Advanced Materials

Research Highlights for Materials Characterization

1-10 of 16 Results

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.

Magnetic fluctuations are good for superconductivity
— 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.

Polar ordering induced by oxygen vacancies
— 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
— 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
— 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
— 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
— 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.


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