Preparation of Room-Temperature Photoluminescent Nanoparticles by Ultrafast Laser Processing of Single-Crystalline Ge

A nanostructured germanium surface was prepared by irradiating single-crystalline Ge with femtosecond laser pulses under an ambient condition. The processed samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, and Raman spectroscopy. The results have demonstrated that the processed area contains small, nanosized particles attached to microstructures. Photoluminescence in the visible region as well as asymmetric broadening of the Raman spectral feature and its downward peak shift were observed from the processed Ge surface. Our approach can be applied to pattern photoluminescent Ge nanostructures with a spatial resolution of what?