In this work, transparent amorphous-MgNb 2 O 6 thin films were fabricated on ITO/glass substrates using the sol-gel method. The change in the chemical states, as well as the optical and dielectric properties of MgNb 2 O 6 films at various annealing temperatures is investigated. In this study, MgNb 2 O 6 films exhibited the amorphous phase when the annealing temperature was below 600°C. From X-ray photoelectron spectroscopy, the major parts of the films' chemical states can be indexed as Mg 2+ , Nb 5+ , Nb 4+ , and O 2À . Furthermore, the Nb 4+ element can be reduced at higher annealing temperatures. The average transmission percentage in the visible range (k = 400-800 nm) is over 80% for all MgNb 2 O 6 /ITO/glass samples, whereas the optical band gap (E g ) for all samples is estimated at~4 eV. In addition, the dielectric constant was calculated to be higher than 20 under a 1 MHz AC electric field, with a leakage current density below 2 3 10 À7 A/cm 2 at 1 V. In this study, the fabrication procedure and experiment results of MgNb 2 O 6 films are introduced for transparent microelectronics.
In this study, ilmenite‐MgTiO3 films were sputtered on p‐type Si(111) substrates and the extrinsic effects, such as grain size, crystallinity, and orientation of photoluminescence (PL) properties of the films are discussed. To reduce the effect of oxygen vacancies (act as shallow defects) on PL emissions in the films, oxygen (O2) was introduced as the sputtering gas and the excitation light source (λ = 532 nm) which has a corresponding energy (hν = 2.33 eV) below the shallow defect states was used. In this study, intense near‐infrared (NIR) PL emission centered at 810.1 nm at room temperature can be observed when the MgTiO3 thin films exhibit the preferred (003)‐orientation and accompanied by the presence of hexagon‐shaped grains. In this study, the experiment results reveal that the NIR emission intensity of MgTiO3 films highly depend on crystal orientation and/or grain morphology.
The effects of annealing atmosphere (N2, air and O2) on the electrical properties of sol–gel‐derived MgNb2O6/ITO heterostructures are discussed in this work. All samples exhibited the amorphous phase and were highly transparent. The percentage of Nb4+ content increased when the films were annealed in the oxygen‐deficient conditions, which could lead to semiconducting films. In addition, the results show that the electrical properties of sol–gel‐derived MgNb2O6 thin films could be tuned based on the annealing atmosphere. Moreover, the conduction mechanisms of MgNb2O6/ITO heterostructures are also discussed in this study. The results show that MgNb2O6 thin films have potential for use in multifunctional optoelectronic applications, due to their flexible electrical properties and good transparency.
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.
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