zo/Rs 1/((1+nsub)) σOP/σDC ]〗2
(you can find this equation on the paper by Ellmer et al. http://www.nature.com/nphoton/journal/v6/n12/abs/nphoton.2012.282.html
However, the calculated FOM obtained was negative in value and I do not know how to explain this.
There are only even exponents in your equation. So I don't see how you can get negative values out of it unless you set in complex values for n_sub.
Maybe, this is the reason?
"The choice of the exponent reflected the limits of the transparency of available coatings more than thirty years ago; since then, new materials appeared exhibiting higher than 90 per cent transmission for which the Haacke figure of merit breaks down."
see the link
http://arxiv.org/pdf/1005.3125.pdf
There are only even exponents in your equation. So I don't see how you can get negative values out of it unless you set in complex values for n_sub.
Otherwise you can obtain simply from T10/ Sheet resistance.
That was in the paper of Haacke.
[G. Haacke, "New figure of merit for transparent conductors", J. Appl. Phys, vol. 47, pp. 4086-4089, 1976.]
Hi Gert, yes, of course imaginary numbers (or complex) will lead to negative FOMs. I'm no specific expert in the points discussed here. However, you can define a complex refraction index, so the outcome of the formula migjt become negative. But I don't know whether the use of a complex refractive index is intended in the formula.
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