We have experimentally determined a phase diagram for cylinder-forming polystyrene-block-polybutadien-block-polystyrene triblock copolymer in thin films. The phase behavior can be modeled in great detail by dynamic density functional theory. Deviations from the bulk structure, such as wetting layer, perforated lamella, and lamella, are identified as surface reconstructions. Their stability regions are determined by an interplay between surface fields and confinement effects.

The nanoscale control afforded by scanning probe microscopes has prompted the development of a wide variety of scanning probe-based patterning methods. Some of these methods have demonstrated a high degree of robustness and patterning capabilities that are unmatched by other lithographic techniques. However, the limited throughput of scanning probe lithography has prevented their exploitation in technological applications. Here, we review the fundamentals of scanning probe lithography and its use in materials science and nanotechnology. We focus on the methods and processes that offer genuinely lithography capabilities such as those based on thermal effects, chemical reactions and voltage-induced processes. Published in:Nature Nanotechnology 9, 577-587 (2014) Progress in nanotechnology depends on the capability to fabricate, position, and interconnect nanometre-scale structures. A variety of materials and systems such as nanoparticles, nanowires, two-dimensional materials like graphene and transition metal dichalcogenides, plasmonics materials, conjugated polymers and organic semiconductors are finding applications in nanoelectronics, nanophotonics, organic electronics and biomedical applications. The success of many of the above applications relies on the existence of suitable nanolithography approaches. However, patterning materials with nanoscale features aimed at improving integration and device performance poses several challenges. The limitations of conventional lithography techniques related to resolution, operational costs and lack of flexibility to pattern organic and novel materials have motivated the development of unconventional fabrication methods [1][2][3] .Since the first patterning experiments performed with a scanning probe microscope in the late 80s, scanning probe lithography (SPL) has emerged as an alternative lithography for academic research that combines nanoscale feature-size, relatively low technological requirements and the ability to handle soft matter from small organic molecules to proteins and polymers. Scanning probe lithography experiments have provided striking examples of its capabilities such as the ability to pattern 3D structures with nanoscale features 4 , the fabrication of the smallest field-effect transistor 5 or the patterning of proteins with 10 nm feature size 6 . Figure 1a shows a general scheme of SPL operation. There is a variety of approaches to modify a material in a probe-surface interface which have generated several SPL methods. Scanning probe lithographies can be either classified by emphasizing the distinction between the general nature of the process, chemical versus physical, or by considering if SPL implies the removal or addition of material. However, we consider it is more inclusive and systematic to classify the different SPL methods in terms of the driving mechanisms used in the patterning process, namely thermal, electrical, mechanical and diffusive methods (Fig. 1b). Challenges in nanoscale lithographyThe workhorse of large volume CMOS fabrication, o...

We experimentally establish a phase diagram of thin films of concentrated solutions of a cylinder forming polystyrene-block-polybutadiene-block-polystyrene triblock copolymer in chloroform. During annealing the film forms islands and holes with energetically favored values of film thickness. The thin film structure depends on the local thickness of the film and the polymer concentration. Typically, at a thickness close to a favored film thickness parallel orientation of cylinders is observed, while perpendicular orientation is formed at an intermediate film thickness. At high polymer concentration the cylindrical microdomains reconstruct to a perforated lamella structure. Deviations from the bulk structure, such as the perforated lamella and a wetting layer are stabilized in films thinner than approximately 1.5 domain spacings.

For patterning organic resists, optical and electron beam lithography are the most established methods; however, at resolutions below 30 nanometers, inherent problems result from unwanted exposure of the resist in nearby areas. We present a scanning probe lithography method based on the local desorption of a glassy organic resist by a heatable probe. We demonstrate patterning at a half pitch down to 15 nanometers without proximity corrections and with throughputs approaching those of Gaussian electron beam lithography at similar resolution. These patterns can be transferred to other substrates, and material can be removed in successive steps in order to fabricate complex three-dimensional structures.

We investigate in detail the processes involved when soft polymeric materials are imaged with TappingMode atomic force microscopy (TM-AFM). Measuring lateral arrays of amplitude/phase vs distance (APD) curves, we are able to determine quantitatively the amount of tip indentation and reconstruct the shape of the "real" surface of the sample. Moreover, contrast inversion in height and TappingMode phase images is explained on the basis of attractive and repulsive contributions to the tip-sample interaction. The experiments are performed on surfaces of poly(styrene-block-butadiene-blockstyrene) (SBS) triblock copolymers acting as a model system.