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Representative transparent conductive oxide films, such as tin-doped indium oxide (ITO) and indium–zinc oxide (IZO) films, were deposited by dc magnetron sputtering using corresponding oxide targets under various total gas pressures (Ptot) ranging from 0.3 to 3.0 Pa. The ITO films deposited at a Ptot lower than 0.7 Pa were polycrystalline and were found to have a large compressive stress of about 1.5 ×109 Pa, whereas the ITO films deposited at 1.5–3.0 Pa were amorphous and had a low tensile stress. In contrast, all the IZO films deposited at a Ptot range of 0.3–3.0 Pa showed an entirely amorphous structure, where the compressive stress in the IZO films deposited at a Ptot lower than 1.5 Pa was lower than that in the ITO films. Such compressive stress was considered to be generated by the atomic peening effect of high-energy neutrals (Ar0) recoiled from the target or high-energy negative ions (O-) accelerated in the cathode sheath toward the film surface.

Amorphous indium–gallium–zinc oxide (a-IGZO) films were deposited by DC magnetron sputtering and post-annealed in air at 300–1000 °C for 1 h to investigate the crystallization behavior in detail. X-ray diffraction, electron beam diffraction, and high-resolution electron microscopy revealed that the IGZO films showed an amorphous structure after post-annealing at 300 °C. At 600 °C, the films started to crystallize from the surface with c-axis preferred orientation. At 700–1000 °C, the films totally crystallized into polycrystalline structures, wherein the grains showed c-axis preferred orientation close to the surface and random orientation inside the films. The current–gate voltage (I d–V g) characteristics of the IGZO thin-film transistor (TFT) showed that the threshold voltage (V th) and subthreshold swing decreased markedly after the post-annealing at 300 °C. The TFT using the totally crystallized films also showed the decrease in V th, whereas the field-effect mobility decreased considerably.

We report that temperature dependence of Hall mobility of the strongly disordered films In2O3-ZnO. We made targets by mixing ZnO into In2O3 at the ratio 0.5 ~ 2 wt%. Sputtering those targets on glass substrate by DC magnetron method, amorphous films with 25 nm thickness were obtained. By annealing at T = 150 ~ 350 OC in the air, oxygen defect decreased and the conductance decreased. We obtained films with conductivity 0.2mS/m ~ 300S/m. In the temperature range T = 90~300K, we measured the Hall effect of these films. The density of electron was 4 × 1018 ~ 1.2 × 1022 m−3 at the room temperature. The Hall mobility μH shows the thermal-activation-like temperature dependence μH = AT−1/2 exp(EB/kBT), where EB is activation energy. By fitting, we obtained EB = 60 ~ 86 meV.

We investigated the magneto-conductivity Δ in three dimensional indium zinc oxide films with different resistivity ρ prepared by postannealing in air. The weak localization theory was fitted to data of Δ H) at temperatures below 50K by the use of suitable inelastic scattering time τi(T) and spin-orbit(S-O) scattering time τi. We found the ρ dependences of both times τ and τi in a range 1.5 × 10−3Ω < ρ 300K)

We study the effect of annealing in high vacuum on the transport properties for In2O3-ZnO films. We prepared indium zinc oxide films by the DC-magnetron sputtering method using an In2O3-ZnO target (89.3 wt % In2O3 and 10.7 wt % ZnO). The annealing temperature is from 373 to 773K. From the XRD analysis, we find that all as deposited films are amorphous. In addition we find that amorphous films are crystallized by annealing at a temperature above 773 K over 2 hours. The temperature dependence of resistivity ρ of all amorphous films shows metallic behaviour. On the other hand, ρ(T) of poly In2O3-ZnO films shows semi-conducting behaviour. We carry out a detailed analysis of the temperature dependence of Hall mobility. The activation energy Ed has been obtained from the slope of the carrier concentration Ne vs. the inverse temperature plot at high temperatures. We found that the Ed takes values between 0.43 and 0.19 meV. Meanwhile, temperature dependence of Ne for poly-In2O3-ZnO films did not show activation-like behaviour. This behaviour is thought to be causally related to impurity conduction band.

Oxide thin-film transistors (TFTs) were fabricated using a polycrystalline In–Ga–O (IGO) thin film as the n-channel active layer by direct current magnetron sputtering. The 50-nm-thick IGO TFT showed a field-effect mobility of 39.1 cm2 V-1 s-1, a threshold voltage of 1.4 V, and a subthreshold gate voltage swing of 0.12 V/decade. The polycrystalline IGO thin film showed the cubic bixbyite structure of In2O3 without an obvious preferred orientation. The average grain size of polycrystalline IGO was approximately 10 µm. The high mobility of IGO TFT is related to the In2O3 crystalline phase and large grain size of the IGO film.

Thin In2O3-ZnO (IZO) films were prepared by DC-magnetron sputtering with changing the weight concentration x of ZnO, 0 ? x ? 0.07. As-grown amorphous IZO films show the metallic characteristic but do not show superconductivity. We have investigated the T and H dependence of the resistivity ? and Hall coefficient for annealed films with thickness d = 350 nm in air. It is found that the films with 0 ? x ? 0.03 show superconductivity. Transition temperature Tc and the carrier density n of these films are ? 2.0 K and 1025 -1026 m-3, respectively. The annealed In2O3-ZnO films were examined by a high resolution transparent electron microscopy. This investigation reveals that films annealed at 300 ?C are sufficient crystalline. There is a difference of crystal structures between the superconducting film and normal film. We studied the upper critical magnetic field HC2 (T) for the film with x = 0.005. From the slope of dHc2/dT, we obtain the coherent length ?(0) ? 100 A at T = 0 K and the coefficient of the electronic heat capacity ? ? 3.2 (J/m3K2) which is small compared with that of other oxide materials.