Sputtering of silicon and glass substrates with polyatomic molecular ion beams generated from ionic liquids

The effect of irradiating 1-ethyl-3-methylimidazolium positive (EMIM+) or dicyanamide negative (DCA–) ion beams using an ionic liquid ion source was characterized concerning its sputtering properties for single crystalline Si(100) and nonalkaline borosilicate glass substrates. The irradiation of the DCA– ion beam onto the Si substrate at an acceleration voltage of 4 and 6 kV exhibited detectable sputtered depths greater than a couple of nanometers with an ion fluence of only 1 × 1015 ions/cm2, while the EMIM+ ion beam produced the same depths with an ion fluence 5 × 1015 ions/cm2. The irradiation of a 4 kV DCA– ion beam at a fluence of 1 × 1016 ions/cm2 also yields large etching depths in Si substrates, corresponding to a sputtering yield of Si/DCA– = 10, and exhibits a smoothed surface roughness of 0.05 nm. The interaction between DCA– and Si likely causes a chemical reaction that relates to the high sputtering yield and forms an amorphous C-N capping layer that results in the smooth surface. Moreover, s...