With block copolymer microdomains

Helfand has presented a general theory of inhomogeneous polymeric systems and has applied it to the interface between immiscible honmpolymers and to block copolymers In order to simplify the problem of the numerical calculation of the microdomain sizes, he has derived from his general theory a narrow interface approximation The values predicted by the simplified theory for the dimensions of the lamellar block copolymer microdomains are in good agreement with the experimental results ... 

Lithography with a Pattern of Block Copolymer Microdomains as a Positive or Negative Resist... 

Lithography with Self-Assembled Block Copolymer Microdomains... 

Figure 9.1 Schematic of block-copolymer microdomains in thin films. Panels a and b show one layer of spheres and cyUnders, respectively (darker component). Note the additional wetting layers above and below the microdomains that serve to satisfy the interfacial constraints the specific configuration varies depending upon the copolymer system. Panel c shows lamellar sheets oriented parallel to the substrate by the strong alignment influence of the substrate and vacuum/polymer interfaces. (Reproduced with permission from the American Association for the Advancement of Science)...

The earliest work on imaging block copolymer microdomains relied heavily upon transmission electron microscopy (TEM), and it still proves to be a useful tool to this day [19]. Samples are either microtomed or solvent cast to produce thin (ca. 100 nm) sections. PS-PI or PS-PB samples can be stained with osmium tetroxide to increase contrast. Osmium tetroxide reacts selectively with unsaturated double bonds such as found in PI or PB microdomains so as to provide mass contrast [21]. Unfortunately, TEM requires that the samples be freestanding or transferred to a transparent support (e.g. carbon), a cumbersome and time-consuming process that is largely incompatible with silicon or GaAs wafers. While silicon nitride membranes can be employed for TEM, these expensive and delicate structures are not easily accessible to all researchers [22]. 

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