Dear Santano,

Oxide semiconductors that behave as metal like in the sense that their conduction band is partially filled. All what you can measure is their work-function phi.

The work function phi is energy required to free electrons from their Fermi level to the vacuum free electron level. There are number of methods that can be used to measure phi one of the methods is the vibrating capacitor Kelvin method.

It can be measured also by photo electric emission in photocathodes.

The density of the electrons can be measured by the Hall effect.

The mobility can be determined knowing the conductivity and the electron density.

Best wishes

Please refer to the following article.

https://www.semanticscholar.org/paper/The-absolute-energy-positions-of-conduction-and-of-Xu-Schoonen/baca1e8fd0d7d9bed4c028c8d366668c9734ab10

UPS (ultraviolet photoelectron spectroscopy) to determine the top of the valance band and IPES (inverse photoelectron spectroscopy) to determine the bottom of the conduction band. If IPES is not available you should determine the bandgap (for instance from the absorption coefficient spectrum via the Tauc model) and add its value to the energy location of the top of the valance band in order to estimate the location of the bottom of the conduction band.

In order to find out valence and conduction bands positions, you need first to know the energy bandgap value. Therefore you need to measure and/or to calculate the energy bandgap of your oxide material as follows:

1. One very efficient experimental technique of energy bandgap measurements is optical absorption spectroscopy (not to confuse with spectrometry) technique which can be better done through optical transmission spectroscopy experiments (transmission is almost exactly the reverse phenomenon of absorption, where the sample is more aborsbing it is less transmitting and vice-versa). In the case of oxides with Eg>2eV, you need UV optical spectroscopy.

2. One very efficient and ''direct'' way to calculate theoretically the energy bandgap of a given material is to perform ab-initio density-functional-theory (DFT-FP-LAPW GGA and LDA) based calculations with so-called TB-mBJ correction (Tran-Blaha modified Beck Johnson) to improve energy bandgap calculations. In this case, you get not only the value of the energy bandgap, but much more the full energy band structure of the material with the exact positions of valence and conduction bands extrema in the Brillouin zone.

Hello dear Santanu Podder

You can determine better the BAND-GAP between valence band and conduction band for your material. For this, you could try next procedures:

1. Try to perform a UV-VIS DRS spectrum. With the data, you can use Tauch Methodology and then determine Band-gap.

2. Use computational methodology. If you have the .cif of your solid it is possible to simulate a part or an approximation using computational tools such as Gaussian or Vasp. With this approximation you can determine the position of the Valence band and then to obtain the information that you need.

**I had the opportunity to perform both methodologies and the results are very similar and besides, in the literature are reported as very effective.

If you have a doubt, please contact me.

Kind regards,

Julián Sánchez-Patinök

Dear Santano,

Oxide semiconductors that behave as metal like in the sense that their conduction band is partially filled. All what you can measure is their work-function phi.

The work function phi is energy required to free electrons from their Fermi level to the vacuum free electron level. There are number of methods that can be used to measure phi one of the methods is the vibrating capacitor Kelvin method.

It can be measured also by photo electric emission in photocathodes.

The density of the electrons can be measured by the Hall effect.

The mobility can be determined knowing the conductivity and the electron density.

Best wishes

Thank you very much for all the valuable information

Xu, Yong, and Martin AA Schoonen. "The absolute energy positions of conduction and valence bands of selected semiconducting minerals." American Mineralogist 85, no. 3-4 (2000): 543-556.

Hey,

As per my knowledge Taut plot will give you the idea of optical band gap. but for TOC's optical and electronic band gaps are different. So in order to get the electronic band gap you can use low temperature STM.

But it does not give the absolute value of Valence band or Conduction Band for that you have to use UPS.