Chemical methods developed over the past two decades enable preparation of colloidal nanocrystals with uniform size and shape. These Brownian objects readily order into superlattices. Recently, the range of accessible inorganic cores and tunable surface chemistries dramatically increased, expanding the set of nanocrystal arrangements experimentally attainable. In this review, we discuss efforts to create next-generation materials via bottom-up organization of nanocrystals with preprogrammed functionality and self-assembly instructions. This process is often driven by both interparticle interactions and the influence of the assembly environment. The introduction provides the reader with a practical overview of nanocrystal synthesis, self-assembly, and superlattice characterization. We then summarize the theory of nanocrystal interactions and examine fundamental principles governing nanocrystal self-assembly from hard and soft particle perspectives borrowed from the comparatively established fields of micro...

Self-Assembly of Colloidal Nanocrystals: From Intricate Structures to Functional Materials

2.4. Block Copolymer Containing Hybrids 151 3. Block Copolymer Ordering in Thin Films 153 3.1. General Process Steps 153 3.2. Morphology of Thin Films 154 3.3. Thickness-Dependent Nanopatterning 154 3.3.1. Ultrathin Films: Monomolecular Films 155 3.3.2. Sub-L0 Thick Films 155 3.3.3. Thick Films 157 3.4. Placement Control: Directed Self-Assembly (DSA) 162 3.4.1. Topographic Guiding Patterns: Graphoepitaxy 163

Block copolymer based nanostructures: materials, processes, and applications to electronics.

Advances in synthetic polymer chemistry have unleashed seemingly unlimited strategies for producing block polymers with arbitrary numbers (n) and types (k) of unique sequences of repeating units. Increasing (k,n) leads to a geometric expansion of possible molecular architectures, beyond conventional ABA-type triblock copolymers (k = 2, n = 3), offering alluring opportunities to generate exquisitely tailored materials with unparalleled control over nanoscale-domain geometry, packing symmetry, and chemical composition. Transforming this potential into targeted structures endowed with useful properties hinges on imaginative molecular designs guided by predictive theory and computer simulation. Here, we review recent developments in the field of block polymers.

http://science.sciencemag.org/content/sci/336/6080/434.full.pdf

Multiblock Polymers: Panacea or Pandora’s Box?

Self-assembling materials are the building blocks of bottom-up nanofabrication processes, but they need to be templated to impose long-range order and eliminate defects. In this work, the self-assembly of a thin film of a spherical-morphology block copolymer is templated using an array of nanoscale topographical elements that act as surrogates for the minority domains of the block copolymer. The orientation and periodicity of the resulting array of spherical microdomains are governed by the commensurability between the block copolymer period and the template period and is accurately described by a free-energy model. This method, which forms high-spatial-frequency arrays using a lower-spatial-frequency template, will be useful in nanolithography applications such as the formation of high-density microelectronic structures.

https://science.sciencemag.org/content/sci/321/5891/939.full.pdf

Graphoepitaxy of self-assembled block copolymers on two-dimensional periodic patterned templates.

Generating laterally ordered, ultradense, macroscopic arrays of nanoscopic elements will revolutionize the microelectronic and storage industries. We used faceted surfaces of commercially available sapphire wafers to guide the self-assembly of block copolymer microdomains into oriented arrays with quasi-long-range crystalline order over arbitrarily large wafer surfaces. Ordered arrays of cylindrical microdomains 3 nanometers in diameter, with areal densities in excess of 10 terabits per square inch, were produced. The sawtoothed substrate topography provides directional guidance to the self-assembly of the block copolymer, which is tolerant of surface defects, such as dislocations. The lateral ordering and lattice orientation of the single-grain arrays of microdomains are maintained over the entire surface. The approach described is parallel, applicable to different substrates and block copolymers, and opens a versatile route toward ultrahigh-density systems.

https://science.sciencemag.org/content/sci/323/5917/1030.full.pdf

Macroscopic 10-terabit-per-square-inch arrays from block copolymers with lateral order.

Methods to pattern substrates with dense periodic nanostructures that combine top-down lithographic tools and self-assembling block copolymer materials are provided. According to various embodiments, the methods involve chemically patterning a substrate, depositing a block copolymer film on the chemically patterned imaging layer, and allowing the block copolymer to self-assemble in the presence of the chemically patterned substrate, thereby producing a pattern in the block copolymer film that is improved over the substrate pattern in terms feature size, shape, and uniformity, as well as regular spacing between arrays of features and between the features within each array compared to the substrate pattern. In certain embodiments, the density and total number of pattern features in the block copolymer film is also increased. High density and quality nanoimprint templates and other nanopatterned structures are also provided.

https://science.sciencemag.org/content/sci/321/5891/936.full.pdf

Density multiplication and improved lithography by directed block copolymer assembly

The characterization of photoresists during the image formation process has traditionally relied on bulk methods during or after development. This article shows that it is not necessary to develop the photoresist in order to obtain significant information about the image formation process in x‐ray, electron beam, and UV lithography. The characterization of the image formation process in chemically amplified photoresists prior to development is difficult due to their sensitivity to electrons used in scanning electron microscopy and the weak changes in dielectric constant needed for optical microscopy. The advent and development of the atomic force microscope (AFM) have allowed local surface measurements of exposure induced changed in photoresists with sub‐μm scale resolution and negligible modification of the sample. A series of chemically amplified resists, positive and negative, have been studied with a variety of exposure radiation (electron beam, x‐ray, and UV). The results discussed in this article fo...

Latent image formation: Nanoscale topography and calorimetric measurements in chemically amplified resists

L'invention concerne des procedes pour faconner des substrats ayant des nanostructures periodiques denses combinant des outils de lithographie par voie descendante (« top-down ») et des materiaux copolymeres sequences a auto-assemblage. Selon divers modes de realisation, les procedes consistent a faconner chimiquement un substrat, a deposer un film de copolymeres sequences sur la couche d'imagerie faconnee chimiquement et a laisser le copolymere sequence s'auto-assembler en presence du substrat faconne chimiquement, d'ou la production d'un motif dans le film de copolymeres sequences qui est ameliore par rapport au motif de substrat en termes de taille, de forme et d'uniformite des caracteristiques, ainsi qu'en termes d'espacement regulier entre des reseaux de caracteristiques et entre les caracteristiques a l'interieur de chaque reseau, par rapport au motif du substrat. Dans certains modes de realisation, la densite et le nombre total de caracteristiques du motif dans le film de copolymeres sequences sont egalement accrus. L'invention concerne egalement des modeles de nano-impression de haute qualite et de forte densite et d'autres structures nano-faconnees.

Juan J. Depablo

Papers

Density multiplication and improved lithography by directed block copolymer assembly

Latent image formation: Nanoscale topography and calorimetric measurements in chemically amplified resists

Multiplication de densité et lithographie améliorée grâce à un ensemble de copolymères séquencés dirigé