pH-Dependent Selective Thickness Control of Polyelectrolyte Nanolayers on SiO2 and Cu Surfaces

A strategy for selective formation of an organic film on SiO2 surface while minimizing its deposition on Cu surface is proposed. The organic film was deposited by spin coating a polyamine solution and an aromatic carboxylic acid solution in a sequential fashion. Then the ionically bonded film that consisted of the polyamine and aromatic carboxylic acid was formed. It was found that the thickness of the film was controlled by the simple pH adjustment of the polyamine solution. Under basic pH conditions, the thickness of the film was almost the same on both substrates. However, under acidic pH, the Cu layer was thinner and the thickness was constant on the SiO2. After baking the organic film, a single 10 nm scale thick covalently bonded organic film was obtained on the SiO2, while a similar to 0.5 nm thick film was obtained on the Cu.