Nanostructured solid-state materials: from fundamental properties to optoelectronic technologies

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Transport of charges in solid-state materials, in particular semiconductors, is the basis of many modern-day technologies ranging from the transistor, to light emitter, and solar cells. Modifications and / or organization of the structure of these materials at the nanoscale are natural research avenues to reduce the size of devices and to continually develop innovative devices that take advantage of new phenomena, including quantum confinement effects. The elementary excitations and charge transport mechanisms are found to be fundamentally different in these nanostructures and nanostructured materials. New properties can also emerge from the assembly of nanostructures and the engineering of composite nanomaterials on a macroscopic scale. The terahertz (THz) radiation is an extremely powerful probe to study electronic transport properties in these materials. Technological advances of the last decade have helped develop performant terahertz spectroscopy systems. In particular, it is now possible to work with broadband sources and detectors (0.1 to more than 10 THz, or 0.4 to more than 40 meV) and low-noise THz spectroscopy systems, for the study of transport mechanisms at extremely high frequencies. Time-domain THz spectroscopy techniques can be applied to a large variety of solid-state materials from metals, to semiconductors and insulators. Dynamical phenomena and non-equilibrium properties can also be studied through the use of an additional optical pulsed beam and time-resolved measurements on femtosecond to nanosecond time scales. These state-of-the-art terahertz techniques enable fundamental and applied studies of great interest in the fields of nanotechnologies, materials sciences, electronics and optoelectronics. Considering the spectacular progress in nanofabrication techniques and recent advances in terahertz technologies, longer-term goal of my research program is firstly to push further our fundamental understanding of the electronic properties that can arise from structuring materials at the nanoscale, and assembling nanostructures or engineering nanocomposite materials on a macroscopic scale, and secondly to find ways to exploit these properties for the development of novel devices. Semiconductor nanostructures present great interest for nanoelectronic and optoelectronic applications. In this research program, we will contribute to a deeper understanding of the impact of various experimental parameters on equilibrium and non-equilibrium transport mechanisms in nanostructures such as nanowires and mesoscopic porous and polycrystalline structures. A large variety of new exotic materials provokes a great excitement in the community of advanced materials, recently. Emergent properties of these materials can now be probed using time-domain THz spectroscopy tools.