Wavelength and coherence effects on the growth mechanism of silicon nanopillars and their use in the modification of spontaneous lifetime emission of BODIPY dye molecules

Silicon nanopillars are grown by an electrochemical\udanodization of p-type silicon wafers at low current densities\udin a hydrofluoric acid solution. CW, white light, and various\udUV pulsed lasers are employed as illumination sources\udin sample preparation to study wavelength and coherence\udeffects on the growth mechanism of the nanopillars. Coherence\udis observed to be the foundation of regularity in obtaining\udconical shapes. The pillar size is found to be almost linearly\udproportional to the employed illumination wavelength\udduring their growth. BODIPY dye molecules are chemically\udattached to these silicon nanopillars and the radiative decay\udrates are investigated by means of a time-resolved fluorescence\udexperiment. The decay rate of the dye molecules embedded\udin the vicinity of various size pillar tips is significantly\udaffected due to different apex angles of the conical\udnature. It is demonstrated that the pillar size and the separation\udbetween pillars can be adjusted if one uses a coherent\udlight source with an appropriate wavelength during the\udcourse of fabrication process