Substrates patterning

5 Probing Surface-Attached Redox Macromolecules Mt/SECM-AFM 

FIGURE 17.15 Direct electrochemical contact between an incoming AFM-SECM probe and the redox Fc heads of nanometer-sized, flexible chains (such as PEG or DNA), end-grafted onto an electrode substrate. The Fc heads are alternatively oxidized at the tip and reduced back at the substrate. For clarity, the tip is not drawn to scale. The chains are pictured in the mushroom conformation. (Adapted with permission from Abbou, J., Anne, A., and Demaille, C., Probing the structure and dynamics of end-grafted flexible polymer chain layers by combined atomic force—Electrochemical microscopy. Cyclic voltammetry within nanometer-thick macromolecular poly(ethylene glycol) layers, J. Am. Chem. Soc., 126,10095-10108, 2004. Copyright 2004 American Chemical Society.) 

At very close tip-substrate separation, an unpredicted peak was observed in the current response. Analysis of the force curve and random walk simulations of the chain conformation enabled this peak to be attributed to compression-induced conformational change of the end-grafted chains overcompressed chains elongate to escape confinement. These results illustrate the power of SECM-AFM in being able to characterize, in situ, the dynamics of end-grafted polymer chains. Moreover, as SECM-AFM allows the force and current responses associated with chain compression to be simultaneously measured, the interplay between chain conformation and dynamics and their modulation upon confinement can be explored. Additionally, as SECM-AFM is a local probe 

Mt/SECM-AFM was also used to explore the conformation and motional dynamics of end-grafted DNA oligonucleotides [16]. Force and current approach curves were recorded at a gold surface bearing a layer of thiol-end grafted Fc-labeled (dT)2o chains, both before and after hybridization 

6 Attaching a Redox SECM Mediator to an SECM-AFM Probe Tarm/SECM-AFM 

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Bottom-Up Block Copolymer Patterns Directed by Top-Down Substrate Patterns... 

The formation of bottom-up block copolymer patterns within or on top-down substrate patterns is the basis for so-called templated self-assembly processes, in which long-range order and orientation of microdomain patterns can be imposed by a template or guide . These top-down templates can take a variety of forms including periodic thickness profiles and chemically patterned surfaces. 

The synthesis and electrochemical properties of carbon films prepared from positive photoresist have been reported.The initial direction for this work was the fabrication of carbon interdigitated electrodes. In this work, positive photoresist was spin coated on a silicon substrate, patterned by photolithography, and pyrolyzed to form the carbon electrode. In more recent work, laser excitation has been used to both pyrolyze the film and to write the electrode pattern. ... 

To clarify the selection of a particular MLR system (ILR, 2LR, or 3LR system) a comparison in terms of process complexity, resolution, aspect ratio, linewidth tolerance, sensitivity and effort required for research and development will be given. Then a comparison between deep-UV and RIE PCM systems in terms of resolution, aspect ratio, substrate patterning processes allowed, temperature stability, resist removal at the alignment sites, tool-controlling parameters, and tool cost will be included. 

Substrate Patterning and Activation Strategies for DNA Chip Fabrication... 

Today the frontier of the fabrication of electronic devices has moved from the micrometer scale down to tens of nanometers scale. Scaled-down conventional devices such as field-effect transistors and devices based on quantum effects are two most prominent examples of the electronic miniaturisation [20, 23,430]. The major challenges in preparation of such devices are (i) growing the substrate materials and (ii) patterning the substrates. Whereas the former rely on self-organisation of the surface structure, the substrate patterning on the nanoscale requires special tools. 

Ternary blends One way to overcome these limitations is the use of ternary polymer blends. This approach makes use of the principle described in section 1.1.2, in which one of the polymer components wets the interface of the other two. By providing a pre-pattemed substrate with surface regions, to which these two polymer segregate, it is possible to form structures in the intercalated polymer with dimensions that are not directly connected to the substrate pattern. 

The main advantage of using a ternary blend (as opposed to the direct replication of Fig. 1.6, where the width of the polymer structures was directly imposed by the substrate pattern), is the relative independence of the structure parameters (width, aspect ratio) with respect to the substrate pattern. The width (and thereby the aspect ratio) of the PMMA rings in Fig. 1.7 is controlled by the relative amount of PMMA in the PS/PMMA/PVP blend. While the lateral periodicity of the polymer structures is determined by the substrate, the structure size is controllable by the relative amount of PMMA in the blend. Similar to the replication technique using two polymers, pattern replication by demixing of ternary blends should be expandable to other polymer system, with the main requirement that one of the components wets the interface of the other two. 

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