Intense Red Photoluminescence Emission of Sol–Gel‐Derived Nanocrystalline Mg₂TiO₄ Thin Films

Abstract

In this work, undoped Mg 2 TiO 4 thin films were fabricated on p-type Si(111) substrates by the sol-gel method, and the red photoluminescence (PL) of the films is introduced and discussed. According to the experimental results, the red emission appears when the films have been thermally treated at higher temperatures, which have a long range and well-organized crystalline arrangement. Furthermore, to have better realization of the red emission mechanism of Mg 2 TiO 4 films, the optical band gap of Mg 2 TiO 4 (E g Mg2TiO4 ) was estimated at 3.7 eV; furthermore, 325 nm (corresponding energy, hm = 3.82 eV > E g Mg2TiO4 ) and 633 nm (corresponding energy, hm = 1.96 eV < E g Mg2TiO4 ) excited light sources were used to clarify the position of the defect levels. In addition, the influence of annealing atmospheres (O 2 , air, and vacuum) on the red emission of our samples is also discussed. A significant variety of red emissions can be found between these annealing conditions: the red emission can be effectively enhanced by O 2 annealing, but weakened by vacuum annealing. Results reveal that the red emission of Mg 2 TiO 4 thin films may be highly dependent on the completeness of the O-X-O (X = Mg, Ti) bonds.

Polarity‐Driven Atomic Displacements at the 2D Mg2TiO4‐MgO (001) Oxide Interface for Hosting Potential Interlayer Excitons

“…MgO has a large bandgap of about 7.9 eV, while Mg 2 TiO 4 is reported to have a bandgap of about 3.7 eV. [85][86][87] Also, Mg 2 TiO 4 has an inverse spinel structure with built-in electrical polarity due to the presence of atomic layers containing only Mg 2+ cations. Thus, when it forms an interface with a non-polar material such as MgO (001), the polar Mg 2 TiO 4 layers near the interface will be displaced to reduce the polar discontinuity which will induce an asymmetric band structure for the different layers of Mg 2 TiO 4 .…”

Semiconductor MgTiO₃, MgTi₂O₅ and Mg₂TiO₄ Double-Oxide Electrodes for Dye-Sensitized Solar Cells

“…In the MgO-TiO 2 binary system, three types of stable double oxides exist, viz., MgTiO 3 , MgTi 2 O 5 and Mg 2 TiO 4 . The band gap of MgTiO 3 , MgTi 2 O 5 and Mg 2 TiO 4 are 3.7 eV, 3.4 eV, and 3.7 eV, respectively [3,4].…”