| Metal oxides ZnO and In2O3 materials with wide bandgap have prospective application in photonics, optoelectronics, spintronics, information storage, solar cell and so on. Electronic structure modified by doping hetergenous metals has been known as the most effective method to improve diverse properties, such as photonics, optoelectronics and electronics. Metal oxide films have been widely used. Most of films were prepared by sputtering ceramic target, so preparation of high quality target is one of bottlenecks to promote application. In this thesis, the crystal and electronic structures, photonics, optoelectronics and magnetic properties of ZnO and In2O3 based materials doped with different kinds and different concentration of the hetergenous metal oxides were studied by first-principles calculations based on the density functional theory (DFT). Some targets of ZnO:Al, ZnO:Co, ZnO:Mn and ITO were prepared by powder metallurgy, and the thin films were obtained by using radio frequency (RF) based on the present target. Properties and microstructure of target and film samples were analysised by using XRD, ESEM and Hall Effect measurement system.The results show that, the Fermi level (EF) of ZnO increases with the increase of Al content, where Al atoms replace the Zn atoms, and EF goes through the conduction band, which reinforces the conductivity of ZnO materials. For doping system Zn1-xCoxO and Zn1-xMnxO, Zn32-nMnO32 configurations were simulated particularly based on available computing simulation source condition. Besides, the most stability of configuration was studied when Mn atoms replace the different position of Zn atoms. A larger supercell is expected to confirm magnetic atoms cluster theoretically if calculation resource permits. The total energy of system is low when spin polarized calculations are performed, and antiferromagnetic structure is favorable in Zn1-xMxO system. For antiferromagnetic system Zn1-xMxO, Co or Mn atoms tend to be parallel in (0001) plane based on current simulation. Magnetic ording behaviour calculations show that magnetic moment of stable system tends to zero, magnetic moment of Co and Mn atoms are 2.430μB and 4.217μB, respectively. The calculated transition pressure from cubic to hexagonal structure of In2O3 within GGA and LDA are 14.9GPa and 10.4GPa, respectively. The result from GGA locates in the experimental data range reported in available literatures, i.e.,15-25GPa. The bandstructures both within LDA and GGA indicate that the second band gap (Eg2) of H-In.203 (high pressure phase) is larger than that of C-In2O3, which implies that the light transmittance and electrical conductivity of H-In2O3 are better than that of C-In2O3. For the transition metals M (where M=Fe, Sn) doping system In15MO24 with cubic phase, the bandgaps of C-In2O3 are both reduced when Fe or Sn element doping, and the bottom of conduction band is composed of Fe 3d or Sn 4d orbital.The relative density up to 95% and intact grain of target ZnO.Co and ZnO:Mn were prepared by sintering at ambient without cold isostatic pressing. The XRD patterns show that Co and Mn atoms replace Zn atoms in ZnO, and the results were verified with binary phase diagram simultaneously. Optimum molding pressure of target ZAO, ZnO:Co and ZnO:Mn are 16MPa, 12MPa and 12MPa, respectively, and optimum sintering temperature is both 1350℃ for one hour. The ZAO thin films were deposited on glass sheet by using radio frequency (RF) magnetron sputtering based on the present ZAO target. After heat treatment, homogeneous microstructure of ZAO thin films and fine grain were obtained. The optical transmission is 88.6% in the visible light spectrum, and the minimum resistivity of the thin film is 2.1 X 10’3Ω·cm. |
PDF Full Text Request