Characterization of Eu doped ZnO micropods prepared by chemical bath deposition on p-Si substrate

Eu3+ Luminescence Enhancement via Bandgap Engineering of Zn1–xMgxO:Eu Epitaxial Thin Films

“…An exemplary survey spectrum of sample M2 is presented in Figure . Zinc is well detected by signals located at 1021.7 and 1044.7 eV, corresponding to the Zn 2p 3/2 and Zn 2p 1/2 core levels, respectively. ,, Magnesium is identified by signals at 1303.3 and 49.7 eV, assigned to Mg 1s and Mg 2p lines, respectively. , The chemical character of europium was identified by analysis of the Eu 3d 5/2 HR spectra recorded for samples M2, M4, and O2.5 (Figure ). The spectra in this BE region were well fitted with two peaks located at 1134.8 and 1125.3 eV, which are characteristic of trivalent and divalent states of europium and reveal the presence of both Eu 3+ and Eu 2+ surface species in ZnMgO matrix of selected samples. , The relative percentage fractions of Eu 3+ /Eu 2+ were calculated to be 75.9/24.1, 82.8/17.2, and 90.1/9.9 for samples M4, M2, and O2.5, respectively.…”

“…However, the effect of europium, at a doping level of 0.6 ± 0.1 at. %, on the Zn 1– x Mg x O bandgap is negligible compared to the effect of the alloyed Mg content . The optical bandgap energy E g , is given by the Tauc’s relation, α h ν = A ( h ν – E g ) n , where “α” is the absorption coefficient of the material, “A” is a constant, “ h ” is the Planck’s constant, and “ν” is the photon frequency.…”

“…Scheme presents a schematic diagram summarizing possible energy transfer mechanisms in Eu-doped Zn 1– x Mg x O thin films. Eu centers can be excited through different pathways: the commonly accepted mechanism for ZnO:Eu is a nonradiative energy transfer from defect centers. – Another mechanism is excitation via energy transfer from free and bound excitons of the Zn 1– x Mg x O host. The proposed scheme takes into account a model developed by Robbins and Dean, predicting that the coupling between excitons and core states of RE impurities increases if the impurity shows transitions quasi-resonant with the absorption edge of the luminescent materials.…”

“…51 However, the standard energy transfer model predicts that its efficiency depends, first of all, on the location of the energy levels of defects and dopants in the bandgap, as proposed by other authors for ZnO:Eu. [25][26][27]49 Similarly, temperature quenching of the PL of REs via back-transfer of energy depends on the depths of the corresponding levels, according to the model of Favennec et al, 52,53 The enhancement of Eu luminescence in Zn 1−x Mg x O does not seem to be justified solely within the framework of Favennec's model, which takes into account the location of the RE-related levels in the band gap. In our opinion, the intrinsic properties of the ZnMgO material play a more significant role.…”

Significance of microstrain in impacting band gap and photoluminescence behavior of Ce-doped ZnO thin films deposited via sol-gel process

“…Defects in intrinsic ZnO thin films impacted structural, optical, and electrical properties, leading to the investigation of metal doped zinc oxide thin films [32]. In order to fabricate a thin layer of ZnO on an appropriate substrate, a number of different techniques have been implemented [33][34][35][36][37][38][39][40][41][42]. The sol-gel method is one among them, because it has several advantages, including a lower overall cost, improved dopant monitoring, ease of handling, efficiency, lowered crystallisation temperature, and the ability to work on a wide scale [43].…”