To calculate the band gap energy of my synthesized TiO2 film on Ti-substrate i need to calculate the molar absorption coefficient and for that i have to calculate the molar concentration of TiO2. But i am little confused- how can i calculate the molar concentration of TiO2 film on Ti-substrate?
By using devices, such as XPS, you can derive the fraction of the surface covered by TiO2 versus Ti, where you can deduce the molar fraction by the analytical chemical calculations
Hope it helps.
Wish you luck!
The paper below can be an example showing how XPS devices work. And by deriving the intensities, the fraction of Ti over TiO2 can be measured:
http://www.iapws.jp/Proceedings/Symposium05/391Konishi.pdf
P.S. If a detailed explanation is required, I can provide more thorough studies on the topic.
you can use XPS spectroscopy for calculate the chemical composition of your film
if your requirement is band gap of TiO2, why dont you measure its UV-visible spectra and calculate by Tauc's Method.
https://www.researchgate.net/post/UV_vis_absorption_spectra
you can use XPS spectroscopy for chemical composition, if you want to calculate only band gap energy then go for Diffuse Reflectance Spectroscopy (DRS) Analysis.
By using cut off wavelength in Kubelka-Munk equation , you can calculate the band gap energy
For thin films, i think its more appropriate to look at the density, thickness, roughness, porosity or surface area rather than molarity. Except if you are looking at the TiO2 sol
You can measure the thickness and refractive index of the film using ellipsometry. Using this information - from which you can deduce the density of the film, by making assumptions as to which phase of TiO2 you have (probably anatase if made at low temperatures), then you can know how much TiO2 you have in the film on a molar basis.
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