Photopatterning of self-assembled monolayers at 244 nm and applications to the fabrication of functional microstructures and nanostructures

摘要

Self-assembled monolayers (SAMs) of alkanethiols have been patterned on micrometre and nanometre length scales by exposure to light from a frequency doubled argon ion laser. Friction force microscopy shows that the patterning speed depends on the nature of the terminal group and is in the order COOH > CH_3, the reverse of the order reported previously using a mercury arc lamp, indicating that a different photo-oxidation mechanism is responsible. It is suggested that this involves the creation of hot electrons at the gold surface that initiate oxidation of the adsorbate. Nanostructures have been fabricated using scanning near-field photolithography (SNP), in which the UV laser is coupled to a near-field scanning optical microscope. During SNP, the rates of writing required for complete oxidation correlate closely with oxidation rates measured during micropatterning, suggesting that the mechanism is essentially the same. SAMs on silver have been patterned, yielding linewidths smaller than 50 nm. The selective alkylation of hydrogen passivated Si has been demonstrated, yielding structures that may be used as resists for etching and demonstrating a powerful new capability-fluid-phase nanophotolithography. Patterned SAMs prepared using SNP have been used to selectively attach polymer nanoparticles, demonstrating their utility for the creation of functional molecular nanostructures. Nanopatterns generated by SNP have also been used as resists, enabling the etching of nanostructures into gold and the fabrication of three-dimensional nanostructures in silicon using a two-stage wet etch process.