Conventional Planar Structure Research Articles

Flexible and Weaveable Capacitor Wire Based on a Carbon Nanocomposite Fiber

A flexible and weaveable electric double-layer capacitor wire is developed by twisting two aligned carbon nanotube/ordered mesoporous carbon composite fibers with remarkable mechanical and electronic properties as electrodes. This capacitor wire exhibits high specific capacitance and long life stability. Compared with the conventional planar structure, the capacitor wire is also lightweight and can be integrated into various textile structures that are particularly promising for portable and wearable electronic devices.

ChemInform Abstract: Novel Solar Cells in a Wire Format

AbstractReview: 48 refs.

Novel solar cells in a wire format

Photovoltaic devices in a wire format have recently attracted increasing attention as, compared with the conventional planar structure, they show unique and promising advantages. For instance, they are light-weight and can be easily woven into clothes or integrated into other structures, which enable applications in electronic textiles and various complex devices. In this tutorial review, the recent advancement in photovoltaic wires including both dye-sensitized and polymer solar cells are described. Two main architectures based on a single core-sheath fiber and twisted fibers are carefully illustrated with an emphasis on the comparison of various substrates which have been focused in past development. The current challenge including low energy conversion efficiency and low stability and future direction of the wire-shaped cell have been finally summarized.

Structured-gate organic field-effect transistors

We report the fabrication and electrical characteristics of structured-gate organic field-effect transistors consisting of a gate electrode patterned with three-dimensional pillars. The pillar gate electrode was over-coated with a gate dielectric (SiO2) and solution processed organic semiconductors producing both unipolar p-type and bipolar behaviour. We show that this new structured-gate architecture delivers higher source–drain currents, higher gate capacitance per unit equivalent linear channel area, and enhanced charge injection (electrons and/or holes) versus the conventional planar structure in all modes of operation. For the bipolar field-effect transistor (FET) the maximum source–drain current enhancements in p- and n-channel mode were >600% and 28%, respectively, leading to p and n charge mobilities with the same order of magnitude. Thus, we have demonstrated that it is possible to use the FET architecture to manipulate and match carrier mobilities of material combinations where one charge carrier is normally dominant. Mobility matching is advantageous for creating organic logic circuit elements such as inverters and amplifiers. Hence, the method represents a facile and generic strategy for improving the performance of standard organic semiconductors as well as new materials and blends.

Polymer photovoltaic wires based on aligned carbon nanotube fibers

Compared with the conventional planar structure, a wire-shaped polymer solar cell which is weavable exhibits unique and promising applications. However, it is rare to realize such a useful structure in polymer solar cells due to the difficulty in finding appropriate electrodes. Herein, we have fabricated polymer photovoltaic wires by using aligned carbon nanotube fibers as electrodes. The high flexibility, high electrical conductivity, and elaborate nanostructure of the nanotube fiber electrode enables an effective charge separation and transport. The resulting wire cell showed an open-circuit voltage, short-circuit current density and fill factor of 0.42 V, 0.98 mA cm−2 and 0.36, respectively, which produce an energy conversion efficiency of 0.15%.

TCAD studies of novel nanoplate amorphous silicon alloy thin-film solar cells

A novel nanoplate-structured thin-film solar cell was investigated that could solve the conflict between light absorption and carrier transport in a p-type amorphous silicon carbide (a-SiC)/i-type amorphous silicon germanide (a-SiGe)/n-type amorphous silicon (a-Si) thin-film solar cell. This structure has an n-type a-Si nanoplate array on the substrate, a-SiC p-layer, and an a-SiGe i-layer which are sequentially grown along the surface of each n-type a-Si nanoplate. Under illumination by sunlight, light is absorbed along the vertical direction of the nanoplate, while the carrier transport is along the horizontal direction. The nanoplate structure may absorb most of the sunlight and provide a thinner film for the effective transport of photon-generated carriers as compared to the conventional planar structure.

Evaluation of a quasi‐coaxial printed circuit board transformer

PurposeThe purpose of this paper is to investigate the possibility of utilizing printed circuit board (pcb) technology to manufacture coaxial transformers and to increase the predictability, accuracy and repeatability of the transformers leakage inductance.Design/methodology/approachThe geometry of a coaxial transformer is approximated using pcb techniques. Several different geometries are presented with the outer coaxial conductor being approximated by discrete conductors varying from four to 36 in number. Finite element methods as well as experimental results are used to support the proposed ideas. A planar transformer is also analyzed in the same way to emphasize the design advantages offered by the proposed quasi‐coaxial transformer.FindingsThe proposed multi‐conductor structures can be applied as co‐axial transformers. The experimental values obtained for the leakage inductance of the coaxial structures correspond well to the predicted values. This is not the case for conventional planar structure where adjustments need to be made in the finite element analysis simulations to accommodate the shortcomings of the analytical calculations.Originality/valueIn applications where the prediction of the leakage inductance of a transformer is important, this method may be applied and has the advantage of conventional pcb manufacture techniques.

Impulse response of a heterojunction MSM photodiode

A two-dimensional model is used to simulate drift of photogenerated carriers in the active region of high-speed photodiodes (metal-semiconductor-metal (MSM) rectifying contacts) that are made as a conventional planar structure and a structure with a heterojunction. These two types of photodiode structures are compared in terms of the impulse response and quantum efficiency. Variation of the planar MSM diode response with decreasing size of the interdigitated contact system is analyzed. The possibility of improving the speed of response of the MSM diode is discussed. It is shown that the structure with an InP/GaInAs heterojunction considerably modifies the transport of photogenerated carriers and remarkably improves the response speed.

Evaluation of Sensitivity on a Capacitive Fingerprint Sensor LSI with a Grounded Wall Structure

This paper describes the sensitivity to capture fingerprint images on a capacitive fingerprint sensor LSI with a grounded (GND) wall structure. We investigated the sensing characteristics of the fingerprint sensor LSI with the GND wall structure in comparison with that of the conventional planar structure. For the analysis, we proposed circuit models based on the GND wall and the planar structure that take account of the finger's resistance, and calculated numerically the sensing characteristics. The analysis revealed that the resistance of the finger degrades the sensitivity and the GND wall structure provides a high sensitivity because it suppresses the finger's resistance. The experimental results confirmed that the proposed models are appropriate and clarified the effect of the GND wall structure on fingerprint images. Therefore, it is concluded that a fingerprint sensor LSI with the GND wall structure achieves a high sensitivity in capturing clear fingerprint images.

Analytical model for threshold voltage and I– V characteristics of fully depleted short channel cylindrical/surrounding gate MOSFET

The present paper proposes an analytical model of threshold voltage and current voltage characteristics for short channel fully depleted cylindrical/surrounding gate MOSFET based on the solution of Poisson’s equation in cylindrical coordinates. The analysis takes into account the field-dependent mobility, velocity saturation and the effect of source/drain resistance. Advantages of surrounding/cylindrical structure over the conventional planar structure are investigated in detail. The results so obtained are in good agreement with simulated data available in the literature.

Multilayered transformer utilizing Mn‐Zn ferrite and its application to a forward‐type DC–DC converter

AbstractThis paper describes the electrical characteristics of a multilayered transformer composed of a Mn‐Zn ferrite core, and primary and secondary conductors positioned alternately not only in the vertical direction but also in the horizontal direction. In order to elucidate the operating characteristics of the two types of transformers, one was given the conventional planar winding structure and the other the new winding structure described above, and a two‐dimensional finite element method that took account of the two conditions and a constant input voltage and load current was introduced. The coupling coefficient of the conventional multilayered transformer deteriorated with increasing load current. But the coupling coefficient of the proposed multilayered transformer was independent of the load current. A forward‐type DC–DC converter using the new multilayered transformer had higher efficiency than a converter using the conventional multilayered transformer. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 1–8, 2001

High-reliability microwave silicon power transistor with stepped electrode structure and TiN diffusion barrier

A high-reliability microwave silicon power transistor is described that has a stepped electrode structure and TiN diffusion barrier. This structure, used for high-power and high-frequency devices, is discussed by comparing it to the conventional planar structure. The new structure permits microwave devices to achieve high levels of performance. For high-power dissipation devices having a beam lead metal system, however, the Au-Si reaction and localized Pt-silicide growth are major failure mechanisms. To improve these failures, the Ti layer must be thickened and further TiN applications in beam lead metal systems are discussed. Experimental results of high-temperature long-term operations proved that high-power microwave transistors with excellent reliability can be obtained by using a stepped electrode structure with TiN diffusion barrier.

Design and characterization of a step-recovery switching transistor

Fast rise time pulses can be generated with a special high-frequency silicon transistor structure having a collector impurity profile designed to control charge storage in the collector. When switched out of saturation it operates in a manner analogous to a step-recovery diode. The theory of operation is discussed along with the design and fabrication of the diffused impurity profiles. Its unique geometry combines planar and mesa technologies. Experimental transistors have a storage time of approximately 2-30 ns followed by a fall time as fast as 0.5 ns. The storage time can be adjusted by varying the initial base current or the driving pulse. The storage time and fall time are accurately characterized by the charge-control model. A transformer input circuit gives the best switching performance. Control devices of conventional planar structure fail to produce fast switching times. They demonstrate the failure of the charge-control model in describing the fall time of planar transistors in general.