Room Temperature Fabrication of Silicon Nanocrystals by Pulsed Laser Deposition

In this work a room temperature single-step physical vapour deposition process is presented for the fabrication of nanosized Si crystals (diameter below 10 nm) embedded in an amorphous matrix, together with unique novel nanostructures consisting of silicon amorphous-crystalline core-shell nanostructures. Pulsed laser deposition in a background atmosphere (Ar or a mixture of < 3 vol. % of H2 in Ar) is used to induce cluster nucleation in the gas phase and to vary the deposition kinetic energy, in order to grow Si films of different morphology and porosity, at the nanoscale, as a function of gas pressure. Relatively high-pressure processing (100 Pa) leads to a hierarchically nanostructured film composed of Si nanocrystals embedded in a columnar porous amorphous matrix, as assessed by high resolution transmission electron microscopy. Raman spectroscopy analysis shows quantum-confinementinduced shift of the Si peak at 520 cm-1, thus confirming the occurrence of nanocrystals. Finally, in-situ silicon oxidation has been effectively shown to be decreased after adaptation of a mixture of few-percent-hydrogen in argon as background gas.