uvvistauc

This R package calculates the optical band gap of semiconductors from UV-Vis spectra using Tauc plots.

The Tauc plot is commonly used for semiconductors with either direct or indirect, forbidden or allowed, band gaps; such as oxides, sulfides, and many others.

A Tauc plot is usually performed manually, that is, the band edge region is identified visually, and then a linear fit to the linear part of the band edge is performed manually and the intersect with the abscissa is calculated to arrive at the optical band gap.

Here I have developed a semi-automatic algorithm, that only requires you to supply four x values: two values that define the mostly linear part on the low-energy side of the band edge, and two values that define the high-energy side of the band edge.

This algorithm returns the calculated optical band gap, the fitted Tauc line, as well as the adjusted R-square of the Tauc fit and its number of fitted data points.

Note that this package expects you to supply your UV-Vis data as absorbance (unitless) vs energy (in electronvolts).

So far, this package has only been tested for ZnO. If you use it with other materials, I would love it if you would let me know!

To learn more about how this package implements the Tauc algorithm, read the vignette.

This package also includes a dataset with a time-series of UV-Vis spectra from an experiment on growing colloidal ZnO nanoparticles.

Install this package

To use this package, install it directly from this repo:

install.packages("remotes")
remotes::install_github("solarchemist/uvvistauc")

If you encounter bugs or have questions please open an issue.

Develop this package

Check out the source code from this repo:

git clone https://github.com/solarchemist/uvvistauc.git

I suggest the following package rebuild procedure (in RStudio IDE):

• Run devtools::check() (in the console or via the Build pane). Should complete with one note about "installed package size" being large and no warnings or errors (be warned, the step creating vignettes ... may take several minutes to finish):

── R CMD check results ───────────────────────────────────────────── uvvistauc 0.5.1.9000 ────
Duration: 6m 0.1s

❯ checking installed package size ... NOTE
    installed size is 10.0Mb
    sub-directories of 1Mb or more:
      doc    8.0Mb
      help   1.8Mb

0 errors ✔ | 0 warnings ✔ | 1 note ✖

• Run devtools::build_vignettes() in the console. This recompiles the vignettes and populates the doc/ directory.
• Manually remove the line doc from .gitignore (the build step keeps adding it).

Contributions welcome

If you would like to add another example dataset, or report errors in the code of offer improvements or any other contribution, you're very welcome. Feel free to contact me.

Citation

To cite uvvistauc in publications use:

Taha Ahmed (2022). The uvvistauc package: calculate optical band gap of semiconductors from UV-Vis spectra using the Tauc method. DOI: 10.5281/zenodo.5814054.

Or see the CITATION.cff (citation file format) file in this repo or in the sidebar.