Effects of Pb Intercalation on the Structural and Electronic Properties of Epitaxial Graphene on SiC

The effects of Pb intercalation on the structural and electronic properties of epitaxial single‐layer graphene grown on SiC(0001) substrate are investigated using scanning tunneling microscopy (STM), noncontact atomic force microscopy, Kelvin probe force microscopy (KPFM), X‐ray photoelectron spectroscopy, and angle‐resolved photoemission spectroscopy (ARPES) methods. The STM results show the formation of an ordered moiré superstructure pattern induced by Pb atom intercalation underneath the graphene layer. ARPES measurements reveal the presence of two additional linearly dispersing π‐bands, providing evidence for the decoupling of the buffer layer from the underlying SiC substrate. Upon Pb intercalation, the Si 2p core level spectra show a signature for the existence of Pb? Si chemical bonds at the interface region, as manifested in a shift of 1.2 eV of the bulk SiC component toward lower binding energies. The Pb intercalation gives rise to hole‐doping of graphene and results in a shift of the Dirac point energy by about 0.1 eV above the Fermi level, as revealed by the ARPES measurements. The KPFM experiments have shown that decoupling of the graphene layer by Pb intercalation is accompanied by a work function increase. The observed increase in the work function is attributed to the suppression of the electron transfer from the SiC substrate to the graphene layer. The Pb intercalated structure is found to be stable in ambient conditions and at high temperatures up to 1250 °C. These results demonstrate that the construction of a graphene‐capped Pb/SiC system offers a possibility of tuning the graphene electronic properties and exploring intriguing physical properties such as superconductivity and spintronics.     

Effects of a small amount of H2O on negative ion mobility and ion-molecule reactions in O2 at atmospheric pressure

In this study, we have measured the negative ion mobility in O₂ at high pressures with a little amount of H₂O concentration between 15 and 17,000 ppb. After that, we carried out a Monte Carlo simulation using mobility of electrons, that of the ions obtained in the measurements, and rate coefficients of ion-molecule reactions. As a result, the mobility value 2.39 cm²/V·s of O₄¯ is obtained in ultrahigh purity O₂ of which the H₂O concentration is between 15 and 100 ppb. Moreover, the mobility decreases with the H₂O concentrations at which the ion species are considered to be O₂¯·(H₂O)_n (_n = 1, 2, 3). Then, we compared the experimental result with that of the simulation and estimated the ion mobility and rate coefficients of ion molecule reactions. Simulation results using estimated values of the ion mobility and rate coefficients agree well with measurement results.     

Gfarm Grid File System

Gfarm Grid file system is a global distributed file system to share data and to support distributed data-intensive computing. It federates local file systems on compute nodes to maximize distributed file I/O bandwidth, and allows to store multiple file replicas in any location to avoid read access concentration of hot files. Data location aware process scheduling improves the file I/O performance of distributed data-intensive computing. This paper discusses the design and implementation of the Gfarm Grid file system, and reports the performance.     

Multi‐temporal analysis of MODIS data to classify sugarcane crop

This paper presents a feasibility study using multi‐temporal Enhanced Vegetation Index (EVI) from Moderate Resolution Imaging Spectroradiometer (MODIS) data to classify sugarcane crop. This study was carried out in São Paulo State which is the major sugarcane producer in Brazil, occupying more than 3.1 million hectares. Cloud‐free MODIS images (16 days mosaics) were acquired over a period of almost 15 months. Samples of sugarcane and non‐sugarcane were randomly selected and cluster analysis was performed to establish similar EVI temporal behaviour clusters. It was observed that EVI was sensitive to variations in land‐use cover mainly due to phenology and land management practices. Therefore, selection of sugarcane samples with similar EVI temporal behaviour for supervised classification was difficult due to both large planting and large harvesting periods. Consequently, cluster analysis was chosen to carry out an unsupervised classification. The best results were obtained in regions occupied by: natural and planted forest, soybean, peanuts, water bodies and urban areas which contrasted with the temporal‐spectral behaviour of sugarcane. The lowest performance was observed mainly in regions dominated by pasture, which has similar temporal‐spectral behaviour to sugarcane. This study provided useful information to define a MODIS image classification procedure for sugarcane crop for the whole State area based on the large amount of cloud‐free MODIS images when compared with other currently available optical sensors.     

A novel pixel memory using integrated voltage‐loss‐compensation (VLC) circuit for ultra‐low‐power TFT‐LCDs

Abstract— A novel pixel memory using an integrated voltage‐loss‐compensation (VLC) circuit has been proposed for ultra‐low‐power TFT‐LCDs, which can increase the number of gray‐scale levels for a single subpixel using an analog voltage gray‐scale technique. The new pixel with a VLC circuit is integrated under a small reflective electrode in a high‐transmissive aperture‐ratio (39%) 3.17‐in. HVGA transflective panel by using a standard low‐temperature‐polysilicon process based on 1.5‐μm rules. No additional process steps are required. The VLC circuit in each pixel enables simultaneous refresh with a very small change in voltage, resulting in a two‐orders‐of‐magnitude reduction in circuit power for a 64‐color image display. The advanced transflective TFT‐LCD using the newly proposed pixel can display high‐quality multi‐color images anytime and anywhere, due to its low power consumption and good outdoor readability.     

Preparation of Fe-N films by r.f. sputtering

Fe-N films over a wide compositional range have been prepared by the reactive sputtering method. Fe-N sputtered films were composed of a single or two phases such as-Fe₂N,-Fe_3.02N,-Fe_3.82N,-Fe₄N and-Fe; however, an unknown phase was observed at a higher nitrogen pressure. A remarkable preferred orientation of the-Fe_3.02N (110) plane parallel to the film surface was observed. The Curie temperature of the sputtered -Fe_3.82N sample was 490° C, which was almost the same as that of-Fe₄N prepared by metal nitriding. The saturation magnetization, _s, of the sputtered Fe-N samples decreased from 151.8 to 42.4 e.m.u.g^–1 with increasing nitrogen content from 7.94 to 24.87 at%, and its coercive force,₁ H _c was found to lie in the range 150 to 600 Oe in the powder form at room temperature.     

Aerial firefighting against urban fire: Mock-up house experiments of fire suppression by helicopters

The Great Hanshin Earthquake in 1995 claimed approximately 6400 lives. The majority was killed in large fires after the earthquake. Roads were cut off and collapsed buildings blocked the access of fire engines to fire fields. Water mains were broken and lack of water prevented firefighting efforts. If aerial firefighting had been effectively applied, many lives could have been saved.     

CW Lasing at 1.35 $mu$m From Ten InAs–Sb : GaAs Quantum-Dot Layers Grown by Metal–Organic Chemical Vapor Deposition

We report the fabrication of GaAs-based quantum-dot (QD) lasers grown by metal-organic chemical vapor deposition (MOCVD) above 1.3 m. We fabricated a laser diode with ten stacked InAs-Sb:GaAs(100) QD layers, grown by antimony-surfactant-mediated growth. Ground-state lasing was obtained under continuous-wave operation at room temperature at 1.35 mum, with a maximum ground state modal gain of 19.3 cm^-1. These values are the highest values reported for MOCVD-grown GaAs-based QD laser.     

Integrated data structure and scheduling approach for manufacturing and transportation using hybrid genetic algorithm

The scheduling systems in industries are required to construct schedule considering many kind of elements. The Advanced Planning and Scheduling (APS) is an approach for combined problems. To realize APS system, it is important to integrate data structure and scheduling algorithm using these data. In this paper, we propose integrated data structure based on Bill of Manufacturing with information technology of XML family and new Multistage Operation-based Genetic Algorithm for scheduling subsystem. The results of numerical experiment validate effectiveness of the proposal methods. Received: June 2005/Accepted: December 2005