Studies in differential charging

TLDR

Differential charging in XPS/ESCA and related spectroscopies arises from various causes and can be mitigated or exploited. The study focuses on how differential charging affects metal and semiconductor dispersion or crystallite growth within insulating matrices. The authors present a series of models that analyze the roles of depth, photoionization centers, detection depth, and compensation currents in the charging process. ESCA can simultaneously probe macromorphology and surface chemistry, as demonstrated in metal catalysis, corrosion, and doped thin‑film studies.

Abstract

A detailed examination is presented of the causes, removal, and use of differential charging in x-ray photoelectron spectroscopy [electron spectroscopy for chemical analysis (ESCA)] and related spectroscopies. Particular attention is devoted to the impact of this phenomenon during the dispersion (or conversely crystallite growth) of metals and semiconductors in insulating matrices. A progressive series of models is described to determine their general and specific roles in the charging process. The effects of depth and interaction are considered for the fields involved (e.g., photoionization centers, detection depth, compensation currents, etc.). Thus, in certain cases, the ESCA may be simultaneously employed to analyze macromorphology, as well as surface and near surface chemistry. Practical examples are described from metals catalysis, corrosion and doped thin films.