Crystalline magnesium nitride ( Mg3N2 ): From epitaxial growth to fundamental physical properties
Résumé
Single-crystalline Mg 3 N 2 thin films are grown on MgO (100) substrates with plasma-assisted molecular beam epitaxy. To prevent the oxidation of the Mg 3 N 2 films and allow further physical characterization, a polycrystalline MgO cap is deposited in situ. The growth orientation of the Mg 3 N 2 films can be tuned from (100) to (111) by changing the growth conditions, and the associated epitaxial relationships have been determined by means of x-ray diffraction. The lattice constant of Mg 3 N 2 films has been monitored as a function of temperature from 300 to 900 K, determining thereby the linear thermal expansion coefficient. Transmission measurements indicate an optical bandgap of crystalline Mg 3 N 2 around 2.9 eV at room temperature, consistent with diffuse reflectance measurements on micrometric Mg 3 N 2 particles. These results demonstrate the possibility of exploiting Mg 3 N 2 as a new crystalline semiconductor in the blue-violet range.
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