| Summary: | 碩士 === 亞洲大學 === 光電與通訊學系 === 107 === In this study, in order to improve the material properties of spinel ZnCo2O4 thin films, the electrical properties of semiconductors were enhanced by extrinsic doping. We studied the crystal structure, microstructure, photoelectric properties and antibacterial properties of doping effects on the ZnCo2O4.
The content ratio of Zn(Co1-xNix)2O4 doping increased from Nix=0 to 0.30, and nickel-doped ZnCo2O4 film maintained a single-phase spinel oxide, and no nickel-related secondary phase structure formed. The replacement of cobalt by nickel causes decreasing effect on the atomic lattice order, resulting in a decrease in the average grain size and a reduction in the roughness of the surface. Both grain size and surface roughness affect the transmittance of the film. The material has translucent optical properties. The transmittance of all films was about 22% ~ 38% at 550nm, and the characteristic peak of absorption was about 400nm. At a higher nickel doping content Nix=0.20 ~ 0.30, the absorption characteristic peak gradually disappears. The direct band gap of the un-doped ZnCo2O4 film was 2.50 eV, and the band gaps of the nickel-doped ZnCo2O4 were 2.45~2.57 eV. All films are p-type semiconductors, and positive divalent nickel can replace positive trivalent cobalt to increase the carrier concentration, resulting in a decrease in resistivity from 312.5 Ω-cm (Nix = 0) to 15.7 Ω-cm (Nix = 0.30). Escherichia coli and Staphylococcus aureus cannot breed and survive on the film, the antibacterial rate of the material can reach more than 99%, Ni-doped ZnCo2O4 has excellent application potential.
For Zn(Co1-xCax)2O4 films, the doping content ratios of Cax were from 0.00 to 0.20, no impurity phase formed in all spinel structure films. The surface had cell-like microstructure. Surface roughness values increased at higher calcium doping contents, and made the grain sizes decreasing. These translucent ZnCo2O4 films had light transmissions of 47% to 58% at wavelength of 600 nm. The absorption characteristics of blue and ultraviolet light of ZnCo2O4 were decreasing as increasing in calcium doping contentin the films. The band gaps of Zn(Co1-xCax)2O4 films increased from 2.46 eV (Cax= 0.00) to 2.51eV (Cax= 0.15), and Ca+2 replaces Co+3 to increase the conductivity and carrier concentration. The optimal doping ratio was Cax= 0.07. The resistivity decreased from 270.5 to 15.4 Ω-cm, and the carrier concentration increased from 2.54 × 1015 to 6.25 × 10 17 cm -3. The anti-S. aureus and E. coli abilities of the films had more than 99% in the UV light irradiation and in the absence of any light source. The p-type Zn(Co1-xCax)2O4 film can be applied to the antibacterial and electronic component.
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