Nanoparticle Formation in Solids

Nanoparticles in solids can be formed through phase separation in mixtures of immiscible components. The relaxation of far-from-equilibrium mixtures towards equilibrium can proceed via self-organization of nanostructures. Depending on the degree of supersaturation, phase separation proceeds via nucleation and growth of nanoparticles or spinodal decomposition.
One of the main goals of materials research using chemical and physical vapour deposition (CVD and PVD) as well as ion beams is to synthesize nanostructures. A great effort is currently devoted to NC fabrication for micro- and optoelectronics by these techniques, because they are compatible with CMOS technology.
At first, the present contribution addresses the Si NC formation in the gate oxide by conventional ion beam synthesis (IBS) and by ion beam mixing of SiO2/Si interfaces, with special emphasis on well-controlled size and position tailoring. The two approaches will be compared and technological challenges will be discussed. Compared to conventional Si NC synthesis by Si+ ion implantation into the gate oxide, ion-beam-induced interface mixing takes advantage of self-alignment, i.e., the Si NCs are formed in SiO2 at a well-controlled distance of ~2 nm from the Si/SiO2 interfaces. Applications in non-volatile nanocrystal memories and in light emitting field-effect transistors (LEFET) are demonstrated.
Then, the phase separation by spinodal decomposition of Si-rich SiO2 layers grown by PVD (or CVD) into isolated Si NCs and percolated Si sponge-like nanostructures will be considered. Promising application in future thin film solar cells will be discussed.
The work is partially supported by BMBF (TUR 09/240).