Phonon localization in periodic uniaxially nanostructured silicon

Phonon spectroscopy of low-dimensional silicon nanostructures may help identify and understand their unique physical properties for potentially enabling new applications. High-resolution Raman spectroscopy reveals that fabrication of such nanostructures can lead to the creation of nanosize crystallites at the silicon interface due to the introduction of defect centers which is most likely responsible for local crystal-symmetry breaking and phonon localization. By examining these nanocrystallites created in periodic crystalline silicon nanodot arrays formed in silicon-on-insulator and their dispersive and power-dependent phonon spectra, we found clear evidence of spatial phonon localization, which in turn suggests a breaking of the fundamental phonon-selection rule limiting radiative recombination in silicon’s indirect band structure.