Thickness uniformity and pinhole density analysis of thin carbon foils using incident keV ions

The detection and characterization of thickness defects (nonuniformities and pinholes) in thin carbon foils is important in applications such as space-based particle analyzers. In this study we present a method of quantifying pinhole locations and sizes using scatter distributions of low energy ions which transit the foils. This technique, which we call transmitted ion mapping (TIM), is particularly suitable for analysis of ultrathin (≤1 μg/cm²) foils in which thickness defects cannot be detected using optical microscopy due to foil transparency. Additionally, the foils are exposed to ion doses of less than 10⁶ ions/cm², so the method is nondestructive to the foils. As an illustration of this method, thickness nonuniformities and pinholes are examined in 0.2 and 0.5 μg/cm² foils using incident 5 keV Ar⁺, Ne⁺, He⁺, and H⁺ ions.