We can estimate both the direct and indirect bandgap of a semiconductor from Tauc plot method. Can we use it (definitely after extracting absorption coefficient from reflection and transmission measurements) for metal to estimate some direct or indirect energy transition near Fermi level? In other words, can we get some critical energy points (not bandgap) from Tauc plot fitting method?
We have to focus that the energy of the band gap, or what is called the Tauc energy, is concentrated in the energy range between 2.5 to 3.25 eV, and if the straight lines fall outside this range here, we must focus that in the range between 3.25 to 4.13 eV, the energy is named the (HOMO /LUMO gap energy) and above 4.13 eV, the charge transfer energy is concentrated. Here it should be that if the straight lines are located in the energy region less than 2.5 eV, then we release on it the critical energy for the optical transition.
Dear Ammar,
So, you mean, for e.g., if I get a direct bandgap near 1 eV and indirect bandgap near or less than 2.3 eV from Tauc plot fitting, these can be thought as critical energy transition in the electronic band structure?
See the plots for example.
Dear Bharat Thapa:
From the first look at the figures, I am certain that you can publish amazing research from this data. You can calculate two energies in direct transition, one of which is a critical energy and the second is the Tauc energy if you can choose and define the correct area to plot a straight line. At the same time, you have two energies in indirect transition, one of which is the energy capable of achieving the principle of energy conservation, which is the energy of an emitted phonon, which is located at the tail of the band as it is clear in the figure.
Dear Ammar,
Thank you very much for your encouragement and for pointing out some other features from the plot. Can you refer me to some papers that describe such things? So far, what I know is that Tauc method is applied for semiconductors or insulators only and it gives an idea about where the bandgap lies. I could not find any literature that can support that Tauc plot can be used for looking at other details such as critical points and phonon energy! If you have any literature, please share with me here.
Regards.