Characteristics improvement of top‐gate self‐aligned amorphous indium gallium zinc oxide thin‐film transistors using a dual‐gate control

In this work, we have reported dual‐gate amorphous indium gallium zinc oxide thin‐film transistors (a‐IGZO TFTs), where a top‐gate self‐aligned TFTs has a secondary bottom gate and the TFT integration comprises only five mask steps. The electrical characteristics of a‐IGZO TFTs under different gate control are compared. With the enhanced control of the channel with two gates connected together, parameters such as on current (I_ON), sub‐threshold slope (SS^?1), output resistance, and bias‐stress instabilities are improved in comparison with single‐gate control self‐aligned a‐IGZO TFTs. We have also investigated the applicability of the dual‐gate a‐IGZO TFTs in logic circuitry such as 19‐stage ring oscillators.     

Human–seat interface analysis of upper and lower body weight distribution

The human–seat interfaces were analyzed to determine the differential distribution of the body weight to the components of seat. Fifteen volunteers were tested on a simulated seat system with two piezoelectric force platforms, one placed as chair seat pan and the other placed on the floor surface as footrest. The seated configurations included back inclines (75° and 80°), upright (90°) and reclines (95°, 105° and 115°), absence or presence of armrest (adjusted at 62–68 cm of height), forward and backward sloping of the seat pan, and supported and unsupported back. The armrest and backrest assemblies were isolated from the force platforms. The difference in the body weight (kgf) to the sum of forces recorded at seat pan and feet yielded the extent of weight transferred to other features (e.g., backrest and armrest). The weight distributed at seat was 10–12% less at back inclines (p<0.01) as compared to upright unsupported sitting. With the backrest reclined beyond 95°, the weight at seat gradually decreased by 9% at 115° recline. The load distributed at feet varied narrowly; however, it was significantly greater (p<0.01) at upright supported back, compared to unsupported back. The height of the armrest was optimized at 68 cm, since the weight distribution at seat pan consistently reduced by 12% at that height, as compared to the absence of armrest (F_(4,524)=8.80, p<0.05). The suggested height of the armrest corresponded to 40% of the body stature of the selected volunteers. The load distributed at feet was 18% greater with the presence of armrest, indicating that a part of the weight of the upper leg fell on the seat pan, when the armrest was absent. The weight fell on the seat in slouch posture was 5% less than in upright sitting, while the weight at feet was marginally higher in slouch than in upright posture. The study maintained that the horizontal as well as 5° forward slope of the seat might be the preferred choice, since the load distributed at seat was highest at backward sloping seat for all conditions of supported and unsupported back. The study reaffirms that the backrest and armrest have conjoint influence in reducing the load distributed at seat, which in turn might help in mitigating stress on the spinal and other paraspinal structures.

Relevance to Industry

The human–seat interface analysis and understanding of body weight distribution to the components of seat may be beneficial for ergo-design application in optimizing parameters for chair configurations that provide comfort and safety to the user.     

Impact of source/drain contacts formation of self‐aligned amorphous‐IGZO TFTs on their negative‐bias‐illumination‐stress stabilities

In this study, we have compared the performance of self‐aligned a‐IGZO thin‐film transistors (TFTs) whereby the source/drain (S/D) region's conductivity enhanced in three different ways, that is, using SiN_x interlayer plasma (hydrogen diffusion), using calcium (Ca as reducing metal) and using argon plasma (changing the atomic ratio). All these TFTs show comparable characteristics such as field‐effect mobility (μ_FE) of over 10.0 cm²/(V.s), sub‐threshold slope (SS^‐1) of 0.5 V/decade, and current ratio (I_ON/I_OFF) over 10⁸. However, under negative‐bias‐illumination‐stress (NBIS), all these TFTs showed strong degradation. We attributed this NBIS stability issue to the exposed S/D regions and changes in the conductivity of S/D contact regions. The hydrogen plasma‐treated TFTs showed the worst NBIS characteristics. This is linked to increased hydrogen diffusion from the S/D contact regions to the channel.     

Precursor dependent tailoring of morphology and bandgap of zinc oxide nanostructures

Zinc oxide (ZnO) nanoparticles have been synthesized by wet chemical processing from four different zinc precursor materials at room temperature. Synthesis of phase pure material with four different morphologies and orientations have been confirmed through different characterization techniques like, X-ray diffraction, field emission SEM, fourier transformed IR etc. The band gap energies of the synthesized materials were within specific semiconductor limits and the same have been determined from UV–Visible and photoluminescence spectra of the synthesized nanostructured ZnO materials. Thus it is possible to control ZnO nanostructures and morphologies through facile room temperature synthesis and tailor their band gaps for different application purposes.     

Laser deposited biocompatible Ca–P coatings on Ti–6Al–4V: Microstructural evolution and thermal modeling

A high intensity continuous wave diode pumped ytterbium laser source was used to deposit Ca–P coatings on a Ti–6Al–4V biocompatible alloy in order to generate a physically textured surface, enhancing osseointegration. Scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and energy dispersive spectroscopy (EDS) studies were coupled with X-ray and micro diffraction work to determine the structure, composition, and phases present in various zones of a sample prepared across the coating/substrate interaction zone. Three-dimensional thermal modeling was also carried out to determine the cooling rate and maximum temperature experienced by different regions of the substrate. Combining these results provide us with valuable insights regarding the thermo-physical as well as chemical interactions that take place across the coating–substrate interface.     

A Methodology for Determination of �á� Site Occupancies in Nickel Superalloys Using Atom Probe Tomography and X-ray Diffraction

A methodology for determining the preferred site occupancy of various alloying elements within ordered ?á? precipitates was developed and applied to Rene88 samples. The method utilized atom probe tomography and X-ray diffraction techniques with controlled monochromated synchrotron beams to determine element positions. Samples were solutionized at 1423 K (1150 °C) for 30 minutes and cooled at 24 K/min with subsequent aging at 1033 K (760 °C). The synchrotron X-ray diffraction results indicate that niobium prefers to reside on the aluminum sublattice site of the ?á? phase. Additionally, the results indicate that chromium prefers the nickel sublattice sites, while cobalt is likely to occupy both the aluminum and nickel sublattice sites. The X-ray results on the chromium occupancy disagree with atom probe results from the same alloy that indicate that chromium prefers the aluminum sublattice sites.     

Multiple metal coordinating behaviour of the tetrapodal ligand 1,1,1,1-tetrakis[(salicylaldimino)methyl]methane

The tetrapodal ligand 1,1,1,1-tetrakis[(salicylaldimino)methyl]methane (H₄tsam) has been introduced for the first time for metal complexation. Two zinc(II) complexes[Zn₂(tsam)] (1) and [Zn₃(Htsam)₂]·2C₇H₈ (2) have been obtained by reacting zinc acetylacetonate with the ligand in the presence of triethylamine, while a cobalt(III) complex [Co(Htsam)]·CH₃CN·H₂O (3) is obtained when Co(ClO₄)₂·6H₂O is reacted in air. All the compounds have been characterized by their elemental analyses and ESI-MS, IR, UV-VIS and ¹H NMR spectra. The X-ray crystal structures of H₄tsam, 2 and 3 have been determined. Compounds 1 and 2 exhibit fluorescence in solution and the lifetimes of their luminescence decay have been measured. Thermal analysis (TGA, DTA) of 2 with regard to loss of encapsulated toluenes and redox behaviour of 3 have been studied.     

Influence of oxygen ingress on fine scale precipitation of α-Ti during oxidation of Beta21S β-Ti alloy

The formation of a surface oxide layer along with α precipitation in the subsurface oxygen-enriched zone, during the oxidation of a β-Ti alloy, has been investigated using scanning electron microscopy, electron probe micro analysis, X-ray diffraction, (Scanning) transmission electron microscopy, 3D-Atom Probe studies, and nano-indentation. Immediately below the nanocrystalline oxide layer, a two-phase mixture consisting of nanoscale equiaxed α grains and rutile grains are formed. With increasing depth, the α morphology below the oxide layer varied from nanoscale equiaxed to lathlike, coupled with substantial changes in size-scale and nucleation density of α precipitates. A distinct change in the lattice parameters of α and β phases below the oxide layer and the overall micro hardness of the material is also noted. The role of oxygen ingress on the scale and morphology of α precipitation has been discussed.     

Coarsening kinetics of γ′ precipitates in cobalt-base alloys

The expeditious development of novel cobalt-base γ–γ′ alloys as possible next generation superalloys critically depends on achieving a comprehensive understanding of the coarsening kinetics of ordered γ′ precipitates. This paper discusses the coarsening of L1₂ ordered Co₃(W, Al) precipitates in a model ternary Co–10Al–10W (at.%) alloy during isothermal annealing at 800 and 900 °C. The experimentally determined temporal evolution of average size of the γ′ precipitates suggests classical matrix diffusion limited Lifshitz–Slyozov–Wagner coarsening at both temperatures. The γ′ coarsening rate constants have been determined using a modified coarsening rate equation for non-dilute solutions. Furthermore, using the Cahn–Hilliard formulation for interfacial energy, the γ/γ′ interfacial energies at the respective annealing temperatures have been correlated to the concentration profile across the interface that has been experimentally determined using atom probe tomography. The calculated interfacial energies are in comparable range with those observed in nickel-base superalloys. Additionally, this analysis has permitted, for the first time, the determination of the gradient energy coefficient for γ/γ′ interfaces in Co-base alloys, a critical input for phase-field and other simulation models for microstructural evolution.     

Effect of electron beam irradiation on the mechanical,thermal, and dynamic mechanical properties of flyash and nanostructured fly ash waste polyethylene hybrid composites

The effect of electron beam irradiation on the technical properties of fly ash (FA) and nano fly ash (NFA)‐filled waste polyethylene (WPE) composites have been investigated in this article. It is observed that the FA/NFA at 5 wt% imparted enhanced technical properties. The modified composites were prepared by three different methods (1) modification of WPE matrix first by grafting with maleic anhydride (MA) and preparing the composite (2) Preparing WPE‐FA/NFA composites and subjecting to electron beam irradiation. (3) Subjecting the FA/NFA to electron beam radiation first and then preparing composites with WPE. Of the three methods, the composite prepared and then electron beam irradiated gave the best balance in the physico‐mechanical properties. The tensile and flexural strength of WPE increased from 21.2 MPa and 25.4 MPa to 33.0 MPa (57.8%) and 45.8 MPa (72%) respectively at 5 wt% FA‐filled WPE composites, which further increased to 34.5 MPa (65%) and 47.7 MPa (87.8%) respectively with 5 wt% of NFA‐filled WPE composites, after electron beam irradiation. The thermal stability was enhanced upon electron beam irradiation of the composites. The dynamic mechanical properties reveal that the storage modulus reaches the highest value for the irradiated composite corroborating with the flexural modulus throughout the temperature range studied. The fractured surfaces were examined under SEM and were correlated with the mechanical properties. The results indicate that FA/NFA reinforced WPE composites act as an excellent stress raisers preventing crack propagation and enhancing the performance properties on electron beam irradiation. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers