Superlattice

Superlattice is a structure composed of periodically alternating crystalline layers of several substances. Semiconductor superlattices were first grown in the 70's and metallic superlattices in 1980.Superlattices can be produced using various techniques, but the most common are molecular-beam epitaxy and sputtering. With these methods, layers can be produced with thicknesses of only a few atomic spacings. An example of specifying a superlattice is [Fe20V30]20. It describes a bi-layer of 20Å of Iron (Fe) and 30Å of Vanadium (V) repeated 20 times, thus yielding a total thickness of 1000Å or 100nm. The structural quality of the produced superlattices can be verified by means of X-ray diffraction or neutron diffraction spectra which contain characteristic satellite peaks. Other effects associated with the alternating layering are: giant magnetoresistance, tunable reflectivity for X-ray and Neutron mirrors, neutron spin polarization, and changes in the elastic and acoustic properties. Depending on the nature of its components, a superlattice may be called magnetic, optical or semiconducting. The motion of charge carriers in a superlattice is different from that in the individual layers: mobility of charge carriers can be enhanced, which is beneficial for high-frequency devices, and specific optical properties are used in semiconductor lasers). There also exists a class of quasiperiodic superlattices named after Fibonacci. A Fibonacci superlattice can be viewed as a one-dimensional quasicrystal, where either electron hopping transfer or on-site energy takes two values arranged in a Fibonacci sequence.

Further information:

1. Ivan K. Schuller, "A New Class of Layered Materials", Phys. Rev. Lett. 44, 1597 (1980)
2. Morten Jagd Christensen, "Epitaxy, Thin Films and Superlattices", Risø National Laboratory, (1997)
3. Басов Н. Г., Дианов Е. М., Козловский В. И., Крыса А. Б., Насибов А. С., Попов Ю. М., Прохоров A. М., Трубенко П. А., Лазерная электронно-лучевая трубка на основе сверхрешетки ZnCdSe/ZnSe, работающая при Т=300 К, Квант. Электроника, 1995 (22), 8, 756-758
4. Article Spinplasmonics from Wikipedia, the Free Enciclopedia. Available under the license Creative Commons Attribution-Share Alike.

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