Self-aligned offset gated poly-Si TFTs with a floating sub-gate

We have fabricated a self-aligned offset-gated poly-Si thin film transistor (TFT) by employing a novel photoresist reflow process. The gate structure of the new device is consisted of two unique patterns: A main-gate and a sub-gate. The new fabrication method extends the gate-oxide over the offset region. With the assistance of the sub-gate and reflowed photoresist a self-aligned offset region is successfully obtained due to the offset oxide acting as an implantation mask. The poly-Si TFT with symmetrical offsets is easily fabricated and the new method does not require any additional offset mask step. Compared with the misaligned offset gated poly-Si TFTs, excellent symmetric electrical characteristics are obtained     

AptaCDSS-E: A classifier ensemble-based clinical decision support system for cardiovascular disease level prediction

Conventional clinical decision support systems are generally based on a single classifier or a simple combination of these models, showing moderate performance. In this paper, we propose a classifier ensemble-based method for supporting the diagnosis of cardiovascular disease (CVD) based on aptamer chips. This AptaCDSS-E system overcomes conventional performance limitations by utilizing ensembles of different classifiers. Recent surveys show that CVD is one of the leading causes of death and that significant life savings can be achieved if precise diagnosis can be made. For CVD diagnosis, our system combines a set of four different classifiers with ensembles. Support vector machines and neural networks are adopted as base classifiers. Decision trees and Bayesian networks are also adopted to augment the system. Four aptamer-based biochip data sets including CVD data containing 66 samples were used to train and test the system. Three other supplementary data sets are used to alleviate data insufficiency. We investigated the effectiveness of the ensemble-based system with several different aggregation approaches by comparing the results with single classifier-based models. The prediction performance of the AptaCDSS-E system was assessed with a cross-validation test. The experimental results show that our system achieves high diagnosis accuracy (>94%) and comparably small prediction difference intervals (<6%), proving its usefulness in the clinical decision process of disease diagnosis. Additionally, 10 possible biomarkers are found for further investigation.     

Selective wet etching of p-GaN for efficient GaN-based light-emitting diodes

The selective wet etching of a p-GaN layer by using a solution of KOH in ethylene glycol (KE) was studied to enhance the optical and electrical performance of the GaN-based light-emitting diodes (LEDs). The surface of the p-GaN, which was selectively etched in the KE solution, showed hexagonal-shaped etch pits. The light-output power of etched LEDs was improved by 29.4% compared to that of the nonetched LED. This improvement was attributed to the increase in the probability of photons to escape due to the increased surface area of textured surface and the reduction in contact resistance of the ohmic layer resulting from the increased contact area and hole concentration on the textured p-GaN. The reverse leakage current of the LED was also greatly decreased due to the surface passivation and the removal of defective regions from the p-GaN.     

Surface modification of silicon by laser surface treatment: Improvement of adhesion and copper deposition

We have studied the use of lasers for modifying the surface properties of silicon to improve its wettability and adhesion characteristics. Using a 4th harmonic Nd:YAG (λ = 266 nm, pulse) laser, the wettability and adhesion characteristics of the silicon surfaces have been enhanced by laser irradiation. It was found that laser surface treatment of silicon modified the surface energy. By the contact angle measurement, using distilled water, the wetting characteristics of silicon after the laser irradiation show a decrease in the contact angle and a change in the surface chemical composition. In the case of the laser-treated silicon surface, laser direct writing of copper lines has been achieved through pyrolytic decomposition of copper formate by using a focused Ar⁺ laser beam (λ = 514.5 nm, continuous wave (CW)) on the silicon substrates. The deposited lines and surface chemical compositions were measured by energy dispersive x-ray (EDX), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and surface profiler (Alpha Step 500, San Jose, CA) to examine the cross section of deposited copper lines.     

Removal of N-Nitrosamines and Their Precursors by Nanofiltration and Reverse Osmosis Membranes

Rejection of selected N-nitrosamines, a group of probable human carcinogens, and their precursors by nanofiltration (NF) and brackish water reverse osmosis (BWRO) membranes was evaluated using a bench-scale cross-flow filtration apparatus. The tested nitrosamines included N-nitrosodimethylamine, N-nitrosomethylethylamine, N-nitrosopyrrolidine, N-nitrosodiethylamine, N-nitrosodi-n-propylamine, and N-nitrosodi-n-butylamine. The target nitrosamine precursors included secondary amines such as dimethylamine, methylethylamine, diethylamine, and dipropylamine. Rejection of nitrosamines varied greatly depending on the tested membranes (9–75% for NF membranes and 54–97% for BWRO membranes) and the molecular weight of nitrosamines. Experimental data obtained with the BWRO membranes matched well with an irreversible thermodynamic model coupled with film theory. The model further suggested that effective diffusion of nitrosamines through the BWRO membranes is responsible for the relatively low rejections observed experimentally, and the aqueous diffusivity of nitrosamines could be used as an accurate measure of nitrosamine permeability through these membranes. The steady-state rejection of all the tested nitrosamine precursors reached over 98%. This study suggests that a strategy for membrane-based water treatment processes to reduce nitrosamines should consider the removal of precursors before nitrosamines are formed during subsequent disinfection and water distribution.     

Investigation on the valence state of Te ions in the Bi6Ti5TeO22 thin film using X-ray photoelectron spectroscopy

Bi₆Ti₅TeO₂₂ (BTT) thin films were grown on a Pt/Ti/SiO₂/Si(1 0 0) substrate under various conditions and the valence state of the Te ion was investigated. For the BTT films grown at 300 °C, most of the Te ions existed as Te⁴⁺ ions. However, for the 10 mol% Mn-added BTT films grown at 300 °C, Te⁶⁺ ions were found even in the film grown under low oxygen partial pressure (OPP) and their number increased with increasing OPP. This increase was attributed to the presence of Mn²⁺ ions, which assisted the transition of Te⁴⁺ ions to Te⁶⁺ ions in order to maintain the charge balance of the Ti⁴⁺ sites. Furthermore, in the films grown at 300 °C under a high OPP of 80.0 Pa and subsequently annealed at 600 °C under a high oxygen pressure of 101 kPa, most of the Te ions existed as Te⁶⁺ ions. However, for the film grown at 300 °C under low OPP, even though the film was annealed under a high oxygen pressure of 101 kPa, only a few of Te⁶⁺ ions were formed, whereas most of Te ions remained as the Te⁴⁺ ions.     

UV reactor flow visualization and mixing quantification using three-dimensional laser-induced fluorescence

Three-dimensional laser-induced fluorescence (3DLIF) was applied to visualize and quantitatively analyze mixing in a lab-scale UV reactor consisting of one lamp sleeve placed perpendicular to flow. The recirculation zone and the von Karman vortex shedding that commonly occur in flows around bluff bodies were successfully visualized. Multiple flow paths were analyzed by injecting the dye at various heights with respect to the lamp sleeve. A major difference in these pathways was the amount of dye that traveled close to the sleeve, i.e., a zone of higher residence time and higher UV exposure. Paths away from the center height had higher velocities and hence minimal influence by the presence of sleeve. Approach length was also characterized in order to increase the probability of microbes entering the region around the UV lamp. The 3DLIF technique developed in this study is expected to provide new insight on UV dose delivery useful for the design and optimization of UV reactors.     

Channel width effect for organic thin film transistors using TIPS-pentacene employed as a dopant of poly-triarylamine

The effects of the physical channel width on the characteristics of organic thin film transistors (OTFTs), made with 6,13-bis(triisopropyl-silylethynyl)-pentacene (TIPS-pentacene) embedded into poly-triarylamine (PTAA, hole conductor within an active channel), have been examined in this paper. The devices are estimated by measuring the drain-source current (I_DS) for different contact metals such as Au and Ag, at fixed gate and drain voltages. The results show that the threshold voltage (V_T) and I_DS increase with increasing channel width. Furthermore, it has been observed that the field effect mobility is dependent on V_T, which is influenced by the channel width. The OTFTs, produced using Au and Ag contacts, exhibited the highest values of mobility in the saturation regime, namely 5.44 × 10^?2 and 1.33 × 10^?2 cm²/Vs, respectively.     

Photochemical degradation and toxicity reduction of methyl 1-[(butylamino)carbonyl]-1H-benzimidazol-2-ylcarbamate in agricultural wastewater: Comparative study of photocatalysis and sonophotocatalysis

Photochemical degradation and relative toxicity reduction of agricultural wastewater contaminated with methyl 1-[(butylamino)carbonyl]-1H-benzimidazol-2-ylcarbamate (benomyl) by the sonophotocatalytic system was compared with that of the photocatalytic system. Under the optimal conditions, i.e., initial benomyl concentration was 3.2 mg/L, the concentration of TiO₂ was 2 g/L and H₂O₂ concentration was 1.5 mM, the degradation rates with a sonication/UV/TiO₂ system was about 1.5 times higher than with a UV/TiO₂ system and sonication/UV/TiO₂/H₂O₂ system was about 1.3 times higher than with a UV/TiO₂/H₂O₂ system, respectively. Furthermore, the relative toxicity with a sonophotocatalysis was about 18% lower than with a photocatalysis within a reaction time of 120 min.     

Effect of encapsulating agents on dispersion status and photochemical reactivity of C60 in the aqueous phase

This study demonstrates that the degree of C60 clustering in the aqueous phase is strongly dependent on the type and concentration of encapsulating agents, such as surfactant, polymer, and natural organic matter that interact with C60. The degree of C60 clustering was quantitatively analyzed using ultraviolet-visible spectral characteristics. The dispersion status played a critical role in determining the photochemical reactivity of C60, in particular, its ability to mediate energy transfer and to produce singlet oxygen in the presence of oxygen. Consistent with findings in the organic phase, C60 in the aqueous phase lost its intrinsic photochemical reactivity when they formed aggregates. Experiments performed using a laser flash photolysis suggested that the loss of reactivity resulted from a drastic decrease in lifetime of a key reaction intermediate, that is, triplet-state C60. This study suggests that the photochemical reactivity of C60 in the aqueous phase, which has been linked to oxidative damage in biological systems in earlier studies, is strongly dependent on the media environment surrounding C60.