Polar ordering induced by oxygen vacancies
June 02, 2014 — A combination of scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and density functional theory (DFT) calculations show that it is possible to achieve polar order in a superlattice made up of two non-polar oxides by means of oxygen vacancy ordering.
Stable Nanopores in Graphene
June 02, 2014 — The existence of stable holes in graphene has been demonstrated. This is a major step toward the development of robust and reliable graphene-based nanopore devices that could be used, for example, in DNA sequencing.
Clues for absence of superconductivity in an iron-based material
May 27, 2014 — The electronic properties of CaFe2As2, using a combination of bulk transport measurements and surface photoemission spectroscopy, have revealed reasons for the lack of superconductivity. These results support the suggested role of magnetism and spin fluctuations in iron-based superconductors.
Phonon localization drives nanoregions in a relaxor ferroelectric
April 11, 2014 — Neutron scattering measurements reveal that phonon localization drives the generation of polar nanoregions (PNRs) in a relaxor ferroelectric. PNRs facilitate the ability of relaxor ferroelectrics to convert between electrical and mechanical forms of energy, which is used in applications ranging from medical ultrasound to military sonar devices.
New imaging-based chemical analysis of atomic layers
February 14, 2014 — A new Z-contrast image analysis method now allows dopant atoms in two-dimensional materials to be located and quantified. With this ability, the distribution of dopants can be verified as the physical and chemical properties are modified. This new capability was used to study doped molybdenum disulfide in which the optical band gap was tuned between 1.85 and 1.
Glass-like thermal transport in AgSbTe2: nano-scale insights to improve thermoelectric efficiency
May 16, 2013 — A spontaneously forming nanostructure is identified as the origin of the extremely low glass-like thermal conductivity of AgSbTe2.
Graphitic layers suppress the coarsening of single-atom catalyst
May 10, 2013 — Niobium atoms can be stabilized in graphitic layers, and the resulting carbide complex exhibits higher catalytic activity compared to commercial platinum nanoclusters. This stabilization of single atoms overcomes the known problems of coarsening and cost encountered with the alternate approach of noble-metal sub-nanoclusters, which also exhibit excellent catalytic activities.
Neutrons reveal key role of water in polyelectrolyte dynamics
March 26, 2013 — Combined neutron scattering and computational results show that the charge on a water-dissolved polymer accelerates its dynamics through an increase in the amount of water contained within the molecule. Such polyelectrolytes, i.e.
New nanostructured phosphors for photonics and white LEDs
March 12, 2013 — A new family of one-dimensional nanostructures based on novel crystal structures has been discovered that produces strong, tunable, visible-light luminescence.
Combining diffraction theory with electronic-structure theory of solids to decode electron-energy-loss spectra
January 18, 2013 — A theory combining both a material’s electronic structure and electron beam propagation has been developed at Vanderbilt University in conjunction with experimental data obtained at Oak Ridge National Laboratory.