Abstract
The band structure, the density of states and optical absorption properties of Cu-doped ZnO were studied by the first-principles generalized gradient approximation plane-wave pseudopotential method based on density functional theory. For the Zn1-xCuxO (x = 0, x = 0.0278, x = 0.0417) original structure, geometric optimization and energy calculations were performed and compared with experimental results. With increasing Cu concentration, the band gap of the Zn1-xCuxO decreased due to the shift of the conduction band. Since the impurity level was introduced after Cu doping, the conduction band was moved downwards. Additionally, it was shown that the insertion of a Cu atom leads to a red shift of the optical absorption edge, which was consistent with the experimental results.
Highlights
ZnO is a direct band gap n-type semiconductor with an exciton binding energy of 60 meV and a band gap of 3.37 eV at room temperature [1,2,3]
Due to the fine crystal grains, nano-ZnO changes its crystal structure and surface electronic structure, resulting in surface, volume, macroscopic tunneling and quantum size effects, as well as high dispersion and high transparency, which are not found in macroscopic ZnO particles
Ordinary ZnO has found many uses and special functions in optics, magnetism, and mechanics, and there is potential for a wide use as photocatalyst in solar energy applications, battery, UV laser, and lithium ion battery materials
Summary
ZnO is a direct band gap n-type semiconductor with an exciton binding energy of 60 meV and a band gap of 3.37 eV at room temperature [1,2,3]. Ordinary ZnO has found many uses and special functions in optics, magnetism, and mechanics, and there is potential for a wide use as photocatalyst in solar energy applications, battery, UV laser, and lithium ion battery materials. ZnO is extremely important for the control of its inherent defects which control its properties. Studies of Chakraborty et al [10] have shown that 5%–10% Cu-doped ZnO has a lower band gap value than undoped ZnO. Copper doping reduces the recombination of electrons and holes, and the band gap value decreases from 3.21 eV (zinc oxide) to 3.07 eV. Increase in Cu doping leads to an insignificant decrease in the optical band gap of the thin films.
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