Influence of Li-N and Li-F co-doping on defect-induced intrinsic ferromagnetic and photoluminescence properties of arrays of ZnO nanowires

Abstract

The role of N/F co-doping on the defect-driven room-temperature d0 ferromagnetism in group-I element Li doped ZnO nanowire arrays has been investigated. The ferromagnetic signature of pristine ZnO nanowires has enhanced significantly after Li doping but the Li-N co-doping has found to be more effective in the stabilization and enhancement in room-temperature ferromagnetism in ZnO nanowires. Saturation magnetization in Li-doped ZnO nanowires found to increase from 0.63 to 2.52 emu/g and the Curie temperature rises up to 648 K when 10 at. % N is co-doped with 6 at. % Li. On the other hand, Li-F co-doping leads to exhibit much poor room-temperature ferromagnetic as well as visible luminescence properties. The valance state of the different dopants is estimated by x-ray photoelectron spectroscopy while the photoluminescence spectra indicate the gradual stabilization of Zn vacancy defects or defect complexes in presence of No acceptor states, which is found to be responsible for the enhancement of intrinsic ferromagnetism in ZnO:Li matrix. Therefore, the Li-N co-doping can be an effective parameter to stabilize, enhance, and tune zinc vacancy-induced room-temperature d0 ferromagnetism in ZnO nanowires, which can be an exciting approach to prepare new class of spintronic materials.

Defects induced luminescence and tuning of bandgap energy narrowing in ZnO nanoparticles doped with Li ions

“…45,46 In addition to this common hypothesis, the possible presence of Zn(OH) 2 at the surface was identified as a possible reason for the weak UV and the strong visible (broad yellow and green) emission. 50,51 The orange-red emission centered at $640-650 nm is also commonly attributed to the presence of excess oxygen in the samples, such as oxygen interstitial 5,47,48 defects. Other hypotheses include surface dislocations 49 and zinc interstitials are correlated with orange-red luminescence in ZnO.…”

“…Similarly deconvolution of the broad visible band for N and F co-doped ZnO:Li nanowires has been reported. 50 Li and according to the literature, the binding energy of these deconvoluted peaks corresponds to different defects. 51 The peak "c" located at 478 6 1.21 nm (2.59 6 0.01 eV) can be attributed to the electron transition from the shallow donor level of zinc interstitial and oxygen vacancies to the valence band.…”

Fabrication Technology and Characteristics Research of the Acceleration Sensor Based on Li-Doped ZnO Piezoelectric Thin Films

“…As shown in Figure 6a, the binding energy of Zn 2p 3/2 and Zn 2p 1/2 are located around 1021.8 eV, 1044.8 eV, respectively. The peak intensity of the Zn 2p 3/2 state is relatively higher that the Zn 2p 1/2 , clearly prove that the Zn ions in the thin films are mainly in the chemical state of Zn 2+ , and the Zn 0 are correspondingly less [13,14,15]. Figure 6b shows the Li 1s spectra of 5 wt% Li-doped ZnO thin films.…”

“…Figure 6b shows the Li 1s spectra of 5 wt% Li-doped ZnO thin films. The Li 1s peak was observed at around 55.3 eV, the binding energy of Li 1s core level is in the range 52–56 eV [14,15,16]. The quantitative analysis result shows that the weight percentage of Li elements is 4.36 wt% [17].…”

Codoping and Interstitial Deactivation in the Control of Amphoteric Li Dopant in ZnO for the Realization of p-Type TCOs

“…One ultimate challenge is related to the amphoteric nature of Li, since Li on an interstitial site acts as a donor, leading to self-compensation. Thus, codoping with electron acceptor groups has been proposed as a strategy to deactivate the donor capability of interstitial Li atoms and control the electrical properties of the host [ 15 , 16 , 17 ]. The large variability of the degrees of freedom (such as doping techniques, quality of the sample, chemical environments, temperature and pressure, etc.)…”