Nonlinear processing and multiphoton ablation of self-assembled monolayers for application as ultrathin resists and in biochemical sensors

Excerpt

Self-assembled monolayers (SAMs) addressed in this chapter are monomolecular organic coatings, which allow one to adjust a variety of surface properties of solid materials including bioaffinity and chemical resistance [–3]. In view of these opportunities, such organic coatings are widely used as ultrathin resists and functional films in micro- and nanofabrication [–5]. Nonlinear laser processing has evolved as a powerful and versatile means for nanopatterning of SAMs [6, 7]. Generally, laser processing is a maskless and flexible noncontact technique. Also, rapid processing over areas ranging from square centimeters to square decimeters can be carried out on essentially all kinds of support materials at high pressures and in liquids. In recent years femtosecond (fs) lasers have been proven to provide specific perspectives in nonlinear processing and sub-100 nm patterning of organic monolayers [7]. In particular, finely tuned photothermal reactions and multiphoton absorption processes introduce high nonlinearities [8, 9]. In addition, the ultrathin nature of these coatings allows single pulse processing, thus ensuring short processing times [7]. The molecular thickness also ensures well-defined irradiation and burr-free patterning and avoids the formation of bubbles and particles [8, 9]. All these issues represent common problems in ablative fs-laser processing [10, 11]. This chapter reviews recent progress in nonlinear fs-laser processing of organic monolayers, i.e. results from references [–, –15]. Particular emphasis is placed on prospects of tunable fs-laser sources in resonant laser processing of organic monolayers and the application of such coatings as ultrathin resists and functional platforms for fabrication of protein micro- and nanoarrays [–15].