Papers by Keyword: Transparent Conductive Oxide

Abstract: Transparent conductive oxides are materials combining great transparency with high conductivity. In photovoltaic applications, they are developed under thin layer for the realization of upper electrodes of solar cells. Among transparent oxide materials, Zinc Oxide (ZnO) presents unique properties, starting with its first qualities to be abundant, low-cost and non-toxic oxide. Zinc Oxide thin film was deposited on rectangular glass substrate by magnetron sputtering. After an overview of the properties expected for good transparent conductive materials, the effect of distance from the center of the cell on the morphology of the film was investigated by Atomic Force Microscopy (AFM). The scanning was done on different area of the sample as function of the distance from the central position of the direct sputtering jet. As far as the distance increased, it has been noticed a quasi-linear increase in thickness of the ZnO deposited film and a change in the grain shape from spherical to pyramidal with an increase in the size of the particles. Controlling the sputtering distance allows the control of texture, thus of the Haze factor, the photo-generation of excitons, as well the optical transmission of the TCO layer and finally an improvement in the efficiency of the so-built photovoltaic cells.

Abstract: We have prepared nondoped and Cu-doped NiO thin films by sol-gel method on SiO2 substrate using nickel acetate and copper acetate as precursors. Thin films of NiO were formed by thermal annealing of gel films at 500 - 900°C for 10 h in air. X-ray diffraction (XRD) peaks of NiO have been observed at higher annealing temperature than 500°C, and intensity of the peaks increased with annealing temperature until 800°C. On the other hand, the dependency of XRD signal intensity on annealing temperature becomes less significant by Cu-doping. Nondoped NiO films show high transparency at lower annealing temperatures than 800°C. The result means that the film with high crystalline volume ratio is not consistent with the films with high transparency. Cu-doping decreases the transmittance of the films with low crystalline volume ratio. It is considered that the doped Cu atoms exist in amorphous fraction make the transmittance lower. Conductivity of the films is increased with Cu-doping only in the films annealed at 500 - 700°C. The highest conductivity obtained in the Cu-doped film is around 10-6 W-1cm-1 at 600°C. On the other hand, the Cu-doped films show similar conductivity to nondoped films at high annealing temperature, 800 or 900°C.

Abstract: In this study, AZO films were deposited by RF sputtering technique. Then, the state of residual stress in the AZO films was investigated by using spectroscopic ellipsometry (SE) and XRD methods. Our experiments show that a suitable SE model could provide useful indication about the variation of stress in the as-deposited films. However, there is a disparity in the results of the SE fitting and XRD stress analysis for annealed AZO films. Further investigation is required in order to understand the cause of this contradiction. Despite this disparity, the SE technique enables us to monitor strain relaxation in TCO films with a faster and simpler way compared with other methods.

Abstract: Zn (O,S):Al (AZOS) has been proposed as a new type of transparent conductive oxide (TCO) with adjustable band gap energy (E_g) and conduction band position. The novel materials of AZOS with S/(S+O) ratio of 0.00~0.85 were prepared by radio frequency magnetron co-sputtering of ZnO:Al and ZnS targets. The optical properties of the films showed high transmittance of almost over 80% and E_g change with the S/(S+O) ratio. The suitable resistivity for TCO of around 10^-3 Ωcm was obtained at the S/(S+O) ratio of 0.00~0.09, but as the S/(S+O) ratio exceeded 0.40, the resistance increased greatly.

Abstract: Zr,Ga co-doped ZnO transparent conductive films were deposited on glass substrates by DC magnetron sputtering at room temperature.The influence of sputtering pressure on the structural,electrical,and optical properties of Zr,Ga co-doped ZnO films was investigated by X-ray diffraction,scanning electron microscopy (SEM),digital four-point probe,and optical transmission spectroscopy.The lowest resistivity of the Zr,Ga co-doped ZnO film is 3.01×10^-4Ω﹒cm.All the films present a high transmittance of above 91% in the visible range.These results make the possibility for liquid crystal display (LCD) and UV photoconductive detectors.

Abstract: Thin film coatings of fluorine doped tin oxide on glass were first produced in the 1940’s as part of the World War II effort. Generically known as TCO (Transparent Conductive Oxide) Coatings, the primary use was for antifogging coatings for aircraft transparencies using an electrical current to heat the glass assembly. Nearly 60 years later, these coatings are still used in cockpit glazings. Although the first generation coatings were applied using spray pyrolysis on heated glass panes, by 1990 these coatings were being applied directly on the float glass ribbon during the primary glass manufacturing operation, using Atmospheric Pressure Chemical Vapor Deposition (APCVD). As part of a color suppressed multi-layer structure, these coatings met the aesthetic and performance criteria for architectural low E glazings, and spawned new applications in electrochromic devices, heated freezer doors, radiant glass heaters, EMI/RFI Shielding, and the largest growing segment in glass – thin film photovoltaic panels. In this paper we discuss the characteristics of the on-line production, the performance characteristics of the coatings, the end use requirements, and the massive infrastructure in place worldwide to support the volume requirements. We compare the properties of SnO2:F to other emerging TCO materials such as zinc oxide.

Abstract: Indium Tin Oxide (ITO) films were deposited on non-alkali glass substrate by magnetron sputtering using commercial ITO target (target A) and improved ITO target (target B). Depositions were carried out at total gas pressure (Ptot) of 0.5 Pa, substrate temperature (Ts) of RT ~ 300 °C, oxygen flow ratio [O2/(O2+Ar)] of 0 ~ 1.0% and dc power of 100W. Target B showed relatively higher stability in film resistivity with increasing sputtering time, i.e., erosion ratio of target surface. Optimum oxygen ratio to obtain the lowest resistivity was decreased with increasing substrate temperature. The lowest resistivity was 1.06x10-4 6cm for the film deposited using target B at O2/(O2+Ar) ratio of 0.05% and at Ts =300 °C.

Abstract: Multi-component ZnO-In2O3-SnO2 thin films have been prepared by RF magnetron co-sputtering using targets composed of In4Sn3O12(99.99%) [1] and ZnO(99.99%) at room temperature. In4Sn3O12 contains less In than commercial ITO, so that it lowers cost. Working pressure was held at 3 mtorr flowing Ar gas 20 sccm and sputtering time was 30 min. RF power ratio [RF1 / ( RF1 + RF2 )] of two guns in sputtering system was varied from 0 to 1. Each RF power was varied 0~100W respectively. The thicknesses of the films were 350~650nm. The composition concentrations of the each film were measured with EPMA and AES. The low resistivity of 1-2 × 10-3 and an average transmittance above 80% in the visible range were attained for the films over a range of δ (0.3 ≤ δ ≤ 0.5). The films also showed a high chemical stability with time and a good uniformity.

Abstract: In this paper we report some of the recent advances in transparent thin film oxide semiconductors, specifically zinc oxide (ZnO), produced by rf magnetron sputtering at room temperature with multifunctional properties. By controlling the deposition parameters it is possible to produce undoped material with electronic semiconductor properties or by doping it to get either n-type or p-type semiconductor behavior. In this work we refer our experience in producing n-type doping ZnO as transparent electrode to be used in optoelectronic applications such as solar cells and position sensitive detectors while the undoped ZnO can be used as UV photodetector or ozone gas sensor or even as active layer of fully transparent thin film transistors.