Crystalline magnesium nitride (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">M</mml:mi><mml:msub><mml:mi mathvariant="normal">g</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>): From epitaxial growth to fundamental physical properties
P. John, H. Rotella, C. Deparis, Gabriel Monge, Frédéric Georgi, P. Vennéguès, M. Leroux, J. Zúñiga‐Pérez
Abstract
Single-crystalline $\mathrm{M}{\mathrm{g}}_{3}{\mathrm{N}}_{2}$ thin films are grown on MgO (100) substrates with plasma-assisted molecular beam epitaxy. To prevent the oxidation of the $\mathrm{M}{\mathrm{g}}_{3}{\mathrm{N}}_{2}$ films and allow further physical characterization, a polycrystalline MgO cap is deposited in situ. The growth orientation of the $\mathrm{M}{\mathrm{g}}_{3}{\mathrm{N}}_{2}$ 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 $\mathrm{M}{\mathrm{g}}_{3}{\mathrm{N}}_{2}$ 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 $\mathrm{M}{\mathrm{g}}_{3}{\mathrm{N}}_{2}$ around 2.9 eV at room temperature, consistent with diffuse reflectance measurements on micrometric $\mathrm{M}{\mathrm{g}}_{3}{\mathrm{N}}_{2}$ particles. These results demonstrate the possibility of exploiting $\mathrm{M}{\mathrm{g}}_{3}{\mathrm{N}}_{2}$ as a new crystalline semiconductor in the blue-violet range.