Positionally defined, binary semiconductor nanoparticles synthesized by scanning probe block copolymer lithography.

We report the first method for synthesizing binary semiconductor materials by scanning probe block copolymer lithography (SPBCL) in desired locations on a surface. In this work, we utilize SPBCL to create polymer features containing a desired amount of Cd(2+), which is defined by the feature volume. When they are subsequently reacted in H(2)S in the vapor phase, a single CdS nanoparticle is formed in each block copolymer (BCP) feature.

Nanoreactors for studying single nanoparticle coarsening.

The ability to observe intermediate structures as part of coarsening processes that lead to the formation of single nanoparticles (NPs) is important in gaining fundamental insight pertaining to nanostructure growth. Here, we use scanning probe block copolymer lithography (SPBCL) to create "nanoreactors" having attoliter volumes, which confine Au NP nucleation and growth to features having diameters <150 nm on a substrate. With this technique, one can use in situ TEM to directly observe and study NP coarsening and differentiate Ostwald ripening from coalescence processes.

Density doubling of block copolymer templated features.

Block copolymers can be used to template large arrays of nanopatterns with periodicities equal to the characteristic spacing of the polymer. Here we demonstrate a technique capitalizing on the multilayered arrangement of cylindrical domains to effectively double the pattern density templated by a given polymer. By controlling the initial thickness of the film and the solvent annealing conditions, it was possible to reproducibly create density doubled lines by swelling the film with solvent until bilayers of horizontal cylinders were obtained.

Single-molecule protein arrays enabled by scanning probe block copolymer lithography.

The ability to control the placement of individual protein molecules on surfaces could enable advances in a wide range of areas, from the development of nanoscale biomolecular devices to fundamental studies in cell biology. Such control, however, remains a challenge in nanobiotechnology due to the limitations of current lithographic techniques. Herein we report an approach that combines scanning probe block copolymer lithography with site-selective immobilization strategies to create arrays of proteins down to the single-molecule level with arbitrary pattern control.

Hard-tip, soft-spring lithography.

Nanofabrication strategies are becoming increasingly expensive and equipment-intensive, and consequently less accessible to researchers. As an alternative, scanning probe lithography has become a popular means of preparing nanoscale structures, in part owing to its relatively low cost and high resolution, and a registration accuracy that exceeds most existing technologies. However, increasing the throughput of cantilever-based scanning probe systems while maintaining their resolution and registration advantages has from the outset been a significant challenge.

Scanning probe block copolymer lithography.

Integration of individual nanoparticles into desired spatial arrangements over large areas is a prerequisite for exploiting their unique electrical, optical, and chemical properties. However, positioning single sub-10-nm nanoparticles in a specific location individually on a substrate remains challenging. Herein we have developed a unique approach, termed scanning probe block copolymer lithography, which enables one to control the growth and position of individual nanoparticles in situ.

Beam pen lithography.

Lithography techniques are currently being developed to fabricate nanoscale components for integrated circuits, medical diagnostics and optoelectronics. In conventional far-field optical lithography, lateral feature resolution is diffraction-limited. Approaches that overcome the diffraction limit have been developed, but these are difficult to implement or they preclude arbitrary pattern formation.

Using cylindrical domains of block copolymers to self-assemble and align metallic nanowires.

Block copolymer thin films can be used as soft templates for a wide range of surfaces where large area patterns of nanoscale features are desired. The cylindrical domains of acid-sensitive, self-assembled monolayers of polystyrene-poly(2-vinylpyridine) block copolymers on silicon surfaces were utilized as structural elements for the production of parallel metal nanowires. Metal ion loading of the P2VP block with simple aqueous solutions of anionic metal complexes is accomplished via protonation of this basic block, rendering it cationic; electrostatic attraction leads to a high local concentration of metal complexes within the protonated P2VP domain.

Assembly of aligned linear metallic patterns on silicon.

In order to harness the potential of block copolymers to produce nanoscale structures that can be integrated with existing silicon-based technologies, there is a need for compatible chemistries. Block copolymer nanostructures can form a wide variety of two-dimensional patterns, and can be controlled to present long-range order. Here we use the acid-responsive nature of self-assembled monolayers of aligned, horizontal block copolymer cylinders for metal loading with simple aqueous solutions of anionic metal complexes, followed by brief plasma treatment to simultaneously remove the block copolymer and produce metallic nanostructures.

Wettability interpretation of oxygen plasma modified poly(methyl methacrylate).

Poly(methyl methacrylate) (PMMA) has been modified via a dc pulsed oxygen plasma for different treatment times. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), optical profilometer, zeta potential, and advancing contact angle measurements. The measured advancing contact angles of water decreased considerably as a function of discharge.