Electronic structure and luminescence mechanisms in ZnMoO₄crystals

Abstract

Calculations of the band structure, partial densities of states and optical spectra of permittivity, reflectivity and absorption of perfect ZnMoO 4 crystal were performed using the full-potential linear-augmented-plane-wave method. It is shown that the calculated reflectivity spectra reproduce the main features of corresponding experimental spectra in the fundamental absorption region. The bandgap value of ZnMoO 4 is estimated as E g = 4.3 eV. Peculiarities of luminescence excitation spectra corrected for near-surface losses and losses on reflectivity are discussed, taking into account the results of the calculations. It is found that the energy structure of the lower part of conduction band is manifested in the excitation spectra of the intrinsic luminescence. The excitation spectra in the region 4.3-8.0 eV are formed by band-to-band electronic transitions mainly within the molybdate groups MoO 2− 4 , whereas electronic states of Zn 2+ cations are not directly involved into the excitation processes. It is shown that the structure of the intrinsic luminescence excitation spectrum depends on the temperature and mechanisms of the structure modification are discussed.

Effects of Sintering Temperature on the Morphology and Photoluminescence of Eu3+ Doped Zinc Molybdenum Oxide Hydrate

“…The optical bandgap value of the undoped ZnMoO 4 nanoplates can be calculated to be 3.70 eV. This optically derived bandgap value agrees roughly with the theoretically calculated bandgap value of 3.79 eV [9]. A quite similar bandgap value (3.72 eV) is derived for Eu 3+ doped ZnMoO 4 nanoplates.…”

“…In the case of ZnMoO 4 , the band-edge excitonic recombination can be excluded since the bandgap of ZnMoO 4 is about 4 eV [9,10]. Consequently, the defects in ZnMoO 4 should be the candidate of the broadband PL centered at about 550 nm.…”

“…Equation (3) is an indirect semiconductor [9]. In a parabolic band structure, the optical bandgap and absorption coefficient of an indirect semiconductor can be calculated by…”

“…In a distorted Mo-O tetrahedron, the Mo atom is surrounded by four oxygen atoms. Similarly, the Zn atom in a Zn-O pentahedron is surrounded by five oxygen atoms, and the Zn atom in a Zn-O octahedron is surrounded by six oxygen atoms [9]. After substituting the Zn 2+ sites in ZnMoO 4 , the rare-earth ions in the ZnMoO 4 crystal lattice can give off the characteristic emissions of the rare-earth dopants upon ultraviolet excitation.…”

A combined theoretical and experimental study of electronic structure and optical properties of β-ZnMoO4 microcrystals

“…In particular, this synthesis method enables the attainment of pure molybdate at low temperatures (120 o C -160 o C) in micro and nanoscale with excellent photoluminescence (PL) properties [37][38][39][40][41]. From a theoretical perspective, only one recent research [42] has been reported in the literature which shows band structure calculations and partial densities of states for the triclinic structure of α-ZnMoO 4 crystals using the full-potential linear-augmented-plane-wave method.…”