Fabrication of excimer laser annealed poly-Si thin film transistor by using an elevated temperature ion shower doping

We have investigated the effect of an ion shower doping of laser annealed poly-Si films at elevated substrate temperatures. The substrate temperature was varied from room temperature to 300°C when the poly-Si film was doped with phosphorus by a non-mass-separated ion shower. Optical, structural, and electrical characterizations have been performed in order to study the effect of the ion shower doping. The sheet resistance of the doped poly-Si films was decreased from 7 × 10⁶ Ω/sq to 700 Ω/sq when the substrate temperature was increased from room temperature to 300°C. This large change in sheet resistance is due to the fact that the doped films do not become amorphous but remain in the polycrystallinephase. The mildly elevated substrate heating appears to contribute mainly to reduction of ion damages incurred in the poly-Si films in addition to the activation of dopants during the ion shower doping. From the fabricated n-channel poly-Si TFTs, the current crowding effect do not occur because of the low contact source-drain resistance and the field effect mobility of 120 cm²/(V s) has been obtained.     

ADSORPTION OF ASPHALTS AND THEIR SIZE EXCLUSION CHROMATOGRAPHY FRACTIONS ON AGGREGATE SURFACES

The adsorption behavior of two asphalts and their size exclusion chromatography (SEC) fractions from toluene solution onto aggregate was investigated. The effect of the differences in chemistry and molecular size of the asphalt samples on their adsorption behavior on silica, granite and greywacke was determined. The adsorption of asphalts and SEC fractions on SI-1000 silica was well-represented by the Toth model, while the Radke-Prausnitz model better described their adsorption behavior on both granite and greywacke. Combining the adsorption models with the Gibbs adsorption equation of state gave the spreading pressure of each adsorbate species adsorbed on the aggregate surfaces. The spreading pressure predicted the competitive adsorptive edge of the asphalt fractions. The SEC I fractions, containing molecules of larger molecular size and higher heteroatom contents, showed higher spreading pressures than the SEC II fractions, which contained molecules of smaller molecular size and fewer heteroatoms. The asphalts yielded intermediate spreading pressures for SI-1000 silica and granite, but they gave the highest spreading pressure values for greywacke.     

Improved selective repeat ARQ scheme for mobile multimediacommunications

This paper suggests a NAK-based selective repeat (SR) scheme for reliable data transmission in the future land-mobile communications systems supporting multimedia services. The proposed scheme is an improved version of the automatic repeat request defined in IS-707. We analyze the proposed SR under the assumption of a two-states Markov channel. The numerical results show that drastic performance improvement can be achieved at the cost of minor increase in complexity     

Effect of ZnO contents at the surface of brass-plated steel cord on the adhesion property to rubber compound

An effect of ZnO concentration at the surface of brass-plated steel cord on the adhesion property between a rubber compound and a brass-plated steel cord was investigated. Cord composition was determined by an Auger microscope with Ar ion sputtering. Two different steel cords were prepared; one (cord A) had higher ZnO concentration at the cord surface compared to the other (cord B). Pull-out force of unaged adhesion sample of cord A was lower than that of cord B. But the adhesion durability of the humidity-aged adhesion sample of cord A was better than the latter. Rubber coverage of the pull out cord for the unaged adhesion samples of cord A was poor, indicating insufficient formation of an adhesion layer. Pull-out force of the thermal-aged adhesion samples decreased with increasing aging time and that of cord A was lower than that of cord B. The enhancement of rubber coverage during initial aging period could be explained by an additional formation of copper sulfide at the adhesion interphase and an increase of modulus of rubber compound adjacent to the adhesion layer. With further increases of aging time, adhesion interphase grew excessively and the physical property of rubber compound deteriorated significantly, such that rubber coverage of adhesion samples decreased markedly with increasing aging time.     

Analytical and experimental motion analysis of finger follower type cam-valve system with a hydraulic tappet

In this paper, the motion of a finger-follower type cam valve system with a hydraulic tappet was analytically and experimentally studied. First, the exact contact point between cam and follower for each corresponding cam angle was searched by kinematic analysis. Then a 6 degree of freedom lumped spring-damper-mass model was constructed to simulate the valve motion analytically. When constructing the model, most of the parameters were experimentally determined. But several values which are difficult to derive experimentally such as damping coefficients were determined with engineering intuition. In order to show the effectiveness of the analytical model, the predicted cam-valve motion was directly compared with the measured valve and tappet motions.     

Reliability improvement by the suppression of keyhole generation in W-plug vias

This paper describes a mechanism of failures in W-plug vias due to the keyhole generation, and presents the process conditions which enhance the reliability of W-plug vias. For a high aspect ratio via-hole, one of the limiting factors in the reliability of the W-plug is the generation of the keyholes. We have investigated the sensitivities of corresponding technologies and conditions to the generation of the keyholes during the plug process. They include deposition technologies of TiN and deposition conditions of W. Based on the SEM observation and the electromigration failure test, the process conditions of TiN and W have been optimized.     

An enhanced channel-quality indication (CQI) reporting scheme for HSDPA systems

A major evolution of UMTS standard is the high speed downlink packet access (HSDPA). One of key techniques supporting HSDPA is the adaptive modulation and coding (AMC) in which the modulation scheme and the coding rate are adaptively changed according to the downlink channel quality reported by the user equipment (UE). Therefore, the channel quality indication (CQI) reporting scheme is directly related to the accuracy of AMC and the performance of HSDPA. This letter proposes an enhanced CQI reporting scheme that can be used when a proportional fair scheduling algorithm (PFA) is used as a packet scheduling algorithm. The proposed scheme uses a dynamic threshold to filter off redundant CQI reports. With the proposed scheme, the battery capacity of UK can be conserved, maintaining the performance of traditional CQI reporting scheme.     

Channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories

The channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories is investigated. While the trapped charge profile-dependent overerasure is observed in 10-μm-wide device, it is suppressed in 0.22-μm-wide device. Both the overerasure suppression and gradual positive threshold voltage shift in narrow device are explained as an elevated hot hole injection efficiency followed by more pronounced redistribution of the hole profile in the channel-center and the suppression of the lateral migration of injected holes in the channel-edge, by combining the measured endurance characteristics and TCAD simulation results. Main physical mechanisms are three-dimensional distribution of the electric field by gate/drain voltage, increasing interface states, and their trapped charge with cycling in the channel-edge.     

A comparison of LII analysis results from numerical model and experiment at elevated surrounding pressures

With environmental concerns over emitted particulate matters(PM) from combustion systems, various researches have been conducted on reduction and measurement techniques of particulate matters. The LII analysis results from numerical models and experiments in an ethylene/air laminar diffusion flame at elevated pressure up to 2.0 MPa with laser fluence 0.07 J/cm², detection wavelength 400 nm were compared to validate a modified LII numerical model. The lifetime of the LII signal decreased as the elevated pressure increased, so that LII decay time also decreased in both results. In the aspect of heat transfer mechanism, it becomes earlier that dominant conduction starts. This shows that the results matched well under the pressure conditions. It is concluded that the LII numerical model could be applied to decide particle size in TIRE-LII at the high-pressure condition.     

Origin of bistability in polyfluorene-based organic bistable devices

This study examined the origin of bistability in polyfluorene (PFO)-based organic bistable memory devices (OBDs) by changing the bulk properties of PFO and metal electrodes. Two different PFOs with and without internal trap sites and two Al and Au electrodes were used. Bistability was induced in all devices when Al was deposited on PFO. On the other hand, bistable switching was observed only in the PFO device with internal trap sites when Au was deposited on PFO. Therefore, both the formation of internal trap sites and an organic–metal interface are essential for bistability in PFO-based OBDs.