Nanocrystalline Zn1-x CoxO（where x varies from 0 to 0.04 in steps of 0.01） thin films were deposited onto glass substrate by the spray pyrolysis technique at a substrate temperature of 350 ℃. The X-ray diffraction ...Nanocrystalline Zn1-x CoxO（where x varies from 0 to 0.04 in steps of 0.01） thin films were deposited onto glass substrate by the spray pyrolysis technique at a substrate temperature of 350 ℃. The X-ray diffraction patterns confirm the formation of hexagonal wurtzite structure. The crystal grain size of these films was found to be in the range of 11–36 nm. The scanning electron micrographs show a highly crystalline nanostructure with different morphologies including rope-like morphology for undoped ZnO and nanowalls and semispherical morphology for Co-doped Zn O. The transmittance increases with increasing Co^2＋ doping. The optical absorption edge is observed in the transmittance spectra from 530 to 692 nm, which is due to the Co2C absorption bands corresponding to intraionic d–d^＊ shifts. The direct and indirect optical band gap energies decrease from 3.05 to 2.75 eV and 3.18 to 3.00 eV, respectively for 4 mol% Co doping. The electrical conductivity increases with increasing both the Co doping and temperature, indicating the semiconducting nature of these films. The temperature dependence thermal electromotive force measurement indicates that both undoped and Co-doped ZnO thin films show p-type semiconducting behavior near room temperature. This behavior dies out beyond 313 K and they become n-type semiconductors.展开更多
A series of ZnO-CdO thin films of different molar ratios of Zn and Cd have been deposited on glass sub- strate at substrate temperature -360℃ by the spray pyrolysis technique at an ambient atmosphere. X-ray diffracti...A series of ZnO-CdO thin films of different molar ratios of Zn and Cd have been deposited on glass sub- strate at substrate temperature -360℃ by the spray pyrolysis technique at an ambient atmosphere. X-ray diffraction （XRD） studies confirmed the polycrystalline nature of the film and modulated crystal structures ofwurtzite （ZnO） and cubic （CdO） are formed. The evaluated lattice parameters, and crystallite size are consistent with literature. Dislocation density and strain increased in the film as the grain sizes of ZnO and CdO are decreased. The band gap energy varies from 3.20 to 2.21 eV depending on the Zn/Cd ratios in the film. An incident photon intensity dependent I-V study confirmed that the films are highly photosensitive. Current increased with the increase of the intensity of the light beam. The optical conductivity and the optical constants, such as extinction coefficient, refractive index and complex dielectric constants are evaluated from transmittance and reflectance spectra of the films and these parameters are found to be sensitive to photon energy and displayed intermediate optical properties between ZnO and CdO, making it preferable for applications as the buffer and window layers in solar cells.展开更多
文摘Nanocrystalline Zn1-x CoxO（where x varies from 0 to 0.04 in steps of 0.01） thin films were deposited onto glass substrate by the spray pyrolysis technique at a substrate temperature of 350 ℃. The X-ray diffraction patterns confirm the formation of hexagonal wurtzite structure. The crystal grain size of these films was found to be in the range of 11–36 nm. The scanning electron micrographs show a highly crystalline nanostructure with different morphologies including rope-like morphology for undoped ZnO and nanowalls and semispherical morphology for Co-doped Zn O. The transmittance increases with increasing Co^2＋ doping. The optical absorption edge is observed in the transmittance spectra from 530 to 692 nm, which is due to the Co2C absorption bands corresponding to intraionic d–d^＊ shifts. The direct and indirect optical band gap energies decrease from 3.05 to 2.75 eV and 3.18 to 3.00 eV, respectively for 4 mol% Co doping. The electrical conductivity increases with increasing both the Co doping and temperature, indicating the semiconducting nature of these films. The temperature dependence thermal electromotive force measurement indicates that both undoped and Co-doped ZnO thin films show p-type semiconducting behavior near room temperature. This behavior dies out beyond 313 K and they become n-type semiconductors.
基金the Ministry of Science and Information & Communication Technology(MOSICT) of the People's Republic of Bangladesh for providing financial support
文摘A series of ZnO-CdO thin films of different molar ratios of Zn and Cd have been deposited on glass sub- strate at substrate temperature -360℃ by the spray pyrolysis technique at an ambient atmosphere. X-ray diffraction （XRD） studies confirmed the polycrystalline nature of the film and modulated crystal structures ofwurtzite （ZnO） and cubic （CdO） are formed. The evaluated lattice parameters, and crystallite size are consistent with literature. Dislocation density and strain increased in the film as the grain sizes of ZnO and CdO are decreased. The band gap energy varies from 3.20 to 2.21 eV depending on the Zn/Cd ratios in the film. An incident photon intensity dependent I-V study confirmed that the films are highly photosensitive. Current increased with the increase of the intensity of the light beam. The optical conductivity and the optical constants, such as extinction coefficient, refractive index and complex dielectric constants are evaluated from transmittance and reflectance spectra of the films and these parameters are found to be sensitive to photon energy and displayed intermediate optical properties between ZnO and CdO, making it preferable for applications as the buffer and window layers in solar cells.
