Seminars and Events
Nanostructures, Surfaces, Coatings and Molecular Astrophysics
Coordinator: Rául Gago
21 February 2017, 15:00 h. Sala de Seminarios, 182
Atomic Force Microscopy in controlled environment: a powerful tool for original experiments on hybrid systems, biomaterials, and biocomposites
Université Bretagne Sud, CNRS Centre de Recherche C. Huygens
There is a growing research interest on hybrid systems, biomaterials, and biocomposites because of their industrial application demands. Owing unique properties of these materials make more attractive in electronic, medical and transport applications.
Whatever the application field, a constant need of miniaturization, performance, structure lightening necessitates working and exploring the material properties at nanoscale. To do this, one of the most powerful tool is Atomic Force Microscopy (AFM). By using AFM nanoscale tips, which interact with matter due to attractive and repulsive forces, numerous properties can be studied systematically. Due to its strong impact on properties and behaviour, temperature is considered as a key parameter. Indeed, its variations induce a significant change in material behaviour which can be positive (adhesion for example) or negative (electrical change). Consists of tip, micro-lever, photodetector, laser and control loop, the AFM can be used in different modes i.e. tapping, contact, non-contact, and PeakForce QNM. Consequently, a wide selection of measurements can be made under controlled environment (humidity, liquids, temperature, etc.,), and with different purposes such as topography, electrical measurements, force measurements, PeakForce-QNM.
To illustrate the contribution of the technics, different applications are presented. In the first part, a combination of AFM and RX reflectivity is used to understand the structure and interfaces of hybrid nanofilms (Polystyren/Gold) at different temperatures (-20°C to 220°C). In this way, AFM has been used to highlight different properties which are not possible to study by other technics such as electrical behaviour, adhesion and surface characterization with a new method
23 January 2017, 12:00 h. Salón de Actos
Semiconductor nanowire photonics
Friedrich-Schiller-University of Jena, Germany
The miniaturization of light sources, the confinement and manipulation of light on a sub-wavelength scale as well as the detection of single photons are key challenges for the realization of future photonic circuits. Here, semiconductor nanowires are of major interest as a serving material platform, since they do not only offer superior photonic properties, but can also bridge the interface to electronic circuits enabled by their semiconducting properties. The efficient and sub-wavelength waveguiding of light is one of such superior photonic properties specifying nanowires as truly one-dimensional systems for photons. It is also an important prerequisite and defines the geometrical diameter limit for enabling lasing oscillations within nanowire cavities. High pumping powers and gain values are necessary in order to overcome the thresholds for amplified spontaneous emission (ASE) and laser oscillations. We determined those thresholds for both ZnO and CdS nanowires as well as the geometrical limitations. Furthermore, the laser output originating out of the end facet of a single nanowire was detected “head-on”, and a double pump technique was applied to measure the laser dynamics. Finally, I will present in this seminar a route for “optical doping” of such nanowires, which provides a useful benchmark for the future development of these nanoscale devices, as well as the possibility of coupling with plasmonic structures.