Interconnected three-dimensional anodized aluminum oxide (3D-AAO) metamaterials using different waveforms and metal layers for RGB display technology applications

Research into the artificial reproduction of vibrant colours in natural creatures and the reproduction of their structural colours has generated considerable interest. One inorganic material that have been studied for...

ФОРМУВАННЯ ТА ХАРАКТЕРИЗАЦІЯ ПОРИСТОГО АНОДОВАНОГО ОКСИДУ АЛЮМІНІЮ, СИНТЕЗОВАНОГО ЕЛЕКТРОХІМІЧНО У ПРИСУТНОСТІ ОКИСЛЕНОГО ГРАФЕНУ

Purpose of the research: studying the effect of addition of carbon nanosized modifier graphene oxide on the formation of a porous film during the electrochemical oxidation of aluminum.Methods: UV-VIS spectra of graphene oxide suspension were obtained using a spectrophotometer, the thermogravimetric characteristics of anodized alumina were determined using a thermal analyzer, the surface characteristics were determined by the low-temperature nitrogen sorption-desorption method, the surface was calculated by the BET method, the morphology and ultrastructure of the surface were determined using electron microscope.Results: the possibility of using carbon materials for the electrochemical oxidation of aluminum was shown. The obtained electron micrographs indicate the effect of the inserted carbon modifier (graphene oxide) on the morphology of resulting oxide. As a result of this process we observe the formation of the cellular surface of the aluminium oxide with smaller pores compared with sample after synthesis without the modifier.It was shown that the addition of graphene oxide (0.25%) in the oxalic acid (0,3М) electrolyte effects on the stability of the anodizing process, the specific surface area of the sample of anodized aluminum synthesized with graphene oxide is determined as 35.5 m3/g, and it is three times higher than sample without modifier. According to sorption studies, it could be noted that the presence of nanosized graphene oxide in oxalic acid electrolyte leads to the formation of honey-comb pores with a smaller radius (22 nm), while the total volume of micropores increases. The obtained results allow us to conclude that graphene oxide as modifier is promising material for the preparation of anodized aluminum oxide matrices. In the future, these matrices could be used in processes of solutions and gases separation.Conclusions: The addition of graphene oxide into the electrolyte changes structure of porous anodized aluminum oxide and has shown the possibility of controlling the porosity of films.

Single-crystalline silicon nanomembrane thin-film transistors with anodized aluminum oxide as gate dielectric on rigid and flexible substrates

Flexible integrated circuits (ICs) have gained a lot of attentions in recent years for their emerging application in wearable electronics. Flexible thin-film transistors (TFTs) with low-cost and high-performance are highly desirable as essential and fundamental element for most of the flexible applications. In this paper, we fabricated single-crystalline silicon nanomembrane (SiNM) based TFTs with anodized aluminum oxide (AAO) as dielectric material on glass and flexible plastic substrates. Good quality AAO was obtained on plastic substrates at room temperature. AFM was used for surface morphology of AAO gate dielectric layers on different substrates (i.e. glass, polyethylene terephthalate (PET) and SU-8 coated PET). The electrical characteristics of the AAO gate dielectric layers on different substrates were also analyzed with metal- dielectric-metal (MIM) capacitors. SiNMs were processed with complementary metal oxide semiconductor (CMOS) compatible semiconductor process (e.g. photolithography, ion implantation, thermal annealing, reactive ion etching, metal evaporation, etc.), and then transferred to the substrates with AAO/aluminum stack layers. Performances of transistors on glass and plastic substrates were characterized. Compared with the TFT fabricated on glass substrate, TFT fabricated directly on a PET substrate have lower performance due to poor surface roughness. For optimization of the surface roughness, PET was modified with coating SU-8 photoresist. By this way, TFT had properties close to that on glass substrate. AAO that can be manufactured at room temperature provides a simple and low-cost solution for high-performance flexible single-crystalline SiNM TFTs.

Bottom-Up Synthesis of Mesoporous TiO2 Films for the Development of Optical Sensing Layers

Many optical sensors exploit the interesting properties of porous materials, as they ensure a stronger interaction between the light and the analyte directly within the optical structure. Most porous optical sensors are mainly based on porous silicon and anodized aluminum oxide, showing high sensitivities. However, the top-down strategies usually employed to produce those materials might offer a limited control over the properties of the porous layer, which could affect the homogeneity, reducing the sensor reproducibility. In this work, we present the bottom-up synthesis of mesoporous TiO2 Fabry-Pérot optical sensors displaying high sensitivity, high homogeneity, and low production cost, making this platform a very promising candidate for the development of high-performance optical sensors.

Influence of Alloying Elements on the Mechanical Properties of Anodized Aluminum and on the Adhesion of Copper Metallization

The active development of the power electronics market and a constant increase in the prices of components require new materials and approaches, including a power module packaging technology. The use of aluminum instead of copper in the power module baseplate is an interesting and promising solution. The insulated metal baseplate is one of the most extensively developed technologies nowadays. The object of this study is an insulated metal substrate based on anodized aluminum. The main goal of the article is the comparison of copper topology adhesion to an anodized aluminum oxide layer formed on different aluminum alloys with aluminum content of at least 99.3 wt %. Peel test and pull-off adhesions showed a twofold difference for both aluminum alloys. The high ordered defect-free anodized alumina formed on alloys with copper content of 0.06 wt % had a mean pull-off adhesion of 27 N/mm2 and hardness of 489 HV. In the case of the alloy with copper content of around 0.15 wt %, it had hardness of 295 HV and a mean pull-off adhesion of 12 N/mm2. The results of our microstructure investigation showed that anodized alumina based on alloys with copper content of around 0.15 wt % is fragile due to spherical holes. Summing up the results, it can be concluded that not all initial impurities are critical for anodized alumina, but some, specifically copper, dramatically decreased the mechanical properties of anodized alumina.

Synergistic Effects of Fe2O3 Nanotube/Polyaniline Composites for an Electrochemical Supercapacitor with Enhanced Capacitance

α-Fe2O3, which is an attractive material for supercapacitor electrodes, has been studied to address the issue of low capacitance through structural development and complexation to maximize the use of surface pseudocapacitance. In this study, the limited performance of α-Fe2O3 was greatly improved by optimizing the nanotube structure of α-Fe2O3 and its combination with polyaniline (PANI). α-Fe2O3 nanotubes (α-NT) were fabricated in a form in which the thickness and inner diameter of the tube were controlled by Fe(CO)5 vapor deposition using anodized aluminum oxide as a template. PANI was combined with the prepared α-NT in two forms: PANI@α-NT-a enclosed inside and outside with PANI and PANI@α-NT-b containing PANI only on the inside. In contrast to α-NT, which showed a very low specific capacitance, these two composites showed significantly improved capacitances of 185 Fg−1 for PANI@α-NT-a and 62 Fg−1 for PANI@α-NT-b. In the electrochemical impedance spectroscopy analysis, it was observed that the resistance of charge transfer was minimized in PANI@α-NT-a, and the pseudocapacitance on the entire surface of the α-Fe2O3 nanotubes was utilized with high efficiency through binding and conductivity improvements by PANI. PANI@α-NT-a exhibited a capacitance retention of 36% even when the current density was increased 10-fold, and showed excellent stability of 90.1% over 3000 charge–discharge cycles. This approach of incorporating conducting polymers through well-controlled nanostructures suggests a solution to overcome the limitations of α-Fe2O3 electrode materials and improve performance.