Direct observation of ferroelectric field effect and oxygen vacancy screening at ferroelectric–metal interface
August 21, 2014 — Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) studies of ferroelectric–metal interfaces revealed two distinct polarization charge screening mechanisms, with oxygen vacancies compensating negative charge and electrons compensating positive charge.
Magnetic fluctuations are good for superconductivity
August 15, 2014 — Atomic scale measurements of the strength of the magnetic fluctuations in a series of iron-based superconductors were made using high- resolution electron spectroscopy. Surprisingly, the superconducting transition temperature was higher when the magnitude of the fluctuating iron magnetic moment or “spin” was larger.
Thermopower Enhancement in Designer Oxide Superlattices
August 12, 2014 — A layer-by-layer design of 2D oxide superlattices with precisely controlled interface compositions has improved the thermopower of oxide thermoelectrics by 300% compared to that of bulk counterparts. Controlling the 2D carrier density through a new materials design strategy is critical for developing highly efficient thermoelectrics.
Structure-dependent Properties Guide Catalyst Design for Oxygenates Conversion
August 06, 2014 — The catalytic transformation of oxygenates (i.e. aldehydes, alcohols, ketones) on metal oxides to generate value added products such as fuels and additives is of great importance industrially, yet is not well-understood. ORNL researchers have provided new insights into how oxygenates react on metal oxide particles with well-defined structures.
Pulsed Laser Deposition of Photoresponsive Two-Dimensional GaSe Nanosheet Networks
July 31, 2014 — Researchers demonstrated a pulsed laser deposition (PLD) approach to synthesize networks of interconnected metal chalcogenide (GaSe) nanosheets that exhibit high photoresponsivity.
Predictive calculations of cuprate magnetic properties
June 24, 2014 — Magnetic couplings in a realistic cuprate system have been correctly predicted for the first time with highly accurate Quantum Monte Carlo (QMC) calculations. Effective magnetic models of superconductivity (previously reliant on experiment) can now be derived with confidence from theory, which could lead to better fundamental predictions of superconductor behavior.
Cooperative Growth of Large Single-Crystal Graphene Islands
June 12, 2014 — Researchers showed that it is possible to grow large, single-crystal graphene islands by controlling the nucleation density, which determines the growth mechanism.
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.