AFM nanolithography on a mixed LB film of hexadecylamine and palmitic acid

An evenly mixed Langmuir film of hexadecylamine (HDA) and palmitic acid (PA) was prepared on the air–water interface and transferred to a Si substrate for the fabrication of nano-sized patterns. Vibrational spectrum of the transferred film shows that all acid groups of PAs were deprotonated and amine groups of HDAs were protonated by an acid–base reaction. The effect of mixing ratios in atomic force microscopy anodization lithography on the mixed films was investigated in terms of the line width of the protruded pattern. While the line width fabricated on PA film was 221 nm, the width on the mixed film was reduced to 84 nm under the same lithographic conditions. It is believed that the phenomenon was originated from the mixed structure from the interaction of HDA and PA. The chemical composition difference caused by the presence of ammonium cation in resist resulted in reducing the line width fabricated in the mixed Langmuir–Blodgett film.