Impact of geometry on chemical analysis exemplified for photoelectron spectroscopy of black silicon

TL;DR

This paper investigates how nanorough surface geometry, exemplified by black silicon, affects chemical analysis via X-ray photoelectron spectroscopy, revealing that surface topography can significantly influence the interpretation of chemical composition data.

Contribution

It introduces an integral geometric analysis using Minkowski tensors to quantify the impact of surface roughness on XPS measurements, enabling more accurate chemical analysis of nanostructured surfaces.

Findings

Oxide layer on black silicon is about 50% thicker than native oxide on flat silicon.

Surface geometry significantly influences XPS chemical data interpretation.

The method improves layer thickness estimates for nanorough surfaces.

Abstract

For smooth surfaces, chemical composition can be readily analyzed using various spectroscopic techniques, a prominent example is X-ray photoelectron spectroscopy (XPS), where the relative proportions of the elements are mainly determined by the intensity ratio of the element-specific photoelectrons. However, this analysis becomes more complex for nanorough surfaces like black silicon (b-Si) due to the geometry's steep slopes, which mimic local variations in emission angles. In this study, we explicitly quantify this effect through an integral geometric analysis using Minkowski tensors, correlating XPS chemical data with topographical information from Atomic Force Microscopy (AFM). This approach yields reliable estimates of layer thicknesses for nanorough surfaces. For b-Si, we found that the oxide layer is approximately 50% thicker than the native oxide layer on a standard Si wafer. This study underscores the significant impact of nanoscale geometries on chemical property analysis.