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ZnO:Al films were prepared by magnetron sputtering at room temperature. During the growth process, H radicals produced by radio frequency power sources were in situ introduced into ZnO:Al films. By injecting H radicals, the content of Al in ZnO:Al films increased from 3.4 at. % to 6.1 at. %, which could be ascribed to the reaction between H radicals and ZnO as well as the resputtering of the Zn element. Surface morphologies of ZnO:Al films were tuned from smooth shape to sunflower seed-like. Furthermore, ZnO:Al films without injecting H radicals showed highly c-axis preferential orientation and then nearly became amorphous with the addition of H radicals, which corresponds to the results of Raman spectra. The grain boundary potentials decreased due to the removal of oxygen at grain boundaries and an amount of Vo was produced, which was proved by Raman and x-ray photoelectron spectroscopy results. The optimal resistivity of as-grown ZnO:Al films co-doped with H radicals was 1.5 × 10−3 Ω cm at an H2 ratio of 2.3%. The variation of the carrier concentration for annealed ZnO:Al films at different H2 ratios supported the existence of H interstitials and Vo. The optical bandgap varied from 3.44 eV to 3.71 eV with increasing H radicals. [ABSTRACT FROM AUTHOR]

In this paper, the defects of Al doped ZnO films generated by magnetron sputtering in the deposition processes are comprehensively investigated. It is found that oxygen ion bombardment deteriorates the crystallinity and generates oxygen related defects, such as oxygen interstitials (O i ), chemisorbed oxygen at the grain boundaries (O GB ), and oxygen vacancies (V O ). O i and O GB decrease the carrier concentration and mobility of the pristine films remarkably, but they can be removed by hydrogen annealing. However, the grain boundary scattering originated from poor crystallinity cannot be reduced by the annealing below 450 °C. Moreover, the in-situ temperature-dependent resistivity measurement under hydrogen atmosphere suggests that hydrogen atoms are incorporated into the ZnO: Al films and interact with V O . We propose that there are two energetically favorable states for the incorporated hydrogen. The defect configurations of (H 2 ) i and H O + H i are assigned to the high resistivity state (HRS) and low resistivity state (LRS) respectively and the switching between these two states is activated by V O and mediated by a metastable state (H 2 ) * O . The transformation between these two resistivity states leads to a hysteresis loop during the heating and cooling process. [ABSTRACT FROM AUTHOR]

We report a correlation between surface null potential and bistable resistive switching effect in dilutely Al-doped ZnO nearly transparent thin film. The nearly symmetrical bistable resistive switching was observed at low operating potential (±1 V) with good repeatability and stability, driven by surface null potential. We report that above null potential, oxygen vacancies in the proximity of aluminum provide systematic development of conducting paths. While, the switching effect was also observed to be dopant driven in the proximity to ±1 V. The phenomenon was explained using migration of Al3+ in ZnO matrix, which dominates over oxygen vacancies. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, ZnO:Al transparent conducting films were prepared on glass substrate by magnetron sputtering from Al doped ZnO ceramic targets. By measuring and analyzing the structure and electrical properties of films in front of targets at different target-to-substrate distance, it was concluded that the bombardment of energetic oxygen negative ions decreased with increasing target-to-substrate distance, dominating variation of resistivity and the microstructure in erosion area, while numbers of active oxygen decrease with increasing target-to-substrate distance, explaining variation of resistivity in non-erosion area. The influence of target-to-substrate distance on electrical and microstructure properties of ZnO:Al films on drum was also investigated in order to confirming our result. The result indicated that both energetic oxygen negative ions and numbers of active oxygen determined the properties of films on drum. While target-to-substrate distance is less than 95mm, the numbers of energetic oxygen ions are the key factor and vice versa. The optimum resistivity of post-annealed films on drum was 5.1×10−4 Ωcm at target-to-substrate distance of 95mm. [Copyright &y& Elsevier]

Highly transparent indium-free multilayers of TiO2/Cu/TiO2 were obtained by means of annealing. The effects of Cu thickness and annealing temperature on the electrical and optical properties were investigated. The critical thickness of Cu mid-layer with optimal electrical and optical properties was 10 nm, with the figure of merit reaching as high as 5 × 10−3 Ω−1. Partial crystallization of the TiO2 layer enhanced the electrical and optical properties upon annealing. Electrothermal experiments showed that temperatures of more than 100 °C can be reached at a heating rate of 2 °C/s without any damage to the multilayers. The experimental results indicate that reliable transparent TiO2/Cu/TiO2 multilayers can be used for electrothermal application. [ABSTRACT FROM AUTHOR]

Abstract Three types of primer layers, including polyurethane (PU), acrylic, and silicone coatings, were developed and deposited on the poly(methylmethacrylate) (PMMA) substrates. Amorphous transparent indium zinc oxide (IZO) films deposited by direct current magnetron sputtering at room temperature on primer-treated and untreated PMMA substrates were investigated ex situ in terms of surface morphology, adhesion, nanoindentation and electrical properties. AFM images show that the microstructure of IZO films was determined by the morphology of the primer layers. IZO films deposited on silicone and acrylic-treated PMMA substrates presented the least surface roughness, which proved that the silicone and acrylic primer layers were more effective to get a dense surface. Nano-scratch tests indicated that the adhesion of IZO films deposited on substrate treated by silicone-based primer layers was superior to that on PU-treated and untreated substrate, which can be attributed to the better mechanical matches of the IZO/primer/PMMA system and the large values of hardness of the silicone primer, which can counterbalance the indentation load and prevent the failure of the films. Highlights • Mechanical properties of IZO films on PMMA substrates pretreated by three kinds of organic primers were studied. • The adhesion properties of coatings on silicone-treated PMMA was superior to that on PU-treated and untreated substrate. • Nanoindentation technique was used to qualitatively assess the nanomechanical changes of coatings and IZO films. [ABSTRACT FROM AUTHOR]

Zinc-doped indium oxide (IZO) film, as an important transparent conductive oxide, has attracted increasing attention in various scientific and engineering areas. In the present work, discharge-voltage and reactive-oxygen controlled IZO films were grown by magnetron sputtering and studied systematically. The microstructure, element distribution and chemical bonding of IZO films were investigated by X-Ray diffraction (XRD), transmission electron microscope (TEM), Energy Dispersive X-Ray Spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The optical and electrical properties of IZO films were studied by controlled oxygen and discharge voltage. The typical microstructure of IZO films with optimal optical and electric properties has been characterized. High discharge voltage and matched oxygen vacancies could promote the low resistivity of IZO films, which could be determined by the electronic concentration and mobility. • IZO films were grown at room temperature by two strategies of oxygen and discharge voltage. •Oxygen supply promotes the decreases of oxygen vacancies and Zn content. •More oxygen promotes IZO film with higher transparency and larger bandgap. •Both high discharge voltage and matched oxygen content bring IZO film the superior carrier concentration and mobility. [ABSTRACT FROM AUTHOR]