engineering

Zinc selenide

Zinc selenide is a engineering 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 Zinc selenide rather than just read about it. In short: Zinc selenide is the inorganic compound with the formula ZnSe. It is a lemon-yellow solid although most samples have a duller color due to the effects of oxidation.

Key takeaways

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

Reference excerpt

Zinc selenide is the inorganic compound with the formula ZnSe. It is a lemon-yellow solid although most samples have a duller color due to the effects of oxidation. It is an intrinsic semiconductor with a band gap of about 2.70 eV at 25 °C (77 °F), equivalent to a wavelength of 459 nm. ZnSe occurs as the rare mineral stilleite, named after Hans Stille.

Synthesis and properties ZnSe is available in both hexagonal (wurtzite) and cubic (zincblende) polymorphs. In both cases, the Zn2+ and Se2− sites are tetrahedral. The difference in the structures related to close packing motifs, hexagonal vs cubic. Cubic ZnSe is produced by treatment of an aqueous solution of zinc sulfate with hydrogen selenide:

ZnSO4 + H2Se → ZnSe + H2SO4 Heating the cubic form gives hexagonal ZnSe. An alternative synthesis involves heating a mixture of zinc oxide, zinc sulfide, and selenium:

2 ZnO + ZnS + 3 Se → 3 ZnSe + SO2 It is a wide-bandgap semiconductor of the II-VI semiconductor group (since zinc and selenium belong to the 12th and 16th groups of the periodic table, respectively). The material can be n-type doped with, for instance, halogen elements. P-type doping is more difficult, but can be achieved by introducing gallium. Similar to zinc sulfide, ZnSe is produced as microcrystalline sheets by synthesis from hydrogen selenide gas and zinc vapour. Another method of producing is a growth from melt under excessive pressure of inert gas (Ar usually). It can be deposited as a thin film by chemical vapour deposition techniques including MOVPE and vacuum evaporation.

Reactions ZnSe is insoluble in water, but dissolves in concentrated hydrochloric acid. Zinc selenide can slowly react with atmospheric moisture if poorly polished, but this is not generally a serious problem. Except where optics are used in spectroscopy or at the Brewster angle, antireflection or beamsplitting optical coatings are generally employed.

Applications ZnSe is used to form II-VI light-emitting diodes and diode lasers. It emits blue light. ZnSe doped with chromium (ZnSe:Cr) has been used as an infrared laser gain medium emitting at about 2.4 μm. It is used as an infrared optical material with a remarkably wide transmission wavelength range (0.45 μm to 21.5 μm). The refractive index is about 2.67 at 550 nm (green), and about 2.40 at 10.6 μm (LWIR). When free of absorption and inclusions it is ideally suited for CO2 laser optics at 10.6 μm wavelength. It is thus a very important IR material. In daily life, it can be found as the entrance optic in the new range of "in-ear" clinical thermometers, seen as a small yellow window. ZnSe activated with tellurium (ZnSe(Te)) is a scintillator with emission peak at 640 nm, suitable for matching with photodiodes. It is used in x-ray and gamma ray detectors. ZnSe scintillators are significantly different from the ZnS ones.

References

External links Coherent Optical Data optical data & more

Illustrations

Worked examples

Example 1 — a first encounter with Zinc selenide

Start with the simplest possible case. Write down what Zinc selenide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, 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 Zinc selenide 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 Zinc selenide 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 Zinc selenide

In research: Zinc selenide appears in engineering 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 Zinc selenide 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: Zinc selenide is common in secondary-school and first-year university syllabi. It links to neighbouring topics II-VI semiconductors, Laser gain media, Optical materials, so understanding it makes those chapters shorter.
In everyday life: Look for Zinc selenide 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 Zinc selenide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Zinc selenide 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 Zinc selenide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Zinc selenide in simple terms?

Zinc selenide is the inorganic compound with the formula ZnSe. It is a lemon-yellow solid although most samples have a duller color due to the effects of oxidation.

Why does Zinc selenide matter?

Because it connects several engineering 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 Zinc selenide?

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 Zinc selenide.