Eg_calc - Estimating the Band Gap of a Solid from Diffuse...

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Estimating the Band Gap of a Solid from Diffuse Reflectance Data When calculating, the band gap, we are interested in where the material starts to absorb. If you remember looking at molecular orbitals in class, The band gap is the minimum energy needed for an electron to be excited from the top of the valence band to the bottom the conduction band. The band gap is measured using a UV-Vis spectrometer as we did in class. Here is a simple example of how to calculate the band gap from the data that you took: Starting in the UV region (high wavelengths), your sample should (but may not) reflect 100% of the light coming from the source. Once that minimum energy is reached (the band gap energy), then the sample can start absorbing light and electrons are excited from the valence band to the conduction band. When the sample starts absorbing there is a large slope in the graph. The first thing you do is draw a line of best fit along the slope of the line as shown below: The point where the line is tangent to the curve, here at the 50% reflectance mark is
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This note was uploaded on 06/03/2011 for the course CHM 123 taught by Professor Woodward during the Spring '08 term at Ohio State.

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Eg_calc - Estimating the Band Gap of a Solid from Diffuse...

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