Spectroscopic Characterization of Silicon Wire‐Like and Porous Nanolayers in the Process of Metal‐Assisted Chemical Etching of Single‐Crystal Silicon

Abstract

The preparation of single‐crystal silicon (c‐Si) nanowires and porous nanolayers using the two‐stage metal‐assisted chemical etching (MACE) process is studied. The structures are characterized in all stages of the process by spectroscopic ellipsometry and using the following two approaches: 1) with the complex pseudo‐dielectric function ε determined and analyzed and 2) with parameters of simulated multilayer structures determined in the effective medium approximation. With the structural parameters found from scanning electron microscopy (SEM) images taken into consideration, spectra of ψ and Δ are calculated and fitted to the experimental spectra to obtain the best convergence. The thicknesses and the fractions of the components (Si:Air) in the porous Si layers and Si nanowires fabricated in the study are determined. The two‐step MACE method, compared with the single‐step process, is more promising because of the ability to control the morphology of Si nanowires using a preset morphology of Ag nanoparticles (catalyst mask). The spectroscopic ellipsometry and SEM are nondestructive and informative methods of study that can be used to obtain samples with required parameters.