SEM, EDX, AFM, and XPS analysis of surface microstructure and chemical composition of nanograting patterns on silicon substrates

Abstract

This study conducted a comprehensive characterization of the surface and electronic properties of nanograting patterns on a silicon substrate using SEM, EDX, AFM, and XPS techniques. SEM images confirmed well-shaped and periodic nanograting patterns with determined depths (10 nm, 20 nm, or 30 nm) created by the laser interferometry lithography process. EDX elemental mapping confirmed that the surface of the patterns was predominantly silicon, with no significant contaminants such as oxygen or carbon present. AFM topography revealed a uniform surface roughness of up to 5 nm and well-aligned periodic patterns. XPS surface composition spectra, obtained after reactive etching, indicated no metal oxide formation or organic contamination and a clear Si spectrum. XPS scans for low binding energy (0–20 eV) were recorded to extract the valence band (VB) of the patterned surface for three different indent depths. The valence band offset from the valence band edge (E_f-E_v) was calculated to be 0.2 eV for 10 nm, 0.8 eV for 20 nm, and 0.4 eV for 30 nm indents, suggesting that a 20 nm indent depth provided the highest VB offset and thus was the preferred depth to obtain enhanced conductivity of the patterned surface. The comprehensive analysis highlighted the optimal indent depth for improved surface conductivity of nanograting-patterned silicon substrates.