Reflection spectra of microarrays of silicon nanopillars

The optical-reflection spectra of microarrays of silicon nanopillars are studied in the visible and near-IR regions. The microarrays of silicon nanopillars are formed by electron-beam lithography and reactive ion etching. The reflection spectra of nanopillar arrays with pitches of 400, 600, 800, and 1000 nm are measured. The height of nanopillars in the array is 0.5 $\mu$m, and the diameter varies from 150 to 240 nm. It is noted that the spectral features of the reflection are caused by increased absorption of individual nanopillars and interference effects inside the array. A relation between the geometric parameters of nanopillars and the resonance reflection characteristics is determined taking into account the influence of the substrate.