CAM's News page

CAM's jaunt into tech and science news of interest along with occasional commentaries and comments from participating CAM researchers and staff.

CAM is in fact: The Center For Applied Microtechnology at the University of Washington

.The Units of Nanotech: 1 millimeter = 1/1000th of a meter : 1 micron = 1/1000th of a millimeter : 1 nanometer = 1/1000th of a micron

Conference Molecular Motors New Data & Research in Applications for Nanotechnology and Nanomedicine September 14 & 15, 2000 = Royal Sonesta Hotel = Cambridge, MA USA Significant efforts have been achieved in exploring the structure and function of biological and synthetic molecular motors. How these systems might be used to engineer and power nanoscale devices and accelerate their development for practical application will only be a matter of time. With the goal of cross-fertilization between disciplines, this exciting new conference brings together an international faculty to examine molecular motor mechanisms and discuss the exciting potential for integration of biological motors with micro and nanofabricated structures.

Foresight's Molecular Nanotechnology Guidelines "To assure that research in this rapidly emerging field proceeds safely and responsibly. Based on the report of a February 1999 workshop in Monterey, Calif., sponsored jointly by the Foresight Institute and the Institute for Molecular Manufacturing, publication of the Foresight Guidelines begins an open discussion about the appropriate framework within which to develop nanotechnology. "

Note: some of the links listed here are restricted, they include Nature, Science, and some Journals.

From Physical Review Letters: Spin Configurations of a Carbon Nanotube in a Nonuniform External Potential Abstract. We study, theoretically, the ground state spin of a carbon nanotube in the presence of an external potential. We find that when the external potential is applied to a part of the nanotube, its variation changes the single electron spectrum significantly. This, in combination with Coulomb repulsion and the symmetry properties of a finite length armchair nanotube, induces spin flips in the ground state when the external potential is varied. We discuss the possible application of our theory to recent measurements of Coulomb-blocked peaks and their dependence on a weak magnetic field in armchair carbon nanotubes.

From The Journal of Chemical Physics: Characterizing nanoparticle interactions: Linking models to experiments Short Abstract. Self-assembly of nanoparticles involves manipulating particle interactions such that attractions are on the order of the average thermal energy in the system. If the self-assembly is to result in an ordered packing, an understanding of their phase behavior is necessary. Here we test the ability of simple pair potentials to characterize the interactions and phase behavior of silico tungstic acid (STA), a 1.2 nm particle.

From Applied Physics Letters: Scheme for the fabrication of ultrashort channel metal-oxide-semiconductor field-effect transistors Abstract. We present a scheme for the fabrication of ultrashort channel length metal-oxide-semiconductor field-effect transistors (MOSFETs) involving nanolithography and molecular-beam epitaxy. The active channel is undoped and is defined by a combination of nanometer-scale patterning and anisotropic etching of an n⁺⁺ layer grown on a silicon on insulator wafer. The method is self-limiting and can produce MOSFET devices with channel lengths of less than 10 nm. Measurements on the first batch of n-MOSFET devices fabricated with this approach show very good output characteristics and good control of short-channel effects.

From R&D Online: Target Design Is Key To Successful Sputtering Sputtering has several advantages over thermal evaporation by electron-beam or resistance heating. A greater variety of materials can be deposited. Sputtering also offers better thickness control, higher density films, and better composition reproducibility.

Paper in latest Nature is from UW researchers at the Department of Zoology: The segment polarity network is a robust developmental module All insects possess homologous segments, but segment specification differs radically among insect orders. In Drosophila, maternal morphogens control the patterned activation of gap genes, which encode transcriptional regulators that shape the patterned expression of pair-rule genes. This patterning cascade takes place before cellularization. Pair-rule gene products subsequently 'imprint' segment polarity genes with reiterated patterns, thus defining the primordial segments. This mechanism must be greatly modified in insect groups in which many segments emerge only after cellularization.

The latest from Nature: News US scientists seek more funds for high-tech equipment The largest professional body representing US researchers in the life sciences is urging the National Institutes of Health (NIH) to nearly quadruple its contribution to a scheme that helps investigators pay for equipment costing over $100,000. News Feature Chemistry meets computing If individual molecules can be made to process information, they could be the answer to the computer industry's prayers. Philip Ball examines the field of molecular logic, which is at last recording some significant achievements. Brief Communications Materials science: Diffusion of a polymer 'pancake' Thread-like chains of flexible polymers that adsorb to a solid surface assume a flat 'pancake' conformation when the surface coverage is low and are only able to diffuse in two dimensions because so many segments are adsorbed. Here we show that the centre-of-mass diffusion coefficient of the polymer chain, measured at dilute coverage to ensure minimal chain - chain interaction, has a strong power-law dependence on the degree of polymerization. This nonlinear dependence of polymer diffusion on a solid surface contrasts with the linear dependence observed on a fluid membrane. Letters to nature Electronic connection to the interior of a mesoporous insulator with nanowires of crystalline RuO₂ Highly porous materials such as mesoporous oxides are of technological interest for catalytic, sensing and remediation applications: the mesopores (of size 2 - 50 nm) permit ingress by molecules and guests that are physically excluded from microporous materials. Connecting the interior of porous materials with a nanoscale or 'molecular' wire would allow the direct electronic control (and monitoring) of chemical reactions and the creation of nanostructures for high-density electronic materials.

From Physical Review B: Structure and magnetism of well defined cobalt nanoparticles embedded in a niobium matrix Abstract. Our recent studies on Co clusters embedded in various matrices reveal that the co-deposition technique (simultaneous deposition of two beams: one for the preformed clusters and one for the matrix atoms) is a powerful tool to prepare magnetic nanostructures with any couple of materials even though they are miscible. We study both structure and magnetism of the Co/Nb system, which are intimately related. Because such a heterogeneous system needs to be described at different scales, we used microscopic and macroscopic techniques, and in addition local element selective probes based on x-ray absorption. We conclude that our clusters are 3-nm-diameter fcc truncated octahedrons with a pure cobalt core and a solid solution between Co and Nb located at the interface which could be responsible for the magnetically inactive monolayers we found.

From Low Temperature Physics: Hot electrons in nanocontacts Abstract. A theoretical study is made of the temperature of the electron subsystem in a microcontact as a function of the applied voltage. It is shown that in microcontacts whose characteristic linear dimension is of the order of several lattice constants (nanocontacts) a breakdown of thermodynamic equilibrium between the electrons and phonons occurs at high applied voltages. Then the temperature of the electron subsystem is a linear function of the applied voltage, and its absolute magnitude can reach values of the order of the Fermi energy. These results agree with recent experimental data.

From Physical Review Letters: Changing Shapes in the Nanoworld Abstract. What are the mechanisms leading to the shape relaxation of three-dimensional crystallites? Kinetic Monte Carlo simulations of fcc clusters show that the usual theories of equilibration, via atomic surface diffusion driven by curvature, are verified only at high temperatures. Below the roughening temperature, the relaxation is much slower, kinetics being governed by the nucleation of a critical germ on a facet. We show that the energy barrier for this step linearly increases with the size of the crystallite, leading to an exponential dependence of the relaxation time.

From the Journal of Applied Physics: Basic properties of GaAs oxide generated by scanning probe microscope tip-induced nano-oxidation process. From the Introduction "Today, scanning probe microscopes (SPMs) are widely used to produce structural, chemical and electronic modifications to the substrate surface at nanoscales and thus are recognized as possible fabrication tools for the nanoelectronics devices such as single electron transistors (SETs) and SE memories. For this purpose, the atomic force microscope (AFM) tip-generated anodic oxides have been used as etch masks to successfully demonstrate a Si metal-oxide-semiconductor field-effect transistor (MOSFET), and a side-gated FET. More recently, the AFM tip-induced anodic oxide patterns were used as the integral parts, i.e., tunnel barriers, of room temperature operable SETs in metals, such as Ti, and Nb. "

New from Science Magazine: Reports Topographic Mapping of the Quantum Hall Liquid Using a Few-Electron Bubble A scanning probe technique was used to obtain a high-resolution map of the random electrostatic potential inside the quantum Hall liquid. A sharp metal tip, scanned above a semiconductor surface, sensed charges in an embedded two-dimensional (2D) electron gas. Under quantum Hall effect conditions, applying a positive voltage to the tip locally enhanced the 2D electron density and created a "bubble" of electrons in an otherwise unoccupied Landau level. As the tip scanned along the sample surface, the bubble followed underneath. The tip sensed the motions of single electrons entering or leaving the bubble in response to changes in the local 2D electrostatic potential. Carbon Nanotube-Based Nonvolatile Random Access Memory for Molecular Computing A concept for molecular electronics exploiting carbon nanotubes as both molecular device elements and molecular wires for reading and writing information was developed. Each device element is based on a suspended, crossed nanotube geometry that leads to bistable, electrostatically switchable ON/OFF states. The device elements are naturally addressable in large arrays by the carbon nanotube molecular wires making up the devices. These reversible, bistable device elements could be used to construct nonvolatile random access memory and logic function tables at an integration level approaching 10¹² elements per square centimeter and an element operation frequency in excess of 100 gigahertz. The viability of this concept is demonstrated by detailed calculations and by the experimental realization of a reversible, bistable nanotube-based bit. Electrochemical Micromachining The application of ultrashort voltage pulses between a tool electrode and a workpiece in an electrochemical environment allows the three-dimensional machining of conducting materials with submicrometer precision. The principle is based on the finite time constant for double-layer charging, which varies linearly with the local separation between the electrodes. During nanosecond pulses, the electrochemical reactions are confined to electrode regions in close proximity. This technique was used for local etching of copper and silicon as well as for local copper deposition.

From Physics web: Schrodinger's cat comes into view: In 1935 Erwin Schrodinger proposed a famous thought experiment in which a cat was somehow both alive and dead at the same time. Schrodinger was attempting to demonstrate the limitations of quantum mechanics: quantum particles such as atoms can be in two or more different quantum states at the same time but surely, he argued, a classical object made of a large number of atoms, such as a cat, could not be in two different states. Now Jonathan Friedman and co-workers at the State University of New York (SUNY) in Stony Brook have demonstrated a macroscopic Schrodinger cat state for the first time (Nature 406 43). In their experiment a superconducting device is placed in a quantum superposition of two states: one that corresponds to a current flowing through the device in a clockwise direction, and another that corresponds to an anti-clockwise current.

Frustra laborant quotquot se calculationibus fatigant pro inventione quadraturae circuli ~Michael Stifel (1544)

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