Semiconducting nanowires will become important building blocks of the next generation of miniaturized devices. Devices like sensors, light emitters, photovoltaic cells will take advantage of the small dimension of these nanostructures and of the unique features that nanowires offer with respect to their bulk counterpart as, e.g., a larger surface-to-volume ratio, the thermoelectric effect in silicon, the formation of wurtzite lattice structure in (N-free) III-V compounds, the stronger polarization dependence of light coupling as well as light wave-guiding.
Arrays of semiconductor nanowires can be grown on any substrate that stands the growth conditions. This is due to the lack of lattice parameter constraints, which are instead typical of the epitaxial growth. Hence, low-cost, glassy and plastic substrates can be in principle used and are used to grow nanowires. Ordered or disordered arrays will be obtained depending on substrate, growth technique and/or growth conditions.
The activity on semiconductor nanowires at IMM-Rome started in the late 2008 as the natural continuation of the pioneering activity begun at TASC-INFM (now IOM-CNR) a few years earlier. The research on III-V and II-VI compounds (grown at IOM, in Trieste) has continued with particular focus on the optical properties and a new line was opened on silicon nanowires grown by plasma-enhanced chemical vapour deposition.
Research topics include (but are not limited to):
the search for growth seeds alternative to gold (the most used metal to induce the growth but incompatible with the silicon technology platform)
the growth without the use of any metal seed (self-catalysed growth)
the determination of the band structure of wurtzite GaAs nanowires
the optical properties of III-V, II-VI and Si nanowires
Beyond growth, the main experimental activities include continuous-wave and time-resolved photoluminescence, Raman, continuous-wave and fast-transient transmission. Synchrotron radiation is often used for particular studies. Fabrication facilities located in our clean room are used to obtain special nanostructures like hollow or telescopic nanowires.