Advanced Materials


Materials Characterization

graphitic layers viewed at 2 nmCharacterization of materials is a key capability enabling the structure and functionality of materials to be understood, as well as the chemical processes occurring at interfaces, such as those that occur in catalysis, corrosion, and fluid transport. ORNL develops and applies a broad range of electron microscopy and electron spectroscopy techniques to provide insight into the structure and composition of materials at the atomic level. Transmission electron microscopy approaches probe functionalities (electronic structure, magnetism, etc.) and explore materials in operando, using a variety of controlled environments. A variety of scanning probe modalities have been developed to provide both atomic and nanoscale information on materials, including electronic and magnetic behaviors. Chemical imaging, which includes specialized scanning probes combined with optical and mass spectrometry techniques, can provide a wealth of information on chemistry occurring at surfaces. Another area of specializion, atom probe tomography, yields a complete three-dimensional atom-by-atom reconstruction of a specimen. Many of these capabilities are available to the scientific community through the Center for Nanophase Materials Sciences (CNMS) and the Shared Research Equipment (ShaRE) program, both of which are DOE Basic Energy Sciences user facilities. ORNL has state-of-the-art capabilities for examining a range of materials—from geological to biological materials—using nuclear magnetic resonance and mass spectrometry.

In addition to atomic and nanoscale characterization, ORNL has a comprehensive suite of mechanical materials characterization tools, ranging from routine stress/strain testing to specialized nanoindentation techniques used to examine the effects of defects in materials. ORNL also has developed a a suite of characterization techniques specially designed for use in post-irradiation examination of materials. Finally, ORNL is home to two major neutron sources that are utilized for a wide range of different neutron-based materials characterization measurements: the High Flux Isotope Reactor (HFIR) and the Spallation Neutron Source (SNS). These resources are used to study structure of a variety of materials, such as superconductors, advanced alloys and polymers. In addition, many neutron scattering techniques combined with isotopic labeling allow detailed insight into dynamics observed in catalysis, water transport through membranes and lithium transport at battery electrode surfaces. Thus, ORNL has a comprehensive set of characterization tools allowing materials to be understood from the atomic to system level.

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1-5 of 17 Results

New Method Probes Nanoscale Electrostatic Effects
— Electrostatic forces were used to observe charge transfer at the nanoscale between metal and dielectric materials. A new technique was developed to access information about charge transfer, which is a key component in processes such as storage in flash memories, electroforming in memristors, surface electrochemistry, and triboelectricity.

Tracking dopant diffusion pathways in bulk semiconductors
— A scanning transmission electron microscope (STEM) is used to locally excite and directly image the diffusion of single dopant atoms inside bulk single crystals. Although diffusion is a fundamental process that governs the structure, processing and properties of most materials, direct observations of diffusion processes have been elusive and limited to the surfaces of materials, until this work.

Laser speckle analysis resolves mesoscale transitions
— An elegant experimental approach, which requires only simple and widely available equipment, provides previously inaccessible spatial and temporal resolution on coexisting electronic domains in a technologically promising transition-metal oxide.

Creating and Activating a Terahertz Nanorotor in Graphene
— Replacing a hexagonal ring of carbon atoms in a graphene layer with a silicon trimer results in a terahertz rotor (1012 rotations/sec) with low friction. This demonstrates that the ultimate miniaturization of a mechanical device (switch, oscillator, stirrer) down to a triangular arrangement of three atoms is possible.

Direct observation of ferroelectric field effect and oxygen vacancy screening at ferroelectric–metal interface
— 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.


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