Magnesium selenide is an inorganic compound with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

MgSe. It contains

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

and

selenium Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elem ...

in a 1:1 ratio. It belongs to the II-VI family of

semiconductor A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. Its conductivity can be modified by adding impurities (" doping") to its crystal structure. When two regions with different doping level ...

compounds.

Structure

Three crystal structures for MgSe have been experimentally characterized. The

rock-salt structure In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main varieties of ...

is considered to be the most stable crystal structure that has been observed in bulk samples of MgSe, and a cubic

lattice constant A lattice constant or lattice parameter is one of the physical dimensions and angles that determine the geometry of the unit cells in a crystal lattice, and is proportional to the distance between atoms in the crystal. A simple cubic crystal has ...

of 0.55 nm was deduced for this structure. Although attempts at preparing pure

zincblende Sphalerite is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Valley type, and volcanogenic mas ...

MgSe have been unsuccessful, the lattice constant of zincblende MgSe has been extrapolated from

epitaxial Epitaxy (prefix ''epi-'' means "on top of”) is a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited cry ...

thin films of zincblende Mg_xZn_1−xS_ySe_1−x and Mg_xZn_1−xSe grown on

gallium arsenide Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a Zincblende (crystal structure), zinc blende crystal structure. Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monoli ...

, the latter of which was prepared with a high magnesium content (up to 95% Mg, i.e., Mg_0.95Zn_0.05Se). There is good agreement between these and other extrapolations that the lattice constant of pure zincblende MgSe is 0.59 nm. The

wurtzite structure In crystallography, the hexagonal crystal family is one of the six crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the trigonal crystal ...

of MgSe has been observed, but it is unstable and slowly converts to the rock-salt structure.

NiAs Nias (, Nias: ''Tanö Niha'') is an island located off the western coast of Sumatra, Indonesia. Nias is also the name of the archipelago () of which the island is the centre, but also includes the Batu Islands to the southeast and the small ...

- and

FeSi Iron monosilicide (FeSi) is an intermetallic compound, a silicide of iron that occurs in nature as the rare mineral naquite. It is a narrow-bandgap semiconductor with a room-temperature electrical resistivity of around 10 kΩ·cm and unusual ...

-type crystal structures of MgSe are predicted to form by subjecting the rock-salt crystal structure to extremely high pressures.

Electronic properties

Both rock-salt and zincblende MgSe are semiconductors. On the basis of different extrapolations, a room temperature

bandgap In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the ...

of 4.0 eV has been recommended for zincblende MgSe. A room temperature bandgap of 3.9 eV was determined for rock-salt MgSe.

Preparation

Thin films of amorphous, wurtzite and rock-salt MgSe have been prepared by

vacuum deposition Vacuum deposition is a group of processes used to deposit layers of material atom-by-atom or molecule-by-molecule on a solid surface. These processes operate at pressures well below atmospheric pressure (i.e., vacuum). The deposited layers can r ...

of Mg and Se at

cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a univers ...

temperatures, followed by heating and annealing. Compound semiconductor alloys of MgSe, such as Mg_xZn_1−xSe, have been prepared by

molecular beam epitaxy Molecular-beam epitaxy (MBE) is an epitaxy method for thin-film deposition of single crystals. MBE is widely used in the manufacture of semiconductor devices, including transistors. MBE is used to make diodes and MOSFETs (MOS field-effect transis ...

Reactions

Samples of pure MgSe and Mg-rich Mg_xZn_1−xSe (x > 0.7) readily react with water and oxidize in air.

References

{{Selenides Magnesium compounds Selenides II-VI semiconductors