Sidewall spacer defined resonant interband tunneling diodes

We report on a contacting and fabrication scheme for a sub-500 nm InAs/AlSb/GaSb resonant interband tunneling diode (RITD) without using any fine-line lithography. Epitaxial regrowth on patterned substrates combined with sidewall spacer technology is used to define the device dimensions. During regrowth, the crystal facet termination obtained by choosing the appropriate orientation for the device is utilized to make electrical contact to the device in the desired directions and to isolate the device in all other directions. The concept, fabrication process, current-voltage characteristics of the device, and a comparison with RITDs fabricated in a conventional manner are reported.     

Etch characteristics of an amorphous refractory absorber

An ECR etch process for defining sub-0.25 μm features in a TaSiN absorber layer has been developed. A 2000 Å PECVD oxide layer served as a hard mask during the etch. The effect on feature profile has been determined as a function of both rf power and back side temperature. Etch rate uniformity is excellent, with 3σ deviations of less than 4% over the center 40 mm of the substrate. Micro-loading issues associated with the etch process have also been characterized. Minimal line edge roughness is observed, and the feasibility for defining 0.10 μm features has been demonstrated.     

Functionalized polyethylene on property enhancement of lubricating oil and their performance evaluation study

Methyl methacrylate (MMA) functionalized polyethylene additives for improving the properties of lubricating oil has been investigated in which poly(MMA-co-ethylene) were synthesized by using three different polymerization techniques such as miniemulsion, post polymerization and reverse atom transfer radical polymerization with 1.0 molL −1 of MMA and 20 bar of ethylene pressure. The copolymers are block in nature with the composition of 1:3 molar ratios of ethylene:MMA which is independent of polymerization techniques used. ¹H NMR analysis confirmed the successful incorporation of the copolymers in the lubricating oil. Thermogravimetric analysis reveals that the addition of poly(MMA-co-ethylene) increases thermal stability of the additive doped lubricating oil by approximately 40°C with a single stage decomposition pattern. Flash point measurements show an increasing flash point values for copolymer doped lubricating oil. From rheological study, the viscosity index of base lubricating oil has found significant increases from 102 to 129 with the addition of poly(MMA-co-ethylene) and the higher molecular weight (MW) of this copolymer provides better thickening efficiency. However, copolymer with higher MW seems to be more susceptible to mechanical degradation resulting in lower shear stability whereas copolymer with lower MW acts as a better pour point depressant.     

The Use of Capillary Suction Time to Characterize the Surface of Aluminum Hydroxide Suspensions

The capillary suction tine of suspensions of 3 dried aluminum hydroxide powders correlated with the surface area of the powders determined by nitrogen adsorption if the solids content and the aggregation state were controlled. This method isuseful for characterizing the surface area of suspended solids as it avoids possible changes in surface area caused by crying the suspension.     

Emerging ≈800 nm Excited Lanthanide‐Doped Upconversion Nanoparticles

Lanthanide‐doped upconversion nanoparticles can tune near‐infrared light to visible or even ultra‐violet light in emissions. Due to their unique photophysical and photochemical properties, as well as their promising bioapplications, there has been a great deal of enthusiastic research performed to study the properties of lanthanide‐doped upconversion nanoparticles in the past few years. Despite the considerable progress in this area, numerous challenges associated with the nanoparticles, such as a low upconversion efficiency, limited host materials, and a confined excitation wavelength, still remain, thus hindering further development with respect to their applications and in fundamental science. Recently, innovative strategies that utilize alternative sensitizers have been designed in order to engineer the excitation wavelengths of upconversion nanoparticles. Here, focusing on the excitation wavelength at ≈800 nm, recent advances in the design, property tuning, and applications of ≈800 nm excited upconversion nanoparticles are summarized. Benefiting from the unique features of ≈800 nm light, including deep tissue penetration depth and low photothermal effect, the ≈800 nm excited upconversion nanoparticles exhibit superior potential for biosensing, bioimaging, drug delivery, therapy, and three dimensional displays. The critical aspects of such emerging nanoparticles with regards to meeting the ever‐changing needs of future development are also discussed.     

Hydrogen gas sensing of nano-confined Pt/g-C3N4 composite at room temperature

In this study, we report the hydrogen sensing properties of the Pt dispersed graphitic carbon nitride (g-C₃N₄) nanocomposite at room temperature and inert atmosphere. The nanocomposite was synthesized by a wet-chemical approach, where melamine and chloroplatinic acid hexahydrate were used as precursors. The fabrication of the sensor was done by jet nebulizer-based spray pyrolysis setup. Various characterizations were performed for the analysis of the synthesized nanocomposite. Electrical resistance in the presence and absence of the analyte gas was drastically different. The results at different concentrations and film thickness show Pt/g-C₃N₄ to possess good sensitivity towards the hydrogen gas, suggesting that it could be used for reliable hydrogen gas sensing.     

Closed-form expressions for long-term deflections in high-rise composite frames

This paper presents closed-form expressions for rapid prediction of long-term deflections in high-rise steel concrete composite frames subjected to service load. The closed-form expressions predict the inelastic mid-span deflections in beams of frames (typically for 20 years, considering cracking, and time effects, i.e., creep and shrinkage in concrete) from the elastic moments and elastic mid-span deflections (neglecting cracking, and time effects). The expressions also take into account the sagging moments developed in beams due to the substantial differential shortening of adjacent columns in high-rise frames. The expressions can be used for frames with any number of bays and storeys. The expressions have been obtained from trained neural networks. The training, validating, and testing data sets for the neural networks are generated using a hybrid analytical-numerical procedure of analysis. The proposed expressions are verified for example frames of different number of spans and storeys and the errors are shown to be small. The expressions can be used in every day design as they enable a rapid prediction of inelastic deflections with reasonable accuracy for practical purposes without detailed complex analysis and require computational effort that is a fraction of that required for the available methods.