The 323rd MANA Special Seminar
Prof. Jun Lou & Dr. Alberto Zobelli
| Date | March 22, Friday |
| Time | 15:30-15:30 |
| Place | Seminar Room #431, MANA Bldg., Namiki Site, NIMS |
Download PDF file for seminar info.
15:30-16:15
N3L: Exploring Structure-Property-Application Relationship at the Nanoscale
In this talk, I will review some of our recent research efforts in novel nanomaterial fabrication, advanced nanomaterial characterization, and related nanotechnology development for energy and environmental applications. In the first example, we show that under uni-axial tensile loading, single crystalline ultrathin gold nanowires might fracture in both ductile and brittle-like modes, displaying distinctively different fracture morphologies and ductility. In the second example, we highlight our recent development and application of a novel technique, which involves the usage of a silicon based micro-mechanical device that operates in conjunction with a quantitative nanoindenter within an electron microscope, to perform single fiber pullout experiments to study the multi-wall carbon nanotube (MWNT)/polymer (epoxy) interface. Finally, some potentially technological important applications related to energy and environment as well as our latest efforts on synthesis and characterization of two-dimensional materials beyond graphene will be briefly discussed.
Speaker
Prof. Jun Lou, The Nanomaterials, Nanomechanics and Nanodevices Lab (N3L), Department of Mechanical Engineering and Materials Science, Rice University, USA
Chair
Dr. Dmitri Golberg, MANA PI, MANA, NIMS
16:15-17:00
Nanometric resolved cathodoluminescence on few layers h-BN flakes
Hexagonal boron nitride (h-BN) is one of the most promising candidates for light emitting devices in the far UV region, presenting a single strong excitonic emission at 5.8 eV. However, a single line appears only in extremely pure monocrystals that can hardly be obtained only through complex synthesis processes. Common h-BN samples present more complex emission spectra that have been generally attributed to the presence of structural defects. Despite a large number of experimental studies, up to now it was not possible to attribute specific emission features to well identified defective structures. Very recently, the Orsay team has developed a cathodoluminescence detection system integrated within a scanning transmission electron microscope. This unique experimental set up is now able to provide full emission spectra with a resolution as low as few tens of meV associated with an electron probe size of one nanometer. A cathodoluminescence spectrum-image can thus be recorded in parallel with an HAADF image. We present the first nanometric resolved cathodoluminescence on few-layer chemically exfoliated h-BN crystals. We show that emission spectra are strongly inhomogeneous within individual flakes. In particular, light emission in the band gap energy region presents a high spatial localization, typically less than 100 nm. However, emission peaks close to the free exciton line appear in more extended regions. Complementary investigations through high resolution transmission electron microscopy allow to associate these latest additional emission lines with extended crystal deformation such as stacking faults and folds of the planes. State of the art quantum mechanical simulations in the framework of the Bethe Salpeter provide a deeper understanding of the nature of such excitonic emissions.
Speaker
Dr. Alberto Zobelli, Paris Sud University, France
Chair
Dr. Dmitri Golberg, MANA PI, MANA, NIMS