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[Sandia Lab News]

Vol. 51, No. 3        February 12, 1999
[Sandia National Laboratories]

Albuquerque, New Mexico 87185-0165    ||   Livermore, California 94550-0969
Tonopah, Nevada; Nevada Test Site; Amarillo, Texas

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Materials, physics and chemistry

Modern integrated circuit methods were applied to solve a long-standing physics problem -- building a new type of artificially structured optical material. The result? A photonic crystal, which consists of a specially designed arrangement of interlocking silicon rods. The crystals exhibit optical properties analogous to electrons in a crystal where energy bands and energy gaps define the allowed states. This accomplishment represents a major breakthrough toward the realization of ultra-high-efficiency optical devices and loss-free guided-wave optical systems built in silicon. (1700)

A new class of thin film materials, surface alloys, is being explored. The thin film geometry stabilizes alloy compositions not stable in bulk. This suggests possible new coatings with unique properties. The capability to predict and observe the surface alloy structure and stability has been demonstrated. Atomic short-range order in prototypical Pd-Au surface alloys has been measured experimentally by in-situ scanning tunneling microscopy. Comparisons with computational predictions confirm the accuracy of the theoretical approach and establish its usefulness to predict other surface alloy phases. (8700)

We have made thin films with open pores so small that gas molecules can be selectively filtered. Our CRADA team, including Amoco Chemical Co. and New Mexico State University collaborators, provided the computational designs of microstructure that guided the chemical synthesis of the films. The resulting films have a high density of closely size-controlled pores. The goal is to use these molecular sieves to separate valuable hydrocarbon feedstock mixtures into individual molecular components without using the current energy-intensive methods. (1800, 6200, NMSU)

Self-assembled quantum dots in epitaxial strained layers are a promising technology for fabricating semiconductor nanostructures for use in tunable light emitters and quantum transistors at size scales not possible using conventional lithography. By combining finite element modeling with our novel in-situ stress and morphology measurements, we have developed a quantitative understanding of the growth of island arrays, including the critical role of subsurface strain in mediating interactions between dots. This approach is now also being applied to metal films to elucidate weapons performance and aging. (1100)

Sandia is a world leader in developing a fundamental understanding of adhesion, friction, and wear in microelectromechanical systems (MEMS). We have developed novel scanning probe microscope techniques that reveal the mechanical and chemical bonding behavior of lubricants at the molecular level, and unique micromachined structures that quantify adhesion and friction in microsystems. Extensive reliability testing has uncovered the underlying physical mechanisms of micromachine failure. These capabilities enable development of science-based predictive models for micro-machine reliability, important for future defense and industrial needs. (1100, 1700, 1800)

We have developed encapsulants and foams that are easily removable. Encapsulants are needed to protect electronic components in weapons against shock and vibration, but historically have been nearly impossible to remove due to their crosslinking, solvent resistance, and mechanical toughness. Our materials utilize a thermal scheme for removability based upon a reversible chemistry that cures solid at 60C but de-polymerizes to fluid at 90 degrees C. There is great interest in removable encapsulants so that weapon systems can be repaired or maintained over their lifetimes. (1800)

A team of Sandia, industry, and university collaborators are working toward the goal of computationally designing and synthesizing molecular sieve composite (crystalline plus amorphous) membranes for the separation of chemical feedstock molecules. This project is sponsored by DOE with a three-year, $2.4 million cooperative research and development agreement (FY97-99). Recent technical successes include the synthesis of highly oriented crystalline films and defect-free composite films. These successes have been leveraged for additional spin-off funding through grant awards from DOE/Vision 2020 and other organizations. (1800, 6200)

We have discovered a method to generate high pressures using electrokinetically driven flow in packed channels. This technology, termed electrokinetic pumping (EKP), has been used to produce over 9,000 psi pressure and over 20 ml/min flow rate in capillaries packed with micron-size beads. A patent application for a miniature EKP configuration has been filed. Applications being pursued include micro-coolers with Stanford University, arrays of actuators for vehicle control with University of Michigan, and EKP-driven mechanical actuators for a number of Sandia missions. (8300)

We demonstrated a novel three-terminal quantum tunneling transistor that is fabricated in a planar configuration, avoiding the yield and reproducibility limitations of nonplanar fabrication methods. Operation of this double electron layer tunneling transistor (DELTT) is based on control by surface Schottky gates of electron tunneling between two two-dimensional layers, allowing construction of bistable memories and digital logic circuits using a single cell. DELTT holds the potential for ultra-high-speed microelectronics. This advance was selected by Industry Week for a 1998 Technology of the Year award. (1000)

An analytical technique developed at Sandia for scanning electron microscopes is now embodied in a commercial product. The Phase Identification accessory, based on Backscattered Electron Kikuchi Patterns, is produced by Noran Instruments, Inc. on license from Sandia. The Sandia inventors also received an R&D 100 award this year. Recently the system has identified PbO2 particles as small as 0.15 micrometers. This is about 600 times smaller than the diameter of a human hair. It opens up a new area of application in the analysis of environmental particulates. (1800)

The Nonvolatile Field Effect Transistor earned a 1998 Discover Technology Award presented by Discover magazine.The award recognized the discovery of a new effect that could be induced in transistors and used for the storage of digital information in the absence of electrical power. The effect was the voltage-controlled motion of a proton defect complex in the gate oxide of transistors. A sheet of the positively charged defects could be positioned to hold the transistor in the 'on' or 'off' state. The protonic effect is being developed into a technology by Sandia and France Telecom. (1700, 1800)

Last modified: February 12, 1999


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