Influence of Film Thickness and Oxygen Partial Pressure on Cation-Defect-Induced Intrinsic Ferromagnetic Behavior in Luminescent p-Type Na-Doped ZnO Thin Films

Abstract

In this article, we have investigated the effect of oxygen partial pressure (PO2) and film thickness on defect-induced room-temperature (RT) ferromagnetism (FM) of highly c-axis orientated p-type Na-doped ZnO thin films fabricated by pulse laser deposition (PLD) technique. We have found that the substitution of Na at Zn site (NaZn) can be effective to stabilize intrinsic ferromagnetic (FM) ordering in ZnO thin films with Curie temperature (TC) as high as 509 K. The saturation magnetization (MS) is found to decrease gradually with the increase in thickness of the films, whereas an increase in "MS" is observed with the increase in PO2 of the PLD chamber. The enhancement of ferromagnetic signature with increasing PO2 excludes the possibility of oxygen vacancy (VO) defects for the magnetic origin in Na-doped ZnO films. On the other hand, remarkable enhancement in the green emission (IG) are observed in the photoluminescence (PL) spectroscopic measurements due to Na-doping and that indicates the stabilization of considerable amount of Zn vacancy (VZn)-type defects in Na-doped ZnO films. Correlating the results of PL and X-ray photoelectron spectroscopy (XPS) studies with magnetic measurements we have found that VZn and Na substitutional (NaZn) defects are responsible for the hole-mediated FM in Na-doped ZnO films, which might be an effective candidate for modern spintronic technology.

Investigating the Role of Oxygen Vacancies and Lattice Strain Defects on the Enhanced Photoelectrochemical Property of Alkali Metal (Li, Na, and K) Doped ZnO Nanorod Photoanodes

“…Figure b shows the Li 1s core level spectrum, where the sharp peak located at 55.9 eV corresponds to the Li−O bond formation through the substitution of the Zn 2+ ion by the Li + ion. [42] The Na 1s core level XPS spectrum (see Figure c) exhibits a hump around 1071.1 eV, which represents the Na−O bond formation because of the substitution of Na + at the Zn 2+ sites . The deconvoluted core level spectrum (Figure d) of K 2 p shows two major peaks around 293.9 and 295.8 eV corresponding to the K 2 p 3/2 and K 2 p 1/2 , respectively, which indicates the substitution of K + at Zn 2+ sites .…”

The modification of structural and optical properties of nano- and submicron ZnO powders by variation of solvothermal syntheses conditions

“…The origin of the green PL emission, as the most commonly observed defect emission in ZnO nanostructures, is quite controversial. In the recent studies (Ghosh et al 2013;Motaung et al 2014;Panigrahy et al 2010), this emission is associated with singly ionized oxygen vacancies V O ? and/or zinc vacancies V Zn , located mainly on the ZnO surface.…”

Sensitive Room Temperature Photoluminescence-Based Sensing of H2S with Novel CuO–ZnO Nanorods

“…[31][32][33][34] Our earlier works revealed both vapour-solid (V-S) and vapour-liquid-solid (V-L-S) modes of growing ZnO NRs by PLD, and realized controllable growth of both pure and Al-doped ZnO nanomaterials. 32,[35][36][37] PLD NRs produced in this way were shown to offer a PL-based based route to sensing O 2 (at T w ≥ 150 °C).…”