science

Tauc plot

Tauc plot is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tauc plot rather than just read about it. In short: A Tauc plot is used to determine the optical bandgap, or Tauc bandgap, of either disordered or amorphous semiconductors. In his original work Jan Tauc () showed that the optical absorption spectrum of amorphous germanium resembles the spectrum of the indirect transitions in crystalline germanium (plus a tail due to localized states at lower energies), and proposed an extrapolation to find the optical bandgap of thes…

Key takeaways

Tauc plot belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tauc plot to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tauc plot from memory before moving on to harder problems.

Reference excerpt

A Tauc plot is used to determine the optical bandgap, or Tauc bandgap, of either disordered or amorphous semiconductors. In his original work Jan Tauc () showed that the optical absorption spectrum of amorphous germanium resembles the spectrum of the indirect transitions in crystalline germanium (plus a tail due to localized states at lower energies), and proposed an extrapolation to find the optical bandgap of these crystalline-like states. Typically, a Tauc plot shows the photon energy E (= hν) on the abscissa (x-coordinate) and the quantity (αE)1/2 on the ordinate (y-coordinate), where α is the absorption coefficient of the material. Thus, extrapolating this linear region to the abscissa yields the energy of the optical bandgap of the amorphous material. A similar procedure is adopted to determine the optical bandgap of crystalline semiconductors. In this case, however, the ordinate is given by (α)1/r, in which the exponent 1/r denotes the nature of the transition:,,

r = 1/2 for direct allowed transitions r = 3/2 for direct forbidden transitions. r = 2 for indirect allowed transitions r = 3 for indirect forbidden transitions

See also Band gap Urbach energy Kubelka–Munk theory

References

Illustrations

Tauc plot: Tauc representation illustrating the optical bandgap (ETauc~ 0.8 eV) of a film of amorphous Si. The insert shows their corresponding transmittance/reflectance spectra. — Tauc representation illustrating the optical bandgap (ETauc~ 0.8 eV) of a film of amorphous Si. The insert shows their corresponding transmittance/reflectance spectra.

Worked examples

Example 1 — a first encounter with Tauc plot

Start with the simplest possible case. Write down what Tauc plot claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tauc plot before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tauc plot ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tauc plot

In research: Tauc plot appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tauc plot in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tauc plot is common in secondary-school and first-year university syllabi. It links to neighbouring topics Plots (graphics), Semiconductor analysis, Thin films, so understanding it makes those chapters shorter.
In everyday life: Look for Tauc plot outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tauc plot in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tauc plot means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tauc plot out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tauc plot in simple terms?

Why does Tauc plot matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tauc plot?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tauc plot.