An 8.1-ns Column-Access 1.6-Gb/s/pin DDR3 SDRAM With an 8:4 Multiplexed Data-Transfer Scheme

Three circuit techniques for an 8.1-ns column-access 1.6-Gb/s/pin 512-Mb DDR3 SDRAM using 90-nm dual-gate CMOS technology were developed. First, an 8:4 multiplexed data-transfer scheme, which operates in a quasi-4-bit prefetch mode, achieves a 3.17-ns reduction in column-access time, i.e., from 11.3 to 8.13 ns. Second, a dual-clock latency counter reduces standby power by 22% and cycle time from 1.7 to 1.2 ns. Third, a multiple-ODT-merged output buffer enables selection of five effective-resistance values Rtt (20, 30, 40, 60, and 120 Omega) without increasing I/O capacitance. Based on these techniques, 1.6-Gb/s/pin operation with a 1.36-V power supply and a column latency of 7 was accomplished     

Characterization of a distributed feedback laser withair/semiconductor gratings embedded by the wafer fusion technique

Wafer fusion between patterned or structured wafers is very useful in the construction of new optical materials and/or devices that have submicrometer-order structures inside semiconductors. In order to investigate the feasibility of wafer fusion for this purpose, a distributed feedback (DFB) laser wafer developed which has air/semiconductor gratings that are embedded using the wafer fusion technique. In this paper, the characteristics of the newly developed DFB laser and the coupling coefficient are investigated. Single-longitudinal-mode oscillation at 1.28 μm is achieved under pulsed conditions at room temperature with a low threshold current density of 1.3 kA/cm², and the coupling coefficient is estimated to he approximately 100 cm^-1. In addition, high-power surface emission (over 6 mW) is demonstrated due to the large difference between the refractive index of air and that of InP. These results indicate the feasibility of applying wafer fusion techniques to form submicrometer structures in semiconductors, and several other applications are expected     

Photoconductivity of DLC film deposited by pulsed discharge plasma CVD

DLC films were deposited by a new pulsed DC discharge plasma chemical vapour deposition (CVD) using hydrogen and methane gas mixture. When methane concentration (Cm) i.e. CH₄/(H₂ + CH₄) was increased from 3 to 40%, the graphitization of the carbon film increases as evident from Raman study. When Cm was increased to 30%, DLC film shows photoconducting property. The white light photoconductivity (S = I_l/I_d, where I_l is light current and I_d is dark current) measured with solar simulator under AM 1.5 condition was approximately 20 at room temperature. The photoconductivity was not clear when Cm was lower than 20%. ESR measurements also show that the electron spin density was slightly decreased with decreasing concentration of methane. Thus we can conclude here that at higher concentrations of methane at 30%, Sp² content of the film increases and the DLC film becomes photoconducting.     

A simple and fast method to disperse long single-walled carbon nanotubes introducing few defects

A simple and fast dispersion method that incorporates heating is used to disperse long (more than 10 μm) single-walled carbon nanotubes (SWCNTs) with minimal defects. The method enables a dispersed solution of SWCNTs to be produced in less than 10 min in only three steps: (1) addition of the dispersant, (2) heating, and (3) grinding. The dispersion method does not require sonication, which shortens the SWCNTs and can generate surface defects. SWCNT films were prepared from the dispersed solution, and the films exhibited a resistance of 380 Ω/sq at a transparency of 64.8%. This dispersion method can be easily scaled up, making it useful for the preparation of dispersed SWCNTs for commercial and industrial applications.     

Stress intensity factor for transient thermal stresses in a transversely isotropic infinite body with an external circular crack

Summary The present work deals with the transient thermal stress in a transversely isotropic infinite body with an external circular crack. The surface cooling of the crack depends on position and time. Since it it usually very difficult to obtain an analytical solution for the temperature field, a finite difference formulation with respect to a tive variable is introduced. In the first step, applying this method to the general heat conduction equation in an orthotropic body, a very compact difference equation with respect to the spatial variables is obtained. In the second step, this method is applied to the transient thermoelastic problem in a transversely isotropic infinite body with an external circular crack subjected to heat exchange on the crack surface. Thermal stresses are analyzed by means of the transversely isotropic potential functions method.With 7 Figures     

Mutual injection-locking properties of monolithically-integratedsurface-emitting multiple-quantum-well distributed feedback lasers

The mutual injection-locking properties of a coupled pair of multiple-quantum-well distributed-feedback lasers with grating output couplers were investigated experimentally and theoretically. When the mutual injection locking occurred, the output of one laser decreased while that of the other increased. The locking curve was asymmetric, and a stable and an unstable locking region existed. From the theoretical analysis, it was found that the phase delay with which the electric field emitted from each laser to the other laser significantly influences the locking characteristics. The increase and decrease of the locked output power are caused by the phase delay. It is also shown that the laser which receives the larger optical injection behaves like a slave laser and the laser which has less optical injection behaves like a master laser, and the shape of the locking curve is determined by the balance between the α parameter and the thermal resistance     

Dynamic spectral width of an InGaAsP/InP electroabsorption light modulator under high-frequency large-signal modulation

The first measurements of dynamic spectra of an InGaAsP/InP electroabsorption light modulator under high-frequency large-signal modulation are reported. A spectral broadening factor ? was determined from the relative sideband strength to the carrier, and it decreased with increasing operating electric field in the modulator. The estimated ?-value for full modulation was |?| = 2.3, which can be reduced by designing a modulator to give a more effective change of electro-absorption.