After learning fundamentals of the condensed matter, I focused my research on semiconductor materials and I studied their electronic properties. I'm especially focused on spectrocopic experiments based on the optical properties of semiconductors.
2006-2009
Ph.D : Electronic Properties of Silicon Nanowires obtained by a Catalyzed Growth
For a bottom-up approach, the catalysed growth of nanowires opens the way for numerous applications: vertical nano-transistors with a surrounding gate, core-shell heterostructures and so on... With these new devices, new questions emerge concerning catalyst or surface influences on the nanowire electronic properties.
My work, based on a spectroscopic study with photoluminescence experiments underlined the predominant role of the surface on the electronic properties of nanowires. The surface state passivation allowed to observe the radiative recombination of free carriers of a dense phase: the electron-hole liquid, in gold- and copper-catalysed nanowires. This liquid phase has the singularity to be stable and its density is constant.
This property is unique in semiconductors and led to a quantitative study of the influence of the surface via a modification of the surface/volume ratio. An original method for the surface recombination velocity (SRV) measure has been developed and very low SRV have been measured which is linked to an efficient passivation of surfaces states. The volume properties of gold-catalysed nanowires were found to be very similar to those of standard bulk silicon used in micro-electronics.
Finally, the sacrificial oxidation of silicon allowed to obtain nanowires whose diameter were smaller than 10 nm. The progressive oxidation of nanowires allowed the observation of a shift of the PL line towards lower energy attributed to strains, then the increase of the gap energy is correlated to the carrier quantum confinement.
