Rita Branquinho

Oxide electronic materials provide a plethora of possible applications and offer ample opportunity for scientists to probe into some of the exciting and intriguing phenomena exhibited by oxide systems and oxide interfaces. In addition to the already diverse spectrum of properties, the nanoscale form of oxides provides a new dimension of hitherto unknown phenomena due to the increased surface-to-volume ratio. Oxide electronic materials are becoming increasingly important in a wide range of applications including transparent electronics, optoelectronics, magnetoelectronics, photonics, spintronics, thermoelectrics, piezoelectrics, power harvesting, hydrogen storage and environmental waste management. Synthesis and fabrication of these materials, as well as processing into particular device structures to suit a specific application is still a challenge. Further, characterization of these materials to understand the tunability of their properties and the novel properties that evolve due to their nanostructured nature is another facet of the challenge. The research related to the oxide electronic field is at an impressionable stage, and this has motivated us to contribute with a roadmap on 'oxide electronic materials and oxide interfaces'. This roadmap envisages the potential applications of oxide materials in cutting edge technologies and focuses on the necessary advances required to implement these materials, including both conventional and novel techniques for the synthesis, characterization, processing and fabrication of nanostructured oxides and oxide-based devices. The contents of this roadmap will highlight the functional and correlated properties of oxides in bulk, nano, thin film, multilayer and heterostructure forms, as well as the theoretical considerations behind both present and future applications in many technologically important areas as pointed out by Venkatesan. The contributions in this roadmap span several thematic groups which are represented by the following authors: novel field effect transistors and bipolar devices by Fortunato, Grundmann, Boschker, Rao, and Rogers; energy conversion and saving by Zaban, Weidenkaff, and Murakami; new opportunities of photonics by Fompeyrine, and Zuniga-Perez; multiferroic materials including novel phenomena by Ramesh, Spaldin, Mertig, Lorenz, Srinivasan, and Prellier; and concepts for topological oxide electronics by Kawasaki, Pentcheva, and Gegenwart. Finally, Miletto Granozio presents the European action 'towards oxide-based electronics' which develops an oxide electronics roadmap with emphasis on future nonvolatile memories and the required technologies. In summary, we do hope that this oxide roadmap appears as an interesting up-to-date snapshot on one of the most exciting and active areas of solid state physics, materials science, and chemistry, which even after many years of very successful development shows in short intervals novel insights and achievements.

We report a sol-gel approach to fabricate aluminum-oxy-hydroxide (AlOOH) -based inks for gravure printing of high-dielectric-constant nanocomposite films. By reacting 3-glycidoxypropyl- trimethoxysilane (GPTS) with aluminum-oxide-hydroxide (AlOOH) nanoparticles under constant bead milling, inks suitable for gravure printing were obtained. The calculated relative dielectric constant based on measured capacitances and film thicknesses for the gravure-printed GPTS:AlOOH nanocomposite varied between 7 and 11 at a 10 kHz frequency. The dielectric constant depended on the mixing ratio of the composite and was found to follow the Maxwell-Garnett ternary-system mixing rule indicating presence of micro/nanopores that affect the electrical properties of the fabricated films. Increasing leakage current with increasing AlOOH content was observed. High leakage current was reduced by printing two-layer films. The double-layered gravure-coated films exhibited similar capacitance density but clearly lower leakage current and less electrical breakdowns in comparison to single-layered films having comparable film compositions and film thicknesses. The best composite yielded a capacitance density of 109 ± 2 pF/mm2 at the 10 kHz frequency and a leakage current density of 60 ± 20 µA/cm2 at 0.5 MV/cm electric field as a single layer. The calculated relative dielectric constant at the 10 kHz frequency for this composition was 11.2 ± 0.5. Introduction

Transparent metal oxides thin films are a class of inorganic conductors and semiconductors with significant importance for use in portable electronics, displays, flexible electronics, multi-functional windows and solar cells. Due to the recent development of transparent and flexible electronics, there is a growing interest in depositing metal-oxide thin-film on plastic substrates that can offer flexibility, lighter weight, and potentially lead to cheaper manufacturing by allowing printing and roll- to-roll processing. The plastic substrates, however, limit device processing to below 200oC. In this context, the deposition of high-performance semiconductor thin films from dispersions of pre-prepared oxide nanoparticles at temperatures below 200oC represents a potential key route. This paper reports on the preparation of ZnO transparent thin films using solution- processed nanoparticles (NPs) precipitated from zinc acetate alcoholic solution with potassium hydroxide. The nanoparticles size distribution, microstructure and crystallinity were measured by dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The thin films were deposited by spin-coating onto soda lima glass substrate, using a dispersion of 1wt{%} ZnO NPs. The morphology of the films annealed at 120 and 180oC, observed by atomic force microscopy and cross-section scanning electron microscopy, shows columnar grains with diameter ranging between 20 and 70 nm, depending on the conditions of depositions. Optical measurements indicated high transparency, between 85 and 94 {%}, in the visible range, a direct nature of band-to-band transitions and band gap values between 3,22 and 3,32 eV. The refractive index and extinction coefficient have been calculated from optical transmittance and reflectance spectra.

We present the results obtained with an extended-gate ISFET totally based on amorphous oxides (GIZO as the semiconductor, {\textless}formula formulatype="inline"{\textgreater}{\textless}tex Notation="TeX"{\textgreater}{\$}{\{}hbox{\{}Ta{\}}{\}}{\_}{\{}2{\}}{\{}hbox{\{}O{\}}{\}}{\_}{\{}5{\}}{\{}hbox{\{}:SiO{\}}{\}}{\_}{\{}2{\}}{\$}{\textless}/tex{\textgreater} {\textless}/formula{\textgreater} as the dielectric and {\textless}formula formulatype="inline"{\textgreater}{\textless}tex Notation="TeX"{\textgreater}{\$}{\{}hbox{\{}Ta{\}}{\}}{\_}{\{}2{\}}{\{}hbox{\{}O{\}}{\}}{\_}{\{}5{\}}{\$}{\textless}/tex{\textgreater} {\textless}/formula{\textgreater} as the sensitive layer). A full characterization of the device was performed with constant ionic strength pH buffer solutions, revealing a sensitivity of 40 mV/pH with small hysteresis, and good linearity in the pH 4{&}{\#}x2013;pH 10 range buffer solutions. These results clearly show that it is possible to produce room-temperature disposable and low cost bio-sensors.

The decolorization of aqueous solutions methylene blue (C.I. Basic Blue 9), due to the presence of nanocrystalline Bi2S3, supported on SiO2 submicron particles, was investigated here. For this decolorization process, two distinct characteristics, though related, associated to the role of SiO2/Bi2S3 were identified: (i) high methylene blue adsorption capability and (ii) photocatalytic activity to methylene blue photodecolorization. Effects of experimental parameters on the decolorization process, such as methylene blue and nanocomposite concentrations, pH and Bi2S3 particle size were investigated. The maximum adsorption ability of the SiO2/Bi2S3 was approximately 15.6 mg methylene blue per gram. The complete decolorization of a 16 ppm organic dye solution can be achieved, by an adsorption process, in an extremely short time (less than 5 min), using 1.6 g/L of SiO2/Bi2S3 nanocomposite. The study of the decolorization of the dye by an adsorption-photoassisted decolorization process was carried out by irradiation of a suspension prepared with 100 mL of methylene blue solution (8 ppm) and 50 mg of SiO2/Bi2S3. In these conditions the complete decolorization of the dye, adsorbed and in the solution, was achieved in 40 min. © 2008 Elsevier B.V. All rights reserved.