Anomalous microphotoluminescence of high-aspect-ratio Si nanopillars formatted by dry-etching Si substrate with self-aggregated Ni nanodot mask

Microphotoluminescence (μ-PL) of high-aspect-ratio Si nanopillars fabricated by etching Ni-nanodot∕SiO2 masked Si substrate is investigated. The 320-nm-tall Si nanopillars obtained by CF4∕Ar mixed inductively coupled-plasma reactive ion etching process with density of 2.8×1010cm−2 further shrink size from 30to6nm by oxidation and etching. Blue-green μ-PL with two decomposed wavelengths at 425 and 475nm is attributed to oxygen-related defects on the oxidized Si nanopillar surface. Defect-related near-infrared PL at 703 and 740nm remains unchanged, while a quantum-confinement-effect-dependent PL blueshifted from 874to826nm as the Si nanopillar size reduces from 7.2to6.0nm is preliminarily observed.