X-ray photoelectron spectroscopy analysis of organic materials etched by charged water droplet impact

Electrospray droplet impact (EDI) has been developed for matrix-free secondary ion mass spectrometry for surface analysis. When a target is etched by EDI, the physical etching on the target is suppressed to minimal, i.e., the occurrence of shallow surface etching. A novel approach to shallow surface etching of polystyrene (PS) by EDI was investigated. The charged water droplets were irradiated to a bulk and a spin coated PS. After irradiation, these samples were analyzed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy. It was found that XPS spectra for PS were independent on the irradiation time by EDI. This indicates that EDI is a unique technique for the surface etching of the organic materials without leaving any damage on the etched surface.