Impact of Copper Doping on the Structural, Electrical and Optical Properties of Auto-Combustion Synthesized ZnO Nanocomposites

Abstract

Nanocomposites of ZnO have been synthesized by auto-combustion technique to study their electrical (dielectric and direct current), optical, and structural properties by increasing copper content in these composites. Techniques used for characterizing these composite nanoparticles involve X-ray diffraction, scanning electron microscopy, UV-vis spectrophotometry, and photoluminescence spectroscopy. X-ray diffraction patterns suggested hexagonal wurtzite structure of ZnO, which remains unchanged upon increasing the amount of Cu dopant. However, there is a noticeable decrease in the particle size with rising Cu content. Morphology of the crystallites, as observed by scanning electron microscopy, is nearly spherical. Dielectric parameters, including dielectric constant and dielectric loss, decrease, whilst AC conductivity increases with the increase of Cu content as well as with the rise of frequency of the applied alternating biasing field. In addition, DC electrical conductivity is also improved by the enhancement of Cu doping percentage and temperature. These variations of electrical parameters of nanocomposites allow their potential utilization in those devices which are operated at high frequencies. Band gap energy Eg, analyzed by UV-vis spectrophotometer, is noticed to decrease upon rising Cu content from 3.39 eV to 2.46 eV, and depicts a red shift from UV to visible light region. PL emission intensity decreased in the studied light spectrum by increasing Cu content implying that the recombination rate of photo-induced charge carriers decreases effectively. Thus, upon Cu doping reduction in Eg occurs, which along with the reduced recombination rates of photogenerated electrons and holes pairs, becomes a cause of the participation of more and more charge carriers in the photocatalysis process in order to degrade the organic compounds.

Gradient doping of Cu(I) and Cu(II) in ZnO nanorod photoanode by electrochemical deposition for enhanced photocurrent generation

“…5c). The decrease in Eg has also been observed by other authors when doping ZnO with Cu [29,41], and is explained by the exchange interactions at the p-d orbitals (3d Zn and 2p O to 3d Cu and 2p O) during the introduction of copper ions in the ZnO lattice [46,50,51]. Additionally, the significant difference in electronegativity between Zn (1.65) and Cu (1.95) atoms may also be a reason for the reduction of the band-gap [52].…”

“…However, for C1ZnO, the peak position of (002) plane moves toward lower angles values when the Cu + concentration is increased (Fig 1b). In general, researches [29,41]. We believe that the oxidation state (+1 or +2) of the Cu ions in the ZnO lattice is responsible for the discrepancy in the above findings.…”

“…The intensity of C1ZnO and C2ZnO peaks decreases with increasing Cu concentration and this decrease is greater for C2ZnO than for C1ZnO. This can be explained by the ionic radius of Cu 2+ (71 p.m), which is slightly smaller than that of Cu + (73 p.m) and close to that of Zn 2+ (74 p.m) [40,41]. The substitution of Zn 2+ in the ZnO lattice with Cu 2+ ions creates shorter bonds than in the presence of Cu + ions, which can degrade the quality of the crystal.…”

Highly efficient visible light active Cu–ZnO/S-g-C3N4 nanocomposites for efficient photocatalytic degradation of organic pollutants

“…4b). 38 In addition, a general broadening in the 4-CZN and SGN peaks and the shi towards the lower angle particular at (002) was noticeable mainly due to Cu doping. 39…”

Ab initio расчеты электронных свойств и перенос заряда в Zn-=SUB=-1-x-=/SUB=-Cu-=SUB=-x-=/SUB=-O со структурой вюртцита

“…На свойства нанопорошков ZnO, легированных медью, влияют эффекты отжига, температура и концентрация легирующей примеси Cu [9] Степень растворимости акцепторных примесей, например (Na, Li и N), ограничивает концентрацию дырок в аналогичных с ZnO соединениях ZnSe и ZnTe [11]. Поэтому изучение закономерностей влияния меди на электронную структуру [12], диэлектрические [13], оптические [14,15], магнитные [16][17][18] и другие физические свойства [19] материалов на основе ZnО n-и p-типа также остается проблемой. В связи с возможностью создания миниатюрных приборов, внимание уделяется также легированным нанокристаллическим порошкам и тонким пленкам ZnO [20].…”