500 eV Ar+ ion impact and the electrospray droplet impact (EDI), in which the charged electrospray water droplets are introduced in vacuum, accelerated and allowed to impact the sample, are applied for etching of polyimide (PI). After the bombardment, x-ray photoelectron spectroscopy (XPS) was applied to the surface analysis. Although oxygen and nitrogen are selectively etched by Ar+ ion impact, the XPS spectra did not change with prolonged charged water droplets irradiation, i.e., EDI is capable of shallow surface etching for PI with little damage of the sample after irradiation. (c) 2010 American Vacuum Society. [DOT: 10.1116/1.3420465]