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-nanodotSi O2 masked Si substrate is investigated. The 320-nm -tall Si nanopillars obtained by C F4 Ar mixed inductively coupled-plasma reactive ion etching process with density of 2.8× 1010 cm-2 further shrink size from 30 to 6 nm by oxidation and etching. Blue-green μ-PL with two decomposed wavelengths at 425 and 475 nm is attributed to oxygen-related defects on the oxidized Si nanopillar surface. Defect-related near-infrared PL at 703 and 740 nm remains unchanged, while a quantum-confinement-effect- dependent PL blueshifted from 874 to 826 nm as the Si nanopillar size reduces from 7.2 to 6.0 nm is preliminarily observed.