Matter Adsorbed on Nanoscale Devices

University Of Washington, Seattle WA

Investigators

Abstract

Technical Abstract This project will measure the properties and phases of matter in the form of a single layer of atoms or simple molecules deposited on one, two, or bundled single-walled carbon nanotubes. With already designed, constructed and tested very sensitive one- and two-suspended nanotube mechanical oscillators vibrating in the upper megahertz range to act as extremely sensitive mass balances (at the level of a few atoms), this project will measure mass adsorption isotherms using atoms from the He isotopes to Xe, and the interesting molecules of hydrogen, nitrogen and oxygen. Due to the pristine surface and very low mass of the suspended nanotubes, this project will map accurately phase boundaries, measure critical and tri-critical parameters of two-dimensional (2d) matter, study 2d to one-dimensional (1d) crossover behavior as a function of temperature and adsorbed mass, obtain excellent values of heats of adsorption for both classical and quantum mechanical monolayers, and study the effect of surface adsorbates on the electronic properties of the substrate, which may lead to the fabrication of new ultra sensitive matter specific detectors. For those systems of interest, this project will measure the crystalline structure and the phonon spectrum of the adsorbates through an international collaboration using the facilities in Grenoble, France. Graduate and undergraduate students participating are being trained in contemporary electronic, thermodynamic, scanning and scattering measurement techniques, all applicable to nanotechnology. Non Technical Abstract. Films of atoms or molecules just one layer thick (said to be "two-dimensional") condense and solidify at lower temperatures than regular "three-dimensional" matter. Lines of atoms (the extreme "one-dimensional" case) are expected not to condense or solidify even all the way down to absolute zero of temperature. To explore this fascinating limit, this project will measure the properties of matter in the form of a single layer of atoms or simple molecules confined to the surface of one or two individual single-walled carbon nanotubes. With nanotube mechanical oscillators which we have already designed, constructed and tested acting as extremely sensitive mass balances (which can detect just a few atoms on the surface), this project will measure mass deposition at many different temperatures, with atoms ranging from the isotopes of helium (low mass) to xenon (large mass), and the molecular forms of hydrogen, nitrogen and oxygen which are of great practical interest. This project also will study their effect on the electrons moving in the nanotubes, which may lead to new, more sensitive and gas-specific detectors. For certain systems this project will also measure the arrangement and the vibrational spectrum of the adsorbates through an international collaboration using facilities in Grenoble, France.This project involves graduate and undergraduate students who are being trained in contemporary electronic, thermodynamic, scanning and scattering measurement techniques applicable to nanotechnology, over a wide range of temperatures.