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Lang, Sloppy, Ghassemi, and Taheri publish in ACS Applied Materials and Interfaces

Posted in News on September 11th, 2014 by admin – Comments Off

Andrew Lang, Jennifer Sloppy, Hessam Ghassemi, Dr. Taheri, and colleagues’ latest paper, titled “Atomic-scale characterization of oxide thin films gated by ionic liquid,” has been published online in ACS Applied Materials and Interfaces.

From the abstract: “Ionic liquids (ILs) have received considerable interest for use in electrostatic gating in complex oxide systems. Understanding the ionic liquid/oxide interface, and any bias-induced electrochemical degradation, is critical for the interpretation of transport phenomena. The integrity of the interface between ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate and La1/3Sr2/3FeO3 under various biasing conditions was examined by analytical transmission electron microscopy, and we report film degradation in the form of an irreversible chemical reaction regardless of the applied bias. This results in an intermixing region of 4-6 nm at the IL/oxide interface. Electron energy loss spectroscopy shows La and Fe migration into the ionic liquid, resulting in secondary phase formation under negative bias. Our approach can be extended to other ionic liquid/oxide systems in order to better understand the electrochemical stability window of these device structures..”

The accepted proof of the paper can be accessed here.

More information is available on the ACS website.

Hartshorne, Jablonski, Taheri, and colleagues publish in Small

Posted in News on August 13th, 2014 by admin – Comments Off

Matthew Hartshorne, Michael Jablonski, Dr. Taheri, and colleagues’ latest paper, titled “Observation of self-assembled core–shell structures in epitaxially embedded TbErAs nanoparticles,” has been published online in Ultramicroscopy.

From the abstract: “Self-assembled core–shell structured rare-earth nanoparticles (TbErAs) are observed in a III–V semiconductor host matrix (In0.53Ga0.47As) nominally lattice-matched to InP, grown via molecular beam epitaxy. Atom probe tomography demonstrates that the TbErAs nanoparticles have a core–shell structure, as seen both in the tomographic atom-by-atom reconstruction and concentration profiles. A simple thermodynamic model is created to determine when it is energetically favorable to have core–shell structures; the results strongly agree with the observations.”

The accepted proof of the paper can be accessed here.

More information is available on the Wiley website.

DCG hosts visiting professor, Miryam Arredondo

Posted in News on August 1st, 2014 by admin – Comments Off

The DCG is pleased to be hosting Dr. Miryam Arredondo, lecturer from the School of Mathematics and Physics at Queen’s University–Belfast in Northern Ireland. Dr. Arredondo’s work involves the study of ferroelectric domain dynamics using transmission electron microscopy. While here she will be conducting in situ microscopy studies with the group.

For more information, please visit Dr. Arredondo’s research website.

Ghassemi, Harlow, Taheri, and colleagues publish in Journal of Materials Chemistry A

Posted in News on August 1st, 2014 by admin – Comments Off

Dr. Hessam Ghassemi, Wayne Harlow, Dr. Taheri, and colleagues’ latest paper, titled “In situ environmental transmission electron microscopy study of oxidation of two-dimensional Ti3C2 and formation of carbon-supported TiO2,” has been published online in the Journal of Materials Chemistry A.

From the abstract: “Two-dimensional Ti3C2, also known as “MXene”, was oxidized in air under two different oxidizing regimes in order to produce carbon-supported TiO2. In situ TEM analysis coupled with Raman spectroscopy revealed the formation of either anatase nanoparticles or planar rutile nanocrystals, which were controlled by the time, temperature and heating rate.”

The accepted proof of the paper can be accessed here.

More information is available on the Royal Society website.

Hartshorne, Taheri, and colleagues publish in Ultramicroscopy

Posted in News on June 12th, 2014 by admin – Comments Off

Matthew Hartshorne, Dr. Taheri, and colleagues’ latest paper, titled “Specimen preparation for correlating transmission electron microscopy and atom probe tomography of mesoscale features,” has been published online in Ultramicroscopy.

From the abstract: “Atom-probe tomography (APT) provides atomic-scale spatial and compositional resolution that is ideally suited for the analysis of grain boundaries. The small sample volume analyzed in APT presents, however, a challenge for capturing mesoscale features, such as grain boundaries. A new site-specific method utilizing transmission electron microscopy (TEM) for the precise selection and isolation of mesoscale microstructural features in a focused-ion-beam (FIB) microscope lift-out sample, from below the original surface of the bulk sample, for targeted preparation of an APT microtip by FIB-SEM microscopy is presented. This methodology is demonstrated for the targeted extraction of a prior austenite grain boundary in a martensitic steel alloy; it can, however, be easily applied to other mesoscale features, such as heterophase interfaces, precipitates, and the tips of cracks.”

The accepted proof of the paper can be accessed here.

More information is available on the Elsevier website.

Spurgeon defends doctoral thesis

Posted in News on June 3rd, 2014 by admin – Comments Off

Steven Spurgeon has successfully defended his doctoral thesis, titled, “Correlating Interfacial Structure and Magnetism in Thin Film Oxide Heterostructures Using Transmission Electron Microscopy and Neutron Reflectometry.”

Winkler, Jablonski, Taheri and colleagues publish in Nano Letters

Posted in News on May 12th, 2014 by admin – Comments Off

Christopher Winkler, Michael Jablonski, Dr. Taheri, and colleagues’ latest paper, titled “Real-time observation of local strain effects on non-volatile ferroelectric memory storage mechanisms,” has been published online in the Nano Letters.

From the abstract: “We use in situ transmission electron microscopy to directly observe, at high temporal and spatial resolution, the interaction of ferroelectric domains and dislocation networks within BiFeO3 thin films. The experimental observations are compared with a phase field model constructed to simulate the dynamics of domains in the presence of dislocations and their resulting strain fields. We demonstrate that a global network of misfit dislocations at the film-substrate interface can act as nucleation sites and slow down domain propagation in the vicinity of the dislocations. Networks of individual threading dislocations emanating from the film-electrode interface play a more dramatic role in pinning domain motion. These dislocations may be responsible for the domain behavior in ferroelectric thin-film devices deviating from conventional Kolmogorov-Avrami-Ishibashi dynamics towards a Nucleation Limited Switching model.”

The accepted proof of the paper can be accessed here.

More information is available on the ACS website.

Vetterick defends doctoral thesis

Posted in News on May 9th, 2014 by admin – Comments Off

Vetterick Defense

Greg Vetterick has successfully defended his doctoral thesis on the “Radiation Tolerance Mechanisms in Nanocrystalline BCC Iron!”

Winkler defends doctoral thesis

Posted in News on March 14th, 2014 by admin – Comments Off

Winkler Defense

Christopher Winkler has successfully defended his doctoral thesis on the “Characterization of the Dynamic Behavior of Bismuth Ferrite Thin Films Under DC Bias Using In Situ Transmission Electron Microscopy.” Chris has accepted a senior research scientist position at Virginia Tech.

For more information, see the ICTAS Nanoscale Characterization and Fabrication Laboratory website.

Barr, Vetterick, Taheri, and colleagues publish in Acta Materialia

Posted in News on January 27th, 2014 by admin – Comments Off

Christopher Barr, Greg Vetterick, Dr. Taheri, and colleagues’ latest paper, titled “Anisotropic radiation-induced segregation in 316L austenitic stainless steel with grain boundary character” has been published online in the Acta Materialia.

From the abstract: “Radiation-induced segregation (RIS) and subsequent depletion of chromium along grain boundaries has been shown to be an important factor in irradiation-assisted stress corrosion cracking in austenitic face-centered cubic (fcc)-based alloys used for nuclear energy systems. A full understanding of RIS requires examination of the effect of the grain boundary character on the segregation process. Understanding how specific grain boundary structures respond under irradiation would assist in developing or designing alloys that are more efficient at removing point defects, or reducing the overall rate of deleterious Cr segregation. This study shows that solute segregation is dependent not only on grain boundary misorientation, but also on the grain boundary plane, as highlighted by markedly different segregation behavior for the Σ3 incoherent and coherent grain boundaries. . .”

The accepted proof of the paper can be accessed here.

More information is available on the Springer website.