Markus Hund

Electric Field Alignment of a Block Copolymer Nanopattern: Direct Observation of the Microscopic Mechanism

Using quasi-in-situ scanning force microscopy we study the details of nanopattern alignment in ABC terblock copolymer thin films in the presence of an in-plane electric field. Because of the surface interactions and electric field the lamellae are oriented both perpendicular to the plane of the film and parallel to the electric field. We identified two distinct defect types which govern the orientation mechanism. Ring-like (tori) and open-end defects dominate at the early stage of the orientation process, while mainly classic topological defects (disclinations and dislocations) are involved in long-range ordering at the late stages. Comparison of the time evolution of the defect density with the evolution of the orientational order parameter suggests that tori-defects are essential for the effective reorientation. Further, the quasi-in-situ SFM imaging allowed us to elucidate the influence of the electric field strength on the propagation velocity of the topological defects.

Large scale alignment of a lamellar block copolymer thin film via electric fields: a time-resolved SFM study

We have devised a novel route towards a nanoscopically striped surface pattern with long range order the self-assembly of an ABC triblock terpolymer thin film exposed to an in-plane electric field. the interplay between surface interactions and the effect of the electric field the lamellae were oriented both perpendicular to the plane of the film and parallel to the electric field. Moreover, quasi scanning force microscopy measurements were used to follow the reorientation process as a function of time and to yield insight into the microscopic steps eventually leading to the ordered microdomain structure.

SiCN Nanofibers with a Diameter Below 100 nm Synthesized via Concerted Block Copolymer Formation, Microphase Separation, and Crosslinking

SiCN fibers with a mean diameter of 50 nm and an aspect ratio of up to 100 are produced in a two-step process by R. Kempe and co-workers. The key step to fabricate the longitudinal and cross-sectional views of the mesofibers shown here is a concerted block-copolymer synthesis, microphase separation, and cross linking at 140 °C followed by pyrolysis at 1100 °C. Inexpensive components like a commercially available silazane and polyethylene are linked. The fibers may find application in electronic devices, as components of ceramic matrix composites, as fiber beds in high-temperature nano-filtering like diesel fine dust removal, or as thermally robust and chemically inert catalyst supports. Furthermore, the SiCN nanofibers introduced on page 984 are a promising alternative to ultrathin carbon fibers, due to their oxidation resistance.

On the alignment of a cylindrical block copolymer: a time-resolved and 3-dimensional SFM study

In a combined quasi in situscanning force microscopy study we close trace the alignment process of thin polymer films of poly(styrene)-b-poly(2-vinylpyridine)-b-poly(tert-butyl methacrylate) triblock terpolymer exposed to a high electric in-plane field and solvent vapor. Our experiments show that in this triblock terpolymer a perforated lamella structure forms the basis for the core–shell cylindrical structure. Further we observe a hexagonal superstructure during the alignment process that occurs with solvent vapor annealing in the presence of a high electric field (6–15 V μm−1). The electric field induced reorientation includes a rupture-and-growth mechanism and the rotation of the hexagonal lattice. We reconstruct the 3D-structure of the aligned microdomains with quasi in situSFM nanotomography. The gained 3D reconstructions lead to a detailed understanding of the polymer film behavior in the border region between perforated lamella and the cylindrical phase. Combining time-resolved SFM datasets with 3D reconstructions, we present a model for the rearrangement of the polymer cylinders on the basis of a hexagonally perforated lamella. One-dimensionally aligned core–shell cylinders could form the basis for electrically isolated nanowires once the cylinder core is metalized.

Design of a scanning probe microscope with advanced sample treatment capabilities: An atomic force microscope combined with a miniaturized inductively coupled plasma source

We describe the design and performance of an atomic force microscope (AFM) combined with a miniaturized inductively coupled plasma source working at a radio frequency of 27.12 MHz. State-of-the-art scanning probe microscopes (SPMs) have limited in situ sample treatment capabilities. Aggressive treatments such as plasma etching or harsh treatments such as etching in aggressive liquids typically require the removal of the sample from the microscope. Consequently, time consuming procedures are required if the same sample spot has to be imaged after successive processing steps. We have developed a first prototype of a SPM which features a quasi in situ sample treatment using a modified commercial atomic force microscope. A sample holder is positioned in a special reactor chamber; the AFM tip can be retracted by several millimeters so that the chamber can be closed for a treatment procedure. Most importantly, after the treatment, the tip is moved back to the sample with a lateral drift per process step in the 20 nm regime. The performance of the prototype is characterized by consecutive plasma etching of a nanostructured polymer film.

Going beyond the Surface: Revealing Complex Block Copolymer Morphologies with 3D Scanning Force Microscopy

We report on the quasi in situ scanning force microscopy nanotomography which proved to be a key method to effectively obtain a three-dimensional (3D) microdomain structure of a complex ABC triblock morphology. As an example, we studied polybutadiene-block-poly(2-vinyl pyridine)-block-poly(tert-butyl methacrylate) (BVT) thin triblock terpolymer films. We realized a controlled erosion of the material by using low-pressure plasma etching coupled to the scanning force microscope. The 3D reconstruction provides insights into the structural behavior in very thin volume elements revealing morphological details not accessible with other methods.

Recent Developments in In Situ SFM of Block Copolymers: 3D Volume Structures and Dynamics

This chapter uses various research examples to illustrate how recent developments in scanning force microscopy (SFM) allow a detailed understanding of complex soft matter structures. The central focus lies in the introduction to the technical working principle of quasi in situ SFM (QIS-SFM) which is supported by selected applications for the analysis of dynamic and structural behavior of block copolymer films under solvent vapor annealing in the presence of a high electric field. We demonstrated that the internal film structure can be reconstructed tomographically with high depth resolution by a combination of topography and phase imaging after successive surface erosion via low-pressure plasma treatment. The QIS-SFM has a large potential, which goes significantly beyond the problems and systems reported here.

Quasi in situ scanning force microscope with an automatic operated reaction chamber

We describe the design and performance of a quasi in situ scanning force microscope with an automatic operated reaction chamber. The design provides a repetitive hermetically sealed sample environment for successive processing. The reaction chamber is based on a combination of a flexure-guided cover, a piezo-positioning system and a force applicator system. An axial force seals the cover against the reactor enabling flow-through applications at low pressure, ambient pressure, or elevated pressure. The position stability of the sample relative to the probe is characterized and a full automated operation of the instrument is explored by the alignment of an ABC terblock copolymer thin film undergoing solvent vapor annealing in the presence of a high electric field. Due to the high electric field strength and the sharp scanning force microscope tip it is impossible to perform in situ scanning in the presence of the electric field.