tauc

Tauc refers most often to the Tauc plot, a graphical method used in materials science to estimate the optical band gap of a material from its absorption data. The plot is named after Jan Tauc, who introduced the relationship in the study of amorphous semiconductors in the 1960s.

The underlying idea is the Tauc relation, which links the absorption coefficient α to the photon energy hv near the absorption edge through a form such as αhv ≈ B(hv − Eg)^n, where Eg is the optical band gap, B is a constant, and n depends on the nature of the electronic transition (direct or indirect, allowed or forbidden). To extract Eg, researchers plot a transformed quantity versus hv (for example, (αhv)^{1/n} versus hv) and identify a linear region. Extrapolating this linear portion to the energy axis where the absorption vanishes gives an estimate of the band gap. In practice, common variants for many amorphous semiconductors are (αhv)^{1/2} versus hv or (αhv)^2 versus hv, chosen based on the expected transition type.

Applications of the Tauc plot span a range of materials, including amorphous silicon, chalcogenide glasses, metal oxides, and organic semiconductors. The method is widely used for quick, comparative band-gap assessment but can be influenced by disorder, tail states, and measurement noise, which may affect the precision of Eg.

Tauc is also a surname, most notably associated with Jan Tauc, the physicist linked to the plot’s development. See also optical absorption edge and Urbach tail.