Browsing by Author "Medjaldi Malika"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Magnetic and Electronic Structure Studies of Nanocrystalline (Co2Mn)40Ni60 Alloy
    (ACTA PHYSICA POLONICA A ; Polska Akademia Nauk, 2021-07-01) Medjaldi Malika; Dadda Noureddine
    Nanocrystalline (Co2Mn)40Ni60 (wt%) alloy powder was prepared by high-energy ball milling under an argon atmosphere. Structure, microstructure, and magnetic properties were investigated by means of X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. The X-ray diffraction analysis indicates that after 30 h of milling, a highly disordered (Co, Mn, Ni) solid solution emerges, having an average crystallite size of around 60 nm and a lattice parameter of about 3.5411 Å. Magnetization-field curves indicate the existence of ferromagnetic behavior irrespective of the milling time with a low hysteresis loop, a typical characteristic of a soft magnetic material. The magnetic properties, however, are found to be sensitive to the milling time: i.e. the ratio Mr=Msat manifests the formation of multi-domains magnetic structure. Diverse magnetic parameters were acquired from the approach to magnetic saturation. The electronic structure of the ferromagnetic (Co2Mn)40Ni60 alloy performed by self-consistent ab initio calculations based on the Korringa–Kohn–Rostocker method combined with the coherent potential approximation, reveals that the total DOS is mainly due to the 3d-like states of the constituent elements Mn, Co and Ni.
  • No Thumbnail Available
    Item
    Study of Undoped and Indium Doped ZnO Thin Films Deposited by Sol Gel Method
    (silicon journal, 2018-04-14) Medjaldi Malika
    In this paper, we report the effects of Indium doping concentrations (from 0 to 10wt%) on the structural, morphological, and optical properties of deposited In doped ZnO (IZO) thin films prepared by the sol–gel method through the dip coating technique. X-ray diffraction (XRD) analysis indicates that all ZnO thin films have a polycrystalline nature with a hexagonal wurtzite phase with (002) as a preferential orientation. XRD results demonstrate that the particle size of ZnO decreased with the increase in Indium concentrations. Raman scattering spectra confirmed the wurtzite phase and the presence of intrinsic defects in our samples. Energy dispersive spectroscopy (EDS) and the X-ray photoelectron spectroscopy (XPS) measurements, confirmed the presence of zinc, oxygen and indium elements which is in agreement with XPS results. The photoluminescence (PL) spectra of the films exhibit defects-related visible emission peaks, with intensities differing owing to different concentrations of zinc vacancies. UV–Vis spectrometer measurements show that all the films are highly transparent in the visible wavelength region (≥70%) and presented two different absorption edges at about 3.21 eV and 3.7 eV, these may be correspond to the band gap of zinc oxide and indium oxide respectively.
  • No Thumbnail Available
    Item
    Study of Undoped and Indium Doped ZnO Thin Films Deposited by Sol Gel Method
    (JOURNAL OF NANO- AND ELECTRONIC PHYSICS, 2022-12-27) Medjaldi Malika
    1 wt. % Co-doped ZnO (CZO) thin films of varying thicknesses (3, 5 and 7 layers, which correspond to 403, 545 and 725 nm as thickness) are deposited using the sol-gel method onto glass substrates by dip coating technique. Zinc acetate dehydrate, cobalt acetate, 2-methoxyethanol and ethanolamine are used as primary materials, solvent and stabilizer, respectively. The thermally annealed films are characterized to study the structural, surface morphology, electrical and optical properties. X-ray diffraction (XRD) shows that these films have a polycrystalline hexagonal structure (wurtzite structure with space group P63mc), possessing compressive stress and presenting a preferred orientation along the (002) plane. We note that the particle size increases when the thickness increases. The surface morphology of the prepared CZO thin films is investigated by atomic force microscopy (AFM). It reveals the emergence of a uniform columnar structure and shows that the particle size and the root mean square (RMS) of CZO increase with increasing thickness. UV-visible spectroscopy shows (in the visible region) a transmittance between 75 and 86 % for all the films, strong absorption (in the UV region) and a decrease in the optical band gap. Moreover, the near band edge (NBE) and visible emissions detected by photoluminescence are affected by the thickness. The electrical conductivity of the sample with 725 nm is found to be 4.43 (cm) – 1.