Study of ZnO and Ni-doped ZnO synthesized by atom beam sputtering technique

Abstract

Zinc oxide (ZnO) and Ni-doped zinc oxide (ZnO:Ni) films are prepared by atom beam sputtering with an intent of growing transparent conducting oxide (TCO) material and understanding its physical properties. The crystalline phases of the films are identified by the grazing angle X-ray diffraction (GAXRD) technique. Thicknesses of the films are measured by ellipsometry. Chemical states of the elements present in the films are investigated by X-ray photoelectron spectroscopy (XPS), which indicates the presence of Ni in the ZnO environment in a divalent state. Average transmission across the ZnO:Ni film was determined to be ∼ 83% in the visible region, which is less than that (∼ 90%) of undoped ZnO films. The resistivity measured by van der Pauw technique of the ZnO:Ni film (∼ 9 × 10 −3 Ω cm) is two orders of magnitude smaller as compared to its undoped counterpart (1 Ω cm). For ZnO:Ni film an average carrier concentration of ∼ 1.4 × 10 19 cm −3 was observed by Hall measurements. Two important mechanisms reported in the literature viz. influence of d-d transition bands and electron scattering from crystallites/grains are discussed as the possible causes for the increase in conductivity on Ni doping in ZnO.

Synthesis and characterization of Ni-doped ZnO: A transparent magnetic semiconductor

“…A set of ZnO and ZnO:Ni films ($60 nm) were deposited by FAB sputtering technique [19,20] on silicon and quartz substrates kept at room temperature. The schematic arrangement of the deposition setup is shown in Fig.…”

“…Wakano et al [13] have also established that ZnO:Ni films exhibit n-type conduction up to 25% of Ni content . It was discussed earlier [20,30] that the Ni-d states appearing near the E F (Fermi energy) may split into e g and t 2g states under the influence of tetrahedral crystal field of ZnO. The t 2g states on hybridization with p-orbitals of the valence band further split into bonding and anti-bonding states.…”

“…6a) clearly indicate only different planes of ZnO. The films grown under similar conditions [20] have been studied by X-ray photoelectron spectroscopy (XPS), which reveals a satellite structure in Ni 2p core level spectrum, indicating O (2p)-Ni (3d) charge transfer transition or hybridization [27,28]. Therefore, Ni may be incorporated in the ZnO matrix as interstitial or substitutional impurities.…”

Photoluminescence and optical properties of nanostructure Ni doped ZnO thin films prepared by sol–gel spin coating technique

“…Furthermore Ni 2+ (0.69Å) has the same valence compared to Zn 2+ and its radius is close to Zn 2+ (0.74Å), so it is possible for Ni 2+ to replace Zn 2+ in ZnO lattice. Some researches on Ni doped ZnO have been reported and several results showed that the luminescence properties of ZnO were changed after doping of Ni [30][31][32][33]. By doping Ni into ZnO, a composite material with magnetic and optical properties could be obtained.…”

Investigation of structural, morphological and optical properties of nickel zinc oxide films prepared by sol–gel method

“…They can be used in optoelectronic devices and it is useful material for the optoelectronic devices as transparent conducting oxide (TCO) [1]. Also, recently there is growing interest in nickel oxide (NiO), which is a metal oxide material, because of its applications in many areas.…”