Sang Ho Oh

Understanding the nature of solid-liquid interfaces is important for many processes of technological interest, such as solidification, liquid-phase epitaxial growth, wetting, liquid-phase joining, crystal growth, and lubrication. Recent studies have reported on indirect evidence of density fluctuations at solid-liquid interfaces on the basis of x-ray scattering methods that have been complemented by atomistic simulations. We provide evidence for ordering of liquid atoms adjacent to an interface

In vapor-liquid-solid (VLS) growth, the liquid phase plays a pivotal role in mediating mass transport from the vapor source to the growth front of a nanowire. Such transport often takes place through the liquid phase. However, we observed by in situ transmission electron microscopy a different behavior for self-catalytic VLS growth of sapphire nanowires. The growth occurs in a layer-by-layer fashion and is accomplished by interfacial diffusion of oxygen through the ordered liquid aluminum atoms.

Unprecedented reactivity and high stereoselectivity were observed in the ring opening of meso anhydrides under mild conditions with a cinchona-alkaloid-based sulfonamide catalyst (see scheme). Computation of the catalyst–transition-state analogue (right; gray C, white H, green F, blue N, red O, yellow S) provided insight into the origin of the stereoselectivity. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z801636_s.pdf or fr

To investigate the mechanism of f1012g twinning in magnesium (Mg) single crystal and its influence on mechanical size effects and strain rate dependent deformation behavior, in-situ microcompression of Mg 2110 pillars of various sizes from 0.5 mm to 4 mm was carried out in a scanning electron microscope (SEM) and also in a transmission electron microscope (TEM), covering strain rates from 10 4 to 10 2 s 1 . The in-situ observations directly showed that the pile-up of prismatic <a> dislocations a

Aberration-corrected scanning transmission electron microscopy (STEM) is used to reveal individual Au atom configurations inside Si nanowires grown by Au-catalyzed vapor-liquid-solid (VLS) molecular beam epitaxy (MBE). We identify a substitutional and three distinct interstitial configurations, one of which has not been previously identified. We confirm the stability of the observed point defect configurations by density functional theory (DFT) calculations. The observed number densities of the

The interface-type resistive switching devices exhibiting bipolar and multi-level resistive switching have been considered as the key component for neuromorphic device applications. To directly observe the microscopic details of underlying electrochemical redox reactions occuring at a metal/oxide interface, we implemented in situ resistive switching of TiN/Pr_0.7Ca_0.3MnO₃ (PCMO)/Pt junction devices in a transmission electron microscope (TEM). The in situ TEM obser

The elastic-to-plastic transition during the deformation of a dislocation-free nanoscale volume is accompanied by displacement bursts associated with dislocation nucleation. The dislocations that nucleate during the so-called "pop-in" burst take the form of prismatic dislocation loops (PDLs) and exhibit characteristic burst-like emission and plastic recovery. Here, we report the in-situ transmission electron microscopy (TEM) observation of the initial plasticity ensued by burst-like emission of

The mechanical properties of high-entropy alloys (HEAs) are still not deeply understood. Detailed knowledge of the strengthening mechanism, especially, the atomistic origin of solid solution hardening and its interplay with dislocation plasticity is needed. Here, we report on the dislocation glide behavior of a FeCoCrNiMn face-centered cubic (FCC) single crystal studied by in situ deformation in a transmission electron microscope (TEM). The threshold shear stress for dislocation glide in a thin

Despite a longstanding controversy surrounding TiO₂ materials, TiO₂ polymorphs with heterojunctions composed of anatase and rutile outperform individual polymorphs because of the type-II energetic band alignment at the heterojunction interface. Improvement in photocatalysis has also been achieved via black TiO₂ with a thin disorder layer surrounding ordered TiO₂. However, localization of this disorder layer in a conventional single TiO₂ nano

Misfit relaxation by dislocations in perovskite SrRuO3/SrTiO3 (001) heterostructure with low lattice mismatch (f=0.64%) was studied. Pure edge misfit dislocations (MDs) with a Burgers vector of the a〈011〉 type were found to be the major interfacial defects responsible for the misfit relief. They were introduced by half-loops expansion from the film surface as well as by extension of pre-existing dislocations in the substrate. These 45°-MDs formed along the 〈100〉 directions in a rectangular grid

Beispiellose Reaktivität und hohe Stereoselektivität wurden bei der Ringöffnung von meso-Anhydriden unter milden Bedingungen mit einem Sulfonamidkatalysator auf Cinchonaalkaloidbasis beobachtet (siehe Schema). Die Berechnung des Übergangszustandsanalogons des Katalysators (rechts; grau C, weiß H, grün F, blau N, rot O, gelb S) gab Einblick in den Ursprung der Stereoselektivität. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2008/z8