Nanopatterned Self-Assembled Monolayers by Using Diblock Copolymer Micelles as Nanometer-Scale Adsorption and Etch Masks

Nanometer-scale patterning of surfaces is a highly relevant and interesting topic of research today, owing to its potential contributions to device miniaturization and creation of novel functional interfaces with applications ranging from electronics to biomedicine. Several methods of nanopatterning are known, for example, nanoimprint lithography, laser interferometry, extreme ultraviolet interference lithography, shadow mask lithography, and scanning-probe-microscopy-based lithographic methods. Although the topographical and chemical structuring of surfaces by using one or more of these techniques is well-established and is state-of-the-art, these methods also suffer from some drawbacks. They either involve a costly mask fabrication step, heavy infrastructure investments, clean-room conditions, or are restricted to the patterning of comparatively small areas only. One alternative method of surface structuring that addresses some of these drawbacks is block copolymer lithography, where use is made of polymer masks derived from selfassembly of block copolymers. This process has gained popularity owing to facile fabrication of sub-100 nm structures on macroscopic areas. The preparation of nanometer-scale masks by using phase-separated block copolymer thin films frequently involves working with appropriate film thickness and surface energy, an annealing step to order the polymer domains, and selective degradation and removal of one of the domains. Many of the advantages of this method can also be realized in a much simplified approach by using block copolymer micelles deposited from solution. The attractiveness of the latter approach lies in the fact that the micellar films can be readily prepared on a wide variety of substrates, and in addition, their dimensions and spacing can be tuned in a straight-forward manner, without having to change the polymer molecular weights. Micellar thin films, even in their as-coated form, can be used for structuring surfaces