Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Learn the basic properties and designs of modern VLSI devices, as well as the factors affecting performance, with this thoroughly updated second edition. The first edition has been widely adopted as a standard textbook in microelectronics in many major US universities and worldwide. The internationally-renowned authors highlight the intricate interdependencies and subtle tradeoffs between various practically important device parameters, and also provide an in-depth discussion of device scaling and scaling limits of CMOS and bipolar devices. Equations and parameters provided are checked continuously against the reality of silicon data, making the book equally useful in practical transistor design and in the classroom. Every chapter has been updated to include the latest developments, such as MOSFET scale length theory, high-field transport model, and SiGe-base bipolar devices.

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Fundamentals of Modern VLSI Devices

A prevalent and pervasive view of designing is that it can be modeled using variables and decisions made about what values should be taken by these variables. The activity of designing is carried out with the expectation that the designed artifact will operate in the natural world and the social world. These worlds impose constraints on the variables and their values; so, design could be described as a goal-oriented, constrained, decision- making activity. However, design distinguish- es itself from other similarly described activities not only by its domain but also by additional necessary features. Designing involves exploration, exploring what variables might be appropriate. The process of explo- ration involves both goal variables and deci- sion variables. In addition, designing involves learning: Part of the exploration activity is learning about emerging features as a design proceeds. Finally, design activity occurs within two contexts: the context within which the designer operates and the context produced by the developing design itself. The designer’s perception of what the context is affects the implication of the context on the design. The context shifts as the designer’s perceptions change. Design activity can be now characterized as a goal-oriented, con- strained, decision-making, exploration, and learning activity that operates within a con- text that depends on the designer’s percep- tion of the context.

Design Prototypes: A Knowledge Representation Schema for Design

Creativity: Flow and the Psychology of Discovery and Invention

Cognitive engineering

The formation of a nanometer-size oxide pattern on silicon using a scanning probe microscope (SPM) has been widely reported in the literature No analytical model has been proposed, however, to explain the variation of the oxide height with both polarization and speed of the SPM tip In this letter, we explain quantitatively the variation of the oxide height with the polarization and the speed of the tip with a model based on field induced oxidation Data analysis also allows us to estimate the thermal activation energy of the oxidation process, (∼015 eV) This low value is compared with activation energies measured for thermal and plasma oxidation of silicon

Nanooxidation using a scanning probe microscope : an analytical model based on field induced oxidation

A comparison between scanning tunneling microscope (STM) and atomic force microscope (AFM) nanolithography techniques based on local oxidation of silicon is proposed. This work deals with the three different near-field microscopy techniques, namely, STM, AFM in contact mode (CM-AFM), and tapping mode (TM-AFM), all of them operated in air. The thickness and width of oxide stripes are studied as a function of the applied probe–sample voltage, the speed of the probe and the setpoint (current, applied force, and vibration amplitude for STM, AFM contact, and tapping, respectively). The advantages and drawbacks of each technique are analyzed, establishing TM-AFM as the best candidate for scanning probe microscope nanolithography.

Characterization of scanning tunneling microscopy and atomic force microscopy-based techniques for nanolithography on hydrogen-passivated silicon

This article investigates the extraction of low Schottky barrier heights in the perspective of integration of metal–oxide–semiconductor field effect transistors (MOSFET) with a metallic source/drain. A test structure composed of two back-to-back junctions is proposed to characterize materials with a low Schottky barrier. To complete the proposed measurement setup, particular attention is placed on a Schottky transport model that continuously combines thermionic emission, field emission, and barrier lowering due to image charge. In the case of platinum silicide (PtSi) contact, it is shown that Arrhenius plots can be accurately reproduced over a wide range of temperature and applied bias. A consolidation of the measurement strategy and of the associated transport model is also performed through measurements and simulations on a long channel p-type Schottky barrier silicon-on-insulator MOSFET with PtSi source/drain. A excellent agreement between simulated and experimental current-voltage characteristics is o...

Measurement of low Schottky barrier heights applied to metallic source/drain metal–oxide–semiconductor field effect transistors

As an attempt to considerably reduce the equivalent contact resistivity of Schottky junctions, this letter studies the integration of rare-earth silicides, known to feature the lowest Schottky barriers (SBs) to electrons, coupled with a dopant segregation based on arsenic (As+) implantation. Both erbium (Er) and ytterbium (Yb) have been considered in the implant-before-silicide (IBS) and implant-to-silicide flavors. It is shown that the two schemes coupled with a limited thermal budget (500degC) produce an SB below the target of 0.1 eV. The implementation of IBS arsenic-segregated YbSi1.8 junctions in an n-type SB-MOSFET is demonstrated for the first time resulting in a current-drive improvement of more than one decade over the dopant-free counterpart.

Arsenic-Segregated Rare-Earth Silicide Junctions: Reduction of Schottky Barrier and Integration in Metallic n-MOSFETs on SOI

This article proposes an enhanced oxidation model for scanning probe microscope (SPM) nanolithography that reproduces the power-of-time law reported for tip-induced anodic oxidation. It is shown that the space charge resulting from nonstoichiometric states strongly limits the oxidation rate. The direct relationship between the oxide thickness and time is provided by integration of the oxide rate equation. Measurements on SPM-induced oxides generated on a titanium surface are compared to theory. The predominant role of the space charge is corroborated by electrical measurements on oxide barriers that exhibit current fluctuations due to Coulombic effects.

Emmanuel Dubois

Papers

Nanooxidation using a scanning probe microscope : an analytical model based on field induced oxidation

Characterization of scanning tunneling microscopy and atomic force microscopy-based techniques for nanolithography on hydrogen-passivated silicon

Measurement of low Schottky barrier heights applied to metallic source/drain metal–oxide–semiconductor field effect transistors

Arsenic-Segregated Rare-Earth Silicide Junctions: Reduction of Schottky Barrier and Integration in Metallic n-MOSFETs on SOI

Kinetics of scanned probe oxidation: Space-charge limited growth