New Transparent Conducting Oxide Thin Films

Transparent conductive oxide films of both In₂O₃:Mo (IMO) and In₂O₃:W (IWO) were successfully fabricated by using DC reactive magnetron sputtering from metallic targets of In/Mo and In/W, respectively. The dependence of electrical, optical and structure properties of both IMO and IWO films on deposition parameters, such as oxygen partial pressure and substrate temperature, etc. was investigated in detail. A novel technique, channel spark ablation (CSA), was used to deposited IMO films as well. IMO films grown at room temperature are studied, too. The effect of W-Pt co-doped indium oxide surface layer on work function of IWO films was studied. The electronic structure of IWO and IMO was studied for the first time using first-principles calculation method based on density function theory (DFT). p-type SrCu₂O₂, CuAlO₂ and CuFeO₂ ceramics synthesized by solid state reaction were investigated. SrCu₂O₂, CuAlO₂ and CuFeO₂ films were prepared by CSA technique. The results show that:IMO films prepared by DC reactive magnetron sputtering and channel spark ablation are poly-crystalline bixbyite structure. The lowest electrical resistivity of IMO films deposited by sputtering method was 3.7×10^-4 ohm·cm and the best carrier mobility of IMO was about 50 cm²V^-1s^-1. The lowest electrical resistivity of IMO films deposited by using CSA technique was 4.8×10^-4 ohm·cm and the best mobility of IMO films was about 49.6 cm²V^-1s^-1. The average visible transmission of the IMO film was over 80%.High quality IWO films were firstly developed by using DC reactive magnetron sputtering. The lowest electrical resistivity of IWO films was 2.7×10^-4 ohm-cm and the best mobility in IWO films was about 57 cm²V^-1s^-1 The average visible transmission of the IWO films was over 80%. The optical band gap was more than 3.9 eV, and the reduced effective mass (m_VC) was obout 0.54 m_e. The carrier mobility in IWO films is higher than that in undoped In₂O₃ films.There were no other new compounds and change of crystal structure of In₂O₃ in IWO films. W substituted In site in lattic of In₂O₃ in IWO films. W exists in W⁶⁺ in IWO films deposited at lower sputtering current; however, W exists in W⁶⁺ and W⁴⁺ in IWO films grown at higher sputtering current. The preferential orientation of IWO films is (222) or (400), the relative intensity of (222) and (400) depend on sputtering parameters such as oxygen partial pressure, doping content, substrate temperature and sputtering pressure, etc.IMO films were also deposited from metallic targets by DC reactive magnetron sputtering at room temperature. However, the structure of IMO films is amorphous, and the surface of IMO films is smooth. The opto-electrical properties of IMO films grown at room temperature are sensitive to oxygen partial pressure. As-deposited IMO films show good electrical property and high optical transmission. The films are characteristic of the lowest resistivity of 5.9×10^-4 ohm·cm, high Hall mobility of 20.2 cm²V^-1s^-1, and the average optical transmission more than 80%.The work function of IWO film with a W-Pt co-doped modified layer (In₂O₃:Pt,W) reached the maximum value of 5.5 eV, increased 0.8 eV comparing with 4.7 eV of IWO films. The surface layer of In₂O₃:Pt,W haven't change the roughness of IWO films. The chemical state of Pt in In₂O₃:Pt,W layer is Pt²⁺ and Pt⁰. W-Pt co-doping method is a effective way of modified IWO work function. Average visible transmission of In₂O₃.Pt,W/IWO films is more than 80%, with direct optical band gap of 3.97eV.The calculated results show that the valence bands of indium oxide are composed mainly of O 2p states and the conduction bands consisted mainly of In 5s states. Doping has no effect on the top of valence band of In₂O₃, However, the bottom of conduction band is changed with Sn, W or Mo doping. The hybridization of In 5s states and Sn 5s states contributes to the bottom of conduction band of ITO. The bottom of conduction band of IWO and IMO is due to W 5d states and Mo 4d states, respectively. Further, the calculated state of density indicated that the content of doping W or Mo is much fewer than that of doping Sn in order to obtain the same carrier concentration by doping, thus, there are much fewer impurity scattering centers in IWO or IMO films than those in ITO films, which lead to the higher mobility in IMO films than that in ITO films. Therefore, W and Mo are potential doping elements which result in high mobility In₂O₃ films.SrCu₂O₂, CuAlO₂ and CuFeO₂ ceramics synthesized by solid state reaction exhibite p-type conductivity. The resistivity of SrCu₂O₂, CuAlO₂ and CuFeO₂ is 200 ohm·cm, 56 ohm·cm, 21 ohm·cm, respectively, p-type SrCu₂O₂, CuAlO₂ and CuFeO₂ films were prepared by using CSA technique, p-type CuAlO₂ films have good optical transmittance.