Proposed Fabrication Method Research Articles

Design and fabrication of highly efficient GaN-based light-emitting diodes

A promising fabrication method and an innovative geometrical design for highly efficient GaN-based light-emitting diodes (LEDs) were investigated based on the current spreading phenomenon. Based on theoretical considerations, it was possible to determine the critical transparent-electrode thickness, which resulted in significant improvements in the electrical and optical characteristics of LEDs. In addition, we were able to define conditions for an ideal geometrical design and the resulting product exhibited significant improvements in characteristics in spite of the fact that a transparent electrode, acting as a p-type current spreader, was not used. Considering the simple fabrication process and good device performance, the proposed fabrication methods, as well as the innovative geometrical design, have considerable promise for use in practical applications.

All-solid-state electronic tongue and its application for beverage analysis

Disposable all-solid-state planar-type potentiometric electronic tongue has been developed with the carbon paste electrode array screen-printed on a polymeric substrate. Highly cross-sensitive solvent polymeric membranes based on different matrices [e.g. poly(vinyl chloride) (PVC), aromatic polyurethane, and polypyrrole (Ppy)] and doped with common electroactive components for potentiometric measurements (e.g. various plasticizers, and cation- and anion-selective ionophores) were deposited on the screen-printed carbon paste electrodes (SCPEs). It was observed that an incorporation of 10 wt.% of Prussian Blue (PB; Fe 4(III)[Fe(II)(CN) 6] 3) into a commercially available carbon paste and electrochemical preanodization of SCPEs in KCl solution at 1.6 V provide the all-solid-state planar-type electrodes with significantly improved potentiometric stability. The proposed fabrication method gives possibility for simple and reproducible mass-production of low-cost disposable electronic tongue microsystems. The practical utility of all-solid-state disposable electronic tongue chips has been demonstrated with a flow injection cell for the analysis of potable waters, soft drinks, and beers. It is shown that the potentiometric measurements with the SCPE-based all-solid-state chips and the combined use of chemometric methods (e.g. principal components analysis, partial least regression (PLS), and principal component regression (PCR)) for the analysis of obtained data sets successfully discriminate various types of samples according to their tastes.

Silicon single-electron transistors with sidewall depletion gates and their application to dynamic single-electron transistor logic

Novel single-electron transistors (SETs) with side-wall depletion gates on a silicon-on-insulator nanometer-scale wire are proposed and fabricated, using the combination of the conventional lithography and process technology. Clear Coulomb oscillation originated from the two electrically induced tunnel junctions and the single Si island between them is observed at 77 K. The island size dependence of the electrical characteristics shows the good controllability and reproducibility of the proposed fabrication method. Furthermore, the device characteristics are immune to gate bias conditions, and the position of Coulomb oscillation peak is controlled by the sidewall depletion gate voltage, without the additional gate electrode. Based on the current switching by sidewall gate voltage, the basic operation of the dynamic four-input multifunctional SET logic circuit is demonstrated at 10 K. The proposed SET offers the feasibility of the device design and optimization for SET logic circuits, in that its device parameters and circuit parameters are controllable by the conventional VLSI technology.

Side-Gate Design Optimization of 50 nm MOSFETs with Electrically Induced Source/Drain

50 nm metal oxide semiconductor field effect transistors (MOSFETs) with two poly-Si side-gates are designed. We discuss the device structure and its fabrication process. Then, we investigate the improvement in device performance focusing on short channel effect, current drivability and hot carrier effect with two-dimensional and two-carrier device simulation. The proposed fabrication method maintains compatibility with the conventional MOS technology. The simulation results reveal that when the side-gate length is equal to the main-gate length, the device can be operated in an optimal condition.

DISTRIBUTED FLEXIBLE TACTILE SENSOR USING PIEZOELECTRIC FILM

The prototype of the tactile sensor which has 8 × 8 array using piezoelectric film was fabricated. In the fabrication procedure, the electrode patterns and the common electrode of the thin conductive tape are attached to the both sides of the 28 üm thickness piezoelectric film using conductive adhesive. The sensor is covered with polyester film for insulation and attached to the rubber base for a stable structure. The proposed fabrication method is simple and easy to make the sensor. The sensor has the advantages in the implementing for practical applications because its structure is flexible and the shape of the each tactile element can be designed arbitrarily. The signals of a contact force to the tactile sensor are sensed and processed in the DSP system in which the signals are digitalized and filtered. Finally, the signals are integrated for taking the force profile. The processed signals of the output of the sensor are visualized in a personal computer, the shape and force distribution of the contact object are obtained. The reasonable performance for the detection of the contact state was verified through the sensing examples.

Down-Sizing in Analytical Chemistry. Fabrication of a micro-channel chip for electrophoresis by using a Photosensitive epoxy resin as an etching mask.

In this paper, we present a new fabrication method that uses a UV-sensitive epoxy resin as an etching mask for a micro-channel electrophoresis chip. We have used it to separate fluorescein and fluorescein-5-sulfonic acid. The device was fabricated in a 50mm square of soda glass by using micro-lithographic patterning and wet etching techniques. The proposed method does not need for plating and etching of Au/Cr masks. An etched bottom plate was covered with a top plate drilled access holes into it and permanently bonded in an oven by heating at 560∼580°C. The chip had a separation channel and a sample injection channel. The separation channel was 80μm wide and 20μm deep. Using a micro-fabricated chip with a separation length of 10mm and a separation voltage of 800V, the electrophoresis of a fluorescein and fluorescein-5-sulfonic acid mixture gave two well-separated peaks. Detection was achieved using a laser-induced fluorescence microscope. The HETP of this chip was 3∼4μm for fluorescence samples, and a separation coefficient of 2.2 was realized. The proposed fabrication method is very simple and easy, and has given separation and detection results for fluorescein derivatives.

LiNbO_3 platforms for optical fiber alignment

A technique for incorporating a groove into a LiNbO(3) substrate is described. Both V grooves for fiber alignment and vertical grooves for waveguide end-face formation can be fabricated with this technique. The proposed fabrication method is based on an excimer-laser ablation and a high-speed rotation saw cut for LiNbO(3) . The former process provides a variety of cross-sectional groove shapes by changing the ablation mask shape of LiNbO(3) , and the latter provides an optical-quality cutting face. The proposed fabrication method is simple and provides low-cost optical platforms not only for LiNbO(3) but also for glasses, polymers, and semiconductors.

Method of fabrication of ISFET-based biosensors on an Si–SiO 2–Si structure

A new ISFET-based biosensors fabrication method, based on an Si–SiO 2–Si structure is presented. The method was demonstrated by constructing glucose sensor and its performance was evaluated experimentally. The preliminary results of investigation of the behaviour of developed glucose sensor in human urine are presented. The proposed fabrication method can be applied to various BioFETs.

In-Situ Fabrication of Gate Oxide and Poly-Si Film by XeCl Excimer Laser Annealing

We have proposed a new method to form the gate oxide and recrystallize the polycrystalline silicon (poly-Si) active layer simultaneously. During the irradiation of excimer laser, the poly-Si film is recrystallized while the oxygen ion impurities, which are injected into the amorphous silicon (a-Si) film, are activated by laser energy and react with silicon atoms to form SiO2. Our experimental results show that a high quality oxide, a poly-Si film with fine grain, and a smooth and clean interface between oxide and poly-Si film have been successfully obtained by the proposed fabrication method. The maximum oxide breakdown electric field which exceeds 7 MV/cm is obtained.

Fabrication of light-turning mirrors in buried-channel silica waveguides for monolithic and hybrid integration

A technique for incorporating a mirror into the core of a silica-based channel waveguide is described. Both up reflecting mirrors for hybrid integration and down-reflecting mirrors for monolithic integration can be fabricated using this technique. The proposed fabrication method is based on a combination of low temperature hollow cathode PECVD for silica-based waveguide deposition and a novel technique for forming a reflecting facet by wet chemical etching of PECVD silica.

The development of milliKelvin Si bolometers for future X-ray array devices

Silicon bolometers are currently under development for milliKelvin operation; these devices are being produced using Si wafer fabrication technology. The design and performance of individual bolometers, using doped layers with a thickness in the range 0.2 to 2 μm are described. The use of epitaxial growth to replace ion implantation for improved performance is discussed. For future use in space based X-ray astronomy, such devices could be fabricated as complete one or two dimensional arrays with integrated isolation and support. The proposed fabrication method for such arrays is outlined.