Organic field-effect transistors with ultrathin gate insulator

We have used a commercially available Mylar film coated with a thin (≈60 nm) layer of aluminium and an ultrathin (≈3.5 nm) SiO₂ layer as flexible substrate for the manufacture of bottom-gate organic field-effect transistors (OFETs). We show that the SiO₂ layer has insulating properties with a breakdown voltage of 1.6 V and a capacitance of ≈1 μF/cm². We have manufactured organic field-effect transistors using this substrate, regioregular poly(3-hexylthiophene) (rrP3HT) as a p-type semiconductor, and gold source and drain contacts. This results in OFETs that operate with voltages on the order 1 V.     

Percolation threshold related to field-effect transistors using thin multi-walled carbon nanotubes composites

We fabricated thin-film field-effect transistors (TF-FETs) using thin multi-walled carbon nanotubes (t-MWCNTs) and poly (methyl methacrylate) (PMMA) composites as the active layer. The gate-dependent current–voltage characteristics, the current on/off ratio (I_on/off), and the dc conductivity (σ_dc) were measured as a function of various weight (wt.%) of t-MWCNTs. The typical p-type FET characteristics were observed. We found that the field-effect I_on/off increased rapidly for TF-FETs with a wt.% of t-MWCNTs below 0.6. For the TF-FETs with a wt.% of t-MWCNT above 0.6, the I_on/off was relatively low. From the measured σ_dc as a function of the wt.% of t-MWCNTs, the percolation threshold (p_c) was observed to be approximately 0.6 wt.% for the t-MWCNT composites. We infer that the TF-FET characteristics are closely related to the p_c for the charge conduction of the t-MWCNTs composites.     

Micropatterning of liquid crystalline polyacetylene derivative by using self-organization processes

Side-chain type liquid crystalline polyacetylene, which has mesogenic moieties as side chains, is one of the promising materials for practical applications in the electronics. Micropatterning of the conductive polymer is a significant issue in this field. We show a simple method to fabricate micropatterns of side-chain type liquid crystalline polyacetylene derivative. Under dry condition, stripes patterns and lattice pattern were formed based on the fingering instability and stick-slip motion of the receding meniscus. Honeycomb-patterned polymer film was obtained by casting polymer solution under humid condition. The micropatterns drastically changed by changing solution concentration and preparation conditions.     

Study of nanoparticles synthesized in reverse micelles using liquid chromatography method

Liquid chromatography, which makes it possible to investigate interphase processes, is an additional method for studying inverse micellar systems without changing their properties in the process of sample preparation. In the case of using these systems to synthesize nanoparticles (NPs), it becomes possible to determine their adsorption characteristics, to investigate the processes of modifying surface adsorbents by NPs, to determine their sizes, and to divide them into fractions according to their sizes and surface properties of the micelles. The method is simple and rapid and permits one to use standard, relatively inexpensive equipment and can be applied in many physicochemical studies of NPs synthesized in micellar solutions.     

The synergistic ability of Al2O3 nanoparticles to enhance mechanical response of hybrid alloy AZ31/AZ91

AZ31/AZ91 hybrid alloy nanocomposite containing Al₂O₃ nanoparticle reinforcement was fabricated using solidification processing followed by hot extrusion. The nanocomposite exhibited similar grain size to the monolithic hybrid alloy, reasonable Al₂O₃ nanoparticle distribution, non-dominant (0 0 0 2) texture in the longitudinal direction, and 25% higher hardness than the monolithic hybrid alloy. Compared to the monolithic hybrid alloy (in tension), the nanocomposite synergistically exhibited higher 0.2%TYS, UTS, failure strain and work of fracture (WOF) (+12%, +7%, +99% and +108%, respectively). Compared to the monolithic hybrid alloy (in compression), the nanocomposite exhibited higher 0.2%CYS and UCS, and lower failure strain and WOF (+5%, +3%, −7% and −7%, respectively). The beneficial effects of Al₂O₃ nanoparticle addition on the enhancement of tensile and compressive properties of AZ31/AZ91 hybrid alloy are investigated in this paper.     

Effect of annealing on the conversion of ZnS to ZnO nanoparticles synthesized by the sol-gel method using zinc acetate and thiourea

A systematic study is presented on the conversion of zinc sulfide to zinc oxide nanoparticles as a function of annealing temperature. Zinc acetate dihydrate (Zn(CH₃COO)₂.2H₂O) and thiourea (NH₂CSNH₂) are used as precursors to synthesize ZnS and then ZnO. The aqueous solution of the precursor was refluxed at 90 °C for over 12 h. The synthesized complex was then annealed at 300 °C, 500 °C, 700 °C, and 900 °C in air for one hour. From elemental analyses, it was found that the as-synthesized powder is a mixture of ZnS and ZnO, which annealing later converts to the zinc oxide phase only. The morphological observations revealed spherical particles of various sizes (20 nm to 300 nm) while increasing the annealing temperatures. A drastic change in the vibration bands is noticed with annealing. Photoelectron peaks related to sulfur and carbon are observed for synthesized powder, whereas, these peaks disappeared when annealed at 500 °C.     

Transient liquid phase diffusion bonding of copper alloy to stainless steel using CuMn alloys as interlayer

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From diamond to crystalline silicon carbonitride: effect of introduction of nitrogen in CH4/H2 gas mixture using MW-PECVD

Microwave plasma enhanced chemical vapor deposition (MW-PECVD) is considered as one of the most successful growth techniques in recent diamond and crystalline carbon nitride investigations. In this study, we tried to synthesize crystalline carbon nitride film using MW-PECVD by gradually increasing the content of nitrogen into H₂/CH₄ gas mixture. Well-faceted crystalline diamond films could be synthesized with a H₂/CH₄ gas ratio of 198:2. With the gradual increase of nitrogen content up to 3% in the gas mixture diamond film quality deteriorates seriously, and the morphological crystal size and growth rate of diamond coatings decreased significantly. With the nitrogen gas content increased to approximately 6–22%, a lot of separated round diamond or diamond-like carbon particles formed on the surface rather than a continuous film. Only with the nitrogen content increased above 72%, could some tiny crystals with a type of hexagonal facet form on the silicon surface, together with many large, round diamond particles. With the further increase of nitrogen gas content above 90%, many large, well-faceted hexagonal crystals formed on Si surface. However, XRD, energy dispersive X-ray spectrometry, X-ray photoelectron spectroscopy and nano-indentation analysis indicated that these crystals were actually silicon carbonitride (Si–C–N) with a crystalline structure of Si₃N₄ modified with the introduction of carbon atoms, rather than carbonitride as expected and regarded.