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In this study, the effect of annealing atmosphere on the electrical properties, optical properties, microstructure and defects of ZnO∶Al films was investigated in detail. The crystallization, surface and fracture morphologies, electrical properties, resistivity, transmittance, Raman vibration and photoluminescence of ZnO∶Al films were characterized by SEM, XRD, Hall effect test instruments, ultraviolet-visible spectrophotometer, Raman spectra and PL spectra. The results show that after annealing in air atmosphere, the carrier concentration of AZO films decreases from 1.63 × 1020 cm−3 to 7.1 × 1018 cm−3, the optical band gap varies from 3.51 eV to 3.37 eV, the transmittance in NIR increased and the band edge emission in PL spectrum shifted from 3.49 eV to 3.34 eV. On the other hand, while the carrier concentration of AZO films annealing in H2 atmosphere was 5.3 × 1020 cm-3, the optical band gap increases to 3.78 eV, the transmittance in NIR decreases remarkably, the emission intensity of the band edge increases by more than 10 times and the band edge emission in PL spectrum shifts to 3.57 eV. Furthermore, the 4 order LO phonons are observed in ZnO:Al films annealed in air.

With the increasing wide application of organic or polymer substrates, amorphous transparent conducting oxides (a-TCOs) had been widely applied to thin-film transistors, polymer/organic solar cells, electrochromic devices, electromagnetic shielding and other areas due to the combined transparency and conductivity as well as stable properties, processing compatibilities with current technologies and free of post-annealing. A-TCOs films were not the amorphous counterpart of crystalline TCOs but prepared with special elements under certain conditions. After the brief introduction to the working principle of TCO, the even general amorphous transparent semiconducting oxide was addressed intensively. It was worth to note that compared with c-TCOs and classic silicon, the features of electronic structure of a-TCOs were the cations with special configuration (n-1)d10ns0. The stable amorphous structure and excellent properties can be conserved due to larger overlap integral between the adjacent atoms, high mobility and robustness. Particularly, the near range structure characterization such as the medium range order, band structure described by density of states and the metastability of amorphous structure and the related properties were introduced as well. Afterwards, the properties and features of N-type and P-type a-TCOs were exampled in details, especially the indium-based systems, such as excellent a-In-Zn-O films. Less example of P-type a-TCOs were shown as no general principle had been formed for that. Finally, many state-of-art applications including thin-film transistor are introduced. Based upon the current status and emerging trend, three potential research perspective directions of a-TCO have been delivered:(1) to further investigate non-indium based a-TCO; (2) to develop on the P-type TCO with novel principle and material systems; (3) to enable the alternative application that occupied by conventional silicon previously.

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]

Transparent conductive films (TCFs) have received much research attention in the area of aeronautical canopies. However, bad wear, corrosion resistance and weak erosion performance of TCFs dramatically limit their scalable application in the next-generation aeronautical and optoelectronic devices. To address these drawbacks, three types of optically transparent coatings, including acrylic, silicone and polyurethane (PU) coatings were developed and comparatively investigated ex situ in terms of Taber abrasion, nanoindentation and sand erosion tests to improve the wear-resistance and sand erosion abilities of ITO-coated PMMA substrates. To elucidate the sand erosion failure of the coatings, the nanoindentation technique was employed for quantitative assessment of the shape recovery abilities under probe indentation. Results show that the PU topcoats can greatly enhance the sand erosion properties, which were superior to those of acrylic and silicone topcoats. This result can be attributed to the good toughness and self-healing properties of PU topcoats. Additionally, high hardness and good Taber abrasion properties of the ITO films and silicone topcoats did not have an obvious or affirmatory effect on the sand erosion abilities, based on their brittleness and irreparable properties under sand erosion. [ABSTRACT FROM AUTHOR]

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]

We report a potential way to enhance and tune the multiferroic and resistive switching properties of BiFeO3 nanoparticles through dilute aliovalent Li(1+) doping (0.046 atomic percent) at the Fe(3+) sites of BiFeO3. The high purity of the samples and the extent of doping were confirmed by different physical characterizations. Enhanced multiferroic properties with a magnetic moment per Fe atom ≈ 0.12 μB and electric polarization ≈ 49 μC cm(-2) were observed in one of the Li(1+) doped samples. A phenomenological model has been proposed to support the observed magnetic behavior of the doped samples. From a potential application point of view, we further report on the doping concentration and polarization coercivity dependent highly stable resistive switching behavior (endurance cycles >10(3) and stability >10(6) s) of Li-doped BiFeO3 nanoparticles. The stable complementary resistive switching behavior (1 bit operation) for >50 cycles and under voltage pulse for 10(3) cycles in the doped BiFeO3 at a low operating bias is reported. Thus, dilute aliovalent Li(1+) doping enables tunability of the ferroic and resistive switching properties of BiFeO3and shows it to be a promising multiferroic material.