Morphology dependent PL quenching of multi-zone nanoporous silicon: Size variant silicon nanocrystallites on a single chip

Highlights: • Fabrication of multi-zone structured nano-porous silicon on a single chip is presented. • Combinatorial effect of laser beam and spiral platinum electrode is observed. • Each zone in spiral structure has a unique and distinct morphology. • Sensing study enables preparation of optimized nano-porous silicon for desirable applications. Fabrication and optical sensing studies of single plane multi-zone nano-porous silicon (n-PS) prepared using laser-induced electrochemical etching technique is presented. Single plane multi-zone pertains to lateral formation of zones in silicon bearing step pore- and nano-crystallites size on the same plane. Different morphologies assembled in the form of a spiral shaped pattern on n-PS. Such novel pattern was a consequence of coupling between laser illumination and spiral shaped counter electrode used during silicon etching. The morphology analysis was done by recording profiles of characteristic LO phonon mode of silicon Raman spectra. The asymmetry and Raman peak shift helped in discerning the multi-zone morphology and it was complimented by Scanning Electron Microscopy (SEM) and photoluminescence (PL) studies. A wide range alcohol concentration (10–200 ppm) was tested using PL quenching technique. A direct correlation between morphology of n-PS and ethanol sensitivity was ascertained. Maximum sensing response of 40% was achieved at the centre and it decreased towards the periphery of the spiral pattern. The present simple and low cost fabrication technique allows fabrication of multiple morphologies on a single chip in one step and enables preparation of optimized n-PS for desirable applications.