Three crystal structures for MgSe have been experimentally characterized. The rock-salt structure is considered to be the most stable crystal structure that has been observed in bulk samples of MgSe, and a cubic lattice constant of 0.55 nm was deduced for this structure.[2] Although attempts at preparing pure zincblende MgSe have been unsuccessful,[3] the lattice constant of zincblende MgSe has been extrapolated from epitaxial thin films of zincblende MgxZn1-xSySe1-x and MgxZn1-xSe grown on gallium arsenide, the latter of which was prepared with a high magnesium content (up to 95% Mg, i.e., Mg0.95Zn0.05Se).[3][4] There is good agreement between these and other extrapolations that the lattice constant of pure zincblende MgSe is 0.59 nm.[1][2] The wurtzite structure of MgSe has been observed, but it is unstable and slowly converts to the rock-salt structure.[5]
NiAs- and FeSi-type crystal structures of MgSe are predicted to form by subjecting the rock-salt crystal structure to extremely high pressures.[2]
Electronic properties
Both rock-salt and zincblende MgSe are semiconductors. On the basis of different extrapolations, a room temperature bandgap of 4.0 eV has been recommended for zincblende MgSe.[1][2] A room temperature bandgap of 3.9 eV was determined for rock-salt MgSe.[2][3]
Preparation
Thin films of amorphous, wurtzite and rock-salt MgSe have been prepared by vacuum deposition of Mg and Se at cryogenic temperatures, followed by heating and annealing.[5] Compound semiconductor alloys of MgSe, such as MgxZn1-xSe, have been prepared by molecular beam epitaxy.[3][4]
Reactions
Samples of pure MgSe and Mg-rich MgxZn1-xSe (x > 0.7) readily react with water and oxidize in air.[2][3]
^ abcdeJobst, B., Hommel, D., Lunz, U., Gerhard, T., Landwehr, G. (1996). "E0 band-gap energy and lattice constant of ternary Zn1−xMgxSe as functions of composition". Applied Physics Letters. 69 (1): 97–99. doi:10.1063/1.118132. ISSN1077-3118.
