Highly Crystalline Soluble Acene Crystal Arrays for Organic Transistors: Mechanism of Crystal Growth During Dip‐Coating

The preparation of uniform large‐area highly crystalline organic semiconductor thin films that show outstanding carrier mobilities remains a challenge in the field of organic electronics, including organic field‐effect transistors. Quantitative control over the drying speed during dip‐coating permits optimization of the organic semiconductor film formation, although the kinetics of crystallization at the air–solution–substrate contact line are still not well understood. Here, we report the facile one‐step growth of self‐aligning, highly crystalline soluble acene crystal arrays that exhibit excellent field‐effect mobilities (up to 1.5 cm V^?1 s^?1) via an optimized dip‐coating process. We discover that optimized acene crystals grew at a particular substrate lifting‐rate in the presence of low boiling point solvents, such as dichloromethane (b.p. of 40.0 °C) or chloroform (b.p. of 60.4 °C). Variable‐temperature dip‐coating experiments using various solvents and lift rates are performed to elucidate the crystallization behavior. This bottom‐up study of soluble acene crystal growth during dip‐coating provides conditions under which one may obtain uniform organic semiconductor crystal arrays with high crystallinity and mobilities over large substrate areas, regardless of the substrate geometry (wafer substrates or cylinder‐shaped substrates).     

A Discrete‐Amplitude Pulse Width Modulation for a High‐Efficiency Linear Power Amplifier

A new discrete‐amplitude pulse width modulation (DAPWM) scheme for a high‐efficiency linear power amplifier is proposed. A radio frequency (RF) input signal is divided into an envelope and a phase modulated carrier. The low‐frequency envelope is modulated so that it can be represented by a pulse whose area is proportional to its amplitude. The modulated pulse has at least two different pulse amplitude levels in order that the duty ratios of the pulse are kept large for small input. Then, an RF pulse train is generated by mixing the modulated envelope with the phase modulated carrier. The RF pulse train is amplified by a switching‐mode power amplifier, and the original RF input signal is restored by a band pass filter. Because duty ratios of the RF pulse train are kept large in spite of a small input envelope, the DAPWM technique can reduce loss from harmonic components. Furthermore, it reduces filtering efforts required to suppress harmonic components. Simulations show that the overall efficiency of the pulsed power amplifier with DAPWM is about 60.3% for a mobile WiMax signal. This is approximately a 73% increase compared to a pulsed power amplifier with PWM.     

Dependence of the linewidth enhancement factor on the number of compressively strained quantum well in lasers

We have systematically studied the well number dependence of the linewidth enhancement factor in strained quantum-well (QW) lasers and have demonstrated experimentally that the linewidth enhancement factor can be reduced from /spl sim/9.4 to /spl sim/2.0 by increasing the number of compressively strained QW's from 2 to 8. This behavior is primarily due to an increase in the differential gain with the number of QW's.     

A novel simplified process for fabricating a very high densityp-channel trench gate power MOSFET

A novel simplified fabrication method of a very high density p-channel trench gate power MOSFET using four mask layers and nitride/TEOS sidewall spacers is realized. The proposed process showed improved on-resistance characteristics of the device with increasing cell density and the cost-effective production capability due to the lesser number of processing steps. By using this process technique, a remarkably increased high density (100 Mcell/inch²) trench gate power MOSFET with a cell pitch of 2.5 μm could be effectively realized. The fabricated device had a low specific on-resistance of 1.1 mΩ-cm² with a breakdown voltage of -36 V     

Improvement of kink and beam steering characteristics of 0.98-μmGaInAs-GaInP high-power lasers utilizing channel ion implantation

We demonstrate a kink and beam steering free operation of 0.98-μm GaInAs-GaInP high-power ridge waveguide (RW) lasers utilizing channel ion implantation. The ion-implanted regions along the both sides of the ridge effectively suppressed the excitation of higher order lateral modes, which causes beam steering and kink. The maximum power without beam steering and kink has been achieved over 250 mW for channel ion-implanted RW lasers with 1.8-3.7-μm ridge width, compared to 120-mW maximum power without the channel ion implantation     

A Real-Time Video Decoder for Digital HDTV

In this paper, an architecture for real-time digital HDTV video decoding is presented. Our architecture is based on a dual decoding datapath controlled in a fixed schedule with an efficient write-back scheme for anchor pictures. The decoding datapath is synchronized at the block (8 × 8 pixels) level. Unlike other decoding approaches such as the slice bar decoding method and the cross-divide method, our scheme reduces memory access contention problem to achieve real-time HDTV decoding without a high cost in overall decoder buffers, architecture, and bus. In comparison to data-flow approaches, our method eliminates the complexity associated with tagged data operations. Our anchor picture storage is organized to minimize page-breaks during memory accesses. Simulation shows that with a relatively low rate 81 MHz clock, our decoder can decode MPEG-2 MP@HL HDTV in real-time, based on an ATSC video format of 1,920 × 1,080 pixels/frame at 30 frames/s, at a bit rate of 18 to 20 Mbps.     

Effect of External Viscous Load on Head Movement

Quantitative measurements of horizontal head rotation were obtained from normal human subjects intending to make "time optimal" trajectories between targets. By mounting large, lightweight vanes on the head, viscous damping B, up to 15 times normal could be added to the usual mechanical load of the head.     

An iterative FEM for scattering by a 3-D cavity-backed aperture

A finite-element method (FEM)-based hybrid method (or iterative FEM) is successfully applied to a three-dimensional (3-D) scattering problem without the effect of internal resonance. With only a small number of meshes around a 3-D scatterer, this FEM is shown to give an accurate result through several iterative updates of the boundary conditions. To confirm the efficiency of this method, scattering from a 3-D cavity-backed aperture is analyzed and the results obtained are compared with the same obtained by another conventional method     

Image Independent Driving Power Reduction for High Frame Rate LCD Televisions

In this letter, the constant driving power reduction ratio has been achieved for column drivers regardless of the input image by incorporating a new static power reduction scheme into the previous dynamic power reduction method. The measured power reduction ratio is around 50% for a 120 Hz liquid crystal display panel in such cases of still input video and fallback.     

On the selective counting of third-order products

A practical and efficient method is presented for the counting of third-order products generated by an arbitrary number of carriers with arbitrary power spectral shapes. In particular, three selective counting procedures (i.e. sorting by position, sorting by position and group, and sorting by position, group, and kind) are introduced in a systemic way, based upon a discrete third-order Volterra model. The advantage of the counting algorithm is that (1) the algorithm provides the exact counting of third-order products of all eleven possible groups; (2) the counting process requires only two multiplications for the selective counting of third-order products at each position, and the algorithm, which is thus efficient, can be easily implemented