School of Physics - Research Publications

Permanent URI for this collection

http://hdl.handle.net/11343/309

Filters

2003 - 2006 5
Reset filters

Settings
Statistics
Citations
Start date: 2000 × End date: 2009 × Subject: Theoretical Physics; Condensed Matter Physics - Structural Properties ; Physical Sciences ×

Search Results

Now showing 1 - 5 of 5
  • Item
    No Preview Available
    Instabilities leading to vortex lattice formation in rotating bose-einstein condensates
    Martin, Andrew ; VAN BIJNEN, RICK ; DOW, ANITA JANE ; PARKER, NICHOLAS ; O'Dell, (The Australian Institute of Physics, 2006)
  • Item
    Thumbnail Image
    Spectroscopic imaging of single atoms within a bulk solid
    Varela, M ; Findlay, SD ; Lupini, AR ; Christen, HM ; Borisevich, AY ; Dellby, N ; Krivanek, OL ; Nellist, PD ; Oxley, MP ; Allen, LJ ; Pennycook, SJ (AMERICAN PHYSICAL SOC, 2004-03-05)
    The ability to localize, identify, and measure the electronic environment of individual atoms will provide fundamental insights into many issues in materials science, physics, and nanotechnology. We demonstrate, using an aberration-corrected scanning transmission electron microscope, the spectroscopic imaging of single La atoms inside CaTiO3. Dynamical simulations confirm that the spectroscopic information is spatially confined around the scattering atom. Furthermore, we show how the depth of the atom within the crystal may be estimated.
  • Item
    Thumbnail Image
    Lattice-resolution contrast from a focused coherent electron probe. Part I
    Allen, LJ ; Findlay, SD ; Oxley, MP ; Rossouw, CJ (ELSEVIER, 2003-07)
    To develop a Bloch wave framework for lattice-resolution contrast derived from coherent or incoherent scattering of an electron probe focused onto a crystal, boundary conditions which influence the propagation of an arbitrarily distorted coherent electron probe are addressed. These boundary conditions are particularly relevant for a probe focused within a unit cell, and lead to a general theory which hinges on Bloch wave excitation amplitudes being written as a function of beam position and focus. Whereas antisymmetric Bloch states are not excited for an incident plane wave at an exact zone axis orientation, these states may be strongly excited depending on probe focus and position within the unit cell. Equations for both coherent and incoherent lattice image contrast in scanning transmission electron microscopy are derived for any detector configuration in the Bloch wave framework. An equivalent expression amenable to evaluation via multislice techniques is also described. It is shown explicitly how mixed dynamic form factors for incoherent scattering should be taken into account for annular dark field or backscattered electron detectors, as well as for characteristic losses detected by X-ray emissions or by electron energy loss spectroscopy. A background contribution from "absorbed" electrons is included in the theory. The contribution of cross-talk from neighbouring columns to incoherent contrast is examined within the context of this theoretical framework.
  • Item
    Thumbnail Image
    Exit wave reconstruction at atomic resolution
    ALLEN, LESLIE ; MCBRIDE, WILLIAM ERIC ; O'LEARY, NICOLE LOUISE ; OXLEY, MARK PETER ( 2004)
  • Item
    Thumbnail Image
    Atomic-resolution electron energy loss spectroscopy imaging in aberration corrected scanning transmission electron microscopy
    Allen, LJ ; Findlay, SD ; Lupini, AR ; Oxley, MP ; Pennycook, SJ (AMERICAN PHYSICAL SOC, 2003-09-05)
    The "delocalization" of inelastic scattering is an important issue for the ultimate spatial resolution of innershell spectroscopy in the electron microscope. It is demonstrated in a nonlocal model for electron energy loss spectroscopy (EELS) that delocalization of scanning transmission electron microscopy (STEM) images for single, isolated atoms is primarily determined by the width of the probe, even for light atoms. We present experimental data and theoretical simulations for Ti L-shell EELS in a [100] SrTiO3 crystal showing that, in this case, delocalization is not significantly increased by dynamical propagation. Issues relating to the use of aberration correctors in the STEM geometry are discussed.