Structural Properties and ELNES of Polycrystalline and Nanoporous Mg₃N₂

Abstract

Nanoporous, high-purity magnesium nitride (Mg3N2) was synthesized with a liquid ammonia-based process, for potential applications in optoelectronics, gas separation and catalysis, since these applications require high material purity and crystallinity, which has seldom been demonstrated in the past. One way to evaluate the degree of crystalline near-range order and atomic environment is electron energy-loss spectroscopy (EELS) in a transmission electron microscope. However, there are hardly any data on Mg3N2, which makes identification of electron energy-loss near-edge structure (ELNES) features difficult. Therefore, we have studied nanoporous Mg3N2 with EELS in detail in comparison to EELS spectra of bulk Mg3N2, which was analyzed as a reference material. The N-K and Mg-K edges of both materials are similar. Despite having the same crystal structure, however, there are differences in fine-structural features, such as shifts and absences of peaks in the N-K and Mg-K edges of nanoporous Mg3N2. These differences in ELNES are attributed to coordination changes in nanoporous Mg3N2 caused by the significantly smaller crystallite size of 2–6 nm compared to the larger (25–125 nm) crystal size in a bulk material.

Strain-Induced Valence Band Splitting Enabling Above-Bandgap Exciton Luminescence in Epitaxial Mg3N2 Thin Films

“…Such features in the N K -edge spectrum are associated with the transition from the core N 1s level to antibonding N 2 ps – Mg 3 ps hybridized states. Theoretically calculated density of states (DOS) shows that the valence band edge near the Fermi-level is mostly dominated by N 2p states, similar to other nitrides, ,, and conduction band states appear from the hybridization of N 2p, 2s and Mg 3s, 3p orbitals. , The peak A (∼404.9 eV) at the edge onset is assigned to the N 1s π* transition, and the prominent B peak (∼410.9 eV) corresponds to the N 1s σ* transition . Such antibonding states originate through N 2ps – Mg 3ps hybridized states.…”

“…22,23 The peak A (∼404.9 eV) at the edge onset is assigned to the N 1s π* transition, and the prominent B peak (∼410.9 eV) corresponds to the N 1s σ* transition. 45 Such antibonding states originate through N 2ps − Mg 3ps hybridized states. The higher energy spectral features C, D, and above (not marked) may be attributed to higher-lying hybridized states of N and Mg orbitals.…”

Impact of synthesis conditions on the morphology and crystal structure of tungsten nitride nanomaterials

“…Sample synthesis and preparation for TEM are a critical aspect as past analyses of related nanoscaled nitrides have shown high reactivity of the material with water or oxygen. 40,41 Exposure to the ambient atmosphere swily results in deleterious reactions of the nitrides to form hydroxides and oxides. Therefore, sample synthesis was performed in Schlenk lines with Argon.…”

Bandgap evolution of Mg3N2 under pressure: Experimental and theoretical studies

“…Furthermore, the electronic and optical properties of Mg 3 N 2 have been aroused considerable attention because of its prospective application in phosphor-converted light emitting diodes (pc-LEDs), as a visible-light-activated luminescent material. [6,7] In particular, Mg 3 N 2 was suggested to be an promising alternative to AlN and Ga 1 Al 1−n N in optoelectronics. [8] It is generally believed that Mg 3 N 2 has a direct bandgap structure.…”