Novel field-induced gray-level selective patterning of self-assembled aminosilane monolayer on SiO₂ surfaces by scanning probe bond-breaking lithography

We demonstrated a successful strategy for combining the straightforward scanning probe chemical bond-breaking lithography and selfassembly monolayer (SAM) techniques for constructing nanoscale architectural structures of gold nanoparticles (AuNPs) onto modified SiO₂ surfaces. The hydroxyl-terminated surface of the sample substrate was modified by silanization with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS) molecules. Local-field-induced scanning probe bond-breaking lithography is adopted to selectively decompose the chemical bonds of AEAPTMS SAMs on aminosilane-modified SiO2 surfaces. From the experiments, a tip bias of less than 4.5V cannot effectively decompose chemical bonds of AEAPTMS SAMs. Gray-level selectively patterned pictures were successfully observed on a modified 2.5-nm-thick SiO₂ surface by applying dc voltage (2.5-5.5 V) between the atomic force microscopy (AFM) conductive tip and the SiO₂ surface under ambient conditions. After the scanning probe selective decomposition of AEAPTMS SAMs, AuNPs with negative-charged citrate surfaces were selectively anchored in the selective patterning region via Coulomb electrostatic force. With proper control, it is considered that this novel technique can be applicable to the generation of various nanofabricated devices.