Structural, electrical and optical properties of copper-doped zinc oxide films deposited by spray pyrolysis

Abstract

The effect of copper doping on structural, electrical, and optical properties of zinc oxide films was evaluated. Copper-doped films (ZnO:Cu) were successfully deposited on a glass substrate by spray pyrolysis at doping levels of 0, 2.5, and 7.5 at% (ZnO, ZC2.5, ZC7.5). All films were polycrystalline, single-phase with ZnO hexagonal wurtzite structure. The films presented nanostructured crystallites, from 36.7 to 38.2 nm. Cu doping increased the electrical conductivity of the ZnO films; this change was proportional to the Cu concentration. The films presented high optical transmittance of 70-80% in the visible wavelength. The energy gap decreased upon Cu doping. The photoluminescence spectrum of all films displayed an intense ultraviolet emission and a weaker blue emission. The emissions shifted to lower wavelengths with increasing dopant concentrations. ZC7.5 presented the most promising properties for an application as transparent conducting oxide: intense optical transmittance and UV photoluminescence, also the lowest electrical resistivity.

Sol–Gel-Derived Cu-Doped ZnO Thin Films for Optoelectronic Applications

“…For a transparent conducting oxide material, high transmittance is an important property that can reveal the morphological homogeneity and crystalline quality of the deposited films for the optical applications. 28 The optical transmittance in Cu-doped ZnO thin films is smaller than pristine ZnO, which may be due to the increase of absorbing and scattering centers with the incorporation of Cu 2+ ions. The Cu 3d orbital is much shallower than the Zn 3d orbital, and when a Cu atom occupies a Zn site inside the ZnO lattice, it introduces two strong effects: first, the strong d–p interaction between Cu and O moves O 2p up, which narrows the direct fundamental energy gap, and second, the Cu 3d orbital creates impurity bands above the ZnO valance band.…”

“…All deposited films exhibit intense optical transmittance within the visible spectrum. For a transparent conducting oxide material, high transmittance is an important property that can reveal the morphological homogeneity and crystalline quality of the deposited films for the optical applications . The optical transmittance in Cu-doped ZnO thin films is smaller than pristine ZnO, which may be due to the increase of absorbing and scattering centers with the incorporation of Cu 2+ ions.…”

The effect of small addition of copper on the growth process, structure, surface charge and adsorption properties of ZnO films in the pyrolysis of dithiocarbamates

“…6-7 at%, it is energetically favorable for excess atoms to combine into copper clusters (interstitial segregation) or Cu/Zn clusters and increase the number of defects. [131][132][133][134] In the case of the formation of a solid solution of copper and zinc oxides, significant lattice deformations of zinc oxide are observed when copper is placed in the zinc matrix. 135 (2) The active phase of most copper-zinc materials is the centers of copper, in one form or another, located on the surface of zinc oxide/sulfide(s).…”

Photodegradation of Ciprofloxacin-Zinc Complexes Produced at the Interface of ZnO and Cu-Doped ZnO Crystals

“…In addition, there are other contributions that correspond to a mixed oxidation state of elemental Cu, which has already been observed in similar structures 43,45,46 . The divalent state of Cu was also supported by the XRD pattern, in which the peaks changed to higher angles owing to the smaller interplanar spacing 47 . The profile for O 1s was broad and asymmetrical, as shown in Figure 3C, which indicates the presence of multi-component oxygen species on the surface region, similar to the result exhibited by pure ZnO.…”