Project

Discipline

structure-property relation; nanowires; optical spectroscopy

Lead
Microscope confocal pour la correlation directe entre les proprietés structurales et optiques des nanostructures.
Lay summary
Les nanostructures semiconductrices avec des tailles de l'ordre du nanomètre ont un grand interêt parce qu'elles peuvent avoir des proprietés que le même matériau en taille plus grande.  Ces nouvelles propriétés peuvent être utiles pour developer des nouvelles applications dans les domaines de l'énergie, l'électronique ou la santé. Ici, nous allons installer une nouvelle experience pour investiguer les propriétés optiques des nanostructures et pouvoir les correler directement avec leur structure. Ceci va nous permetre de comprende des propriétés particulières liées aux défauts et/ou nouvelles phases cristallographiques. Cet instrument peut travailler à des temperatures si basses que 4.2K, et ceci est obtenu grâce à la liquefaction de l'helium in situ.

Direct link to Lay Summary

Last update: 11.03.2013

Active participation

Number	Title	Start	Funding scheme

Semiconductor structures with nanoscale dimensions represent a wide and interdisciplinary field in basic and applied research. It fosters the exploration of new materials combinations and the discovery of novel functional properties of matter. We are particularly interested in semiconductor nanowires: filamentary crystals with a diameter of the order of few to tens of nanometers. Nanowires have opened up new avenues in areas such as optoelectronics, sensing and energy harvesting. The direct correlation between the structure and functional properties at the nanoscale has proven to be key for a deep understanding of materials engineering. This is especially important in the case of novel materials, as statistical variations within one sample can mislead the interpretation of local measurements, thereby delaying the progress in the field. In this project, we request funding for the purchase of a special instrument that will enable us to directly correlate different properties on the same nanoscale object (mostly nanowires, but not strictly). In particular, we ask for a scanning confocal microscope which will allow us to measure simultaneously the optical and electric properties of an individual nanoscale object with high spatial resolution from 4.2 to 300 K. Experiments will include photoluminescence, Raman spectroscopy and photoconductivity. Making use of dedicated markers, we will correlate the optical and electronic properties directly by transmission electron microscopy performed on one and the same nanowire or nanodevice. The new types of heterostructures we plan to study include: i) the combination of III-V semi-conductors with silicon within one and the same nanowire, ii) phase segregated quantum dots in a nanowire iii) crystal-phase engineered quantum dots, and iv) antimony-based alloys intro-duced into a GaAs or InAs nanowire. All these structures will be realized with a molecular beam epitaxy machine in our laboratory. In particular, we will avoid the usage of external metal catalyst to drive the nucleation and growth of nanowires. In this way, we will be able to attribute the measured properties exclusively to the heterostructures and not to impurities incorporated. Finally, we would like to add that the requested equipment will strengthen our current collabo-rations within EPFL. In particular, we will be able to better explore in detail the functional and structural properties of novel carbon and chalcogenide layered nano-materials synthetized in the laboratories of Prof. Frauenrath and Prof. Kis, respectively. As a consequence, we will ex-pand our possibilities in terms of characterization of nanoscale materials. Overall, this micro-scope we will allow us to achieve a leading position in the creation and characterization of nanodevices with novel functionality based on engineered semiconductor nanowires and be-yond.